Pharmacokinetics of [14C]-atrazine in rhesus monkeys, single-dose intravenous and oral administration

This is the first study regarding the pharmacokinetics of [C-14]-atrazine conducted with rhesus monkeys. The animals received one dose (0.25 mg) intravenously (IV) or three doses (1, 10, or 100 mg) orally. Plasma, urine, and feces were collected at defined times up to 7 days post-dosing. Sample radioactivity was measured to determine the mass equivalent. IV administered [C-14]-atrazine disappeared rapidly from blood, with an elimination half-life of about 5.5 +/- 1.1 h. The pharmacokinetic profiles of [C-14]-atrazine following oral administration at the three dose levels show that kinetic parameters such as AUC and C-max are linearly correlated with the dose. Seven days after dosing, urinary and fecal excretion of [C-14]-atrazine reached 99% of total administered dose in the IV group and 91-95% in the three oral dose groups. In the IV-administered monkeys, approximately 85% of the dose was excreted in urine and 12% in feces. In three oral dose groups, urinary and fecal radioactivity recoveries approximated 57% and 21%, 58% and 25%, and 53% and 35%, respectively. More than 50% of the total urinary excreted radioactivity was found within the first 24 h after dosing. In conclusion, the principal elimination of [C-14]-atrazine, IV and orally administered, is via urine. The oral bioavailability was 60% or higher. There was a significant linear correlation between administered oral dose and plasma concentration. Overall oral dose accountability ranged from 91% to 95%. Data generated may be useful in the risk assessment of human exposure to environmental atrazine contamination.