A study of two twice-weekly and once-weekly continuation regimen of tuberculosis chemotherapy, including a comparison of two durations of treatment. 1. First report: the results at 18 months.

The controlled clinical trial reported here was undertaken in Central Bohemia, West Slovakia and Prague. Patients in whom pulmonary tuberculosis had been newly diagnosed and confirmed bacteriologically were given standard triple chemotherapy with streptomycin, PAS and isoniazid for 6 weeks or 3 months. Continuation chemotherapy was streptomycin and isoniazid given either twice weekly or once weekly, to make a total duration of treatment of 12 or 18 months. Overall there were no significant differences in the bacteriological response at 18 months, 98 per cent of the 13 week S2H2, 99 per cent of the 6 week S2H2 and 94 per cent of the 13 week S1H1 patients having a favourable response. However, the S1H1 regimen was at a disadvantage for rapid acetylators of isoniazid but not for slow acetylators, 16 per cent of 37 rapid acetylators having an unfavourable response compared with none of 62 slow acetylators. Comparing the 12- and 18-month duration, there was no evidence in the twice- weekly regimens that 18 months of chemotherapy offered any therapeutic advantage. However, there was a suggestion that there might be some benefit in continuing to 18 months with the once-weekly regimen.