Development of a population pharmacokinetic model characterizing the tissue distribution of azithromycin in healthy subjects

Macrolide and Ketolide Antibiotics Inhibit the Cytotoxic Effect of Trastuzumab Emtansine in HER2-Positive Breast Cancer Cells: Implication of a Potential Drug-ADC Interaction in Cancer Chemotherapy

Macrolides are widely used for the long-term treatment of infections and chronic inflammatory diseases. The pharmacokinetic features of macrolides include extensive tissue distribution because of favorable membrane permeability and accumulation within lysosomes. Trastuzumab emtansine (T-DM1), a HER2-targeting antibody-drug conjugate (ADC), is catabolized in the lysosomes, where Lys-SMCC-DM1, a potent cytotoxic agent, is processed by proteinase degradation and subsequently released from the lysosomes to the cytoplasm through the lysosomal membrane transporter SLC46A3, resulting in an antitumor effect. We recently demonstrated that erythromycin and clarithromycin inhibit SLC46A3 and attenuate the cytotoxicity of T-DM1; however, the effect of other macrolides and ketolides has not been determined. In this study, we evaluated the effect of macrolide and ketolide antibiotics on T-DM1 cytotoxicity in a human breast cancer cell line, KPL-4. Macrolides used in the clinic, such as roxithromycin, azithromycin, and josamycin, as well as solithromycin, a ketolide under clinical development, significantly attenuated T-DM1 cytotoxicity in addition to erythromycin and clarithromycin. Of these, azithromycin was the most potent inhibitor of T-DM1 efficacy. These antibiotics significantly inhibited the transport function of SLC46A3 in a concentration-dependent manner. Moreover, these compounds extensively accumulated in the lysosomes at the levels estimated to be 0.41-13.6 mM when cells were incubated with them at a 2 μM concentration. The immunofluorescence staining of trastuzumab revealed that azithromycin and solithromycin inhibit the degradation of T-DM1 in the lysosomes. These results suggest that the attenuation of T-DM1 cytotoxicity by macrolide and ketolide antibiotics involves their lysosomal accumulation and results in their greater lysosomal concentrations to inhibit the SLC46A3 function and T-DM1 degradation. This suggests a potential drug-ADC interaction during cancer chemotherapy.

Distribution of Macrolide Resistant Mycoplasma genitalium in Urogenital Tract Specimens From Women Enrolled in a US Clinical Study Cohort

BACKGROUND

This study evaluated the distribution of macrolide-resistant Mycoplasma genitalium in multiple urogenital specimens collected from women enrolled in a prospective multicenter US clinical study.

METHODS

Four female urogenital specimens (vaginal swab, urine, endocervical swab, ectocervical brush/spatula) collected from each subject were tested using a transcription-mediated amplification (TMA) assay for M. genitalium. TMA-positive specimens were evaluated by reverse transcription-polymerase chain reaction and bidirectional Sanger sequencing of M. genitalium 23S rRNA to identify the presence of macrolide-resistance-mediating mutations (MRMs) at base positions 2058/2059.

RESULTS

Of 140 women with ≥1 TMA-positive specimens, 128 (91.4%) yielded M. genitalium 23S rRNA sequence. MRMs were found in 52% of vaginal specimens, 46.3% of urine specimens, 37.8% of endocervical specimens, and 46% of ectocervical specimens. There were 44 unique specimen type/sequence phenotype combinations of M. genitalium infection. Most (81; 63.3%) women had single specimen-sequence phenotype (macrolide-susceptible, MRM, or both) infections, while 24 (18.8%) women had multiple specimen-sequence phenotype concordant infections, and 23 (17.9%) women had multiple specimen-sequence phenotype discordant infections. The sensitivity for any single specimen type to detect overall urogenital tract macrolide-resistant M. genitalium infection status was 96.3% for vaginal swab samples, 82.6% for urine samples, 70.8% for endocervical swab samples, and 82.1% for ectocervical brush/spatula liquid Pap samples.

CONCLUSIONS

The distribution of M. genitalium infections in female urogenital tract specimens is highly complex, with multiple phenotypic combinations of the organism infecting a significant proportion of women at different anatomic specimen collection sites. Vaginal swab sampling yielded the highest sensitivity for identifying women with macrolide-resistant M. genitalium urogenital tract infections.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review-Part II

In patients that are admitted to intensive care units (ICUs), the clinical outcome of severe infections depends on several factors, as well as the early administration of chemotherapies and comorbidities. Antimicrobials may be used in off-label regimens to maximize the probability of therapeutic concentrations within infected tissues and to prevent the selection of resistant clones. Interestingly, the literature clearly shows that the rate of tissue penetration is variable among antibacterial drugs, and the correlation between plasma and tissue concentrations may be inconstant. The present review harvests data about tissue penetration of antibacterial drugs in ICU patients, limiting the search to those drugs that mainly act as protein synthesis inhibitors and disrupting DNA structure and function. As expected, fluoroquinolones, macrolides, linezolid, and tigecycline have an excellent diffusion into epithelial lining fluid. That high penetration is fundamental for the therapy of ventilator and healthcare-associated pneumonia. Some drugs also display a high penetration rate within cerebrospinal fluid, while other agents diffuse into the skin and soft tissues. Further studies are needed to improve our knowledge about drug tissue penetration, especially in the presence of factors that may affect drug pharmacokinetics.

Macrolide Treatment Failure due to Drug–Drug Interactions: Real-World Evidence to Evaluate a Pharmacological Hypothesis

Macrolide antibiotics have received criticism concerning their use and risk of treatment failure. Nevertheless, they are an important class of antibiotics and are frequently used in clinical practice for treating a variety of infections. This study sought to utilize pharmacoepidemiology methods and pharmacology principles to estimate the risk of macrolide treatment failure and quantify the influence of their pharmacokinetics on the risk of treatment failure, using clinically reported drug–drug interaction data. Using a large, commercial claims database (2006–2015), inclusion and exclusion criteria were applied to create a cohort of patients who received a macrolide for three common acute infections. Furthermore, an additional analysis examining only bacterial pneumonia events treated with macrolides was conducted. These criteria were formulated specifically to ensure treatment failure would not be expected nor influenced by intrinsic or extrinsic factors. Treatment failure rates were 6% within the common acute infections and 8% in the bacterial pneumonia populations. Regression results indicated that macrolide AUC changes greater than 50% had a significant effect on treatment failure risk, particularly for azithromycin. In fact, our results show that decreased or increased exposure change can influence failure risk, by 35% or 12%, respectively, for the acute infection scenarios. The bacterial pneumonia results were less significant with respect to the regression analyses. This integration of pharmacoepidemiology and clinical pharmacology provides a framework for utilizing real-world data to provide insight into pharmacokinetic mechanisms and support future study development related to antibiotic treatments.

Synergistic Adverse Effects of Azithromycin and Hydroxychloroquine on Human Cardiomyocytes at a Clinically Relevant Treatment Duration

Adverse effects of drug combinations and their underlying mechanisms are highly relevant for safety evaluation, but often not fully studied. Hydroxychloroquine (HCQ) and azithromycin (AZM) were used as a combination therapy in the treatment of COVID-19 patients at the beginning of the pandemic, leading to higher complication rates in comparison to respective monotherapies. Here, we used human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) to systematically investigate the effects of HCQ, AZM, and their combination on the structure and functionality of cardiomyocytes, and to better understand the underlying mechanisms. Our results demonstrate synergistic adverse effects of AZM and HCQ on electrophysiological and contractile function of iPSC-CMs. HCQ-induced prolongation of field potential duration (FPDc) was gradually increased during 7-day treatment period and was strongly enhanced by combination with AZM, although AZM alone slightly shortened FPDc in iPSC-CMs. Combined treatment with AZM and HCQ leads to higher cardiotoxicity, more severe structural disarrangement, more pronounced contractile dysfunctions, and more elevated conduction velocity, compared to respective monotreatments. Mechanistic insights underlying the synergistic effects of AZM and HCQ on iPSC-CM functionality are provided based on increased cellular accumulation of HCQ and AZM as well as increased Cx43- and Nav1.5-protein levels.

Model-Informed Drug Development for Anti-Infectives: State of the Art and Future

Model-informed drug development (MIDD) has a long and rich history in infectious diseases. This review describes foundational principles of translational anti-infective pharmacology, including choice of appropriate measures of exposure and pharmacodynamic (PD) measures, patient subpopulations, and drug-drug interactions. Examples are presented for state-of-the-art, empiric, mechanistic, interdisciplinary, and real-world evidence MIDD applications in the development of antibacterials (review of minimum inhibitory concentration-based models, mechanism-based pharmacokinetic/PD (PK/PD) models, PK/PD models of resistance, and immune response), antifungals, antivirals, drugs for the treatment of global health infectious diseases, and medical countermeasures. The degree of adoption of MIDD practices across the infectious diseases field is also summarized. The future application of MIDD in infectious diseases will progress along two planes; "depth" and "breadth" of MIDD methods. "MIDD depth" refers to deeper incorporation of the specific pathogen biology and intrinsic and acquired-resistance mechanisms; host factors, such as immunologic response and infection site, to enable deeper interrogation of pharmacological impact on pathogen clearance; clinical outcome and emergence of resistance from a pathogen; and patient and population perspective. In particular, improved early assessment of the emergence of resistance potential will become a greater focus in MIDD, as this is poorly mitigated by current development approaches. "MIDD breadth" refers to greater adoption of model-centered approaches to anti-infective development. Specifically, this means how various MIDD approaches and translational tools can be integrated or connected in a systematic way that supports decision making by key stakeholders (sponsors, regulators, and payers) across the entire development pathway.

Pharmacokinetic considerations regarding the treatment of bacterial sexually transmitted infections with azithromycin: a review

Rates of bacterial sexually transmitted infections (STIs) continue to rise, demanding treatments to be highly effective. However, curing infections faces significant challenges due to antimicrobial resistance in Neisseria gonorrhoeae and Mycoplasma genitalium and especially treating STIs at extragenital sites, particularly rectal chlamydia and oropharyngeal gonorrhoea. As no new antimicrobials are entering the market, clinicians must optimize the currently available treatments, but robust data are lacking on how the properties or pharmacokinetics of antimicrobials can be used to inform STI treatment regimens to improve treatment outcomes. This paper provides a detailed overview of the published pharmacokinetics of antimicrobials used to treat STIs and how factors related to the drug (tissue distribution, protein binding and t½), human (pH, inflammation, site of infection, drug side effects and sexual practices) and organism (organism load and antimicrobial resistance) can affect treatment outcomes. As azithromycin is commonly used to treat chlamydia, gonorrhoea and M. genitalium infections, and its pharmacokinetics are well studied, it is the main focus of this review. Suggestions are also provided on possible dosing regimens when using extended and/or higher doses of azithromycin, which appropriately balance efficacy and side effects. The paper also emphasizes the limitations of currently published pharmacokinetic studies including oropharyngeal gonococcal infections, where very limited data exist around ceftriaxone pharmacokinetics and its use in combination with azithromycin. In future, the different anatomical sites of infections may require alternative therapeutic approaches.

Investigational Treatments for COVID-19 may Increase Ventricular Arrhythmia Risk Through Drug Interactions

Many drugs that have been proposed for treatment of coronavirus disease 2019 (COVID-19) are reported to cause cardiac adverse events, including ventricular arrhythmias. In order to properly weigh risks against potential benefits, particularly when decisions must be made quickly, mathematical modeling of both drug disposition and drug action can be useful for predicting patient response and making informed decisions. Here, we explored the potential effects on cardiac electrophysiology of four drugs proposed to treat COVID-19: lopinavir, ritonavir, chloroquine, and azithromycin, as well as combination therapy involving these drugs. Our study combined simulations of pharmacokinetics (PKs) with quantitative systems pharmacology (QSP) modeling of ventricular myocytes to predict potential cardiac adverse events caused by these treatments. Simulation results predicted that drug combinations can lead to greater cellular action potential prolongation, analogous to QT prolongation, compared with drugs given in isolation. The combination effect can result from both PK and pharmacodynamic drug interactions. Importantly, simulations of different patient groups predicted that women with pre-existing heart disease are especially susceptible to drug-induced arrhythmias, compared with diseased men or healthy individuals of either sex. Statistical analysis of population simulations revealed the molecular factors that make certain women with heart failure especially susceptible to arrhythmias. Overall, the results illustrate how PK and QSP modeling may be combined to more precisely predict cardiac risks of COVID-19 therapies.

Background review for the '2020 European guideline for the diagnosis and treatment of gonorrhoea in adults'

Gonorrhoea is a major public health concern globally. Increasing incidence and sporadic ceftriaxone-resistant cases, including treatment failures, are growing concerns. The 2020 European gonorrhoea guideline provides up-to-date evidence-based guidance regarding the diagnosis and treatment of gonorrhoea. The updates and recommendations emphasize significantly increasing gonorrhoea incidence; broad indications for increased testing with validated and quality-assured nucleic acid amplification tests (NAATs) and culture; dual antimicrobial therapy including high-dose ceftriaxone and azithromycin (ceftriaxone 1 g plus azithromycin 2 g) OR ceftriaxone 1 g monotherapy (ONLY in well-controlled settings, see guideline for details) for uncomplicated gonorrhoea when the antimicrobial susceptibility is unknown; recommendation of test of cure (TOC) in all gonorrhoea cases to ensure eradication of infection and identify resistance; and enhanced surveillance of treatment failures when recommended treatment regimens have been used. Improvements in access to appropriate testing, test performance, diagnostics, antimicrobial susceptibility surveillance and treatment, and follow-up of gonorrhoea patients are essential in controlling gonorrhoea and to mitigate the emergence and/or spread of ceftriaxone resistance and multidrug-resistant and extensively drug-resistant gonorrhoea. This review provides the detailed background, evidence base and discussions, for the 2020 European guideline for the diagnosis and treatment of gonorrhoea in adults (Unemo M, et al. Int J STD AIDS. 2020).

2020 European guideline for the diagnosis and treatment of gonorrhoea in adults

Gonorrhoea is a major public health concern globally. Increasing incidence and sporadic ceftriaxone-resistant cases, including treatment failures, are growing concerns. The 2020 European gonorrhoea guideline provides up-to-date evidence-based guidance regarding the diagnosis and treatment of gonorrhoea. The updates and recommendations emphasize significantly increasing gonorrhoea incidence; broad indications for increased testing with validated and quality-assured nucleic acid amplification tests and culture; dual antimicrobial therapy including high-dose ceftriaxone and azithromycin (ceftriaxone 1 g plus azithromycin 2 g) OR ceftriaxone 1 g monotherapy (ONLY in well-controlled settings, see guideline for details) for uncomplicated gonorrhoea when the antimicrobial susceptibility is unknown; recommendation of test of cure (TOC) in all gonorrhoea cases to ensure eradication of infection and identify resistance; and enhanced surveillance of treatment failures when recommended treatment regimens have been used. Improvements in access to appropriate testing, test performance, diagnostics, antimicrobial susceptibility surveillance and treatment, and follow-up of gonorrhoea patients are essential in controlling gonorrhoea and to mitigate the emergence and/or spread of ceftriaxone resistance and multidrug-resistant and extensively drug-resistant gonorrhoea. For detailed background, evidence base and discussions, see the background review for the present 2020 European guideline for the diagnosis and treatment of gonorrhoea in adults (Unemo M, et al. Int J STD AIDS. 2020).

Predictions of Systemic, Intracellular, and Lung Concentrations of Azithromycin With Different Dosing Regimens Used in COVID-19 Clinical Trials

Azithromycin (AZ), a broad-spectrum macrolide antibiotic, is being investigated in patients with coronavirus disease 2019 (COVID-19). A population pharmacokinetic model was implemented to predict lung, intracellular poly/mononuclear cell (peripheral blood monocyte (PBM)/polymorphonuclear leukocyte (PML)), and alveolar macrophage (AM) concentrations using published data and compared against preclinical effective concentration 90% (EC₉₀ ) for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). The final model described the data reported in eight publications adequately. Consistent with its known properties, concentrations were higher in AM and PBM/PML, followed by lung tissue, and lowest systemically. Simulated PBM/PML concentrations exceeded EC₉₀ following the first dose and for ~ 14 days following 500 mg q.d. for 3 days or 500 mg q.d. for 1 day/250 mg q.d. on days 2-5, 10 days following a single 1,000 mg dose, and for > 20 days with 500 mg q.d. for 10 days. AM concentrations exceeded the 90% inhibitory concentration for > 20 days for all regimens. These data will better inform optimization of dosing regimens for AZ clinical trials.

Investigational treatments for COVID-19 may increase ventricular arrhythmia risk through drug interactions

Many drugs that have been proposed for treatment of COVID-19 are reported to cause cardiac adverse events, including ventricular arrhythmias. In order to properly weigh risks against potential benefits, particularly when decisions must be made quickly, mathematical modeling of both drug disposition and drug action can be useful for predicting patient response and making informed decisions. Here we explored the potential effects on cardiac electrophysiology of 4 drugs proposed to treat COVID-19: lopinavir, ritonavir, chloroquine, and azithromycin, as well as combination therapy involving these drugs. Our study combined simulations of pharmacokinetics (PK) with quantitative systems pharmacology (QSP) modeling of ventricular myocytes to predict potential cardiac adverse events caused by these treatments. Simulation results predicted that drug combinations can lead to greater cellular action potential prolongation, analogous to QT prolongation, compared with drugs given in isolation. The combination effect can result from both pharmacokinetic and pharmacodynamic drug interactions. Importantly, simulations of different patient groups predicted that females with pre-existing heart disease are especially susceptible to drug-induced arrhythmias, compared males with disease or healthy individuals of either sex. Overall, the results illustrate how PK and QSP modeling may be combined to more precisely predict cardiac risks of COVID-19 therapies.

Excessive lysosomal ion-trapping of hydroxychloroquine and azithromycin

A recent report identified significant reductions or disappearance of viral load in COVID-19 patients given a combination of hydroxychloroquine and azithromycin. The present communication discusses some common pharmacokinetic properties of these two drugs that may be linked to a potential underlying mechanism of action for these antiviral effects. The physicochemical properties of both hydroxychloroquine and azithromycin are consistent with particularly high affinity for the intracellular lysosomal space, which has been implicated as a target site for antiviral activity. The properties of both drugs predict dramatic accumulation in lysosomes, with calculated lysosomal drug concentrations that exceed cytosolic and extracellular concentrations by more than 50 000-fold. These predictions are consistent with previously reported experimentally measured cellular and extracellular concentrations of azithromycin. This is also reflected in the very large volumes of distribution of these drugs, which are among the highest of all drugs currently in use. The combination of hydroxychloroquine and azithromycin produces very high local concentrations in lysosomes. The clinical significance of this observation is unclear; however, the magnitude of this mechanism of drug accumulation via ion-trapping in lysosomes could be an important factor for the pharmacodynamic effects of this drug combination.

Pharmacokinetics of Macrolide Antibiotics and Transport into the Interstitial Fluid: Comparison among Erythromycin, Clarithromycin, and Azithromycin

Recent research has found higher levels and longer total exposure of azithromycin, a macrolide antibiotic agent, in the interstitial fluid of the skin than in the plasma. This unique distribution is expected to contribute to its antimicrobial activity at the primary infection site. However, it remains unclear whether this characteristic distribution in the extracellular tissue space is common to macrolide antibiotics or if it is azithromycin-specific, with most macrolides largely localized intracellularly. In this study, we investigated pharmacokinetic characteristics of erythromycin and clarithromycin in the interstitial fluid of the skin of rats after intravenous drug administration, and compared the results with our previously reported results on azithromycin. Interstitial fluid samples were directly collected from a pore on the skin using a dissolving microneedle array. We found that the total macrolide concentrations in the interstitial fluid were significantly different among three macrolides. The rank order of the interstitial fluid-plasma concentration ratio was azithromycin (3.8 to 4.9) > clarithromycin (1.2 to 1.5) > erythromycin (0.27 to 0.39), and this ratio was stable after dosing, whereas higher drug levels in the skin tissue than in the plasma were observed for all three macrolides. Our results suggest that lower erythromycin concentrations in the interstitial fluid than in the plasma contributes to the emergence of bacterial resistance in the extracellular tissue space. Monitoring of total macrolide concentrations in interstitial fluid may provide valuable information regarding antimicrobial effects and the emergence of bacterial resistance for the development of an appropriate pharmacokinetics-pharmacodynamics-based dosing strategy.

Antibiotic Resistance of Campylobacter Species in a Pediatric Cohort Study

The objective of this study was to determine the phenotypic patterns of antibiotic resistance and the epidemiology of drug-resistant Campylobacter spp. from a low-resource setting. A birth cohort of 303 patients was followed until 5 years of age. Stool samples from asymptomatic children (n = 10,008) and those with diarrhea (n = 3,175) were cultured for Campylobacter Disk diffusion for ciprofloxacin (CIP), nalidixic acid (NAL), erythromycin (ERY), azithromycin (AZM), tetracycline (TE), gentamicin (GM), ampicillin (AMP), amoxicillin and clavulanic acid (AMC), ceftriaxone (CRO), chloramphenicol (C), and trimethoprim-sulfamethoxazole (TMS) was determined. Antibiotic resistances in Campylobacter jejuni and non-C. jejuni isolates from surveillance and diarrhea samples were compared, and the association between personal macrolide exposure and subsequent occurrence of a macrolide-resistant Campylobacter spp. was assessed. Of 917 Campylobacter isolates, 77.4% of C. jejuni isolates and 79.8% of non-C. jejuni isolates were resistant to ciprofloxacin, while 4.9% of C. jejuni isolates and 24.8% of non-C. jejuni isolates were not susceptible to azithromycin. Of the 303 children, 33.1% had been diagnosed with a Campylobacter strain nonsusceptible to both azithromycin and ciprofloxacin. Personal macrolide exposure did not affect the risk of macrolide-resistant Campylobacter Amoxicillin and clavulanic acid (94.0%) was one of the antibiotics with the highest rates of susceptibility. There is a high incidence of quinolone- and macrolide-resistant Campylobacter infections in infants under 24 months of age. Given the lack of association between personal exposure to macrolides and a subsequent Campylobacter infection resistant to macrolides, there is a need to evaluate the source of multidrug-resistant (MDR) Campylobacter This study provides compelling evidence to propose amoxicillin/clavulanic acid as a treatment for campylobacteriosis.

Azithromycin enhances anticancer activity of TRAIL by inhibiting autophagy and up-regulating the protein levels of DR4/5 in colon cancer cells in vitro and in vivo

Background

Azithromycin is a member of macrolide antibiotics, and has been reported to inhibit the proliferation of cancer cells. However, the underlying mechanisms are not been fully elucidated. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively targets tumor cells without damaging healthy cells. In the present study, we examined whether azithromycin is synergistic with TRAIL, and if so, the underlying mechanisms in colon cancers.

Methods

HCT-116, SW480, SW620 and DiFi cells were treated with azithromycin, purified TRAIL, or their combination. A sulforhoddamine B assay was used to examine cell survival. Apoptosis was examined using annexin V-FITC/PI staining, and autophagy was observed by acridine orange staining. Western blot analysis was used to detect protein expression levels. In mechanistic experiments, siRNAs were used to knockdown death receptors (DR4, DR5) and LC-3B. The anticancer effect of azithromycin and TRAIL was also examined in BALB/c nude mice carrying HCT-116 xenografts.

Results

Azithromycin decreased the proliferation of HCT-116 and SW480 cells in a dose-dependent manner. Combination of azithromycin and TRAIL inhibited tumor growth in a manner that could not be explained by additive effects. Azithromycin increased the expressions of DR4, DR5, p62 and LC-3B proteins and potentiated induction of apoptosis by TRAIL. Knockdown of DR4 and DR5 with siRNAs increased cell survival rate and decreased the expression of cleaved-PARP induced by the combination of azithromycin and TRAIL. LC-3B siRNA and CQ potentiated the anti-proliferation activity of TRAIL alone, and increased the expressions of DR4 and DR5.

Conclusion

The synergistic antitumor effect of azithromycin and TRAIL mainly relies on the up-regulations of DR4 and DR5, which in turn result from LC-3B-involved autophagy inhibition.

Electronic supplementary material

The online version of this article (10.1186/s40880-018-0309-9) contains supplementary material, which is available to authorized users.

Pharmacokinetics of a single 1g dose of azithromycin in rectal tissue in men

Chlamydia is the most common bacterial sexually transmitted infection among men who have sex with men. Repeat infection following treatment with 1g azithromycin is common and treatment failure of up to 22% has been reported. This study measured the pharmacokinetics of azithromycin in rectal tissue in men following a single 1g dose to assess whether azithromycin reaches the rectal site in adequate concentrations to kill chlamydia. Ten healthy men took a single oral dose of 1g azithromycin and provided nine self-collected swabs and one blood sample over 14 days. Participant demographics, medications, sexual behaviour, treatment side effects, lubricant use and douching practices were recorded with each swab. Drug concentration over time was determined using liquid chromatography-mass spectrometry and total exposure (AUC0-∞) was estimated from the concentration-time profiles. Following 1g of azithromycin, rectal concentrations peaked after a median of 24 hours (median 133mcg/g) and remained above the minimum inhibitory concentration for chlamydia (0.125mcg/mL) for at least 14 days in all men. AUC0-∞ was the highest ever reported in human tissue (13103((mcg/g).hr)). Tissue concentrations were not associated with weight (mg/kg), but data suggest that increased gastric pH could increase azithromycin levels and diarrhoea or use of water-based lubricants could decrease concentrations. High and sustained concentrations of azithromycin were found in rectal tissue following a single 1g dose suggesting that inadequate concentrations are unlikely to cause treatment failure. Factors effecting absorption (pH and diarrhoea) or drug depletion (douching and water-based lubricants) may be more important determinants of concentrations in situ.

Transport of Azithromycin into Extravascular Space in Rats

Recent clinical trials showed a prolonged retention of subinhibitory concentrations of unbound azithromycin in the interstitial fluid of soft tissues despite the fact that azithromycin is extensively distributed in tissues. In these clinical trials, interstitial fluid samples were obtained by using the microdialysis method, and it was established that drug concentrations represent protein-unbound drug concentrations. The present study was designed to measure total azithromycin concentrations in the interstitial fluid of the skin of rats by directly collecting interstitial fluid samples from a pore formed on the skin by a dissolving microneedle array. The total azithromycin concentrations in interstitial fluid of the skin were about 4 to 5 times higher than those in plasma throughout the experimental period, and stasis of the azithromycin concentration in interstitial fluid was observed when the concentration of azithromycin in plasma was at the lower limit of quantification. In addition, the skin/plasma concentration ratio transiently increased after dosing (from 4.3 to 83.1). Our results suggest that azithromycin was trapped inside white blood cells and/or phagocytic cells in not only blood but also interstitial fluid, resulting in a high total azithromycin concentration and the retention of its antimicrobial activity at the primary infection site. The stasis of azithromycin in interstitial fluid and skin would lead to long-lasting pharmacological effects (including those against skin infection) at concentrations exceeding the MIC.

Comparison of doxycycline with azithromycin in treatment of pharyngeal chlamydia infection

Recent data suggest that azithromycin may not be as effective as doxycycline in eradication of genital chlamydial infection. The aim of this study was to compare the eradication rate of pharyngeal Chlamydia trachomatis infection after treatment with azithromycin 1 g stat with that of doxycycline 100 mg twice a day for seven days. A prospective open-label observational study was conducted on patients with pharyngeal Chlamydia trachomatis diagnosed at Whittall Street Clinic, University Hospitals Birmingham, Birmingham, UK, between July 2012 and July 2013. We confirmed eradication of pharyngeal Chlamydia trachomatis with a negative test of cure. We treated all our patients with azithromycin 1 g stat until February 2013. At that stage, we offered doxycycline to patients with pharyngeal Chlamydia trachomatis A total of 398 patients (52 men, 346 women) were diagnosed with pharyngeal Chlamydia trachomatis during the study period. Of the 172 patients included in the final analysis, 78 were treated with azithromycin and 64 with doxycycline. Treatment failure was identified among 8/78 (10%) patients treated with azithromycin and 1/64 (2%) treated with doxycycline (absolute difference: 8 percentage points, 95% CI: 0-17%, p = 0.041). In our study, doxycycline 100 mg twice a day for seven days was associated with less treatment failure of oropharyngeal chlamydia compared with azithromycin 1 g stat Future randomised studies should investigate whether patients with pharyngeal Chlamydia trachomatis should be followed up with a test of cure when treated with azithromycin, or be treated with doxycycline.

Synergistic hepatoprotective potential of ethanolic extract of Solanum xanthocarpum and Juniperus communis against paracetamol and azithromycin induced liver injury in rats

Previously explored combination therapies mostly involved the use of bioactive molecules. It is believed that herbal compounds containing multiple plant products have synergistic hepatoprotective effects and could enhance the desired actions. To investigate the combination of ethanolic fruits extract of Solanum xanthocarpum (SX) and Juniperus communis (JC) against Paracetamol (PCM) and Azithromycin (AZM) induced liver toxicity in rats. Liver toxicity was induced by combine oral administration of PCM (250 mg/kg) and AZM (200 mg/kg) for 7 days in Wistar rats. Fruit extract of SX (200 and 400 mg/kg) and JC (200 and 400 mg/kg) were administered daily for 14 days. The hepatoprotective activity was assessed using liver functional test, oxidative parameters and histopathological examination. The results demonstrated that combine administration of AZM and PCM significantly produced liver toxicity by increasing the serum level of hepatic enzymes and oxidative parameters in liver of rats. Histopathological examination also indicated that AZM and PCM produced liver damage in rats. Chronic treatment of SX and JC extract significantly and dose-dependently attenuated the liver toxicity by normalizing the biochemical factors and no gross histopathological changes were observed in liver of rats. Furthermore, combine administration of lower dose of SX and JC significantly potentiated their hepatoprotective effect which was significant as compared to their effect per se. The results clearly indicated that SX and JC extract has hepatoprotective potential against AZM and PCM induced liver toxicity due to their synergistic anti-oxidant properties.