Plasma fentanyl concentrations and analgesic effects during full or partial exposure to transdermal fentanyl patches in cats.
OBJECTIVE
To compare plasma fentanyl concentrations and analgesic efficacy during full or partial exposure to 25-microg/h transdermal fentanyl patches (TFPs) in cats undergoing ovariohysterectomy.


METHODS
Randomized controlled clinical trial.


METHODS
16 client-owned cats.


METHODS
Cats were randomly assigned to receive full or partial exposure to a TFP; patches were applied approximately 24 hours prior to ovariohysterectomy. Rectal temperature, heart rate, respiratory rate, blood glucose concentration, and blood pressure were measured and pain severity was assessed periodically for 72 hours after patch application. Venous blood samples were collected for determination of plasma fentanyl concentration 0, 6, 12, 18, 24, 36, 48, 60, and 72 hours after patch application.


RESULTS
Mean +/- SD steady state plasma fentanyl concentration in cats in the full TFP exposure group (1.78 +/- 0.92 ng/mL) was significantly greater than concentration in cats in the partial exposure group (1.14 +/- 0.86 ng/mL). Steady state plasma fentanyl concentrations were evident between 18 and 72 hours after patch application. Subjective scores used to evaluate analgesic efficacy were not significantly different between treatment groups.


CONCLUSIONS
Results suggest that delivery of fentanyl from TFPs can be reduced by decreasing the amount of exposed surface area. In cats weighing < 4 kg (9 lb), exposure to half a 25-microg/h TFP appears to provide adequate analgesia following ovariohysterectomy.
VetSurg Inc., 20051 Ventura Blvd, Ste I, Woodland Hills, CA 91364, USA.
Charisse D
CD
Davidson
Glenn R
GR
Pettifer
Jack D
JD
Henry
D000279:Administration, Cutaneous; D000698:Analgesia / Q000379:methods / Q000662:veterinary*; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000097:blood; D000818:Animals; D002415:Cats / Q000097:blood* / Q000502:physiology / Q000601:surgery; D004305:Dose-Response Relationship, Drug; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage* / Q000097:blood; D007044:Hysterectomy / Q000662:veterinary; D010052:Ovariectomy / Q000662:veterinary; D010147:Pain Measurement / Q000662:veterinary; D010149:Postoperative Pain / Q000517:prevention & control / Q000662:veterinary*; D016896:Treatment Outcome
D000701:Analgesics, Opioid; D005283:Fentanyl