Weight loss in cats may be an indicator of something more serious. Changes in your cat's appetite, and accompanying weight loss, can be early indicators or underlying diseases such as thyroid, kidney and inflammatory bowel disease. Mirataz (mirtazapine transdermal ointment) is the first and only FDA-approved transdermal medication for the management of weight loss in cats, and can help your cat gain weight. Miratz is a transdermal ointment applied to the inside of your cat's ear. See your veterinarian if you notice symptoms of weight or appetite loss.