In a Dear Veterinarian Letter, the U.S. Food and Drug Administration reminded veterinarians of the differences between Mirataz (mirtazapine transdermal ointment), an animal drug that the FDA approved in May 2018 with demonstrated safety and effectiveness to manage undesired weight loss in cats, compared to the use of compounded formulations of transdermal mirtazapine, which some veterinarians started prescribing before there was an FDA-approved product available. FDA approval of this drug means that veterinarians have an approved mirtazapine product with known safety, efficacy, and quality to provide to their patients rather than relying on the only previously available products that are compounded from bulk drug substances that are unapproved animal drugs.
Unlike FDA-approved Mirataz, compounded formulations of transdermal mirtazapine have not been reviewed by the FDA for safety or effectiveness and may vary in quality and potency. 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.
Manufactured for Kindred Biosciences Inc., Mirataz is a prescription animal drug that is intended to be 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.