Non-specific urethritis. A placebo-controlled trial of minocycline in conjunction with laboratory investigations.

The results of a double-blind therapeutic trial on 81 men suffering from non-specific urethritis (NSU) show that minocycline was more effective than a placebo. Before treatment Chlamydia trachomatis was isolated from 31 per cent. of the men, ureaplasmas from 58 per cent., and Mycoplasma hominis from 7-5 per cent. There is evidence that chlamydiae are a cause of urethritis. However, after minocycline therapy improvement in the clinical response of patients from whom only ureaplasmas were isolated was less significant, so that the evidence that these organisms are pathogenic is less convincing. Possible reasons for this are discussed, as are the implications of finding minocycline-resistant ureaplasmas in at least 6 per cent. of the patients who harboured these organisms. The symptoms and signs of patients from whom micro-organisms were not isolated also improved after minocycline therapy, implying that the aetiological agents in this group of patients are antibiotic-sensitive. However, the results do not exclude the possibility that a minocycline-resistant agent is the cause of urethritis in a minority of patients.