Perioperative pharmacokinetics of transdermal fentanyl in elderly and young adult patients.

The perioperative pharmacokinetics of transdermally-delivered fentanyl were compared in 10 young adult (mean [range] age 32.7, [25-38] yr) and eight elderly (mean [range] age 73.7 [64-82] yr) patients following abdominal surgery. Transdermal fentanyl patches designed to release 50 micrograms h-1 were applied 2 h preoperatively and left in place for 72 h. Plasma fentanyl concentrations were measured by radioimmunoassay during patch application and for 30 h after patch removal. The mean half-time (time for plasma concentrations to double after patch application) was 4.2 h in the younger group and 11.1 h in the elderly group (P < 0.005). Mean maximum plasma concentrations were 1.9 ng ml-1 and 1.5 ng ml-1 in the younger and elderly groups respectively (ns). There were no differences in the time at which maximum plasma concentrations occurred (tmax), elimination half-life after patch removal, or AUC(0-infinity).