Suprofen, a potent antagonist of acetic acid-induced writhing in rats.

A new standardized acetic acid-induced writhing test in rats is described in detail and its methodology is discussed briefly. The described method has proved to be useful for evaluating the anti-writhing activity of narcotic analgesics, non-narcotic anti-inflammatory compounds and narcotic-antagonists with analgesic activity. A direct quantitative comparison of anti-writhing activity was made between orally administered acetyl-salicylic acid, phenylbutazone, indometacin, tolmetin, ketoprofen and alpha-methyl-4-(2-thienylcarbonyl)benzeneacetic acid (suprofen) in a specially designed experiment. Among the known non-narcotic, non-steroidal anti-inflammatory compounds suprofen appeared to be the most potent antagonist of acetic acid-induced writhing in rats, about 200 to 300 times as potent as acetyl-salicylic acid and phenylbutazone, 15 to 30 times as potent as indometacin and tolmetin, and about 6 times as potent as ketoprofen.