Evaluation of transdermal fentanyl patches for analgesia in cats undergoing onychectomy

Objective-To evaluate efficacy and safety of using transdermal fentanyl pat ches (TFP) for analgesia in cats undergoing onychectomy. Design-Randomized controlled clinical trial. Animals-45 client-owned cats weighing greater than or equal to 2.7 kg (5.9 lb) undergoing onychectomy, onychectomy and ovariohysterectomy, or onychect omy and castration. Procedure-Cats were randomly assigned to be treated with a TFP (25 mu g/h) or butorphanol; TFP were applied a minimum of 4 hours before surgery (appro x 8 hours prior to extubation). Rectal temperature, heart rate, respiratory rate, force applied by the forelimbs, and serum fentanyl concentration wer e measured, and temperament, recovery, degree of sedation. severity of pain , severity of lameness, and appetite were scored before and periodically fo r up to 40 hours after surgery. Results-Cats treated with a TFP had better recovery scores at 2 of 4 evalua tion times, lower sedation scores at 2 of 8 evaluation times, and lower pai n scores at 6 of 8 evaluation times, compared with cats treated with butorp hanol. Use of a pressure-sensitive mat to evaluate force applied by the for elimbs did not reveal any differences between groups but did reveal a signi ficant difference between preoperative and postoperative values. Mean +/- S D serum fentanyl concentrations were 1.56 +/- 1.08, 4.85 +/- 2.38, 4.87 +/- 1.56, and 4.35 +/- 2.97 ng/ml approximately 8, 24, 32, and 48 hours, respe ctively, after TFP placement. Conclusions and Clinical Relevance-Results suggest that use of a TFP (25 mu g/h) for postoperative analgesia in cats undergoing onychectomy with or wi thout surgical sterilization is safe and effective.