Rapacuronium bromide (
rapacuronium;
ORG-9487) is a nondepolarising muscle relaxant (NMBA) with a low potency [90% effective dose (ED90) 1 mg/kg], which to some extent is responsible for its rapid onset of action. Because of the high plasma clearance (5.3 to 11.1 mg/kg/min) of
rapacuronium, its clinical duration of action following single bolus doses up to 2 mg/kg in adults is short (i.e. <20 minutes).
Rapacuronium forms a pharmacologically active 3-desacetyl metabolite,
ORG-9488, which may contribute to a delay in spontaneous recovery after repeat bolus doses or infusions. After
rapacuronium 1.5 mg/kg clinically acceptable intubating conditions are achieved within 60 to 90 seconds in the majority of adult and elderly patients undergoing elective anaesthesia. However, in a rapid-sequence setting. intubating conditions are less favourable after
rapacuronium 1.5 to 2.5 mg/kg than after
succinylcholine. The most prominent adverse effects of
rapacuronium (
tachycardia,
hypotension and
bronchospasm) are dose-related, and in particular pulmonary adverse effects are observed more frequently under conditions of a rapid-sequence induction in adults. Therefore, it seems worthwhile to consider only doses of
rapacuronium < or = 1.5 mg/kg to facilitate rapid tracheal intubation, and to use
succinylcholine or
rocuronium rather than
rapacuronium in a rapid-sequence setting.
Rapacuronium, however, is a suitable alternative to
mivacurium chloride (
mivacurium) and
succinylcholine for short procedures (e.g. ambulatory anaesthesia).
Rocuronium bromide (
rocuronium) is a relatively low-potent, intermediateacting NMBA. Its main advantage is the rapid onset of neuromuscular block whereby good or excellent intubating conditions are achieved within 60 to 90 seconds after
rocuronium 0.6 mg/kg (2 x ED95), and within 60 to 180 seconds after smaller doses (1 to 1.5 x ED95). Larger doses of
rocuronium (> or = 1 mg/kg) seem to be suitable for rapid-sequence induction under relatively light anaesthesia. However, it is still a matter of controversy whether, in the case of an unanticipated difficult intubation, the long duration of
rocuronium administered in such large doses outweighs the many adverse effects of
succinylcholine.
Rocuronium has mild vagolytic effects and does not release
histamine, even when administered in large doses.
Rocuronium is primarily eliminated via the liver and its pharmacokinetic profile is similar to that of
vecuronium bromide (
vecuronium). Unlike
vecuronium,
rocuronium has no metabolite.
Cisatracurium besilate (
cisatracurium), the IR-cis, 1'R-cis isomer of
atracurium besilate (
atracurium) is approximately 4 times more potent than
atracurium. The onset time of
cisatracurium is significantly slower than after equipotent doses of
atracurium. The recommended intubating dose is 0.15 to 0.2 mg/kg (3 to 4 times ED95). Over a wide range of clinically relevant doses the recovery properties of
cisatracurium are affected by neither the size of the bolus dose nor by the duration of infusion. Unlike
atracurium,
cisatracurium does not trigger histamine release. Like
atracurium,
cisatracurium undergoes Hofmann elimination. In contrast to
atracurium,
cisatracurium does not undergo hydrolysis by nonspecific plasma
esterases. Moreover, about 77% of the
drug is cleared by organ-dependent mechanisms.