Veterinary compounding: In vitro assessment of Methimazole-based foam for feline hyperthyroidism

Abstract

Veterinary compounding: In vitro assessment of Methimazole-based foam for feline hyperthyroidism Areej Alshikhey, Raimar Löbenberg, Michael Doschak Objective: Hyperthyroidism is one of the most common feline endocrine disorders due to excess production of active thyroid hormone in middle-aged cats. The management involves oral or transdermal antithyroid drug delivery. The use of transdermal medications in cats has become popular in veterinary medicine due to the ease of administration compared to oral medications. We hypothesized that microemulsion-based system could improve the in vitro flux of Methimazole using a Franz cell model. Method: A concentrations of 2.5% of Methimazole were incorporated into Labrafac-based microemulsion formulations with Labrasol as a surfactant and Plurol Oleique as cosurfactant to be used for transdermal delivery of Methimazole. The in vitro studies were carried out using Franz cell apparatus with a diffusional surface area of 1.79 cm2 and synthetic membranes. A direct comparison of release profiles using Franz diffusion cells between Methimazole-loaded microemulsion and commercial formulations of transdermal Methimazole were performed. Purified water was used as the receptor fluid, and the temperature maintained at 32 ± 0.5°C. The withdrawn samples were appropriately diluted and calculated at different time points 30 min, 1, 2, 4, and 6hrs using HPLC. Result: The obtained result of in vitro study indicated that the foamable microemulsion system might be a candidate carrier for transdermal delivery of Methimazole. Cumulative drug percentage releases through hydrophobic synthetic membranes into the receptor media were found to be 84.64% in Methimazole-loaded microemulsion compared to 47.86%, 33.53%, 33.08% in Lipoderm, Versapro, PLO vehicle, respectively, p< 0.05. Conclusion: Hence the microemulsion system is one of the promising tools for percutaneous delivery of Methimazole. The release profiles obtained from in vitro permeability tests might be used for predicting the in vivo permeability of the formulation. Findings from the current research work evidenced that foam-based microemulsion formulation was superior to cream-based formulations; thus, ME-based foam might be a potential vehicle for enhancing the transdermal penetration of Methimazole.