Atropine substitutes and the writhing syndrome in mice

The mouse writhing test has been used to evaluate analgesic drugs. In the present work the protective effect of atropine sulfate and eight of its substitutes was studied against acetic acid-induced writhing in mice. This was compared with the protection afforded by noramidopyrine, a non-narcotic analgesic. Both the time of onset of writhing and the number of writhes over a period of 15 min was recorded. The results seem to indicate some correlation between chemical structure and protective effect. Dicyclomine hydrochloride and orphenadrine hydrochloride produced an effect comparable with that of noramidopyrine, while atropine sulphate, oxyphenonium bromide and piperidolate hydrochloride were less potent. Homatropine methylbromide, mepenzolate methylbromide, amprotropine phosphate and penthienate bromide were ineffective.