Pinadoline is a competitive PGE2 antagonist. It is an analgesic agent. Pinadoline demonstrated the antinociceptive activity in the rat using the writhing and the formalin tests. In the writhing test, pinadoline was significantly more potent than inhibitors of PG synthesis, but less potent than opiate analgesics. In the formalin test, pinadoline appeared less active than aspirin and ibuprofen and more active than acetaminophen. Pinadoline does not possess the antiinflammatory activity of aspirin and ibuprofen and may be more like acetaminophen, which had diminished antiinflammatory activity. At high concentrations, pinadoline is a non-competitive antagonist of serotonin in guinea-pig ileum.