Azithromycin In Plasma Research Articles

UHPLC-MS/MS method for the determination of azithromycin in human plasma of pediatric patients.

The presence of azithromycin in the human plasma of pediatric patients was determined with a UHPLC-MS/MS assay. Sample preparation was done by protein precipitation, and the separation was achieved on a C18 column by the gradient mixture of the mobile phase A (0.1% acetic acid and 3mM ammonium acetate in water) and the mobile phase B (0.1% acetic acid and 3mM ammonium acetate in the solution of acetonitrile, methanol, and water, 47.5/47.5/5, V/V/V). The multiple reaction monitoring mode was adopted to monitor the precursor-to-product ion transitions of m/z 749.6 → m/z 591.5 for azithromycin and m/z 753.6 → m/z 595.5 for azithromycin-13 C-d3 (the internal standard) at the positive ionization mode. The calibration curve ranged from 0.5 to 500.0ng·mL-1 , and the correlation coefficient was greater than 0.99. The intra- and inter-batch precision was less than 13.7%. Accuracy determined at four concentrations ranged from 99.5 to 110.8%. The extraction recoveries were more than 95%, and the matrix effects were 98-100%. The stability under various conditions was acceptable with the accuracy deviation within 9.2%. In conclusion, our method was simple, sensitive, and reliable for quantifying azithromycin in plasma among pediatric patients.

Azithromycin concentrations during long-term regimen, a pilot study in patients with MALT lymphoma

In view of the antineoplastic effects of the macrolide clarithromycin in mucosa associated lymphatic tissue (MALT)-lymphoma, we performed a pilot study assessing levels of azithromycin in plasma, peripheral blood mononuclear cells (PBMC) and polymorphonuclear leukocytes (PMN) of MALT-lymphoma patients to determine the pharmacokinetics and potential influences of respective concentrations on the therapeutic outcome. In total 16 patients with MALT-lymphoma received 1.5 g of oral azithromycin once-weekly over 6 months. Blood was sampled directly prior to the following dose every 4 weeks during treatment. Drug levels were analysed by high performance liquid chromatography in plasma and intracellularly in PBMC and PMN. They were correlated with patients’ age, weight and body-mass-index and compared between patients responsive or unresponsive to treatment. Mean azithromycin plasma levels of all patients were 58.97 ± 30.48 ng/ml, remaining stable throughout the treatment period. Correlation analysis of plasma azithromycin showed no significance. Intracellular PBMC concentrations were 6648 ± 8479 ng/ml, without any significant difference between responders and non-responders. Mean PMN levels were 39,274 ± 25,659 ng/ml and significantly higher in patients unresponsive to treatment (t = 2.858, p = 0.017). Our drug regime led to continuously high plasma and exceedingly high intracellular concentrations of azithromycin in PBMC and PMN. Age, weight or body-mass-index had no significant influence on plasma levels and thence should not be considered in dosage finding. High AZM levels in PBMC did not lead to a better treatment response, whereas enrichment in PMN suggested a poorer outcome. The threshold for immunomodulatory effects on lymphoma cells might not have been reached. Additionally, the finding of stable plasma and intracellular concentrations over months with high-dose azithromycin administered in intervals might also be important for the further design of azithromycin-based trials against MALT-lymphoma.Trial registration: EudraCT 2016-001521-13, 14/06/2016.

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.

Effect of Fuke Qianjin tablets on pharmacokinetics of Azithromycin in rats with chronic pelvic inflammatory disease

To investigate the effect of Fuke Qianjin tablets on the pharmacokinetics of Azithromycin(AZM) in rats with chronic pelvic inflammation, and evaluate the rationality of the drug combination. The animal models of chronic pelvic inflammatory disease were established by intrauterine injection of mixed bacterial suspension plus mechanic injury in female Sprague-Dawley(SD) rats. The model rats were randomly divided into control group and drug combination group. The rats in control group were given with Azithromycin 10 mg•kg⁻¹•d⁻¹ by intragastric administration, while the rats in drug combination group were given with Fuke Qianjin tablets 1.66 g•kg⁻¹•d⁻¹ by intragastric administration 2 hours after the equivalent dose of azithromycin, once a day, consecutively for 7 days. Plasma samples were collected at different time points and the concentration of AZM in plasma was determined by high performance liquid chromatography coupled with mass spectrometry(HPLC-MS). ADAPT 5.1 software was used to calculate the pharmacokinetic parameters of each group by Inverse Gaussian Function model. SPSS software was used for the statistical analysis of data in each group. The results showed that Fuke Qianjin tablets had no significant effects on the main pharmacokinetic parameters of AZM, including CLt, CLd, MIT and F. The study showed that Fuke Qianjin tablets can be combined with azithromycin for treatment of chronic pelvic inflammation disease.

Safety, tolerability and pharmacokinetic properties of coadministered azithromycin and piperaquine in pregnant Papua New Guinean women.

The aim of the present study was to investigate the safety, tolerability and pharmacokinetics of coadministered azithromycin (AZI) and piperaquine (PQ) for treating malaria in pregnant Papua New Guinean women. Thirty pregnant women (median age 22years; 16-32weeks' gestation) were given three daily doses of 1g AZI plus 960mg PQ tetraphosphate with detailed monitoring/blood sampling over 42days. Plasma AZI and PQ were assayed using liquid chromatography-mass spectrometry and high-performance liquid chromatography, respectively. Pharmacokinetic analysis was by population-based compartmental models. The treatment was well tolerated. The median (interquartile range) increase in the rate-corrected electrocardiographic QT interval 4h postdose [12 (6-26) ms(0) (.5) ] was similar to that found in previous studies of AZI given in pregnancy with other partner drugs. Six women with asymptomatic malaria cleared their parasitaemias within 72h. Two apararasitaemic women developed late uncomplicated Plasmodium falciparum infections on Days 42 and 83. Compared with previous pregnancy studies, the area under the concentration-time curve (AUC0-∞ ) for PQ [38818 (24354-52299) μg h l(-1) ] was similar to published values but there was a 52% increase in relative bioavailability with each dose. The AUC0-∞ for AZI [46799 (43526-49462) μg h l(-1) ] was at least as high as reported for higher-dose regimens, suggesting saturable absorption and/or concentration-dependent tissue uptake and clearance from the central compartment. AZI-PQ appears to be well tolerated and safe in pregnancy. Based on the present/other data, total AZI doses higher than 3g for the treatment and prevention of malaria may be unnecessary in pregnant women, while clearance of parasitaemia could improve the relative bioavailability of PQ.

Determination of Azithromycin in Biological Samples by LLLME Combined with LC

A simple liquid–liquid–liquid microextraction (LLLME) technique combined with liquid chromatography (LC) was developed for the extraction and quantitative determination of azithromycin (AZI) in biological fluids. In this technique, AZI was extracted from 2.5 mL basic sample solution (donor phase) at pH 10.5 into an organic phase (90 μL), for 30 min. Then back-extracted into a 5 μL microdrop acidic aqueous solution (acceptor phase) at pH 2.5 immersed in the organic phase from the tip of a microsyringe for 20 min with a stirring rate of 800 rpm and donor phase temperature of 35 °C. After a prescribed time, the acceptor microdrop was returned into the microsyringe and injected into the LC. Optimization of experimental parameters on LLLME efficiency was investigated. Under optimized conditions, a preconcentration factor of 85 and limit of detection of 0.03 μg mL−1 were obtained. The calibration curve was linear (r 2 = 0.998) in the concentration range of 0.1–15 μg mL−1. Within-day relative standard deviation (RSD) (S/N = 3) and between-day RSD were 5.1 and 6.8%, respectively. Finally, the feasibility of the proposed method was evaluated by extraction and determination of AZI in plasma and urine samples and satisfactory results were obtained.

Pharmacokinetics of azithromycin in plasma and sinus mucosal tissue following administration of extended-release or immediate-release formulations in adult patients with chronic rhinosinusitis

This study compared the pharmacokinetics of azithromycin (AZI) following administration of extended-release (ER) and immediate-release (IR) formulations in plasma and sinus mucosa in patients with chronic rhinosinusitis. Patients ( n = 71) were randomised 1:1 to receive a single dose of AZI-ER 2 g or up to three doses of AZI-IR 500 mg daily. Paired plasma and sinus tissue samples were taken during endoscopic sinus surgery at 2–168 h (four patients per time point) after the first dose. Samples were measured by a validated liquid chromatography/mass spectrometry assay. Pharmacokinetics were determined using composite concentration–time profiles. Comparison between formulations showed that within the first 24 h, the AZI area under the plasma concentration–time curve (AUC 24) for ER was 5.2- and 7.0-fold higher than IR in plasma and sinus tissue, respectively. Comparison between matrices showed that the AUC 24 and AUC 168 in sinus tissue were 28.2- and 62.2-fold higher than in plasma for the ER formulation, whilst the AUC 24 in sinus tissue was 21.1-fold higher than in plasma for IR formulation. These results indicated that AZI has good penetration into sinus tissue regardless of formulation; however, dosing of AZI-ER (2 g) increased AZI exposure within the first 24 h compared with the Day 1 dose of 500 mg IR regimen.

Quantitative determination of azithromycin in human plasma by liquid chromatography–mass spectrometry and its application in a bioequivalence study

A sensitive, rapid liquid chromatographic–electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2 mL) was extracted with methyl tert-butyl ether–hexane (50:50, v/v), organic phase was transferred to another clear 1.5 mL Eppendorf tube and evaporated to dryness at 40 °C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150 mm × 2.1 mm i.d., 5 μm), together with a mobile phase containing of 20 mM ammonium acetate (pH 5.2)–acetonitrile–methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2 mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000 ng/mL with r = 0.9977. The limit of quantification for azithromycin in plasma was 2 ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.

Pharmacokinetics of Azithromycin in Plasma, Blood, Polymorphonuclear Neutrophils and Sputum During Long-Term Therapy in Patients With Cystic Fibrosis

Chronic therapy with the macrolide antibiotic azithromycin (AZM) is widely practiced in the treatment of patients with cystic fibrosis (CF) and chronic lung infection with Pseudomonas aeruginosa. Azithromycin dosage is variable, based on published studies, and not supported by pharmacokinetic data. This study describes the pharmacokinetics of the long-term administration of AZM (500 mg per day) in CF patients. AZM concentrations were quantified in the plasma, blood, isolated polymorphonuclear neutrophils (PMNNs), and sputum of 8 adult CF patients. The AZM distribution t1/2 was 0.1 hours in plasma. The (mean +/- standard deviation) elimination t(1/2) was 102 +/- 20 hours in plasma, 180 +/- 68 hours in blood, and 289 +/- 166 hours in PMNNs. The C(max) of AZM was 0.67 +/- 0.31 mg/L in plasma and 2.01 +/- 0.74 mg/L in blood, of which 1.44 +/- 0.69 mg/L was found in PMNNs. In sputum the concentration of AZM ranged from 12 to 53 mg/L and was still detectable at concentrations in the range 4 to 27 mg/L 10 days after the last dose. On average, the concentration in PMNNs was 2100 times the C(plasma) 24 hours after dosing AZM. These results confirm the accumulation of AZM in PMNNs. The authors conclude that sputum levels are elevated far above plasma and blood concentrations. The long t(1/2) in blood and PMNNs and the slow decrease in sputum levels indicate a less frequent dosing schedule (for instance once weekly) should be studied in future clinical trials of AZM in patients with cystic fibrosis.

Quantitative determination of azithromycin in plasma, blood and isolated neutrophils by liquid chromatography using pre-column derivatization with 9-fluorenylmethyloxycarbonyl-chloride and fluorescence detection

In this study, a high-performance liquid chromatographic method with pre-column derivatization and fluorescence detection was optimised and validated for the quantification of azithromycin (AZM) in plasma. Clarithromycin (CLM) was used as an internal standard. Pre-column derivatization was done with 9-fluorenylmethyloxycarbonyl-chloride. Recovery from blood and polymorphonuclear neutrophils (PMNNs) isolated by a gravity separation procedure was also assessed. Analytical separation was carried out using a C18 column as stationary phase and acetonitril–phosphatebuffer as mobile phase. Peak quantification was carried out by excitation at 267 nm and detection at 317 nm. A lower limit of quantitation of 0.042 ± 0.017 mg/l in plasma, 0.119 ± 0.065 mg/l in blood and 0.072 ± 0.036 in water was achieved. Linearity was assessed from 0 to 1.5 mg/l in plasma and blood and from 0–9 mg/l in water. The analytical method proved to be applicable in a pharmacokinetic study of AZM in a Cystic Fibrosis patient.

PHARMACOKINETICS OF AZITHROMYCIN IN LUNG TISSUE, BRONCHIAL WASHING, AND PLASMA IN PATIENTS GIVEN MULTIPLE ORAL DOSES OF 500 AND 1000 MG DAILY

The present study compares the pharmacokinetics of azithromycin in plasma, lung tissue, and bronchial washing after oral administration of 500 mg (standard dose) versus 1000 mg daily for 3 days. Samples were taken during surgery for lung resection at various time points up to 204 h after the last drug dose, and azithromycin levels were analyzed by HPLC method. Azithromycin was widely distributed within the lower respiratory tract; sustained concentrations of the drug were detectable at the last sampling time (204 h) in lung tissue and bronchial washing, with long terminal half-lives of 132.86 and 74.32 h at 500 mg daily and 133.32 and 70.5 h at 1000 mg daily, respectively. Doubling the drug dose resulted in a remarkable increase in lung area under the curve (AUC, 1318 hx μg g −1 vs 2502 hx μg g −1) and peak tissue concentration (9.13±0.53 μg g −1 vs 17.85±2.4 μg g −1). In addition to this, enhanced azithromycin penetration from plasma into bronchial secretion and lung tissue was evidenced by the increase in the ratio of AUC bronchial washing versus AUC plasma (2.96 vs 5.27 at 500 and 1000 mg, respectively) and AUC lung versus AUC plasma (64.35 vs 97.73 at 500 and 1000 mg, respectively). In conclusion, the exposure of lung and bronchial washing to azithromycin is increased by doubling the dose, which results in favorable pharmacokinetic profile of the drug in the lower respiratory tract.

Pharmacokinetics of azithromycin in foals after i.v. and oral dose and disposition into phagocytes.

The properties of azithromycin suggest that it may be an alternative to erythromycin for treatment of Rhodococcus equi pneumonia in foals. To investigate this possibility, the disposition of azithromycin in plasma, polymorphonuclear leukocytes (PMN), and alveolar cells was examined after a single administration in foals. Azithromycin suspension was administered orally (p.o.) at a dose of 10 mg/kg to five healthy 2-3-month-old foals. Two weeks later, azithromycin for injection was administered by intravenous (i.v.) infusion at a dose of 5 mg/kg to the same foals. Plasma samples were collected after p.o. and i.v. administration. Peripheral blood PMN and bronchoalveolar lavage fluid and alveolar cells were collected after p.o. administration. Azithromycin concentrations were determined by reverse-phase high-performance liquid chromatography (HPLC) with coulometric electrochemical detection. Azithromycin p.o. absorption was variable with a mean systemic availability of 39% (+/-20%). The plasma half-life was 16 and 18.3 h after i.v. and p.o. administration, respectively. Azithromycin had a very large volume of distribution (V(d)) of 11.6 L/kg [V(d(ss))] and 12.4 L/kg [V(d(area))]. The large V(d) can be attributed to high tissue and intracellular concentrations, exhibited by the high concentration of azithromycin in PMN and alveolar cells. The PMN half-life was 49.2 h. Dosage of 10 mg/kg of azithromycin p.o. once daily for foals with R. equi pneumonia is recommended for further study.

Determination of erythromycin, clarithromycin, roxithromycin, and azithromycin in plasma by high-performance liquid chromatography with amperometric detection

In this study, a high-performance liquid chromatographic method was developed for the quantitative determination of erythromycin (EM), roxithromycin (RXM), and azithromycin (AZM) in rat plasma with amperometric detection under a standardized common condition using clarithromycin (CAM) as an internal standard. This method was also proved to be applicable for the determination of CAM by employing RXM as an internal standard. Each drug was extracted from 150 μl of plasma sample spiked with internal standard under an alkaline condition with tert.-butyl methyl ether. The detector cell potential for the oxidation of the drugs was set at +950 mV. The linearity of the calibration curves were preserved over the concentration ranges of 0.1–10 μg/ml for EM and RXM, and 0.03–3.0 μg/ml for CAM and AZM. Coefficients of variation and relative error were less than 9% and ±7%, respectively. The analytical method presented here was proved to be useful for the investigation of the pharmacokinetic characteristics of EM, CAM, RXM, and AZM in rats.

Periodontal tissue disposition of azithromycin in patients affected by chronic inflammatory periodontal diseases.

The recognition that periodontal diseases are associated with specific pathogens has led to interest in the use of antibacterial drugs for inhibition of these microorganisms. On these bases, the present study was aimed at evaluating the tissue distribution of the new macrolide antibiotic azithromycin in patients subjected to oral surgery for chronic inflammatory diseases of both marginal and periapical periodontium. Thirty-two patients were treated with azithromycin 500 mg/day orally for 3 consecutive days, and drug concentrations in plasma, saliva, normal gingiva, and pathological periodontal tissues were evaluated. For this purpose, samples of blood, saliva, normal gingiva, granulation tissue, and radicular granuloma or cyst wall (from dentigerous cyst) were collected during oral surgery or 0.5, 2.5, 4.5, and 6.5 days after the end of pharmacological treatment; then, azithromycin levels were measured by a microbiological plate assay, using Micrococcus luteus NCTC 8440 as the indicator organism. The concentrations of azithromycin in plasma, saliva, normal gingiva, and pathological tissues reached the highest values 12 hours after the last dose (0.37+/-0.05 mg/l, 2.12+/-0.30 mg/l, 6.30+/-0.68 mg/kg, and 11.60+/-1.50 mg/kg, respectively) and then declined gradually. Consistent levels of the drug in normal gingiva and pathological tissues could be detected, however, up to 6.5 days, indicating that azithromycin was retained in target tissues for a long time after the end of treatment. Moreover, azithromycin levels in both normal gingiva and pathological tissues exceeded the minimum inhibitory concentrations of most pathogens involved in the pathophysiology of chronic inflammatory periodontal diseases. Notably, azithromycin levels in pathological tissues were significantly higher than those in normal gingiva 0.5, 2.5, and 4.5 days after the last dose. The present results indicate a marked penetration of azithromycin into both normal and pathological periodontal tissues, suggesting that azithromycin represents a promising option in both adjunctive and prophylactic treatments of chronic inflammatory periodontal diseases.

Simultaneous high-performance liquid chromatography analysis of azithromycin and two of its metabolites in human tears and plasma.

This article describes a high-performance liquid chromatographic (HPLC) method for the measurement of azithromycin (AZI) and two of its metabolites, 9a-N-desmethylazithromycin (ADES) and N-desmethylazithromycin (NDES), in human tears and plasma. The drug, metabolites, and internal standard (n-propylazithromycin [IS]) were detected electrochemically after injection of the extracted sample into the HPLC system. The peak height ratio (AZI, ADES, or NDES to IS) varied linearly, with concentrations in the ranges of 0.1 mg/L to 2.0 mg/L (tears) and 0.01 mg/L to 2.0 mg/L (plasma) of AZI, ADES, and NDES; the correlation coefficient (r) was more than 0.994 mg/L for all of the compounds (n=6). The analysis of tear samples collected at different intervals within 12 hours to 144 hours after a dose of 20 mg/kg of AZI from a trachoma patient yielded concentrations ranging from 1.52 mg/L to 0.34 mg/L for AZI, 0.79 mg/L to 0.27 mg/L for ADES, and 1.99 mg/L to less than 0.20 mg/L for NDES. The concentration of AZI in plasma ranged from 0.15 mg/L to 0.01 mg/L, whereas ADES and NDES were undetectable.

Determination of macrolides in biological matrices by high-performance liquid chromatography with electrochemical detection

A liquid chromatographic method for the determination of macrolide antibiotics is described using a cyanopropyl column which proved to be as efficient or superior to the normally used apolar reversed-phase columns. The recovery of the macrolides from water and plasma was 80–90%. Using 0.5 ml of plasma, 30 ng/ml of clarithromycin, 50 ng/ml of roxithromycin and 10 ng/ml of azithromycin could be determined with acceptable precision and accuracy. The method has been employed in pharmacokinetic studies in humans for the determination of roxithromycin, clarithromycin and azithromycin in plasma, serum and other biological matrices. The particular selectivity of the cyanopropyl phase may also allow the simultaneous determination of erythromycin and its prodrug esters.

A Phase I Determination of Azithromycin in Plasma during a 6-Week Period in Normal Volunteers after a Standard Dose of 500mg Once Daily for 3 Days

The pharmacokinetics of azithromycin were evaluated in 12 healthy volunteers. This was an open study in 12 healthy male subjects. Participants received a single dose of 2 x 250mg azithromycin (two azithromycin capsules) administered orally in the fasting state with 240ml water on three consecutive days. After oral intake of two capsules of 250mg azithromycin over three consecutive days (the normal treatment regimen in adults), azithromycin was present in measurable levels in plasma (>5 microg/L) for 7 to 17 days after the beginning of treatment. The apparent elimination half-life was very long (observed range: 49 to 108 hours, i.e. about 2 to 4.5 days). From the results in plasma, one can extrapolate that the azithromycin concentration would remain above 1 microg/L (corresponding to concentrations in tissues above 0.1 mg/L) for up to 15 to 30 days following treatment. The elimination half-life of azithromycin (average of 76 hours) was in agreement with values of depletion rates in tissues corresponding to a half-life of 60 to 72 hours. In conclusion, the utility of the long exposure of patients with benign respiratory infections to azithromycin and to subinhibitory concentrations of azithromycin should be questioned.

Gynaecological tissue levels of azithromycin

In an open study the concentrations of azithromycin in plasma, urine, peritoneal fluid and gynaecological tissue in 20 patients undergoing elective gynaecological surgery were compared. Patients were allocated to one of four groups and all patients received a single 500 mg oral dose of azithromycin prior to surgery. In Group I, the dose was administered 24 h before surgery. In Groups II, III and IV it was administered 48, 72 and 96 h, respectively, prior to surgery. A total of 19 patients completed the study; one patient had peri-operative complications and did not proceed to surgery. High concentrations of azithromycin were found in gynaecological tissue up to 96 h after administration. The mean maximum observed concentration 24 h after administration was 1.44 +/- 0.22 micrograms/g. Using all data, the depletion rate constant was 0.0104 h-1, equivalent to a half-life of approximately 67 h. The mean concentration of drug in peritoneal fluid was approximately 9% of the mean concentration in gynaecological tissue. Tissue and peritoneal fluid azithromycin concentrations were much higher than plasma levels at the time of surgery. Detectable plasma levels were only found in four patients from Groups I and II. Six percent of the total dose was excreted in the urine during the seven-day period after drug administration. The single dose of azithromycin was well tolerated by all the patients in this study and no treatment-related side effects or laboratory test abnormalities were seen. It is concluded that a single 500 mg oral dose of azithromycin produces high and sustained levels in gynaecological tissue up to 96 h after administration.