Antagonism of non-steroidal anti-inflammatory drugs and narcotic analgesics against ethacrynic acid induced writhing.

Thiol-group reactive agents [alloxan, N-ethyimaleimide (NEM), ethacrynic acid, p-chlormercuribenzoate (PCMB)] were shown to induce a writhing syndrome in mice and rats when injected i.p. in appropriate dosage. Non-steroidal anti-inflammatory agents, narcotic analgesics and also psychotropic drugs inhibit the syndrome elicited in rats by ethacrynic acid. Rats pretreated with cysteine i.p. show a greatly reduced nociceptive response to ethacrynic acid or alloxan.