Diethylphosphorus metabolites in serum and urine of persons poisoned by phosalone

The presence and elimination rate of phosalone and its diethylphosphorus metabolites in blood serum and urine were studied in persons who had ingested a concentrated phosalone solution. Phosalone was detected only in serum samples. As it was rapidly hydrolysed and eliminated from the body, its diethylphosphorus metabolites were a more sensitive indicator of exposure. The concentration decrease of phosalone in serum and of total diethylphosphorus metabolites in serum and urine followed the kinetics of a biphasic reaction. The faster elimination half-times in serum, calculated for two persons, were 2.3 and 3.4 h for phosalone and 3.4 and 38.6 h for total diethylphosphorus metabolites. In the faster phase the average elimination half-time of total urinary metabolites in five persons was 25 +/- 17 h. The kinetic data for total urinary metabolites in a person occupationally exposed to phosalone indicated an early and very fast elimination phase (elimination half-time 1.3 h), which was overlooked in poisoned persons. The proportions of single metabolites in total urinary metabolites in poisoned persons depended on whether the total amount of diethylphosphorus metabolites was above 1000 or below 1000 nmol/mg creatinine. Diethylphosphorodithioate predominated at high and diethylphosphate at low concentrations of total metabolites. The correlation between the maximum concentrations of total metabolites, measured in urine of poisoned persons on the day of admission to hospital or a day later, and the initial depression of serum cholinesterase (EC 3.1.1.8) and erythrocyte acetylcholinesterase (EC 3.1.1.7) activities was poor (r = 0.6).