Transdermal Methimazole for Feline Hyperthyroidism

Hyperthyroidism is a common disorder in older cats causing detrimental adverse effects if left untreated. The three most recommended treatment options include thyroidectomy, radioiodine treatment, and antithyroid medication therapy. Oral methimazole has been the most widely used option due to low cost and accessibility. The topical application of transdermal methimazole is an ideal route of administration for cat owners. The purpose of this review article is to give insight into the efficacy and recommended indication for use of the pluronic lecithin organogel (PLO) formulated transdermal delivery system of methimazole, in the treatment of feline hyperthyroidism. PLO compounded methimazole is uniquely transported through the skin, and chronic use has been shown effective in treating feline hyperthyroidism. In many cases, once daily application of the gel has provided enough methimazole activity for lowering hormone levels. The compounded formulation also allows for more individualized dosing than the oral tablets. There is limited information regarding long-term treatment of PLO methimazole, however, the formulation continues to satisfy both veterinarians and owners, and effectively lower serum thyroxine (T4) concentrations.