A comparative study of the efficacy and tolerability of single and split doses of ivermectin and diethylcarbamazine in periodic brugian filariasis

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Abstract
The use of ivermectin in lymphatic filariasis (both bancroftian and brugian) has been recently explored in several studies. We report in this paper, for the first time, a direct comparison of the efficacy and tolerability of single doses of ivermectin and diethylcarbamazine (DEC) in brugian filariasis. We also present our findings on the use of split doses of ivermectin and DEC on microfilaraemia levels and the occurrence of adverse reactions. Fifty male, asymptomatic microfilaraemics drawn from the Alleppey District, Kerala, India, were allocated one of the following five treatment regimens in a double blind randomized study: (1) single oral 6 mg/kg dose of DEC; (2) single oral 6 mg/kg dose of DEC preceded by 1 mg/kg DEC primer; (3) single oral 220 μg/kg dose of ivermectin; (4) single oral 200 μg/kg dose of ivermectin preceded by a 20 μg/kg ivermectin primer; or (5) a single oral 400 μg/kg dose of ivermectin preceded by a 20 μg/kg ivermectin primer. The kinetics of microfilaria clearance differed in the two (DEC/ivermectin) groups in the first month post-treatment. At the end of 1 year there were no differences in the microfilaria levels in the two DEC-tested groups and the 420 μg/kg ivermectin group. The safety of the 400 μg/kg dose of ivermectin was established in this study which has also shown that, currently, this dose would be the best choice for brugian filariasis. Patients in the ivermectin groups had significantly lower adverse reaction scores than patients who had received DEC. There was no advantage in splitting the dose of either DEC or ivermectin, either in terms of efficacy or tolerability. Lymphadenitis, lymphangitis or scrotal reactions, which were reported in previous studies to be indicative of a macrofilaricidal effect of anti-filarial drugs, were not observed in the present study. The ability of single doses of either ivermectin or DEC to achieve prolonged suppression of microfilaraemia (up to 1 year), as demonstrated in the present study, should be helpful in the design of better control strategies for lymphatic filariasis.