FDA to Veterinarians: Use Approved Mirtazapine Product

September 21, 2018
American Veterinarian Editorial Staff

The FDA is reminding veterinarians of the potential dangers of using nonapproved compounded formulations of transdermal mirtazapine to manage undesired weight loss in cats.

In an open letter to veterinarians, the FDA’s Center for Veterinary Medicine is reminding veterinarians of the differences between the recently approved animal drug Mirataz (mirtazapine transdermal ointment) and compounded formulations of transdermal mirtazapine.

Before Mirataz was approved in May, some veterinarians were prescribing a compounded formulation of mirtazapine to manage undesired weight loss their feline patients.


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FDA approval of this drug, the agency noted, means that the product’s safety, efficacy, and quality have been proven. Compounded formulations, on the other hand, have not been reviewed by the FDA for safety or effectiveness and may vary in both quality and potency. “As with many compounded transdermal drugs, the rate and degree of absorption are unknown and may vary to deliver too little or too much of the active ingredient, making treatment outcomes unpredictable,” the letter reads in part.

Manufactured by Kindred Biosciences Inc., Mirataz is applied topically on the inner surface of the cat’s ear once daily for 14 days. Mirataz must be prescribed by a licensed veterinarian because a trained professional is needed to correctly diagnose the cause of weight loss in cats and determine whether the drug is an appropriate treatment.

Read the full letter on the FDA website.