Effect of metrifonate on blood cholinesterases in children during the treatment of schistosomiasis.

In a controlled clinical trial, Tanzanian schoolchildren with urinary schistosomiasis, many of whom had coexisting hookworm infection, were randomly allocated to one of three groups that were treated with doses of 7.5, 10.0, and 12.5 mg per kg of body weight, respectively, of metrifonate, orally, up to 3 times at 14-day intervals. No serious side effects were observed during or after the administration of single or repeated doses. A few hours after medication, plasma cholinesterase was almost completely inhibited, regardless of the dose given, while erythrocyte cholinesterase was almost completely inhibited, regardless of the dose given, while erythrocyte cholinesterase was inhibited down to 40-60% of the pretreatment level, depending on the dose. Plasma cholinesterase was inhibited to a greater extent than erythrocyte cholinesterase but showed a more rapid recovery of activity. A moderate accumulation of unreactivated erythrocyte cholinesterase occurred at all dose levels with this regime. Four weeks after the last dose of drug, plasma cholinesterase activity was nearly normal in all the treated children. Erythrocyte cholinesterase activity returned to normal 8-15 weeks after the last dose. The therapeutic results confirmed the efficacy of metrifonate against Schistosoma haematobium. There was an additional though less striking effect against hookworm.