Minocycline in the treatment of nongonococcal urethritis: its effect on Chlamydia trachomatis.

The effect of minocycline on nongonococcal urethritis (NGU) was investigated, with particular reference to its action against Chlamydia trachomatis. Preliminary laboratory studies showed that the drug was active against a laboratory chlamydial strain (Lb4f) in vitro. A group of 133 men with first attacks of NGU was then treated with minocycline, 100 mg twice daily for 3 weeks. Isolates of C trachomatis were obtained from 33 of these men before treatment; all of them gave negative results on cell culture after therapy. Of the 133 patients, 119 (90%) had symptoms on their first attendance, but after one week's treatment only 16 of the 133 (12%) and after 3 weeks 6 of the 133 (5%) had symptoms. All 133 men had demonstrable urethritis initially; by the end of the first week of treatment only 43 of the 133 (32%) and by the end of the third week 32 of the 133 (24%) had evidence of urethritis. There were no differences in clinical response between the Chlamydia-positive and Chlamydia-negative groups. A group of 24 female sexual contacts of men with NGU yielded C trachomatis on cell culture. After 3 weeks' therapy with minocycline all these women gave negative results on cell culture. It is concluded that minocycline is a useful addition to existing remedies for NGU. The future structure of treatment trials for NGU is discussed.