PHARMACODYNAMICS AND PHARMACOKINETICS OF CISATRACURIUM IN GERIATRIC SURGICAL PATIENTS

Background: Cisatracurium, one of ten stereoisomers that comprise atra curium, is more potent than atracurium and has less propensity to rele ase histamine. This study compares the pharmacokinetics and pharmacody namics 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-ti dal). 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 con centration versus time data were fit to compartmental models. Pharmaco kinetic parameters were determined assuming that elimination occurred from the central compartment only. This provides accurate clearance an d half-life estimates but underestimates V-ss (reported herein as V-ss '). The pharmacodynamic response was described by the neuromuscular bl ocking profile. Results: Onset to 90% paralysis (mean +/- SD) was dela yed in the elderly (3.4 +/- 1.0 vs. 2.5 +/- 0.6 min). Recovery profile s were the same for both groups. Elimination half-life was minimally p rolonged in the elderly (25.5 +/- 3.7 vs. 21.5 +/- 2.4 min). The V-ss' 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 . kg(-1). min(-1)). Conclusions: There are minor differ ences in the pharmacokinetics of clsatracurium between elderly and you ng patients. These differences are not associated with changes in reco very profile after a single bolus dose, although the mean time to onse t was approximately 1 min longer in elderly patients.