Muscle relaxants: a clinical update

The new nondepolarizing muscle relaxant rocuronium belongs to the chemical group of aminosteroidal muscle relaxants and is similar to vecuronium in its chemical structure and pharmacologic action. The principal clinical advantage of rocuronium over vecuronium is the short time to onset of the neuromuscular block. The two other new muscle relaxants, mivacurium and cis-atracurium, belong to the group of benzylisoquinoline muscle relaxants. Mivacurium is rapidly degraded in plasma and its principal characteristic is, hence, a short duration of action. Cis-atracurium is one of the 10 stereoisomers of atracurium. While its action is similar to that of atracurium, it does not release histamine and its administration is not accompanied by marked changes in blood pressure or heart rate. Even the simple tactile monitoring of the neuromuscular transmission enables the clinician to adjust the doses of these and other muscle relaxants to the needs of individual patients. Precise adjustment of the doses of muscle relaxants contributes to their safer clinical use by avoiding an excessively deep and unnecessarily prolonged neuromuscular block.