Plasma concentrations of pralidoxime methylsulphate in organophosphorus poisoned patients

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Abstract
Using pharmacokinetic data from healthy human volunteers in a bicompartmental pharmacokinetic model, a repeated dose scheme for pralidoxime methylsulphate (Contrathion®) was developed producing plasma levels remaining above the assumed “therapeutic concentration” of 4 mg·1−1. Using the same data, it was found that a concentration of 4 mg · 1−1 could also be obtained by a loading dose of 4.42 mg · kg−1 followed by a maintenance dose of 2.14 mg · kg−1 · h−1. In order to study the pharmacokinetic behaviour of pralidoxime in poisoned patients, this continuous infusion scheme was then applied in nine cases of organophosphorus poisoning (agents: ethyl parathion, ethyl and methyl parathion, dimethoate and bromophos), and the pralidoxime plasma levels were determined. The mean plasma levels obtained in the various patients varied between 2.12 and 9 mg·1−1. Pharmacokinetic data were calculated, giving a total body clearance of 0.57±0.271· kg−1· h−1 (mean ± SD), an elimination half-life of 3.44±0.90 h, and a volume of distribution of 2.77±1.451 ·kg−1.