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Dimethylphosphorus metabolites in serum and/or urine of persons poisoned by malathion or thiometon

The urinary excretion rates of dimethylphosphate, -phosphorothioate and -phosphorodithioate were studied in six persons of whom four had ingested a concentrated solution of malathion and two of thiometon. The concentration decrease of single and total dimethylphosphorus metabolites followed the first-order kinetics with the initial rate constant faster and the later one slower. The excretion rate of total metabolites in the faster phase depended on the their initial concentration in urine. At concentrations higher than 100 nmoles/mg of creatinine the excretion half-times ranged from 7.5 to 15.4 h and at lower concentrations from 40.3 to 55.4 h. Two persons poisoned by malathion were taken blood serum samples for the analysis of the parent pesticide and its metabolites on a daily basis after hospitalization. The parent pesticide was detectable in serum for only one day after the poisoning. The concentration of total malathion dimethylphosphorus metabolites in serum decreased very quickly within 0.5 day after hospitalization. The total metabolite elimination half-times were 4.1 and 4.7 h in the initial faster, and 53.3 and 69.3 days in the later slower elimination phase. There was no correlation between maximum concentrations of total metabolites measured in serum and/or urine on the day of admission to hospital and the initial depression of serum cholinesterase (BChE, EC 3.1.1.8) and erythrocyte acetylcholinesterase (AChE, EC 3.1.1.7).

Dimethyl phosphate; dimethyl phosphorothioate; dimethyl phosphorodithioate; kinetics of elimination from blood and urine

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