Appetite stimulants are medications designed to trigger the desire to eat. In the Chronic Kidney Disease (CKD) cat, these are essential tools to combat Dysrexia (fluctuating appetite) and prevent the muscle wasting of Cachexia.
The "Override" Switch It is important to understand that these drugs do not always fix the underlying nausea. Instead, they chemically stimulate the brain's hunger centers to override the "I feel sick" signal. This is why they are most effective when combined with Anti-Emetics like Cerenia or Zofran.
Mirtazapine (Mirataz) Originally a human antidepressant, Mirtazapine is the most widely used appetite stimulant in cats.
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Mechanism: It increases levels of norepinephrine and serotonin in the brain. Interestingly, it acts on similar receptors to Zofran, meaning it has mild anti-nausea properties in addition to stimulating hunger.
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Transdermal Gel: While pills exist, the FDA approved gel (Mirataz) is the gold standard. You apply a 1.5 inch ribbon of gel to the inside of the cat's ear (pinna) once daily. This avoids the stress of pilling a cat that already refuses to eat.
- Ear Irritation: A common side effect of the transdermal gel is Contact Dermatitis. The chemical carrier can irritate the delicate skin of the ear, causing redness (erythema), flaky skin, or scabs. To minimize this, you must alternate ears every day (Left on Monday, Right on Tuesday) and gently wipe away the old residue with a damp cloth or tissue before applying a new dose.
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The "Happy" Side Effects: Mirtazapine can cause behavioral changes. Owners often report their cats becoming unusually vocal (the "Mirtazapine Meow"), affectionate, or hyperactive.
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Serotonin Syndrome: If the dose is too high, the cat may become agitated, tremble, or have dilated pupils. This is why the transdermal ointment is safer; it delivers a slow, steady dose unlike the spike from a pill.
Capromorelin (Elura) Elura is a liquid medication specifically FDA approved for weight loss in CKD cats.
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Mechanism: It mimics Ghrelin, the body's natural "hunger hormone." When the stomach is empty, it normally releases Ghrelin to tell the brain to eat. Elura floods the system with this signal.
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The Usage: It is a liquid given orally once daily.
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Side Effects: The most common side effect is hypersalivation (drooling) immediately after dosing. More importantly, it can slightly lower blood pressure and heart rate, so it should be used with caution in cats with significant heart disease or those already on high doses of blood pressure medication.
Cyproheptadine This is an older antihistamine that has a side effect of increased appetite. It is rarely used now because Mirtazapine and Elura are significantly more effective and have fewer sedative side effects.
The "Food Aversion" Warning Never force feed a cat without a tube, and be careful when introducing new foods while the cat is nauseous. If a cat feels sick and you force a specific food on them, they will develop a permanent psychological aversion to that flavor. Appetite stimulants help the cat choose to eat, which preserves their relationship with food.
Disclaimer: This content is for educational purposes only and does not constitute veterinary medical advice. Always consult with your primary care veterinarian or a veterinary internal medicine specialist regarding your cat’s specific condition.