The fate of the rodenticide flocoumafen in the rat: Retention and elimination of a single oral dose

A single oral dose of 0.14 mg kg^?1 of ¹⁴C] flocoumafen to rat, which gave a transient, non-lethal, effect, was rapidly absorbed, radioactivity appearing in the blood maximally at 4 h and falling to half maximum value by 8 h. The maximum effect on prothrombin time was at 24 h and the value returned to normal by 48 h. Elimination of radioactivity was very slow, with less than 0.5% of the dose in the urine up to 7 days after dosing, and 23-26% in the faeces (more than half of which appeared in the first 24 h). Most of the administered radioactivity (74-76%) was retained 7 days after dosing. Approximately half of the dose was in the liver; it was eliminated with a halflife of 220 days. At 48 h after dosing, most of the hepatic radioactivity comprised unchanged flocoumafen. Treatments of flocoumafen-dosed rats with warfarin or with cytochrome P450-inducing doses of phenobarbitone were without effect on the hepatic residue of flocoumafen.