THE PET PHARMACY By Wendy C. Brooks, DVM, DipABVP Educational Director, VeterinaryPartner.com

(For Veterinary Information Only)

Brand Name: Periactin

Available In 4 mg Tablets

Background

Cyproheptadine is an antihistamine that in many ways is similar to other antihistamines with which we are more familiar. Histamine, a biochemical mediator of inflammation, works by binding to histamine receptors. The histamine receptors we usually want to inactivate in combating allergic reactions are called H1 receptors and this is the type inactivated by cyproheptadine. (There are H2 receptors but those are responsible for acid secretion in the stomach.)

Cyproheptadine also has some other properties of interest. It also antagonizes serotonin, a neurotransmitter, in the brain. This leads to an increase in appetite and often is the reason this medication is used, rather than for its antihistamine effects.

Excess secretion of adrenocorticotropic hormone (ACTH), the hormone that stimulates the adrenal gland to produce cortisone, is associated with increased serotonin levels in the brain. Cyproheptadine has been used in the treatment of Cushing's disease, where there is excess cortisone production but not with reliable success.

How This Medication Is Used

Cyproheptadine has several uses:

• Appetite stimulation
• Treatment of feline asthma
• Symptomatic relief of itching, particularly in cats.

Side Effects

Drowsiness is a common side effect. Occasionally a cat will have what is called a paradoxic reaction and become excited.

As with other antihistamines, anticholinergic effects occur at higher doses or overdose. These effects include:

• Urine retention
• Increased pressure in the eye (only of concern in patients predisposed to glaucoma)
• Dry mouth
• Increased heart rate
• Elevated body temperature

Interactions with Other Drugs

Sedation side effects are magnified when this medication is used with other sedatives.

Concerns and Cautions

Cyproheptadine is best avoided in patients with glaucoma, recovering from urinary blockage, and those with heart failure.

It is our policy not to give dosing information over the Internet.

Date Published: 4/25/2005 10:29:00 AM