Female genital tissue concentrations of roxithromycin.

A new macrolide, roxithromycin, appears to have some interesting pharmacokinetic characteristics dissimilar to those of erythromycin, e.g. it has the unusual property of a long serum half-life and the possibility of once daily dosing. Moreover tissue levels are higher than those obtained with other macrolides, and the drug is still present in the tissues up to 24 h. after dosing. The pharmacokinetics of roxithromycin were studied in 36 women undergoing gynecological surgery, and divided by means of the time of sampling into six different groups. Each group received an initial 300 mg dose followed by 8 successive doses of 150 mg at 12 h intervals. Blood and tissues samples were taken during surgery at 2, 6, 9, 12, 18 and 24 h after the last dose of roxithromycin and the patients were then allocated to one of the six groups by means of the sampling time. Tissue fragments were obtained from ovary, fallopian tubes, endometrium, myometrium, cervix and vagina immediately after the surgical resection of the organs. Tissue and serum concentrations were determined by the microbiological method using Sarcina lutea ATCC 9341; the lowest limit of detection was 0.01 microg/ml or 0.01 microg/g. Roxithromycin reached the highest concentration at the 9th hour after last administration and its tissue levels would encourage a wide use of this drug as a satisfactory alternative to tetracyclines for the therapy of some gynecological infections.