The Relationship of Dapsone (DDS) Therapy toErythema Nodosum Leprosum. Is it Direct or Indirect?

A double-blind, intemally-controlled clinicaI tr ial is reported of th e effect of dapsone on the severity of erythema nodosum leprosum (EN L) in 17 sulphone resistant lepromatous patients , 16 of whom were suffering from ENL of varying severity .During th e 10 weeks of th e trial, altemative anti-Ieprosy tr eatment was continued unchanged.Dapsone, 100 mg daily in a c.oloured ca psule, was prescribed fo r 14 consecutive days between the th ird and seventh weeks, th e timing being allocated by random distribution, and on th e remaining 56 days an identical placebo capsule was given.The clinicaI severity of the ENL was measured by a number of parameters , and th e intake of ali reaction-suppressing drugs was recorded.No evidence was obtained th at dapsone either immed iately or after an interval, exacerbated or precipitated episodes of ENL.It is concluded that dapsone has no direct ENL-stimulating action per se , but th at ENL results indirect1y , consequent on the drug's chemotherapeutic activity against Mycoba cteri um lepra e.