Transdermal absorption of a liposomeencapsulated formulation of lidocaine following topical administration in cats

Boel A. Fransson Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.

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Kenneth E. Peck Drug Testing Laboratory, Texas Veterinary Medical Diagnostic Laboratory, Texas A&M University, College Station, TX 77843.

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Jennifer K. Smith Drug Testing Laboratory, Texas Veterinary Medical Diagnostic Laboratory, Texas A&M University, College Station, TX 77843.

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Janice A. Anthony Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.

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Katrina L. Mealey Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.

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Abstract

Objective—To determine plasma disposition after dermal application of a liposome-encapsulated formulation of lidocaine in cats.

Animals—6 healthy adult cats with a mean (± SD) body weight of 4.1 ± 0.44 kg.

Procedure—CBC determination and biochemical analysis of blood samples were performed for all cats. Cats were anesthetized by use of isoflurane, and catheters were placed IV in a central vein. The next day, blood samples were obtained from the catheters before and 1, 2, 3, 4, 6, 8, 10, 12, and 24 hours after applying a 4% liposome-encapsulated lidocaine cream (15 mg/kg) to a clipped area over the cephalic vein. Plasma concentrations of lidocaine were analyzed with a high-performance liquid chromatography assay.

Results—Two cats had minimal transdermal absorption of lidocaine, with lidocaine concentrations below the sensitivity of the assay at all but 1 or 2 time points. In the other 4 cats, the median maximum plasma concentration was 149.5 ng/ml, the median time to maximum plasma concentration was 2 hours, and the median area under the concentration versus time curve from zero to infinity was 1014.5 ng·h/ml.

Conclusions and Clinical Relevance—Maximum plasma concentrations of lidocaine remained substantially below toxic plasma concentrations for cats. On the basis of these data, topical administration of a liposome-encapsulated lidocaine formulation at a dose of 15 mg/kg appears to be safe for use in healthy adult cats. (Am J Vet Res 2002;63:1309–1312)

Abstract

Objective—To determine plasma disposition after dermal application of a liposome-encapsulated formulation of lidocaine in cats.

Animals—6 healthy adult cats with a mean (± SD) body weight of 4.1 ± 0.44 kg.

Procedure—CBC determination and biochemical analysis of blood samples were performed for all cats. Cats were anesthetized by use of isoflurane, and catheters were placed IV in a central vein. The next day, blood samples were obtained from the catheters before and 1, 2, 3, 4, 6, 8, 10, 12, and 24 hours after applying a 4% liposome-encapsulated lidocaine cream (15 mg/kg) to a clipped area over the cephalic vein. Plasma concentrations of lidocaine were analyzed with a high-performance liquid chromatography assay.

Results—Two cats had minimal transdermal absorption of lidocaine, with lidocaine concentrations below the sensitivity of the assay at all but 1 or 2 time points. In the other 4 cats, the median maximum plasma concentration was 149.5 ng/ml, the median time to maximum plasma concentration was 2 hours, and the median area under the concentration versus time curve from zero to infinity was 1014.5 ng·h/ml.

Conclusions and Clinical Relevance—Maximum plasma concentrations of lidocaine remained substantially below toxic plasma concentrations for cats. On the basis of these data, topical administration of a liposome-encapsulated lidocaine formulation at a dose of 15 mg/kg appears to be safe for use in healthy adult cats. (Am J Vet Res 2002;63:1309–1312)

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