Azithromycin

Oximation Reactions

The initial step in the synthesis of this compound from erythromycin A is the formation of erythromycin A oxime. nih.govub.edugoogle.comgoogle.com This reaction typically involves the treatment of erythromycin A with hydroxylamine hydrochloride in the presence of a base and a buffer. nih.govub.edu For instance, the synthesis of erythromycin-A Oxime can be achieved by reacting erythromycin A or erythromycin base with hydroxylamine hydrochloride, sodium hydroxide, and acetic acid. ub.edu This step converts the ketone group at position 9 of the erythromycin A lactone ring into an oxime. sci-hub.senih.gov

Beckmann Rearrangement and Derivatives

Following the oximation, the erythromycin A oxime undergoes a Beckmann rearrangement. doaj.orgsci-hub.seub.edugoogle.comgoogle.com This rearrangement is a crucial step as it leads to the expansion of the 14-membered macrolide ring to a 15-membered ring by inserting a nitrogen atom. googleapis.comdoaj.orgresearchgate.net The product of the Beckmann rearrangement of erythromycin A oxime is the 6,9-imino ether of erythromycin A. ub.edugoogle.com Aromatic sulphochlorides can be used as reagents for the Beckmann rearrangement of erythromycin A oxime. doaj.org Research has also explored the Beckmann rearrangement of 9(E)-6-O-methyl-erythromycin oxime to synthesize 6-O-methyl-azithromycin and its aza-ketolide analogue. nih.gov

Reduction Steps

The 6,9-imino ether of erythromycin A, formed after the Beckmann rearrangement, is then subjected to a reduction step. ub.edugoogle.comgoogle.com This reduction transforms the imino ether into 9-deoxo-9a-aza-9a-homoerythromycin, also referred to as this compound precursor or demethyl this compound. ub.edugoogle.comgoogle.compatsnap.comgoogle.com Various reducing agents can be employed, including stoichiometric amounts of reducing agents or hydrogenation under high pressure with platinum. ub.edu Sodium borohydride or potassium borohydride in acidic aqueous solution can also be used for the reduction of erythromycin A 6,9-imine ether. google.compatsnap.com Some synthetic methods describe carrying out the Beckmann rearrangement and reduction reactions in a one-pot process. google.compatsnap.comgoogle.comgoogle.comgoogle.com

Methylation Reactions

The final step in the synthesis of this compound is the reductive N-methylation of 9-deoxo-9a-aza-9a-homoerythromycin. doaj.orgub.edugoogle.comgoogle.com This reaction introduces a methyl group onto the nitrogen atom that was incorporated into the macrolide ring during the Beckmann rearrangement. doaj.orgub.edu Reductive methylation can be carried out using various methods, such as Eschweiler-Clarke conditions (formaldehyde and formic acid) ub.edu or hydrogenation of formaldehyde and hydrogen in the presence of a noble metal catalyst (e.g., Pd, Pt, Rh, or Ru). googleapis.comub.edugoogle.com The methylation of 9-Deoxo-9a-aza-9a-homoerythromycin-A yields 9-Deoxo-9a-methyl-9a-aza-9a-homoerythromycin-A, from which different salts of this compound can be obtained. ub.edu Similar to the reduction step, the reduction and reductive methylation steps can be conducted sequentially in the same reaction vessel using a noble metal catalyst and hydrogen in the presence of formaldehyde. googleapis.comhovione.com

Interaction with 50S Ribosomal Subunit

This compound binds to the 23S rRNA component of the bacterial 50S ribosomal subunit. drugbank.compatsnap.commims.compatsnap.compatsnap.commdpi.commdpi.comnih.govmdpi.comfrontiersin.orgnih.govnih.govmdpi.comrcsb.org This binding occurs at a site located near the peptidyl transferase center (PTC). mdpi.comnih.govmdpi.comrcsb.orgnih.gov The strong affinity of macrolides, including this compound, for bacterial ribosomes is consistent with their broad-spectrum antibacterial activities. drugbank.com The binding site of this compound overlaps with that of other macrolides, such as erythromycin, but its specific structure allows for different interaction dynamics. mdpi.com

23S rRNA Binding Specificity (e.g., A2058, A2059, U2611)

The binding of this compound to the 23S rRNA involves specific interactions with key nucleotides within the ribosomal exit tunnel. Critically, hydrophobic contacts occur between the lactone ring of this compound and a hydrophobic surface formed by the bases U2611, A2058, and A2059. mdpi.comrcsb.orgpnas.org These nucleotides are crucial for this compound binding. rcsb.org Additionally, a hydrogen bond forms between the 2' hydroxyl group of the desosamine sugar of this compound and the N1 atom of A2058. nih.govrcsb.orgpnas.org These interactions help to anchor this compound within the ribosomal exit tunnel. rcsb.org Mutations in nucleotides like A2058 and A2059 of 23S rRNA can lead to macrolide resistance by altering the binding site and reducing the drug's affinity. nih.govpnas.orgrcsb.org Methylation of A2058 can also significantly reduce this compound binding. mdpi.comrcsb.org

Peptide Exit Tunnel Blockade

A key consequence of this compound binding to the 50S ribosomal subunit is the physical obstruction of the nascent peptide exit tunnel. patsnap.commdpi.commdpi.comnih.govmdpi.comfrontiersin.orgnih.govnih.govmdpi.comrcsb.orgrcsb.orgnih.govnih.govresearchgate.netresearchgate.netresearchgate.net This tunnel is approximately 100 Å long and 10–20 Å wide and is the path through which newly synthesized polypeptides exit the ribosome. nih.govresearchgate.net By binding within this tunnel, this compound blocks the egress of the elongating polypeptide chain. rcsb.orgnih.gov This blockage prevents the nascent peptide from passing through, effectively halting protein synthesis. mdpi.com

tRNA Drop-off and Polypeptide Synthesis Inhibition

The blockade of the peptide exit tunnel by this compound inhibits the translocation process, which is the movement of peptidyl-tRNA from the A site to the P site of the ribosome. patsnap.compatsnap.compatsnap.com This interruption halts the elongation of the nascent protein chain. patsnap.compatsnap.com The interference with the progression of the growing chain can lead to the premature detachment of incomplete peptide chains, a phenomenon known as "peptidyl-tRNA drop-off". frontiersin.orgnih.govresearchgate.netfrontiersin.org This increased drop-off can deplete the intracellular pools of aminoacyl-tRNA available for protein synthesis, further contributing to the inhibition of translation. frontiersin.orgnih.govresearchgate.netresearchgate.netfrontiersin.orgasm.org While initially viewed as a simple tunnel plug, recent evidence suggests that macrolides, including this compound, may selectively inhibit the translation of a subset of cellular proteins, and their action can depend on the nascent protein sequence and the antibiotic structure. nih.govmdpi.com

Two-Step Binding Mechanisms

Research indicates that this compound binds to Escherichia coli ribosomes in a two-step process. mdpi.comnih.govresearchgate.netresearchgate.netnih.gov The first step involves the recognition of this compound by the ribosomal machinery and its placement in a low-affinity site located in the upper part of the exit tunnel. mdpi.comnih.govresearchgate.netresearchgate.net This initial step is followed by a slower formation of a final complex. mdpi.comnih.govresearchgate.netresearchgate.net This final complex represents a much tighter binding and is more potent in hindering the progression of the nascent peptide through the exit tunnel. nih.govresearchgate.netresearchgate.net Kinetic and NMR studies have supported this two-step mechanism, suggesting that the first step equilibrates rapidly, while the second step, representing the accommodation of this compound at its final position, is established slowly. researchgate.net

Interactive Data Table: Key this compound-Ribosome Interactions

Mutations in 23S rRNA Genes (e.g., A2058G, C2611T, C2599T)

Mutations in the genes encoding the 23S ribosomal RNA (rRNA), a critical component of the 50S subunit, are frequently associated with this compound resistance. plos.orgrcsb.orgasm.org These mutations can occur at specific nucleotide positions within domain V of the 23S rRNA, which forms part of the macrolide binding site. frontiersin.orgplos.org Notable examples of such mutations include A2058G, A2059G, and C2611T (using Escherichia coli numbering). rcsb.orgasm.orgresearchgate.netsciencegate.appresearchgate.net The A2058G and A2059G mutations, in particular, can lead to high-level this compound resistance. asm.orgresearchgate.netresearchgate.net The C2611T mutation has been linked to low- to mid-level resistance, and the level of resistance can correlate with the number of mutated 23S rRNA gene copies within a bacterial cell. asm.orgresearchgate.netmdpi.com For instance, in Neisseria gonorrhoeae, the C2611T mutation in all four copies of the 23S rRNA gene resulted in an this compound MIC of 4 mg/L in some isolates. nih.gov

Ribosomal Methylation by rRNA Methyltransferases (e.g., Erm genes)

Another significant mechanism is the methylation of the 23S rRNA, primarily at adenine 2058 (A2058), by enzymes encoded by erm (erythromycin ribosome methylation) genes. frontiersin.orgmdpi.comrcsb.orgnih.gov This methylation alters the ribosomal structure, specifically in domain V of the 23S rRNA, which is the macrolide binding site. mdpi.comrcsb.orgnih.gov The addition of one or two methyl groups to A2058 disrupts the binding of this compound to the ribosome, leading to reduced drug efficacy and often conferring cross-resistance to macrolides, lincosamides, and streptogramin B (the MLSB phenotype). mdpi.comrcsb.orgnih.govfrontiersin.org Over 30 different Erm enzymes have been reported in bacteria. mdpi.com The expression of erm genes can be inducible or constitutive, and the level of methylation can influence the degree of resistance. mdpi.comrcsb.orgnih.gov

Mutations in Ribosomal Proteins (e.g., L4, L22)

Mutations in genes encoding ribosomal proteins, particularly L4 (rplD) and L22 (rplV), which are part of the 50S ribosomal subunit, can also contribute to macrolide resistance. mdpi.comasm.orgplos.orgnih.gov These proteins are located near the ribosomal exit tunnel, and mutations can affect the interaction of this compound with its binding site. asm.orgnih.gov While mutations in L4 and L22 have been reported in various bacteria, including Neisseria gonorrhoeae and Haemophilus influenzae, their specific role and the level of resistance they confer can vary. plos.orgasm.orgnih.govresearchgate.net Studies have identified specific mutations in L4, such as G70D, and alterations in L22, including amino acid substitutions, insertions, or deletions, that are associated with increased macrolide MICs. plos.orgasm.org However, the involvement of some previously reported mutations in L4, like G70D, in this compound resistance has also been refuted by recent studies. plos.org

Overexpression and Regulation of Efflux Pumps (e.g., MexAB-OprM, MtrCDE, MsrA, MefA)

Several efflux pump systems are known to contribute to this compound resistance in various bacterial species. The MexAB-OprM pump in Pseudomonas aeruginosa is a well-characterized multidrug efflux system that can expel this compound. mcmaster.ca Its expression can be suppressed by sub-MIC levels of this compound, leading to increased susceptibility to other antibiotics. nih.gov In Neisseria gonorrhoeae, the MtrCDE efflux pump plays a crucial role in resistance to hydrophobic and amphiphilic antimicrobials, including this compound. plos.orgasm.orgfrontiersin.org Overexpression of MtrCDE is often linked to mutations in its regulatory genes. plos.orgfrontiersin.orgasm.org The MsrA and MefA pumps are also associated with macrolide efflux, particularly in staphylococci and streptococci, respectively. frontiersin.orgmdpi.comnih.gov MsrA is an ABC transporter, while MefA is a Major Facilitator Superfamily (MFS) pump. mdpi.com These pumps actively transport macrolides out of the bacterial cell. mdpi.com

Genetic Determinants of Efflux Pump Activity (e.g., mtrR mutations)

The expression and activity of efflux pumps are often regulated by specific genes. Mutations in these regulatory genes can lead to increased efflux pump production and function, resulting in antibiotic resistance. A key example is the mtrR gene in Neisseria gonorrhoeae, which encodes a repressor protein that negatively regulates the expression of the mtrCDE operon. plos.orgfrontiersin.orgmcmaster.ca Mutations in the mtrR gene or its promoter region can lead to decreased MtrR repression, causing overexpression of the MtrCDE efflux pump and contributing to this compound resistance. plos.orgfrontiersin.orgasm.orgmcmaster.ca Specific mutations in the mtrR promoter, such as an A->C substitution at position -24, have been shown to increase MtrCDE efflux and confer resistance. plos.org Mosaic alleles of mtrR and mtrD, potentially acquired through horizontal gene transfer from other Neisseria species, have also been associated with increased this compound resistance in Neisseria gonorrhoeae. mdpi.comnih.govasm.orgnih.gov

Macrolide Phosphotransferases (e.g., Mph(A))

Macrolide phosphotransferases are enzymes that inactivate macrolides by adding a phosphate group to the antibiotic molecule researchgate.netrcsb.orgnih.gov. The gene encoding for these enzymes is often found on mobile genetic elements researchgate.netub.edu. Among the various macrolide phosphotransferases, Mph(A), encoded by the mph(A) gene, is particularly relevant to this compound resistance. Mph(A) has been shown to efficiently inactivate 15-membered macrolides like this compound, in addition to 14-membered macrolides such as erythromycin researchgate.netnih.govresearchgate.net. While Mph(B) and Mph(C) are also macrolide phosphotransferases, studies have indicated that Mph(A) is unique in its ability to confer resistance to this compound nih.govresearchgate.net. The mph(A) gene has been identified as a key macrolide resistance factor in various bacterial species, including Escherichia coli, Salmonella spp., and Shigella spp. ub.edunih.govnih.gov.

Erythromycin Esterases (e.g., Ere(A), Ere(B))

Erythromycin esterases, such as Ere(A) and Ere(B), are enzymes that inactivate macrolide antibiotics through enzymatic hydrolysis of the macrolactone ring nih.govnih.govacs.org. This hydrolysis breaks open the ring structure of the macrolide, destroying its antibacterial activity nih.govresearchgate.net. While named erythromycin esterases, these enzymes can also hydrolyze other macrolides, including 14- and 15-membered macrolides like this compound nih.govresearchgate.net. The genes encoding Ere(A) and Ere(B) are often located on plasmids, contributing to their potential for dissemination among bacterial populations nih.govresearchgate.net. Research has characterized the catalytic mechanisms of these esterases, identifying key residues involved in their function nih.govacs.org.

Global Prevalence and Trends of Resistance Mechanisms Research

Globally, the prevalence of this compound resistance is a growing concern in various pathogens ijpsjournal.comnih.gov. Studies have reported concerning trends of increasing resistance rates in bacteria such as Salmonella species, Escherichia coli, and Neisseria gonorrhoeae ijpsjournal.com. For instance, a systematic review and meta-analysis on Neisseria gonorrhoeae found a significant increase in this compound resistance globally over the past three decades, with a weighted pooled resistance rate of 6% nih.govresearchgate.net. Subgroup analysis revealed an increasing trend in resistance rates from 1988-2013 (2.3%) to 2019-2021 (7.2%) nih.gov. In some regions, the prevalence can be significantly higher; for example, a study in Taiwan reported a 3.1% this compound resistance rate in nontyphoidal Salmonella isolates, which was higher than rates reported in the United States and Europe at the time nih.gov. Research indicates that overuse and misuse of antibiotics contribute significantly to the development and spread of resistance patsnap.comijpsjournal.comfrontiersin.org.

Data on the global prevalence and trends of this compound resistance in Neisseria gonorrhoeae highlights the increasing challenge:

This data suggests a notable increase in this compound resistance in Neisseria gonorrhoeae over the years nih.gov.

Horizontal Gene Transfer and Plasmid-mediated Resistance Mechanisms

Horizontal gene transfer (HGT) plays a crucial role in the dissemination of antibiotic resistance genes, including those conferring resistance to this compound, among bacterial populations ijpsjournal.comasm.orgnih.gov. Plasmids, which are small, circular pieces of DNA, are major vehicles for HGT asm.orgnih.gov. Plasmid-mediated resistance occurs when resistance genes, such as mph(A), erm(B), and erm(42), are located on plasmids and can be transferred between bacteria through processes like conjugation researchgate.netnih.govub.eduasm.org.

Studies have demonstrated the transfer of this compound resistance genes, particularly mph(A), via plasmids in various bacterial species nih.govnih.govresearchgate.net. For example, research on nontyphoidal Salmonella isolates identified mph(A) on different plasmid types, including IncFIB, IncHI2, IncFII, IncC, and IncI plasmids, which also carried other multidrug resistance genes researchgate.net. Conjugative plasmids, such as IncC plasmids, have been shown to mediate the transfer of resistance to multiple antibiotics, including this compound researchgate.net. The rapid spread of macrolide resistance genes, such as mph(A), is often driven by horizontal gene transfer rather than the direct lineage of bacteria nih.gov. Environmental factors and pollutants can also influence plasmid-mediated gene transfer nih.gov.

Uptake by Phagocytes and Fibroblasts in Research Models

Studies in research models have consistently shown that this compound is readily taken up by phagocytic cells, including polymorphonuclear leukocytes (PMNs) and macrophages, as well as by fibroblasts. In vitro studies have demonstrated rapid and extensive uptake of this compound by these cell types. For instance, in cultured human skin fibroblasts, intracellular penetration of this compound occurred rapidly, reaching 10 µg/mg of cellular protein after 3 hours and increasing progressively over a 3-day period. asm.orgnih.gov this compound accumulated up to 21 times more than erythromycin in these fibroblasts. asm.orgnih.gov Similarly, in vitro studies with human peripheral blood PMNs and various cell lines (including phagocytic and epithelial cells) showed that this compound was extensively taken up by PMNs and phagocytic cell lines (RAW 264.7 and THP-1) without saturation during a 3-hour incubation period. researchgate.netasm.org The intracellular concentration in RAW 264.7 cells was approximately 35 times higher than the extracellular concentration after 3 hours. asm.org Mature phagocytes (PMNs and RAW 264.7) accumulated more this compound than nondifferentiated phagocytic precursors (THP-1). asm.org

In vivo studies also support the high concentration of this compound in phagocytes. Studies in mice have shown that this compound is concentrated within macrophages and polymorphonucleocytes. drugbank.com This concentration in phagocytes is thought to contribute to this compound's distribution to inflamed tissues. drugbank.com Following caseinate-induced PMN infiltration in mice, there was a significant increase in peritoneal cavity this compound, most of which was intracellular. researchgate.netnih.gov Human studies have also reported high concentrations of this compound in alveolar macrophages and leukocytes. oup.com

Mechanisms of Intracellular Trapping (e.g., Ion Trapping, High Lipid Solubility)

Several mechanisms contribute to the high intracellular accumulation and retention of this compound. One primary mechanism is ion trapping. This compound is a weak base with a pKa of 8.6. asm.org Due to its dibasic molecular structure, which is unique among many other macrolides, this compound becomes protonated in the acidic environment of lysosomes, which are present in high numbers in phagocytic cells and fibroblasts. asm.orgnih.gov This protonation gives the molecule a net positive charge (+2), inhibiting its diffusion back out of the cell across the lipid membrane. asm.orgnih.gov

In addition to ion trapping, this compound's high lipid solubility also plays a role in its extensive tissue penetration and intracellular accumulation. wikipedia.orgalpha-medicare.commedex.com.bdmedex.com.bd The lipophilic nature of this compound allows it to readily cross cell membranes and accumulate within cellular compartments. wikipedia.orgalpha-medicare.commedex.com.bdmedex.com.bd Some research also suggests that this compound might be a substrate for ABCB1 (P-glycoprotein), which is localized in endosomes and lysosomes and can transport substrates from the cytosol into these vesicles, potentially enhancing its confinement within these acidic organelles. nih.gov This ABCB1-mediated transport could be a supplementary mechanism contributing to the intracellular trapping beyond passive diffusion and protonation. nih.gov

Release from Phagocytic Cells at Infection Sites in Research Models

Research models suggest that phagocytic cells not only accumulate this compound but also play a role in its delivery and release at sites of infection. Once concentrated within phagocytes, this compound can be transported to infection sites as part of the body's natural inflammatory response. oup.comwikipedia.orgalpha-medicare.commedex.com.bdmedex.com.bdnih.gov Studies in vitro have shown that while this compound is generally released slowly from loaded cells in the absence of extracellular drug, its release can be significantly enhanced during active phagocytosis of bacteria. researchgate.netnih.govwikipedia.orgalpha-medicare.commedex.com.bdmedex.com.bd For example, in murine peritoneal macrophages loaded with this compound, the release was significantly enhanced by phagocytosis of Staphylococcus aureus. researchgate.netnih.gov This suggests that phagocytes can act as a delivery system, transporting this compound to the site of infection and releasing it in response to encountering pathogens, thereby delivering high local concentrations of the antibiotic. oup.comwikipedia.orgalpha-medicare.commedex.com.bdmedex.com.bdnih.gov

Distribution in Specific Organs and Tissues (e.g., Lung, Tonsils, Prostate)

Studies in research models and humans have shown particularly high uptake and sustained concentrations of this compound in specific organs and tissues, including the lung, tonsils, and prostate. drugbank.comrwandafda.gov.rwmedsinfo.com.aupfizer.comnih.gov For instance, pharmacokinetic studies have demonstrated that tissue concentrations of this compound can be up to 50 times or more higher than observed peak plasma concentrations. medex.com.bdmedex.com.bdrwandafda.gov.rwmedsinfo.com.aupfizer.com

Research in healthy volunteers administered a single 500 mg dose or multiple doses of 500 mg once daily for 3 days showed high concentrations in these target tissues. pfizer.com

Here is a table summarizing typical this compound concentrations in various tissues compared to plasma:

Note: Concentrations and time points may vary depending on the study design, dosage, and species.

Other tissues where this compound penetrates include skin, bones, cervix, ovaries, uterus, stomach, liver, and gallbladder. nih.gov This widespread tissue distribution and the ability to achieve high concentrations in target organs are considered important for its clinical efficacy. rwandafda.gov.rwmedsinfo.com.au

Extracellular versus Intracellular Concentrations in Tissue Compartments

While this compound achieves very high intracellular concentrations, particularly within phagocytes and fibroblasts, studies have also investigated its distribution in the extracellular space fluid of tissues. Research using techniques like microdialysis in healthy volunteers has allowed for the determination of this compound concentrations in the interstitial space fluid (ISF) of muscle and subcutaneous adipose tissue, alongside concentrations in plasma and white blood cells. nih.govresearchgate.netnih.govasm.orgnih.gov

These studies have shown that this compound concentrations are highest in white blood cells, confirming significant intracellular accumulation. nih.govresearchgate.netnih.govasm.orgnih.gov However, concentrations in the extracellular space fluid of soft tissues (muscle and subcutaneous adipose tissue) were found to be markedly lower than in plasma both during and after treatment. nih.govresearchgate.netnih.govasm.orgnih.gov For example, one study reported that free unbound soft tissue concentrations were markedly lower than in white blood cells, potentially resulting in subtherapeutic levels in the extracellular compartment for some pathogens. nih.gov

Studies comparing macrolide distribution in the interstitial fluid of rat skin found that the ISF-to-plasma concentration ratio was higher for this compound (3.8 to 4.9) compared to clarithromycin (1.2 to 1.5) and erythromycin (0.27 to 0.39), and this ratio remained stable after dosing. mdpi.com However, even with a higher ISF-to-plasma ratio compared to other macrolides, the absolute concentrations in the extracellular space of some tissues may still be lower than intracellular concentrations. The inability of some tissue sampling methods to differentiate clearly between intracellular and extracellular space can make it challenging to precisely determine the drug concentration in the appropriate compartment for targeting specific infections. oup.com Concerns exist that low concentrations in extracellular compartments might favor the emergence of bacterial resistance. oup.comoup.com

The significant difference between intracellular and extracellular concentrations highlights the complex compartmentalization of this compound within tissues, with a substantial portion of the drug sequestered inside cells, particularly those involved in the immune response.

Role of P-glycoprotein (ABCB1) Efflux Transporters in Absorption

P-glycoprotein (ABCB1), an efflux transporter encoded by the ABCB1 gene, is thought to play a key role in the absorption and excretion of this compound. researchgate.netresearchgate.net P-glycoprotein is an apically polarized efflux transporter that can potentially restrict the intestinal absorption of large molecular weight compounds like macrolide antibiotics. researchgate.net

Studies in rats have demonstrated that intestinal and biliary excretion of this compound is facilitated by both P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (Mrp2), indicating that this compound is a substrate for these transporters. researchgate.netnih.gov While P-gp can limit absorption, this compound still exhibits moderate oral bioavailability. researchgate.net

Research using Caco-2 cell models with high P-gp expression has investigated the effect of macrolides on P-gp-mediated efflux of other substrates, such as digoxin. jst.go.jp These studies suggest that this compound has little influence on P-gp-mediated digoxin absorption or excretion, implying it may be a safer macrolide to use concurrently with oral digoxin compared to clarithromycin or roxithromycin, which showed greater P-gp inhibitory capacity. jst.go.jp

Genetic polymorphisms of the ABCB1 gene have also been shown to influence the pharmacokinetics of this compound in some populations. pharmgkb.org

Biliary Excretion Research of Unchanged Drug

Biliary excretion is a major pathway for this compound elimination. drugbank.comcebm.net The drug is mainly eliminated in unchanged form in the feces via biliary excretion and intestinal secretion. drugbank.comnih.gov Over a one-week period, approximately 6% of the administered dose is found as unchanged drug in urine, highlighting the dominance of the biliary route. drugbank.comtandfonline.comdrugbank.comnih.gov

Studies in rats have investigated the contribution of transporters like Mrp2 to biliary excretion. nih.gov Inhibition of Mrp2 significantly decreased the steady-state biliary clearance of this compound in rats, suggesting its involvement in this elimination pathway. nih.gov

Hepatic Metabolism and Enzyme Identification Research

While some hepatic metabolism of this compound does occur, it is generally considered to be limited, and the metabolites are thought to be microbiologically inactive. cebm.netnih.gov In vitro and in vivo studies specifically designed to assess the metabolism of this compound have not been extensively performed or have not identified specific metabolizing enzymes. drugbank.compharmgkb.org

This compound is structurally distinct from other macrolides like erythromycin due to the presence of a methyl-substituted nitrogen in its 15-membered ring, which is thought to prevent its metabolism. drugbank.com Unlike some other macrolides, this compound is a relatively weak inhibitor of CYP3A enzymes, suggesting a lower potential for clinically significant drug interactions mediated through this pathway. pharmgkb.orgcebm.netijpsjournal.com Metabolism is reported to occur through hepatic pathways other than cytochrome P450, further minimizing the risk of such interactions. ijpsjournal.comnih.gov

Despite limited metabolism, the liver plays a role in this compound elimination through biliary excretion. drugbank.com Caution is advised when administering this compound to patients with decreased hepatic function due to its primary elimination route. drugbank.com

Modulation of Cytokine and Chemokine Production

This compound influences the production of a range of cytokines and chemokines, key mediators of inflammation and immune cell recruitment nih.govresearchgate.netijbs.com. It has been shown to decrease the secretion of pro-inflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α nih.govfrontiersin.orgresearchgate.netresearchgate.net. Conversely, this compound can increase the production of the anti-inflammatory cytokine IL-10 nih.govresearchgate.net. This modulation of the cytokine balance contributes to the resolution of inflammation nih.govresearchgate.net. Studies have demonstrated that this compound can decrease IL-8 release and neutrophil airway infiltration in human clinical studies nih.govresearchgate.net. It also reduces the production of leukotriene B4 (LTB4), a potent neutrophil chemoattractant nih.govresearchgate.net. In various models, including human monocytes and macrophages, this compound has been shown to inhibit the production of IL-6, IL-8, and TNF-α frontiersin.orgresearchgate.netresearchgate.net. In cystic fibrosis (CF) patients, this compound treatment led to increased IL-6 and IL-10 release in M1 macrophages mdpi.com.

Below is a table summarizing the reported effects of this compound on key cytokines and chemokines:

Note: The effect on IL-6 can be variable depending on the cell type and experimental conditions.

Inhibition of Inflammatory Signaling Pathways

This compound interferes with crucial intracellular signaling pathways that regulate inflammatory responses nih.govfrontiersin.orgnih.gov. A key mechanism involves the inhibition of the nuclear factor-kappa B (NF-κB) pathway nih.govfrontiersin.orgnih.govnih.govfrontiersin.org. This compound prevents the nuclear translocation of activated NF-κB subunits, thereby reducing the transcription of pro-inflammatory genes nih.govfrontiersin.org. This inhibition of NF-κB signaling contributes significantly to the reduction of pro-inflammatory cytokine production nih.govfrontiersin.orgnih.gov. This compound has also been shown to inhibit the activation of activator protein 1 (AP-1) in human bronchial epithelial cells and neutrophils nih.govnih.gov. Inhibition of these pathways collectively dampens the inflammatory cascade nih.govnih.govfrontiersin.org. Studies have demonstrated that this compound inhibits NF-κB signaling in various cell types, including monocytes and macrophages frontiersin.orgnih.govnih.gov. This inhibition can occur through effects on molecules like IκB kinase (IKKβ) nih.govnih.gov.

Impact on Inflammasome Activation Pathways

This compound has been shown to impact inflammasome activation pathways, which are critical components of the innate immune response responsible for the maturation and secretion of pro-inflammatory cytokines like IL-1β nih.govfrontiersin.orgresearchgate.netfrontiersin.orgnih.gov. Studies suggest that this compound can suppress inflammasome activity nih.govfrontiersin.orgresearchgate.netnih.gov. Mechanistically, this may involve the induction of instability of mRNA for NLRP3, a key component of the NLRP3 inflammasome researchgate.netnih.gov. This compound's effects on upstream signaling pathways like NF-κB and STAT1 may also indirectly influence inflammasome activation researchgate.net. Inhibition of caspase-1, an enzyme activated by inflammasomes to cleave pro-IL-1β into its active form, has also been suggested as a potential mechanism nih.gov.

Macrophage Phenotype Modulation (M1/M2 polarization)

Macrophages exhibit plasticity and can differentiate into distinct phenotypes, primarily pro-inflammatory M1 and anti-inflammatory M2 macrophages frontiersin.orgcreative-diagnostics.com. This compound has been shown to influence macrophage polarization, promoting a shift towards an M2 alternative-like phenotype nih.govfrontiersin.orgatsjournals.orgcreative-diagnostics.comatsjournals.orgresearchgate.net. M1 macrophages are characterized by the production of pro-inflammatory cytokines, while M2 macrophages are involved in the resolution of inflammation and tissue repair frontiersin.orgmdpi.com. Studies using murine macrophage cell lines and primary human monocytes have demonstrated that this compound can inhibit the production of M1 markers and cytokines (e.g., IL-12, IL-6, TNF-α) while increasing the expression of M2 markers and cytokines (e.g., IL-10, CCL18) nih.govfrontiersin.orgmdpi.comatsjournals.orgnih.gov. This polarization shift is mediated, in part, by the inhibition of signaling pathways like NF-κB and STAT1 frontiersin.orgnih.govresearchgate.net. In patients with inflammatory diseases like COPD and systemic lupus erythematosus, this compound administration has been associated with changes in macrophage markers consistent with M2 polarization nih.gov.

Below is a table illustrating the impact of this compound on macrophage polarization markers:

Note: The effect on IL-6 can be variable depending on the cell type and experimental conditions.

Neutrophil Function and Influx Attenuation Mechanisms

Neutrophils are key effector cells in acute inflammation, and their excessive accumulation and activation can contribute to tissue damage nih.govnih.gov. This compound has been shown to attenuate neutrophil function and influx to inflammatory sites nih.govresearchgate.netnih.govatsjournals.org. This involves several mechanisms, including the reduction of neutrophil chemotaxis, which is their directed movement towards inflammatory signals nih.govatsjournals.org. This compound decreases the production of neutrophil chemoattractants like IL-8 and LTB4 nih.govresearchgate.net. It can also directly inhibit neutrophil migration in response to various stimuli atsjournals.org. Furthermore, this compound modulates neutrophil oxidative burst, a process by which neutrophils produce reactive oxygen species to kill pathogens, and can influence neutrophil extracellular trap (NET) release nih.govresearchgate.netnih.gov. These effects collectively reduce the inflammatory potential of neutrophils and limit their accumulation at sites of inflammation nih.govnih.gov. Clinical studies have demonstrated that this compound can decrease neutrophil airway infiltration nih.govresearchgate.net.

Lymphocyte (T and B Cell) Function Modulation (e.g., mTOR pathway, CD27)

This compound has been shown to modulate the function of lymphocytes, including T and B cells. Studies indicate that this compound can suppress T cell activation, partly through the inhibition of the mammalian target of rapamycin (mTOR) signaling pathway. eijppr.comnih.gove-century.usfrontiersin.org Inhibition of mTOR activity by this compound has been observed to blunt the proliferation of activated T lymphocytes. frontiersin.org This effect may be further influenced by increased macrophage production of arginase-1, which depletes arginine, an amino acid required for T cell proliferation. frontiersin.org

Furthermore, this compound impacts T lymphocyte function by altering the CD27 pathway. frontiersin.orgnih.govnih.govresearchgate.net Research using peripheral blood mononuclear cells from healthy donors demonstrated that this compound mediates the downregulation of surface CD27 expression and reduces its extracellular release as soluble CD27. frontiersin.orgnih.govnih.govresearchgate.net Notably, CD27high T cells exposed to this compound showed impaired expansion compared to CD27intermediate and CD27low subsets, linked to defective cell proliferation and division. frontiersin.orgnih.govnih.govresearchgate.net At the molecular level, the CD27high subset exhibited lower mTOR activity. frontiersin.orgresearchgate.net Functionally, this compound treatment led to a marked depletion of helper CD4+ (Th1) and cytotoxic CD8+ T-lymphocyte (Tc1)-associated CXCR3+CD27high effector cells and inhibited the production of the inflammatory cytokine IFN-γ. frontiersin.orgresearchgate.net These findings suggest that this compound modulates T lymphocyte function by targeting the CD27 pathway. frontiersin.orgnih.govnih.govresearchgate.net

While the impact on T cells is more extensively studied, research on the direct effects of this compound on B cell function is less comprehensive. researchgate.net However, the interaction between CD27 and its ligand CD70 is known to regulate B cell proliferation, differentiation, and immunoglobulin production, including IgE. frontiersin.orgnih.gov this compound has been shown to alter CD27 signaling, which could potentially affect B cell differentiation and antibody production. researchgate.net

Natural Killer (NK) Cell Modulation Mechanisms

This compound also modulates the activity of Natural Killer (NK) cells, which are crucial innate effector lymphocytes involved in the response to viral infections. nih.gov In vitro studies have demonstrated that this compound can decrease perforin production in primary human NK cells. nih.govresearchgate.net Additionally, it has been shown to inhibit the production of IFN-γ and TNF-α in an NK cell line (NK-92 cells). eijppr.comresearchgate.net However, one study noted that this compound did not affect cytokine production in IL-15-activated primary NK cells. eijppr.comresearchgate.net These findings suggest that this compound can modulate certain aspects of NK cell activity, such as cytotoxicity and cytokine secretion, without necessarily impairing cell viability. eijppr.comresearchgate.net Given that the mTOR pathway governs NK cell activation, similar to T cells, this compound's impact on this pathway may influence the ability of NK cells to produce cytokines and perform other functions related to inflammation or pathogen clearance. nih.govresearchgate.net

Autophagy Modulation and Flux

This compound has been shown to modulate autophagy, a catabolic process essential for the degradation and recycling of intracellular components. nih.govnih.govresearchgate.netresearchgate.netnih.govbiorxiv.orgbiorxiv.orgnih.govresearchgate.net At therapeutic concentrations, this compound has been observed to increase the number of autophagosomes in macrophages. nih.govnih.govbiorxiv.orgbiorxiv.orgresearchgate.net Molecular studies suggest that this occurs due to the inhibition of autophagosome degradation rather than an increase in their synthesis, indicating a blockage of autophagic flux. nih.govnih.govbiorxiv.orgbiorxiv.orgresearchgate.net This inhibition is thought to be related to this compound's ability to increase lysosomal pH via ion trapping, which can impair the function of lysosomal proteases and block autophagosome-lysosome fusion. biorxiv.orgbiorxiv.org While autophagy is involved in both pathogen elimination and inflammation regulation, the precise impact of this compound's modulation of autophagy in the context of infection and inflammation requires further study. nih.govbiorxiv.orgbiorxiv.org Some research suggests that this blockade of autophagy might potentially promote bacterial residency in certain chronic respiratory diseases. biorxiv.orgbiorxiv.org

Disruption of Protein and Intracellular Lipid Transport Mechanisms

This compound's effects extend to disrupting protein and intracellular lipid transport mechanisms. nih.govresearchgate.net Delayed inhibitory effects on cell function and high lysosomal accumulation are associated with the disruption of these transport processes. nih.govresearchgate.net this compound, being a cationic amphiphilic drug, can interact with phospholipids, potentially affecting membrane organization and fluidity. ucl.ac.be This interaction may contribute to the observed disruption of intracellular trafficking, including the movement of lysosomes along microtubules, which can impact autophagic flux. nih.govucl.ac.be Studies have shown that this compound treatment can reduce the rate of lysosome migration along microtubules. nih.gov Furthermore, this compound treatment has been shown to alter gene expression profiles related to lipid and cholesterol biosynthesis in airway epithelial cells, suggesting an impact on lipid metabolism and transport. plos.org

Phospholipid Retention and Epithelial Barrier Enhancement Mechanisms

This compound is known to induce phospholipid retention within cells. nih.govnih.govdiscovermednews.comresearchgate.netmdpi.com This effect is linked to its cationic amphiphilic nature, allowing it to bind to phospholipids and inhibit their degradation. nih.govdiscovermednews.com Phospholipid retention and vesicle build-up, such as multivesicular bodies and lamellar bodies, have been observed in epithelial cells treated with this compound. nih.govdiscovermednews.comresearchgate.net

This phospholipid retention is thought to contribute to this compound's ability to enhance the epithelial barrier function. nih.govnih.govdiscovermednews.comresearchgate.netmdpi.comresearcher.lifenih.gov Studies on bronchial epithelial cells have shown that this compound treatment increases transepithelial electrical resistance (TEER), a measure of epithelial barrier integrity, and reduces paracellular flux, indicating decreased epithelial permeability. nih.govnih.govdiscovermednews.commdpi.com this compound has demonstrated superiority over other macrolides in enhancing the bronchial epithelial barrier in vitro. discovermednews.commdpi.com This barrier-enhancing effect is considered an important contribution to its therapeutic effectiveness, particularly in respiratory diseases where epithelial barrier function is compromised. researchgate.netnih.gov

Table 1: Effects of this compound on Epithelial Barrier Function in VA10 Cells

Data compiled from sources nih.govdiscovermednews.comresearchgate.netmdpi.com.

Interaction with Glucose-Regulated Protein 78 (GRP78)

Recent research has identified Glucose-Regulated Protein 78 (GRP78) as a novel target of this compound. nih.govresearchgate.net GRP78 is a key chaperone protein involved in the unfolded protein response (UPR) and has roles in various cellular processes, including protein folding, assembly, and transport. nih.govresearchgate.net Studies, particularly in the context of rheumatoid arthritis, suggest that this compound alleviates disease severity by targeting GRP78. nih.govresearchgate.net

This compound has been shown to inhibit GRP78 activity by binding to its catalytic domain. nih.govresearchgate.net This inhibition of GRP78 activity by this compound is required for activating the UPR and for inducing the expression of C/EBP-homologous protein (ChOP) and activating sterol-regulatory element binding protein (SREBP) and its target genes involved in cholesterol and lipid biosynthetic processes. nih.govresearchgate.net Deletion of GRP78 has been shown to abolish the anti-arthritic activity of this compound in experimental models. nih.govresearchgate.net This interaction with GRP78 highlights another molecular mechanism contributing to this compound's non-antibiotic effects, particularly in modulating cellular stress responses and lipid metabolism. nih.govresearchgate.net

Table 2: this compound's Interaction with GRP78 and Downstream Effects

Data compiled from sources nih.govresearchgate.netresearchgate.net.

Mechanisms of Biofilm Formation Reduction

This compound reduces biofilm formation through several proposed mechanisms. One key mechanism involves the inhibition of bacterial motility, including swimming and twitching motility, which are crucial for the initial stages of biofilm development and surface attachment frontiersin.orgasm.org. Studies on Escherichia coli have shown that this compound, at sub-inhibitory concentrations, hindered swimming and twitching motilities in a significant percentage of tested isolates . In Pseudomonas aeruginosa, flagellar and twitching motility are known to be necessary for biofilm development asm.org.

Another mechanism involves the modulation of the extracellular matrix, a key component of biofilms that provides structural integrity and protection dovepress.comfrontiersin.org. Research indicates that this compound can impair the ability of bacteria, such as P. aeruginosa, to produce this matrix frontiersin.org. Specifically, it has been shown to inhibit the expression of pel genes, which are important for bacterial attachment to solid surfaces and biofilm formation in P. aeruginosa frontiersin.org. This compound treatment resulted in no extracellular matrix being observed in the presence of the antibiotic, in contrast to the dense matrix seen in untreated samples frontiersin.org. Furthermore, this compound has been suggested to affect the polymerization of P. aeruginosa alginate, a major component of the biofilm matrix in mucoid strains, potentially through incomplete precipitation of polymerized alginate asm.org.

This compound has demonstrated the ability to reduce biofilm formation in various bacterial species, including P. aeruginosa, Haemophilus influenzae, and Staphylococcus xylosus brieflands.comfrontiersin.orgasm.org. In S. xylosus, sub-inhibitory concentrations significantly reduced biofilm formation, and proteomic analysis revealed that this compound altered the expression of numerous proteins, including those in the histidine biosynthesis pathway frontiersin.org. While macrolides can inhibit biofilm formation in several Gram-negative bacteria, their effect on Gram-positive bacteria like Staphylococcus aureus can be more complex, with some studies suggesting that macrolides might induce biofilm formation in resistant strains, particularly in the early stages mdpi.com.

Data from studies on E. coli isolates demonstrate the reduction in biofilm formation by this compound at sub-inhibitory concentrations.

Table 1: Reduction in Biofilm Formation by this compound in Urinary E. coli Isolates

Studies on P. aeruginosa have also quantified the anti-biofilm effects of this compound.

Table 2: Anti-biofilm Activity of this compound Against P. aeruginosa frontiersin.org

These data indicate that this compound is more effective at preventing biofilm formation (lower BPC50) than eradicating established biofilms (higher MBEC50) frontiersin.org.

Impact on Bacterial Quorum Sensing

This compound significantly impacts bacterial quorum sensing (QS), a cell-to-cell communication system that regulates the expression of virulence factors and biofilm formation frontiersin.orgnih.gov. By interfering with QS, this compound can attenuate bacterial virulence and hinder biofilm maturation brieflands.com.

In P. aeruginosa, this compound has been shown to inhibit the synthesis of autoinducer molecules, which are key signaling molecules in the QS system frontiersin.orgnih.gov. Specifically, it can inhibit the synthesis of 3-oxo-C12-homoserine lactone (3-O-C12 HSL), a signaling molecule regulated by the LasI/LasR system, which is important for biofilm formation frontiersin.orgnih.gov. This compound has been reported to reduce the transcription of lasI and rhlI, genes encoding autoinducer synthases in P. aeruginosa nih.govnih.gov. While the addition of synthetic autoinducers could partially restore the expression of transcriptional activators (lasR and rhlR), it did not restore the expression of the autoinducer synthase gene lasI, suggesting that this compound primarily interferes with autoinducer synthesis nih.gov.

The impact of this compound on QS has been linked to a reduction in the production of QS-regulated virulence factors asm.orgfrontiersin.org. In E. coli, this compound downregulated the gene expression of luxS, a QS-regulating gene, and genes encoding motility . This attenuation of QS in E. coli led to a regression in the production of QS-associated virulence factors and hindered biofilm formation . In P. aeruginosa, this compound treatment resulted in the suppression of QS-regulated virulence factors in a rat model of chronic lung infection frontiersin.org.

Studies have investigated the effect of this compound on the expression of QS-regulated genes in P. aeruginosa.

Table 3: Impact of this compound on Quorum Sensing Related Gene Expression nih.govnih.gov

The interference with QS by this compound contributes to its anti-biofilm activity and its ability to disarm bacteria, making them less virulent and potentially more susceptible to host immune responses and other antimicrobial agents frontiersin.orgspandidos-publications.com.

Limited Inhibition of CYP3A4 Compared to Other Macrolides: Mechanistic Insights

Azithromycin is considered a weak inhibitor of CYP3A4, in contrast to erythromycin and clarithromycin, which are strong inhibitors. wikipedia.orgwikipedia.orgpharmgkb.orgseq.esnih.gov This difference is clinically significant as it results in fewer drug interactions with compounds metabolized by CYP3A4 when this compound is co-administered. wikipedia.orgoup.compfizermedicalinformation.ca

Studies have shown that this compound does not significantly increase the area under the curve (AUC) of co-administered drugs metabolized by CYP3A4, unlike erythromycin and clarithromycin, which can increase AUC values more than five-fold. wikipedia.orgwikipedia.org For example, co-administration of this compound with atorvastatin did not alter the plasma concentrations of atorvastatin, whereas clarithromycin and erythromycin significantly increased statin exposure, raising the risk of myopathy. wikipedia.orgwikipedia.orgseq.es Similarly, this compound has been shown to have no effect on the pharmacokinetics of triazolam, a CYP3A4 substrate, while erythromycin and clarithromycin are potent inhibitors of its biotransformation. researchgate.net

Molecular Mechanisms of Weak Inhibition (e.g., Lactone Ring Structure)

The difference in CYP3A4 inhibition among macrolides is linked to their structural variations, specifically the size and composition of their lactone ring. Erythromycin and clarithromycin possess a 14-membered lactone ring, which is more susceptible to demethylation by CYP3A4. wikipedia.orgwikipedia.org This metabolic process leads to the formation of reactive metabolites, specifically nitrosoalkenes, which can bind covalently and irreversibly to the CYP3A4 enzyme, causing mechanism-based inhibition. wikipedia.orgwikipedia.org

In contrast, this compound is an azalide and contains a 15-membered ring with a methyl-substituted nitrogen at the 9a position. nih.gov This structural difference makes this compound less prone to the demethylation and subsequent nitrosoalkene formation that characterizes the mechanism-based inhibition seen with 14-membered macrolides. wikipedia.orgwikipedia.org Consequently, this compound interferes poorly with the cytochrome P450 system. nih.gov

This compound as a P-glycoprotein Substrate

Genetic polymorphisms in the ABCB1 gene, which encodes P-glycoprotein, have been shown to influence the pharmacokinetics of this compound in healthy individuals. pharmgkb.orgpharmgkb.orgresearchgate.net Patients with specific ABCB1 diplotypes have reportedly shown higher maximum concentrations of this compound. pharmgkb.org

This compound as a P-glycoprotein Inhibitor

In addition to being a substrate, this compound has also been reported to act as an inhibitor of P-glycoprotein. seq.eswikipedia.orgrjptonline.orggerimedrisk.compfizermedicalinformation.cafrontiersin.orgnih.gov This inhibitory activity can affect the transport of other drugs that are P-glycoprotein substrates, potentially leading to increased intracellular and plasma concentrations of these co-administered compounds. pfizermedicalinformation.cagerimedrisk.compfizermedicalinformation.ca

For instance, this compound's inhibition of P-glycoprotein has been suggested as a mechanism for increased levels of digoxin when the two drugs are co-administered. rjptonline.orgpfizermedicalinformation.cahres.ca Similarly, the potential for increased colchicine serum concentrations when taken with this compound is related to this compound acting as a P-glycoprotein inhibitor. rjptonline.orgnih.gov

The dual nature of this compound as both a substrate and inhibitor of P-glycoprotein highlights the complex interplay between the drug and this important efflux transporter.

High-Performance Liquid Chromatography (HPLC) with Diverse Detectors (e.g., UV, Fluorescence, Electrochemical)

High-Performance Liquid Chromatography (HPLC) is a versatile and widely used technique for the analysis of this compound. newbioworld.orgnih.govijpsnonline.com It allows for the separation of this compound from related substances and is considered the method of choice for analyzing this compound in bulk samples and formulations. nih.gov HPLC methods for this compound have been developed using various detectors, including UV, fluorescence, and electrochemical detectors. nih.gov

HPLC with UV detection is commonly employed for the analysis of this compound in tablets and raw materials. nih.govoup.com A simple and validated RP-HPLC method with UV detection at 210 nm has been developed and applied for the analysis of this compound in bulk and pharmaceutical dosage forms. This method utilized a C18 column with a mobile phase of methanol and phosphate buffer (80:20 v/v). nih.govoup.com The method demonstrated good linearity over a concentration range of 0.3–2.0 mg/mL with a correlation coefficient of 0.997. oup.com The accuracy was found to be 100.5% with a relative standard deviation (RSD) of 0.2%. oup.com

HPLC with electrochemical detection has also been used for the analysis of this compound, particularly in human plasma. However, these methods may require specific and expensive detectors. nih.govoup.com

Liquid Chromatography-Mass Spectrometry (LC-MS/MS) and Ultra-Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS/MS)

LC-MS/MS and UPLC-MS/MS are powerful hyphenated techniques that offer high sensitivity and selectivity for the determination of this compound, especially in complex biological matrices like human plasma. ijpsnonline.comresearchgate.netresearchgate.net These methods are frequently used in pharmacokinetic and bioequivalence studies. researchgate.netresearchgate.net

A sensitive and rapid LC-MS/MS method was developed and validated for the quantification of this compound in human plasma, utilizing solid phase extraction for sample preparation. researchgate.netresearchgate.net Another LC-MS/MS method for this compound in human plasma used liquid-liquid extraction and a reversed-phase C18 column with a mobile phase of acetonitrile and 0.1% formic acid in water. researchgate.net This method showed linearity over a concentration range of 5.0-1500.0 ng/mL. researchgate.net

UPLC-MS/MS methods have also been reported for the quantitative estimation of this compound in human plasma, offering advantages such as increased sensitivity, reduced injection volume, and shorter run times. lshtm.ac.uk A validated UPLC-MS/MS method for this compound quantification in human plasma demonstrated linearity over a concentration range of 0.5-2000 ng/mL. lshtm.ac.uk This method was successfully applied to a clinical trial to study the pharmacokinetics of this compound. lshtm.ac.uk LC-MS/MS has shown the highest sensitivity among various analytical techniques for this compound quantification, with a limit of detection of 0.0005 µg/mL. ijpsnonline.com

Hydrophilic Interaction Chromatography (HILIC) coupled with MS has also been explored for this compound analysis, offering benefits such as narrow, symmetrical peak shapes and strong MS signals due to high organic mobile phase concentrations, which is advantageous for analyzing low concentrations in bioanalysis.

Gas Chromatography-Mass Spectrometry (GC-MS)

Gas Chromatography-Mass Spectrometry (GC-MS) can be used for the determination of this compound, particularly for analyzing residues in biological fluids. researchgate.net This method typically involves derivatization of this compound to make it volatile and thermally stable for GC analysis. researchgate.net A GC-MS method for this compound monohydrate residues in biological fluids involves extraction, clean-up, and acetylation with acetic anhydride-pyridine mixture. researchgate.net Detection is performed using single-ion monitoring (SIM) at m/z 200. researchgate.net This method has a detection limit of 2 µg/mL. researchgate.net GC-MS has also been used to study the degradation products of this compound under heating conditions, identifying compounds with specific m/z values. orientjchem.org

High-Performance Thin Layer Chromatography (HPTLC)

High-Performance Thin Layer Chromatography (HPTLC) is a planar chromatography technique used for the analysis of this compound, including the estimation of potential impurities and degradation products. newbioworld.orgoup.comresearchgate.netakjournals.com HPTLC methods offer advantages such as simplicity, rapidity, and cost-effectiveness. oup.comresearchgate.net

A validated stability-indicating HPTLC method for this compound in bulk and capsule forms utilizes silica gel plates and a mobile phase system of n-hexane–ethyl acetate–diethylamine (75:25:10, v/v/v). oup.com Separated bands are detected after spraying with modified Dragendorff's solution. oup.com This method can estimate this compound, its major impurity azaerythromycin A, and other degradation products. oup.com

HPTLC methods have also been developed for the simultaneous estimation of this compound with other drugs in tablet formulations. researchgate.net A stability-indicating HPTLC method for the simultaneous estimation of this compound, fluconazole, and secnidazole used silica gel plates and a mobile phase mixture of toluene‒ethyl acetate‒methanol‒formic acid‒ammonia. researchgate.net Densitometric scanning was performed at 209 nm. researchgate.net This method showed good linearity for this compound in the concentration range of 40‒80 µ g/band . researchgate.net

UV-Visible Spectrophotometry

UV-Visible (UV-Vis) Spectrophotometry is a simple, sensitive, and economical method used for the estimation of this compound in bulk and pharmaceutical formulations. newbioworld.orgbanglajol.infonih.govijpsnonline.com This technique measures the absorbance of UV or visible light by the analyte at specific wavelengths. researchgate.net

UV-Vis spectrophotometric methods for this compound are often based on the inherent absorbance of the molecule or on color reactions. nih.gov One method involves the reduction of potassium permanganate by this compound in alkaline medium, with the decrease in absorbance measured at 547 nm. nih.gov This method was found to be linear for this compound concentrations between 2 and 20 µg/ml. nih.gov

Another UV spectrophotometric method for this compound estimation in pharmaceutical dosage forms utilizes the oxidation of this compound with potassium permanganate to liberate formaldehyde, which then reacts with acetone-ammonium reagent to produce a yellow colored chromogen with maximum absorption at 412 nm. banglajol.info This method showed linearity over the concentration range of 80% to 120% of the working concentration. banglajol.info

UV spectrophotometric methods have also been developed using hydrotropic solubilization techniques to enhance the solubility of this compound. ijpsnonline.com A method using 2M sodium acetate solution as a hydrotropic agent found the absorption maximum of this compound at 221 nm and was linear in the range of 10-50 µg/ml. ijpsnonline.com

UV-Vis spectrophotometry is also used for the simultaneous estimation of this compound with other drugs in combined dosage forms, often employing methods like the area under curve method. wjpsonline.com For example, a UV-Vis spectrophotometric method for simultaneous estimation of this compound and cefixime used wavelength ranges of 219-224 nm for this compound. wjpsonline.com This method showed linearity for this compound in the range of 2.5-15 µg/ml. wjpsonline.com

UV-Vis spectrophotometry is considered a simple, selective, reproducible, and accurate method suitable for routine analysis of this compound in formulations. banglajol.infoijpsnonline.com

Synchronous Fluorescence Spectroscopy

Synchronous fluorescence spectroscopy has been employed for the determination of this compound, particularly in pharmaceutical formulations. This method relies on the synchronous scanning of both excitation and emission monochromators at a fixed wavelength interval (Δλ). nih.govnih.govresearchgate.net

Research has shown that this compound can produce synchronous fluorescence when derivatized in a strongly acidic medium, such as 9.0 mol L⁻¹ HCl. nih.govresearchgate.net Studies have investigated the influence of derivatization conditions, including acid concentration, reaction time, and temperature, to optimize the fluorescence signal. nih.govresearchgate.net Under optimized conditions, a synchronous fluorescence method with a Δλ of 30 nm at 482 nm has been developed for this compound determination in pharmaceutical formulations. nih.govresearchgate.net This method demonstrated a limit of detection (LOD) of 0.23 mg L⁻¹ and a limit of quantification (LOQ) of 0.76 mg L⁻¹. nih.govresearchgate.net The successful application of this procedure for analyzing this compound in pharmaceutical products has been reported. nih.govresearchgate.net

Synchronous fluorescence spectroscopy has also been utilized in studies investigating the interaction of this compound with proteins, such as bovine serum albumin (BSA). nih.gov This technique can provide insights into the conformational changes occurring in the protein upon interaction with this compound. nih.gov While colchicine was observed to reduce the fluorescence intensity of BSA, this compound did not influence BSA quenching in one study. nih.gov

Fourier-transform Infrared (FT-IR) Spectroscopy

Fourier-transform Infrared (FT-IR) spectroscopy is a valuable tool for the structural analysis and quality assessment of this compound, allowing for the identification of functional groups and the study of interactions with excipients or matrix components. amazonaws.comresearchgate.netturkjps.org

FT-IR spectroscopy has been applied for the quantification of this compound in solid tablet and capsule formulations. researchgate.net A method utilizing transmission FT-IR spectroscopy with KBr pellets has been developed for routine quality monitoring. researchgate.net This approach avoids complex sample preparation steps like extraction and solvent consumption. researchgate.net The calibration model for quantification can be based on the characteristic carbonyl (C=O) stretching band of this compound, typically found in the region of 1709–1744 cm⁻¹. researchgate.netscielo.br An excellent regression coefficient (R²) of 0.999 has been achieved for calibration sets, with a low standard error of calibration. researchgate.net

Studies have also used FT-IR to investigate the compatibility of this compound with various excipients used in pharmaceutical formulations. amazonaws.comturkjps.org By comparing the FT-IR spectra of pure this compound, excipients, and their physical mixtures or solid dispersions, researchers can identify potential chemical interactions. amazonaws.comturkjps.orgscielo.br Characteristic peaks for this compound, such as those around 1724 cm⁻¹ (C=O stretch), 1190 cm⁻¹ (C-O-C asymmetrical stretching), and 1049 cm⁻¹ (C-O-C symmetrical stretching), are monitored. scielo.br The preservation of these characteristic peaks in the spectra of mixtures indicates the absence of significant chemical interactions between the drug and excipients. turkjps.org

FT-IR has also been used in studies investigating the phase transformations of this compound crystals. acs.org Combined with techniques like X-ray diffraction and thermal analysis, FT-IR can help characterize different polymorphic forms and amorphous states of this compound. acs.org