Ivermectin for the treatment of Wuchereria bancrofti filariasis. Efficacy and adverse reactions.

Ivermectin treatment was evaluated for efficacy and side effects in 40 patients in South India who had microfilaremia and bancroftian filariasis. Ivermectin was administered once orally at four dose levels (range, 25 to 200 micrograms/kg), and at each it was found to be completely effective in clearing blood microfilariae within five to 12 days. In most patients, microfilariae reappeared by three months; by six months the levels averaged 14% to 32% of pretreatment values in the four study groups, and all groups showed equivalent efficacy. Detailed monitoring identified some side effects in almost all patients: usually fever, headache, light-headedness, myalgia, sore throat, or cough that occurred most prominently 18 to 36 hours after treatment. These were most frequent and severe in patients with the greatest microfilaremia, but only when treated with the two higher doses of ivermectin (100 and 200 micrograms/kg). The low-dose (25 micrograms/kg) ivermectin group, despite equivalent efficacy in parasite killing, had clinical reaction scores that were minimal and that were not correlated with parasitemia. Since efficacy and side effects of ivermectin therapy compare favorably with those reported for treatment with the standard antifilarial drug diethylcarbamazine citrate, the major advantage of single-oral-dose administration makes ivermectin the best candidate to replace diethylcarbamazine as the treatment of choice for bancroftian filariasis.