Effect of high concentrations of non-steroidal and steroidal antiinflammatory drugs on prostaglandin-induced contractions of the guinea-pig isolated ileum.

In addition to their well-known effect at low concentrations on prostaglandin synthesis or their release and production, 11 non-steroidal antiinflammatory drugs and 4 antiinflammatory steroids exhibit at high concentrations a direct antagonism on certain prostaglandin actions. This is demonstrated on PGE1- and PGF2alpha-induced contractions of guinea-pig isolated ileum when compared to acetylcholine-induced contractions. This inhibitory effect is totally reversible after washing out the drugs from the organ bath.