Understanding potential drug interactions of multiple drug therapy influences the induction agents chosen for an individual patient. The use of muscle relaxants is a common aspect of modern anesthesia practice. Succinylcholine, a depolarizing agent, has been used since 1952 but due has numerous adverse side effects. Non-depolarizing neuromuscular blocking agents achieve the same efficacy as succinylcholine without the adverse effects. Rocuronium, an intermediate acting non-depolarizer, provides an alternative for intubation when succinyicholine is not recommended. Rapacuronium, approved in 1999, has a shorter onset and duration of action than rocuromum. The goal of this study was to determine whether the duration of action of rocuronium is affected by the prior administration of rapacuronium or succmylcholine. Quantitative data was obtained from 30 volunteers randomly placed in two groups. For induction, Group A received succinyicholine and Group B received rapacuronium. Both groups received rocuronium for maintenance.