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Cyproheptadine for Dogs, Cats, and Horses

By Barbara Forney, VMD

Last reviewed: 7/12/2022

Commonly prescribed for: Appetite Stimulant; Serotonin Syndrome; Cushing's Disease; Atopic Dermatitis; PPID

Species: Dogs, Cats, and Horses

Therapeutic Class: Antihistamine

Basic Information

Cyproheptadine is an antihistamine that also has anti-serotonin activity. It is well-absorbed orally and has a wide margin of safety. Cyproheptadine is metabolized by the liver and excreted in the urine.

Dogs and Cats

Cyproheptadine is used as an appetite stimulant for sick cats, including those undergoing chemotherapy. When used for this purpose it should be noted that it may take two to three days for the drug to reach full effect. It also is used to treat feline asthma in cats whose condition is not totally controlled by corticosteroids and bronchodilators. Veterinary behaviorists also use cyproheptadine in some cases of inappropriate urine spraying behavior in cats.

Cyproheptadine is used in both dogs and cats as a part of treatment for serotonin syndrome. It has been tried in dogs to treat canine Cushing's Disease although there are other medications that appear to be more effective.

Cyproheptadine has been used to treat atopic dermatitis in both dogs and cats; the general consensus is that there are other more effective drugs.


Cyproheptadine is used in conjunction with other drugs to treat PPID and photic head-shakers. Because animals with PPID usually have clinical signs similar to Cushing's Disease in humans, this condition also may be called equine Cushing's-like Disease (ECD). Pergolide is considered the drug of choice for PPID. Cyproheptadine frequently is combined with pergolide to treat PPID.

Photic head-shakers are a troubling medical/behavioral problem of the horse. Cyproheptadine is prescribed to treat head-shakers because of its antihistamine properties. Cyproheptadine sometimes is combined with carbamazepine. Prohibited in most sanctioned competitions, cyproheptadine is an ARCI Class 4 drug.

Side Effects

Common side-effects include sedation, dry mucous membranes, and increased heart rate.


  • High doses of cyproheptadine have been tested in laboratory animals without causing detectable harm to the fetus. This work has not been done in horses. It is not known if cyproheptadine is excreted in milk.
  • Cyproheptadine should be used in pregnant or lactating animals only if the benefits outweigh the risks. No information was found on cyproheptadine use in breeding stallions.

Drug Interactions

Cyproheptadine may have an additive effect when combined with other central nervous system (CNS) depressant drugs, such as tranquilizers.


Overdose causes similar but more severe side effects.
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