The kinetics of 14C-GR43175 in rat and dog.

GR43175 is a selective 5-HT 1-like receptor agonist which is effective in the acute treatment of migraine. Rats and dogs were dosed intravenously (iv) and orally (po) with 1 mg 14C-GR43175 base (as succinate salt)/kg bodyweight. GR43175 is rapidly absorbed after oral dosing. In dog, 95-100% of the dose is absorbed, but less (25-30%) is absorbed by the rat. The bioavailability is greater than 54% in dog, but lower in rat. Except for the CNS, drug-related material is widely distributed after iv dosing, but is mainly concentrated in the gastrointestinal tract and excretory organs after oral dosing. GR43175 is eliminated from plasma by a combination of renal and metabolic clearance. Some first-pass metabolism occurs in both species. In dog the major route of excretion is in urine (78-83% of the dose) after either route of administration. In rat, urine is also the major route of excretion (71%) after iv dosing. After oral dosing to the rat the major route of excretion is in the faeces (83%). GR43175 is extensively metabolized, after either route of administration, in both species. GR49336, the indole acetic acid derivative of GR43175, is the major metabolite in dog and a major metabolite in rat.