Postoperative analgesia with transdermal fentanyl following lower abdominal surgery.

In a randomised, placebo-controlled, double-blind study involving 81 patients undergoing total abdominal hysterectomy, the postoperative analgesia provided by transdermal fentanyl given at 25, 50, or 75 micrograms.h-1 for 72 h was compared with a placebo group. The efficacy of the Transdermal Therapeutic System was related to the rate of fentanyl delivery, higher rates being associated with significantly lower visual analogue pain scores (24, 20, 17 and 13, for placebo, 25, 50 and 75 micrograms.h-1 respectively) and reduced patient controlled analgesia morphine requirements (44, 38, 33 and 31 mg respectively). Patients' overall sedation scores were not increased by transdermal fentanyl, but respiratory rates decreased with higher transdermal fentanyl dosage.