Nondepolarizing Muscle Relaxants: Cisatracurium

CISATRACURIUM

Physical Structure

Cisatracurium is a stereoisomer of atracurium that is four times more potent. Atracurium contains approximately 15% cisatracurium.

Metabolism & Excretion

Like  atracurium,  cisatracurium  undergoes degradation in plasma at physiological pH and temperature by organ-independent Hofmann elimination. The resulting metabolites (a mono-quaternary acrylate and laudanosine) have no neuromuscular blocking effects. Because of cisatra-curium’s greater potency, the amount of laudanosine produced for the same extent and duration of neu-romuscular blockade is much less than with atra-curium. Nonspecific esterases are not involved in the metabolism of cisatracurium. Metabolism and elimination are independent of renal or liver failure. Minor variations in pharmacokinetic patterns due to age result in no clinically important changes in duration of action.

Dosage

Cisatracurium produces good intubating conditions following a dose of 0.1–0.15 mg/kg within 2 min and results in muscle blockade of intermediate duration. The typical maintenance infusion rate ranges from 1.0–2.0 mcg/kg/min. Thus, it is more potent than atracurium.

Cisatracurium should be stored under refrig-eration (2–8°C) and should be used within 21 days after removal from refrigeration and exposure to room temperature.

Side Effects & Clinical Considerations

Unlike atracurium, cisatracurium does not pro-duce a consistent, dose-dependent increase in plasma histamine levels following administration. Cisatracurium does not alter heart rate or blood pressure, nor does it produce autonomic effects, even at doses as high as eight times ED₉₅.

Cisatracurium shares with atracurium the pro-duction of laudanosine, pH and temperature sensi-tivity, and chemical incompatibility.