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Assessment of serum concentrations and sedative effects of fentanyl after transdermal administration at three dosages in healthy llamas

Tamara L. GrubbRiverview Animal Clinic, 2002 L Schultheis Rd, Uniontown, WA 99179.

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Jenifer R. GoldDepartment of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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John W. SchlipfDepartment of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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A. Morrie CraigDepartment of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Karen C. WalkerDepartment of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Thomas W. RieboldDepartment of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Abstract

Objective—To determine the serum concentrations and sedative effects of fentanyl after transdermal administration at 3 dosages in llamas.

Animals—9 healthy adult female llamas (mean age, 8 ± 3 years; mean weight, 150 ± 18 kg).

Procedure—Llamas were allocated to 1 of 3 groups (3 llamas/group). Fentanyl patches (each providing transdermal delivery of 75 µg of fentanyl/h) were placed on shaved areas of the antebrachium of all llamas. In group 1, llamas were treated with 1 patch (anticipated fentanyl dosage, 75 µg/h). In group 2, llamas were treated with 2 patches (anticipated fentanyl dosage, 150 µg/h). In group 3, llamas were treated with 4 patches (anticipated fentanyl dosage, 300 µg/h). For each llama, the degree of sedation was assessed by use of a subjective scoring system and a blood sample was collected for determination of serum fentanyl concentration at 12, 24, 36, 48, 60, and 72 hours after patch placement.

Results—Following the placement of 4 patches, mean ± SD serum fentanyl concentration in group 3 llamas reached 0.3 ± 0.08 ng/mL within 12 hours. This concentration was sustained for 72 hours. In group 2, application of 2 patches provided inconsistent results; in group 1, application of 1 patch rarely provided measurable serum fentanyl concentrations. No llamas became sedated at any time.

Conclusions and Clinical Relevance—Results suggest that application of four 75 µg/h fentanyl patches provides consistent, sustained serum fentanyl concentrations without sedation in llamas. However, the serum concentration of fentanyl that provides analgesia in llamas is not known. (Am J Vet Res 2005;66:907–909)

Abstract

Objective—To determine the serum concentrations and sedative effects of fentanyl after transdermal administration at 3 dosages in llamas.

Animals—9 healthy adult female llamas (mean age, 8 ± 3 years; mean weight, 150 ± 18 kg).

Procedure—Llamas were allocated to 1 of 3 groups (3 llamas/group). Fentanyl patches (each providing transdermal delivery of 75 µg of fentanyl/h) were placed on shaved areas of the antebrachium of all llamas. In group 1, llamas were treated with 1 patch (anticipated fentanyl dosage, 75 µg/h). In group 2, llamas were treated with 2 patches (anticipated fentanyl dosage, 150 µg/h). In group 3, llamas were treated with 4 patches (anticipated fentanyl dosage, 300 µg/h). For each llama, the degree of sedation was assessed by use of a subjective scoring system and a blood sample was collected for determination of serum fentanyl concentration at 12, 24, 36, 48, 60, and 72 hours after patch placement.

Results—Following the placement of 4 patches, mean ± SD serum fentanyl concentration in group 3 llamas reached 0.3 ± 0.08 ng/mL within 12 hours. This concentration was sustained for 72 hours. In group 2, application of 2 patches provided inconsistent results; in group 1, application of 1 patch rarely provided measurable serum fentanyl concentrations. No llamas became sedated at any time.

Conclusions and Clinical Relevance—Results suggest that application of four 75 µg/h fentanyl patches provides consistent, sustained serum fentanyl concentrations without sedation in llamas. However, the serum concentration of fentanyl that provides analgesia in llamas is not known. (Am J Vet Res 2005;66:907–909)