Disposition of transdermally administered fentanyl in dogs

Andrew E. Kyles From the Departments of Companion Animal and Special Species Medicine (Kyles, Hardie) and Anatomy. Physiological Sciences, and Radiology (Papich), College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough St, Raleigh NC 27606.

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 BVMS, PhD
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Mark Papich From the Departments of Companion Animal and Special Species Medicine (Kyles, Hardie) and Anatomy. Physiological Sciences, and Radiology (Papich), College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough St, Raleigh NC 27606.

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 DVM, MS
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Elizabeth M. Hardie From the Departments of Companion Animal and Special Species Medicine (Kyles, Hardie) and Anatomy. Physiological Sciences, and Radiology (Papich), College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough St, Raleigh NC 27606.

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 DVM, PhD

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Abstract

Objective

To evaluate the disposition of fentanyl after IV and transdermal administrations. The hypothesis was that transdermal administration of fentanyl would result in a measurable plasma opioid concentration.

Design

Each dog received 2 treatments in a randomized, crossover design.

Animals

6 clinically normal Beagles.

Procedure

2 treatments consisting of IV fentanyl (50 μg/kg of body weight) and transdermal fentanyl (50 μg/h) administrations. Plasma fentanyl concentrations were measured at fixed times, and pharmacokinetic values were calculated.

Results

Intravenous pharmacokinetics of fentanyl was similar to those previously described in dogs and provided the distribution and clearance data necessary to calculate the rate of absorption of the transdermally administered opioid. The transdermal fentanyl patch produced average steady-state concentrations of 1.6 ng/ml. The actual rate of delivery of transdermal fentanyl was 35.7 (range, 13.7 to 49.8) μg/h, which represented 71.48% (range, 27.45 to 99.56%) of the theoretical rate of delivery. The mean elimination half-life of fentanyl after patch removal was 1.39 hours.

Conclusions

Transdermally administered fentanyl resulted in fairly constant plasma concentrations, in the range generally considered to be analgesic, from 24 to 72 hours after application of the patch. The rate of drug delivery was less than expected, and there was substantial individual variation.

Clinical Relevance

Transdermally administered fentanyl has the potential to be a clinically useful analgesic regimen in dogs, and further evaluation of its analgesic actions and potential side effects is warranted. (Am J Vet Res 1996; 57:715–719)

Abstract

Objective

To evaluate the disposition of fentanyl after IV and transdermal administrations. The hypothesis was that transdermal administration of fentanyl would result in a measurable plasma opioid concentration.

Design

Each dog received 2 treatments in a randomized, crossover design.

Animals

6 clinically normal Beagles.

Procedure

2 treatments consisting of IV fentanyl (50 μg/kg of body weight) and transdermal fentanyl (50 μg/h) administrations. Plasma fentanyl concentrations were measured at fixed times, and pharmacokinetic values were calculated.

Results

Intravenous pharmacokinetics of fentanyl was similar to those previously described in dogs and provided the distribution and clearance data necessary to calculate the rate of absorption of the transdermally administered opioid. The transdermal fentanyl patch produced average steady-state concentrations of 1.6 ng/ml. The actual rate of delivery of transdermal fentanyl was 35.7 (range, 13.7 to 49.8) μg/h, which represented 71.48% (range, 27.45 to 99.56%) of the theoretical rate of delivery. The mean elimination half-life of fentanyl after patch removal was 1.39 hours.

Conclusions

Transdermally administered fentanyl resulted in fairly constant plasma concentrations, in the range generally considered to be analgesic, from 24 to 72 hours after application of the patch. The rate of drug delivery was less than expected, and there was substantial individual variation.

Clinical Relevance

Transdermally administered fentanyl has the potential to be a clinically useful analgesic regimen in dogs, and further evaluation of its analgesic actions and potential side effects is warranted. (Am J Vet Res 1996; 57:715–719)

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