Overview
Histamine is a chemical that is released in the body in response to inflammation or allergy. This chemical travels throughout the body searching for specific histamine receptors (targets on cells). Once attached to the receptors, histamine will cause swelling, itchiness and other symptoms associated with an allergic response.
There are two types of histamine receptors: H1 and H2. H1 receptors affect small blood vessels and smooth muscles. When histamine attaches to the H1 receptors, the small blood vessels dilate and fluid begins to leak out. This results in tissue swelling and itchiness. In addition, the smooth muscles lining the small airways constrict, causing tightness and some breathing difficulty. H2 receptors affect heart rate and stomach acid secretions. When histamine attaches to H2 receptors, the heart rate increases and stomach acid secretions are increased, potentially increasing the risk of developing ulcers.
Drugs that block the effects of histamine are called antihistamines. There are a number of drugs demonstrating antihistamine effects; some are useful in allergies, others for preventing excessive stomach acid. The effects of the antihistamine depend on whether it binds with the H1 receptors or H2 receptors. There are few drugs that affect both types of receptors.
Cyproheptadine is one type of antihistamine that inhibits the action of histamine, particularly its effect on H1 receptors. This results in a reduction or prevention of swelling and itchiness. Cyproheptadine also has anti-serotonin effects. Serotonin is an important chemical messenger of the brain.
Cyproheptadine is used as an appetite stimulant in cats, but this effect does not appear to occur in dogs.
Cyproheptadine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.
Brand Names and Other Names
This drug is registered for use in humans only.
Human formulations: Periactin® (Merck) and various generic brands
Veterinary formulations: None
Uses of Cyproheptadine
Cyproheptadine is used to treat allergies and allergic reactions. However, other antihistamine drugs are used more often for this purpose.
The most common use of this drug is as an appetite stimulant in cats, which is probably related to the drug's anti-serotonin effects.
Precautions and Side Effects
While generally safe and effective when prescribed by a veterinarian, cyproheptadine can cause side effects in some animals.
Cyproheptadine should not be used in animals with known hypersensitivity or allergy to the drug.
Cyproheptadine should be used with caution in animals with glaucoma, prostate gland enlargement, heart failure or gastrointestinal obstructions.
Cyproheptadine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with cyproheptadine. Such drugs include barbiturates, tranquilizers and monoamine oxidase inhibitors.
The most common adverse effect associated with cyproheptadine is sedation.
Overdose is uncommon and generally results in profound sedation.
How Cyproheptadine Is Supplied
Cyproheptadine is available in 4 mg tablets and 2 mg per 5 ml syrup.
Dosing Information
Medication should never be administered without first consulting your veterinarian.
To treat allergies and allergic reactions, cyproheptadine is dosed at 0.15 to 1 mg per poung (0.3 to 2 mg/kg) twice daily in dogs, and 2 mg per cat twice daily.
For appetite stimulation in cats, the dose is 1 to 4 mg per cat one to two times daily.
The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.
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