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

The urinary excretion rates of dimethyl-phosphate, -phosphorothioate and -p hosphorodithioate were studied in six persons of whom four had ingested a c oncentrated solution of malathion and two of thiometon. The concentration d ecrease of single and total dimethylphosphorus metabolites was biphased, wi th a fast initial rate and a slow later rate. The excretion rate of total m etabolites in the faster phase depended on the initial concentration in uri ne. At concentrations higher than 100 nmol/mg creatinine, the excretion hal f-times ranged from 7.5 to 15.4 h and at concentrations between 52 and 95 n mol/mg creatinine from 34.7 to 55.4 h. Non-metabolized malathion was detect ed only in one urine sample collected from one person immediately after hos pitalization. Two persons poisoned with malathion were taken blood serum sa mples for the analysis of the parent pesticide and its metabolites on a dai ly basis after hospitalization. The parent pesticide was detectable in the serum only one day after the poisoning. The concentration of total malathio n dimethylphosphorus metabolites in serum decreased very quickly within 1.5 days after hospitalization. The total metabolite elimination half-times we re 4.1 and 4.7 h in the initial phase, and 53.3 and 69.3 days in the later slower elimination phase. There was no correlation between maximum concentr ations of total metabolites measured in serum and/or urine on the day of ad mission to hospital and the initial depression of serum cholinesterase (BCh E, EC 3.1.1.8) and erythrocyte acetylcholinesterase (AChE, EC 3.1.1.7). (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.