Pharmacodynamics and Pharmacokinetics of Cisatracurium in Geriatric Surgical Patients

Background: Cisatracurium, one of ten stereoisomers that comprise atracurium, is more potent than atracurium and has less propensity to release histamine. This study compares the pharmacokinetics and pharmacodynamics of cisatracurium in elderly and young patients.

Methods: Twelve elderly (aged 65-82 yr) and 12 younger patients (aged 30-49 yr) were anesthetized with nitrous oxide, fentanyl, and isoflurane (0.7%, end-tidal). The mechanomyographic response to train-of-four stimulation was assessed every 15 s after the administration of cisatracurium (0.1 mg/kg). Arterial samples were obtained over 6 h. Plasma cisatracurium concentration versus time data were fit to compartmental models. Pharmacokinetic parameters were determined assuming that elimination occurred from the central compartment only. This provides accurate clearance and half-life estimates but underestimates Vss (reported herein as Vss '). The pharmacodynamic response was described by the neuromuscular blocking profile.

Results: Onset to 90% paralysis (mean+/-SD) was delayed in the elderly (3.4+/-1.0 vs. 2.5+/-0.6 min). Recovery profiles were the same for both groups. Elimination half-life was minimally prolonged in the elderly (25.5+/-3.7 vs. 21.5 +/-2.4 min). The Vss ' was larger in the elderly (126 +/-16 vs. 108+/-13 ml/kg), although the clearances were the same for the two groups (5.0+/-0.9 vs. 4.6+/-0.8 ml *symbol* kg sup -1 *symbol* min sup -1).