Relationship between pharmacokinetics and the analgesic effect of indomethacin in the rat

The relationship between the pharmacokinetic properties and the analgesic effect of indomethacin (IDM) was evaluated on a carrageenin-induced inflammation model in the rat. Rats were administered the drug in one of two ways : intravenous (i.v.) IDM bolus or i.v. IDM infusion. The analgesic activity was measured by Randall-Selitto test. No correlation was observed between the analgesic effect and the plasma IDM concentration after i.v. bolus administration of IDM. However, in the case of infusion, IDM produced a dose-dependent analgesic effect. In this paper, we demonstrated that the plasma concentration of IDM maintained by i.v. infusion had a prolonged analgesic effect on the carrageenin-induced inflammation model.