PANCURONIUM
Pancuronium consists of a steroid ring
on which two modified ACh molecules are positioned (a bisquater-nary relaxant).
The steroid ring serves as a “spacer” between the two quaternary amines.
Pancuroniumresembles ACh enough to bind (but not activate) the nicotinic ACh
receptor.
Pancuronium is metabolized
(deacetylated) by the liver to a limited degree. Its metabolic products have
some neuromuscular blocking activity. Excretion is primarily renal (40%),
although some of the drug is cleared by the bile (10%). Not surprisingly,
elimina-tion of pancuronium is slowed and neuromuscular blockade is prolonged
by renal failure. Patients with cirrhosis may require a larger initial dose due
to an increased volume of distribution but have reduced maintenance
requirements because of a decreased rate of plasma clearance.
A dose of 0.08–0.12 mg/kg of pancuronium
pro-vides adequate relaxation for intubation in 2–3 min. Intraoperative
relaxation is achieved by administer-ing 0.04 mg/kg initially followed every
20–40 min by 0.01 mg/kg.Children may require moderately larger doses of
pancuronium. Pancuronium is available as a solu-tion of 1 or 2 mg/mL and is
stored at 2–8°C but may be stable for up to 6 months
at normal room temperature.
Th ese
cardiovascular effects are
causedby the combination of vagal blockade andsympathetic stimulation.
The latter is due to a combination of ganglionic stimulation, catechol-amine
release from adrenergic nerve endings, and decreased catecholamine reuptake.
Large bolus doses of pancuronium should be given with cau-tion to patients in
whom an increased heart rate would be particularly detrimental (eg, coronary
artery disease, hypertrophic cardiomyopathy, aor-tic stenosis).
Increased atrioventricular conduction
and catechol-amine release increase the likelihood of ventricular arrhythmias
in predisposed individuals. The com-bination of pancuronium, tricyclic
antidepressants,and halothane has been reported to be particularly
arrhythmogenic.
Patients who are hypersensitive to
bromides may exhibit allergic reactions to pancuronium (pan-curonium bromide).
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