Interactions of diisopropyl phenol (ICI 35868) with suxamethonium, vecuronium and pancuronium in vitro.

In vitro studies were performed using the rat phrenic nerve-hemidiaphragm preparation to investigate possible interactions between diisopropyl phenol and its solvent, cremophor, with three neuromuscular blocking drugs. Cumulative concentration curves were constructed for the neuromuscular blockers and linear regression analyses performed. Differences in the calculated effective concentration to produce a 50% decrease in twitch height (EC50) and slope showed that diisopropyl phenol potentiated the action of suxamethonium, vecuronium (Org NC 45) and pancuronium. Cremophor potentiated the action of suxamethonium but antagonized the action of the non-depolarizing neuromuscular blockers. The possible mechanisms of action are discussed.