ANALGESIC ACTIVITIES OF PEM-420, THE ACTIVE EUTOMER OF PEMEDOLAC

PEM-420, the active isomer of pemedolac, inhibited the writhing respon ses induced by phenylbenzoquinone (PBQ), acetic acid, and acetylcholin e in mice with ED50's of 0.80, 0.92, and 0.075 mg/kg p.o., respectivel y. In the rat acetic acid writhing assay, PEM-420 exhibited an ED50 va lue of 8.4 mg/kg p.o. In the Randall-Selitto test, PEM-420 raised the pain threshold of the yeast-injected paw (ED50 = 0.55 mg/kg p.o.). Lik e other NSAIDs, PEM-420 inhibited the PBQ-induced production of PGI2 a nd PGE2 in the mouse peritoneal cavity, with ED50 values of 0.5 and 1. 2 mg/kg p.o., respectively. It had weak ulcerogenic liability in rats (acute UD50 = 99 mg/kg p.o. in fasted rats; subacute UD50 = 74 mg/kg/d ay for 4 days in fed rats). The data indicate that PEM-420 is a potent and safe peripheral analgesic.