The need for a rapid-acting non-depolarizing neuromuscular blocking agent with a short duration of action resulted in the synthesis of rapacuronium. The onset of maximum block with rapacuronium occurs in 60–90 s with doses of 1.5–2.5 mg kg−1 with a duration of clinical relaxation of 15–30 min. Rapacuronium provides clinically acceptable intubating conditions in 60 s in a majority of patients with these doses, although the conditions are somewhat inferior to those obtained with succinylcholine in lightly anaesthetized patients, such as those undergoing a rapid-sequence induction. The main drawbacks of rapacuronium are the occurrence of dose-related pulmonary side-effects (increased airway pressure and/or overt bronchospasm) and hypotension and tachycardia. The cause of pulmonary side-effects is not certain but these have been serious enough to make its worldwide introduction doubtful.