Decrease in Vecuronium Infusion Dose Requirements by Nicardipine in Humans

This study was designed to analyze quantitatively the interaction of nicardipine with vecuronium using a constant infusion technique. Forty-seven patients undergoing elective otolaryngeal surgery were anesthetized with isoflurane (1% end-tidal) and nitrous oxide (67%). Patients were randomly assigned to receive one of four doses of nicardipine (0, 1, 2, and 3 micrograms.kg-1.min-1). Vecuronium infusion dose requirement was determined as a constant infusion rate which maintained 90% depression of control twitch tension. Nicardipine significantly decreased the vecuronium requirement in a dose-dependent manner, i.e., the vecuronium doses were 0.70 +/- 0.03, 0.55 +/- 0.04, 0.42 +/- 0.04, and 0.37 +/- 0.05 micrograms.kg-1.min-1 at nicardipine doses of 0, 1, 2, and 3 micrograms.kg-1.min-1, respectively. Nicardipine also reduced both the plasma concentration of vecuronium to maintain the 90% depression and the total plasma clearance of vecuronium. The reversal of the vecuronium effect with neostigmine was not influenced by nicardipine. The results indicate that the vecuronium infusion dose requirements are reduced as much as 53% by a clinical dose of nicardipine.