Ivermectin for the treatment of periodic malayan filariasis: a study of efficacy and side effects following a single oral dose and retreatment at six months.

Ivermectin, a new antifilarial drug and currently the drug of choice for the treatment of onchocerciasis, has been shown to be effective in bancroftian filariasis. We report here, for the first time, the efficacy and safety of the drug in the treatment of filariasis caused by periodic Brugia malayi. Sixty male, asymptomatic microfilaraemics of Alleppey district, Kerala, South India, received single oral doses of ivermectin in a double blind study. Four dosages were used: 20, 50, 100 and 200 micrograms kg-1 body weight. Clearance of microfilariae, which was not complete, began as early as 12 hours post-treatment and was maximal at the end of one month. Microfilaria levels began to rise thereafter and reached 20-50% of pretreatment levels at six months. The two higher doses (100 and 200 micrograms kg-1) were more effective in suppressing microfilaraemia at six months (P < 0.05). After six months, 32 patients were retreated using the same dose of ivermectin that they had received initially. The pattern of clearance was essentially similar to that seen during the first treatment phase and microfilaria levels were 10-35% of pretreatment levels at the end of the next six months. Twenty-eight individuals who were not retreated at six months continued to have increasing levels of microfilariae, reaching 60% of pretreatment levels at the end of the next six months. Side effects (such as fever, headache, myalgia), which were mild to moderate, were seen in most patients and were unrelated to the dose (P > 0.05) or pretreatment levels of microfilariae.(ABSTRACT TRUNCATED AT 250 WORDS)