Current World Health Organization-sponsored studies in the chemotherapy of leprosy.

Until the early 1 980s, dapsone monotherapy administered to known patients was used for control of leprosy. Dapsone was usually administered in a dosage of 100 mg daily for a minimum of 5 years to patients with paucibacillary (PB) leprosy, and for life to patients with multibacillary (MB) leprosy. Because it was a weakly bactericidal and slowly acting drug, dapsone monotherapy led to poor patient compliance and the emergence of dapsone-resistant strains of Mycobacterium leprae. Since 1982, the multidrug therapy (MDT) regimens recommended by the World Health Organization (WHO), which include a combination of rifampicin, clofazimine and dapsone for MB leprosy and rifampicin plus dapsone for PB leprosy, have been applied in national leprosy control programmes in all of the leprosy endemic countries in the world. This therapy has proved to be a most reliable and practical method of treating leprosy. The introduction of MDT in 1982 has resulted in a dramatic reduction of the prevalence of leprosy, from 5 ·4 million registered cases in 1 985 to 0·8 million in 1999. By the end of 1999, more than 10 million patients had been cured by MDT. Follow-up of the large number of patients cured by MDT has revealed very low relapse rates after stopping treatment; the cumulative risk of relapse is less than 1 % over a period of 9 years for both MB and PB leprosy. Despite the success of the standard WHO MDT regimens, there is a need for more effective combined drug regimens. Several WHO-sponsored programmes of research in the chemotherapy of leprosy are currently in progress. The purpose of this report is briefly to describe the programmes and their current status.