Ivermectin, given as a single oral dose, has shown considerable promise as a new treatment for onchocerciasis. We assessed the safety and efficacy of ivermectin and tried to determine the optimal dose. Two hundred Liberians received 100, 150, or 200 micrograms of ivermectin/kg or placebo and were followed up for 12 months. Therapy was associated with only minimal systemic and ocular side effects. A 200-micrograms/kg dose was associated with greater systemic reaction than was a 100-micrograms/kg dose. Each treatment group had significant reduction in skin microfilaria counts by day 3 and a decrease of approximately 95% at three months. At three months the proportion of persons with no microfilariae in a specimen of skin was significantly less in the 100-micrograms/kg group than in the 150-micrograms/kg or 200-micrograms/kg groups. At 12 months, the level of microfilariae in skin was still reduced approximately 80%. Significant reduction in ocular involvement was seen in all groups. These results confirm that single-dose ivermectin is effective and well-tolerated and suggest that 150 micrograms of ivermectin/kg may be the optimal dose for initial therapy.
No appropriate treatment is available for widespread use against onchocerciasis. The two drugs used, diethylcarbamazine (DEC) and suramin, are associated with severe systemic and ocular side effects. The ocular side effects of DEC are well known and include permanent sight-threatening changes and sometimes blindness. ' DEC is therefore recommended only for patients with severe disease, especially those whose sight is severely threatened without treatment." Suramin, which is inherently toxic,' also causes similar ocular changes. "' Invermectin, a semisynthetic macrocyclic lactone widely used in veterinary medicine, shows promise as a microfilaricidal drug that has been better tolerated than Correspondence to Hugh R Taylor, MD,
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