Nondepolarizing Muscle Relaxants: Rocuronium

ROCURONIUM

Physical Structure

Th is monoquaternary steroid analogue of vecuroni-um was designed to provide a rapid onset of action.

Metabolism & Excretion

Rocuronium undergoes no metabolism and is eliminated primarily by the liver and slightly by the kidneys. Its duration of action is not signifi-cantly affected by renal disease, but it is modestlyprolonged by severe hepatic failure and pregnancy. Because rocuronium does not have active metabo-lites, it may be a better choice than vecuronium in the rare patient requiring prolonged infusions in the intensive care unit setting. Elderly patients may experience a prolonged duration of action due to decreased liver mass.

Dosage

Rocuronium is less potent than most other steroi-dal muscle relaxants (potency seems to be inversely related to speed of onset). It requires 0.45–0.9 mg/kg intravenously for intubation and 0.15 mg/kg boluses for maintenance. A lower dose of 0.4 mg/kg may allow reversal as soon as 25 min after intubation. Intramuscular rocuronium (1 mg/kg for infants; 2 mg/kg for children) provides adequate vocal cord and diaphragmatic paralysis for intuba-tion, but not until after 3–6 min (deltoid injection has a faster onset than quadriceps), and can be reversed after about 1 hr. The infusion requirements for rocuronium range from 5–12 mcg/kg/min. Rocuronium can produce a prolonged duration of action in elderly patients. Initial dosage require-ments are modestly increased in patients with advanced liver disease, presumably due to a larger volume of distribution.

Side Effects & Clinical Considerations

Rocuronium (at a dose of 0.9–1.2 mg/kg) has an onset of action that approaches succinyl-choline (60–90 s), making it a suitable alternative for rapid-sequence inductions, but at the cost of a much longer duration of action. This intermediate duration of action is comparable to vecuronium or atracurium.Rocuronium (0.1 mg/kg) has been shown to be a rapid (90 s) and effective agent (decreased fascicu-lations and postoperative myalgias) for precurariza-tion prior to administration of succinylcholine. It has slight vagolytic tendencies.