Plasma fentanyl concentrations and analgesic effects during full or partial exposure to transdermal fentanyl patches in cats

Dr. Charisse D. Davidson VetSurg Inc, 20051 Ventura Blvd, Ste I, Woodland Hills, CA 91364.

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 DVM, MS
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Glenn R. Pettifer Department of Anesthesiology and Pain Management, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

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 DVM, DVSc, DACVA
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Jack D. Henry Jr VetSurg Inc, 20051 Ventura Blvd, Ste I, Woodland Hills, CA 91364.

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 DVM, MS, DACVS

Abstract

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

Design—Randomized controlled clinical trial.

Animals—16 client-owned cats.

Procedure—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 and Clinical Relevance—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-μg/h TFP appears to provide adequate analgesia following ovariohysterectomy. (J Am Vet Med Assoc 2004:224:700–705)

Abstract

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

Design—Randomized controlled clinical trial.

Animals—16 client-owned cats.

Procedure—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 and Clinical Relevance—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-μg/h TFP appears to provide adequate analgesia following ovariohysterectomy. (J Am Vet Med Assoc 2004:224:700–705)

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