Evaluation of transdermal application of glipizide in a pluronic lecithin gel to healthy cats

Objective - To evaluate plasma glipizide concentration and its relationship to plasma glucose and serum insulin concentrations in healthy cats administered glipizide orally or transdermally. Animals - 15 healthy adult laboratory-raised cats. Procedure - Cats were randomly assigned to 2 treatment groups (5 mg of glipizide, PO or transdermally) and a control group. Blood samples were collected 0, 10, 20, 30, 45, 60, 90, and 120 minutes and 4, 6, 10, 14, 18, and 24 hours after administration to determine concentrations of insulin, glucose, and glipizide. Results - Glipizide was detected in all treated cats. Mean ± SD transdermal absorption was 20 ± 14% of oral absorption. Mean maximum glipizide concentration was reached 5.0 ± 3.5 hours after oral and 16.0 ± 4.5 hours after transdermal administration. Elimination half-life was variable (16.8 ± 12 hours orally and 15.5 ± 15.3 hours transdermally). Plasma glucose concentrations decreased in all treated cats, compared with concentrations in control cats. Plasma glucose concentrations were significantly lower 2 to 6 hours after oral administration, compared with after transdermal application; concentrations were similar between treatment groups and significantly lower than for control cats 10 to 24 hours after treatment. Conclusions and clinical relevance - Transdermal absorption of glipizide was low and inconsistent, but analysis of our results indicated that it did affect plasma glucose concentrations. Transdermal administration of glipizide is not equivalent to oral administration. Formulation, absorption, and stability studies are required before clinical analysis can be performed. Transdermal administration of glipizide cannot be recommended for clinical use at this time.