In vitro displacement of vasoactive mediators from plasma proteins: a possible mechanism for pseudo-allergic reactions to neuromuscular blocking drugs.

We have studied the release of prostaglandin F2 alpha (PGF2 alpha) and histamine from serum proteins by neuromuscular blocking drugs using equilibrium dialysis, with tracer quantities of radio-labelled mediators as probes. Small concentrations (0.05-0.25 mmol litre-1) of competitive neuromuscular blocking drugs displaced 16-67% of bound histamine. Greater concentrations of suxamethonium (2 mmol litre-1) were required for histamine displacement (19%). There was a significant release of PGF2 alpha by atracurium 1 mmol litre-1 and pancuronium 0.69 mmol litre-1. These findings suggest an alternative mechanism of histamine release by neuromuscular blocking drugs which may be relevant to adverse reactions during use.