The contribution of muscle relaxants to the advancement of anaesthetic practice: what is required of new compounds?

The introduction of each new muscle relaxant has advanced anaesthetic practice by trying to meet some perceived deficiency in the existing therapeutic armamentarium. Anaesthesiologists need agents which are appropriate to the duration of surgery: they prefer agents which are not subject to drug interaction, have no effect on cardiovascular function, which do not depend significantly on renal excretion, which are easy to reverse, and which have a rapid onset of action. In certain circumstances one of these requirements becomes overridingly important. The latest new addition, rocuronium, fills the gap for an agent with rapid onset while lacking the potentially adverse features of suxamethonium, retaining a medium duration of action and meeting the other requirements set out above as well as any existing agent.