The chemotherapy of leprosy: an interpretive history.

The introduction of effective antimicrobial treatment for leprosy, first with the sulphones by Faget in 1943, was the major scientific development of the twentieth century to actually alter disease course and provide patients reason to hope. Initially promin and solapsone, injectable sulphones, were utilised, but these injectables were soon abandoned for oral dapsone which had the additional advantages of providing superior plasma levels, being generally well-tolerated and exceptionally inexpensive (US $1/year for the standard adult dose of 100mg daily). From that time to the general application of multidrug therapy, largely in the 1980 s, monotherapy with dapsone became the standard of care throughout the world. On this treatment new leprous lesions ceased appearing and further neuropathy generally was prevented. Early diagnosis and the institution of dapsone therapy were hugely successful where applied. As early as the 1950 s it was observed that lepromatous leprosy patients treated for several years relapsed if treatment was stopped when they were still skin-smear positive at treatment cessation, and a policy was adopted of continuing dapsone therapy for 1 year after skin-smear negativity was attained. Yet the outcome in these MB patients was disappointing, almost half becoming smear-positive and more than 25% showing signs of clinical relapse. Furthermore, several clinical investigators noted that generally a duration of dapsone monotherapy for lepromatous leprosy of 5 of so years frequently resulted in disease relapse after the cessation of treatment. Thus for lepromatous leprosy lifelong sulphone therapy was generally recommended. In much of the developing world where leprosy was endemic, then and even now, a medical infrastructure and the availability of a reliable and motivated drug delivery system, especially one that could be depended upon for the provision of lifelong therapy, were often either nonexistent or unreliable.