Ivermectin Plus Diethylcarbamazine: An Additive Effect on Early Microfilarial Clearance

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  • Institut Territorial de Recherches Medicales Louis Malarde, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Papeete, Tahiti, French Polynesia

The effects of ivermectin, diethylcarbamazine (DEC), and the combination of both drugs on levels of microfilaremia (mf) were studied in 30 male Polynesian Wuchereria bancrofti carriers. Microfilarial densities were measured 30 min (H1/2), 1 hr (H1), and 2, 4, 8, 24, and 96 hr (H2, H4, H8, H24, and H96) after supervised single doses of ivermectin plus DEC (400 µg/kg plus 1 mg/kg, respectively, 400 µg/kg plus 3 mg/kg, respectively, and 400 µg/kg plus 6 mg/kg, respectively), DEC (6 mg/kg) alone, and ivermectin (400 µg/kg and 100 µg/kg, respectively) alone given to six groups of five patients each. The results showed that 1) DEC alone or combined with ivermectin induced a rapid clearance of mf after drug intake; at H1/2, the number of circulating microfilariae was reduced to 16%, 8%, 28%, and 31%, respectively, of pretreatment values in the groups receiving ivermectin plus DEC (400 µg/kg plus 1 mg/kg, 400 µg/kg plus 3 mg/kg, and 400 µg/kg plus 6 mg/kg) and DEC (6 mg/kg) alone; 2) ivermectin alone induced a rapid increase of mf densities during the first 2 hr, followed by a sharp decrease from H4 to H96; and 3) between H8 and H96, mf clearance was almost complete with the combination of ivermectin and DEC. A comparison among groups did not show any synergistic interaction between ivermectin and DEC on the clearance of microfilaria, with the effect of each drug being additive to each another.