Randomized, controlled, double-blind trial with ivermectin on Loa loa microfilaraemia:: efficacy of a low dose (∼25 μg/kg) versus current standard dose (150 μg/kg)

Neurological. serious adverse events (SAEs) following ivermectin treatment may occur in individuals harbouring high Loa loa microfilarial densities and are of major concern in the context of mass ivermectin distributions organized in Africa for onchocerciasis and lymphatic filariasis control. As those SAEs are induced by the rapid and massive microfilaricidal effect of a standard dose of ivermectin (150 mu g/kg), we performed a randomized, controlled, double-blind trial to determine whether ivermectin given as: (a) a single tow dose of 1.5 mg (i.e. 25 mu g/kg for a 60 kg person); or (b) two doses of 1.5 mg given at a 2 week interval leads to a more progressive decrease in Loa microfilarial toads compared with the standard dosage. A tow dose of ivermectin brought about a significantly smaller decrease in Loa microfilaraemia than the standard dose. However, this decrease was not sufficiently different from that obtained after the standard dose to be acceptable to public health programmes, which require a wide safety margin. A second tow dose of ivermectin given 15 days after the first dose did not lead to a further decrease in Loa microfilaraemia. Lastly, the variability in the response observed in the group treated with 25 mu g/kg suggests that even lower doses would have no effect on a significant number of patients. Ivermectin given at a low dose (<= 25 mu g/kg) is probably not adequate to prevent the occurrence of post-treatment neurological SAEs. (c) 2007 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.