10 New muscle relaxants

Summary In a little over 10 years, six new muscle relaxants have been introduced into clinical practice. The first two, the intermediate-duration vecuronium and atracurium were outstanding drugs and clearly an advance over the long-acting drugs which had been available previously. The next two, the long-acting doxacurium and pipecuronium were relics of an earlier era, and have made little clinical impact. Mivacurium created a new class, the short-acting nondepolarizer, and caused succinylcholine to be reclassified as an ultrashort-acting drug. However, mivacurium has neither the rapid onset nor the ultrashort duration of succinylcholine and is to some extent still trying to establish a significant clinical role. Rocuronium is the first non-depolarizer to have an onset approaching that of succinylcholine, and has spurred the development of drugs of low potency. It is likely that we will see the introduction of at least two more drugs, ORG 9487 and 51W89 by the end of this decade, but the goal of a nondepolarizing relaxant which is a complete replacement for succinylcholine still seems some distance in the future.