The analgesic activity of imidazopyridine derivatives.

Analgesic and antipyretic activities of 2-(4-(2-imidazo-[1,2-a]pyridylphenyl)propionic acid (Y-9213) were studied with various experimental models. The analgesic activity of Y-9213 was found to be more potent than that of indometacin and morphine in the silver nitrate, Randall-Selitto, and phenylquinone writhing tests. Y-9213 also showed an analgesia in the tail pinch and electric stimulation test. On the warm water induced foot withdrawal reflex, Y-9213 was more effective in spinal-sectioned mice than in intact mice similarly to mephenesin and diazepam. Y-9213 was also proved to possess antipyretic activity as potent as indometacin and to be devoid of morphine-like property. Y-9213 exhibited little effect on the respiration and cardiovascular system in dogs. Y-9213 was found to be rapidly absorbed and eliminated from the blood with a half-life of about 2.5 h in rats. These findings indicate that Y-9213 may be an effective and well tolerated antipyretic and analgesic agent.