Transdermal fentanyl against postoperative pain

60 patients (ASA class I-II) undergoing knee arthrotomy received in a double blind fashion, a transdermal drug delivery system, containing either fentanyl (delivery rate of 75 micrograms/hour)--Fentanyl TTS--or placebo. The system remained in place for 24 hours. Even when piritramid was added as escape analgesia, all respiratory and hemodynamic parameters, as well as blood gas analysis showed no statistical significant difference between both groups (fentanyl or placebo). One patient had evidence of a beginning respiratory depression, but no specific therapy was needed. No significant side effects were seen. Concerning escape medication, a highly statistically significant difference in favour of Fentanyl TTS was found (p less than 0.001).