Relapse rate and incidence of dapsone resistance in lepromatous leprosy patients in Addis Ababa: risk factors and effect of short-term supplementary treatment.

A clinical trial was initiated at ALERT, Addis Ababa, Ethiopia, to study the effect of one-year supplementary treatment on the incidence of dapsone-resistant leprosy in lepromatous patients already on dapsone monotherapy. A total of 806 patients on dapsone therapy were assigned to one of four groups. The first group served as a control group, the second received a combination tablet of thiacetazone and INH (Thiazina) daily for 12 months, the third group received Thiazina daily for 12 months plus rifampin daily during months 1 and 7, and the fourth group received rifampin daily during months 1 and 7 but no Thiazina. Eighty-three percent of the patients were followed for five years after discontinuation of the supplementary treatment. The annual incidence of relapses and dapsone-resistant leprosy in the control group appeared to be 2.3% and 0.7%, respectively. The Thiazina treatment had no significant effect on either the overall relapse rate or the incidence of dapsone-resistant leprosy. The rifampin treatment, on the other hand, did significantly lower the relapse rate and only a single case of dapsone resistance was detected. A high incidence of relapse was found in young female patients. Nineteen of the 45 relapsed patients were bacteriologically negative at the start of the supplementary treatment and six had already been negative for over five years.