A test for analgesics: incoordination in writhing mice.

Acetic acid administered to mice resulted in post-writhing incoordination and a subsequent fall in the rota-rod test. This fall from rota-rod induced by 3% acetic acid was dose-dependently protected by the non-narcotic analgesics. While suprofen was found to be the most potent (ED50 = 15.29 mg/kg), aspirin was found to be the least potent (ED50 = 81.54 mg/kg). The model appears to be more sensitive than the conventional methods for testing non-narcotic analgesics.