Atracurium-receptor kinetics: simple behavior from a mixture

The apparent atracurium-receptor dissociation constant was assayed at the end-plate region of isolated guinea pig muscles. In a parallel series of experiments, the ED50 for producing neuromuscular block in the lumbrical muscle was also determined. The ratio of these two values was similar to the ratio found with classical competitive neuromuscular blocking agents like d-tubocurarine or pancuronium. We conclude that the commercial preparation of atracurium, though a mixture containing isomers of different configurations, behaves kinetically in a manner indistinguishable from what would be expected from a single substance.