Single doses of polyvinylchloride resin formulations of dichlorvos, placebo, or reference drugs were administered orally 2 hours before breakfast to 705 adults found to be harboring 1,361 infections of Trichuris, hookworm, or Ascaris, or all three. Six or twelve mg per kilogram of body weight of dichlorvos resulted in the following infection cure rates as determined by serial stool examinations up to 1 month after treatment: Trichuris infections, 85–94%; hookworm infections, 77–100%; and Ascaris infections, 72–100%. These same doses resulted in the following patient-cure rates: single worm infections as above. Trichuris-hookworm and Trichuris-Ascaris combination, 68–97%; and those patients in whom all three worm infections were present, 62–67%. Minimum to modest depression of the plasma cholinesterase activity and minimum to no depression of the erythrocyte cholinesterase activity were observed at these two levels. No clinical symptoms or significant alterations in the monitoring laboratory studies were noted. Trichuricidal action, broad-spectrum anthelmintic activity, and good tolerance upon single dosage support its potential value in anthelmintic therapy.
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