Distribution, Elimination, and Action of Vecuronium in the Elderly

The effects of age on the pharmacokinetics and pharmacodynamics of vecuronium in eight elderly patients aged 72–86 yr and eight younger adults aged 26–48 yr undergoing elective surgical procedures under nitrous oxide-fentanyl anesthesia were studied. Vecuronium (0.1 mg/kg) was given as an intravenous bolus, and the ulnar nerve was stimulated with a square-wave impulse of 0.2-ms duration. The response to stimulation at a frequency of 0.1 Hz was measured and recorded with a force displacement transducer applied to the thumb. Spontaneous recovery was significantly longer in elderly patients than in younger patients (50% recovery time, 97.1 ± 29 vs 39.8 ± 14 min, mean ± SD; recovery index [25%−75%], 49.4 ± 11 vs 15.0 ± 8 min). In addition, in elderly patients elimination half-life of vecuronium was significantly prolonged (125 ± 55 vs 78 ± 21 min, P = 0.04) and plasma clearance reduced (2.6 ± 0.6 vs 5.6 ± 3.2 mL·kg·min, P = 0.049). The prolonged duration of action of vecuronium in the elderly surgical patients thus appears to be secondary to altered pharmacokinetics consistent with an age-related decrease in renal and hepatic functions.