The drug mirtazapine, used to treat depression in people, has a surprising side effect in pets: It can stimulate appetite and, in some cases, control nausea and vomiting, which are signs of chronic kidney disease (CKD) in cats.
The resulting weight loss is associated with a poor prognosis. Cats who go without eating several days can develop hepatic lipidosis, a potentially fatal liver disease.
A study by Jessica Quimby, DVM, Ph.D., ACVIM, at Colorado State indicated that mirtazapine pills can increase appetite and decrease vomiting in cats with CKD, but many cats resist being given pills.
Dr. Quimby is now evaluating the effectiveness of mirtazapine administered through the skin. A bonus from her previous study: Cats taking the pills for three weeks gained an average of nearly a half pound, a significant increase in this small species.