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.