Objective—To evaluate efficacy and safety of using
transdermal fentanyl patches (TFP) for analgesia in
cats undergoing onychectomy.
Design—Randomized controlled clinical trial.
Animals—45 client-owned cats weighing ≥ 2.7 kg
(5.9 lb) undergoing onychectomy, onychectomy and
ovariohysterectomy, or onychectomy and castration.
Procedure—Cats were randomly assigned to be
treated with a TFP (25 µg/h) or butorphanol; TFP were
applied a minimum of 4 hours before surgery (approx
8 hours prior to extubation). Rectal temperature, heart
rate, respiratory rate, force applied by the forelimbs,
and serum fentanyl concentration were measured,
and temperament, recovery, degree of sedation,
severity of pain, severity of lameness, and appetite
were scored before and periodically for up to 40 hours
Results—Cats treated with a TFP had better recovery
scores at 2 of 4 evaluation times, lower sedation
scores at 2 of 8 evaluation times, and lower pain
scores at 6 of 8 evaluation times, compared with cats
treated with butorphanol. Use of a pressure-sensitive
mat to evaluate force applied by the forelimbs did not
reveal any differences between groups but did reveal
a significant difference between preoperative and
postoperative values. Mean ± SD 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, respectively, after TFP placement.
Conclusion and Clinical Relevance—Results suggest
that use of a TFP (25 µg/h) for postoperative analgesia
in cats undergoing onychectomy with or without
surgical sterilization is safe and effective. (J Am
Vet Med Assoc 2000;217:1013–1020)