Pharmacodynamics of non-depolarizing neuromuscular blocking agents.

When a clinical dose of a competitive neuromuscular blocking drug is given I.V. to a patient, a period of latency is followed by a progressive onset of blockade until a maximum is reached after several minutes. Thereafter, the intensity of block declines gradually. The precise relationship between the dose of drug and the time-course of the effect is complex, being dependent upon both pharmacokinetic and pharmacodynamic factors. Following an examination of pharmacokinetic factors (Miller, 1982), this short review considers the relationship between the plasma concentration of drug and the effect. Numerous studies have sought to elucidate this relationship, using a wide variety of agents and experimental techniques, but controversy still surrounds the mechanism involved (Kopman, 1980; Feldman, 1981; Stanski, 1981). Accepted concepts will be presented first, followed by those which are arguable or simply speculative.