Treatment of microfilaraemia in asymptomatic brugian filariasis: the efficacy and safety of the combination of single doses of ivermectin and diethylcarbamazine

Although combinations of ivermectin and diethylcarbamazine (DEC) have been shown to be superior to either drug alone in the suppression of bancroftian microfilariae, their efficacy against infections with Brugia malayi has never been investigated. The present, open trial is the first on the efficacy and safety of a combination of single doses of ivermectin and DEC when used against microfilaraemias of brugian filariasis. Twenty-one, asymptomatic but microfilaraemic (109-6934 microfilariae/ml blood, with a median of 841/ml) men, aged 18-48 years, each received oral doses of ivermectin (400 mu g/kg) and DEC (6 mg/kg) as a single treatment. Twelve hours post-treatment, 96.5%-100% of the microfilariae in each subject had been cleared and 12 of the subjects were amicrofilaraemic. A further reduction in microfilarial counts was evident 1 month post-treatment (mean clearance = 99.0%) and the counts continued to fall at least until the last follow-up, at 1 year post-treatment, when the mean clearance was 99.9% and 13 (68.4%) of the 19 subjects then investigated were amicrofilaraemic. All subjects experienced adverse reactions of one form or another, lasting for up to 48 h post-treatment; these included fever, myalgia, headache, and lethargy. Postural hypotension was recorded in two subjects and dilated, inflamed lymphatic channels were seen in another two. The combination of ivermectin and DEC demonstrated a microfilaricidal effect superior to that of either drug used alone, both in the initial rapid clearance of microfilariae and in sustaining the effect for 1 year. This finding has important implications for the control of lymphatic filariasis.