Transdermal Cyclosporine for Cats

Transdermal cyclosporine delivery may minimize problems with oral administration (eg, GI upset). In this crossover study, oral and transdermal blood concentrations of cyclosporine were compared. Cats (n = 6) received oral cyclosporine (5 mg/kg) for 7 days; whole blood was collected on the last day at 2 and 12 hours postadministration. After a 2-week washout period, a compounded transdermal formulation (25 mg in 0.1 mL gel) was applied q24h to the pinna for 21 days. Whole blood was collected at 2 and 12 hours postadministration on days 7, 14, and 21. Random samples of the transdermal formulation showed the cyclosporine concentration to be within 10% of the target concentration of 250 mg/mL. Median blood concentrations after the seventh day of oral administration were 2,208 ng/mL and 1,232 ng/mL at 2 and 12 hours postadministration, respectively. For the transdermal formulation, median blood concentrations 2 and 12 hours postadministration were 37 ng/mL and 37 ng/mL on day 7, respectively. There was no significant difference between day 7 and day 21 serum concentrations at either 2 or 12 hours posttransdermal application. There was a significant difference in blood concentrations between oral and transdermal application. Therapeutic blood concentrations were achieved in only 1 of 6 cats using transdermal cyclosporine.

Commentary

This study was completed before the liquid formulation of feline cyclosporine was available. It is likewise important to note that the dose for cats is 7 mg/kg (vs 5 mg/kg in dogs). In my experience, feline cyclosporine is easily administered and more or less readily acceptable to the cat. There is little scientific support for how well transdermal gels work in veterinary dermatology; the most commonly cited reason for their use is the difficulty in administering oral medication to cats. The pinna is the target application site to prevent licking, but anyone who owns a cat knows that the average cat easily grooms its face and ears. Ideally, with transdermal application to the thin skin, it will be absorbed before the cat grooms it off. Besides lack of proven efficacy of transdermal drugs, there is a real concern for contact or irritant reactions, inconsistent dosing, and increased exposure of the drug to humans. The client may be aware that a medication has been applied to the ear, but other family members (eg, children, other cats) may not.—Karen A. Moriello, DVM, DACVD

Source

Absorption of oral and transdermal cyclosporine in six healthy cats. Miller R, Schick AE, Boothe DM, Lewis TP. JAAHA 50:36-41, 2014.