(for veterinary information only)
4 mg TABLETS
Cyproheptadine is an antihistamine in many ways similar to other antihistamines with which we are more familiar. Histamine, a biochemical mediator of inflammation, works by binding to special 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.
Cyproheptadine has several uses:
- Appetite stimulation
- Treatment of Feline Asthma
- Symptomatic relief of itching, particularly in cats.
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
Sedation side effects are magnified when this medication is used with other sedatives. Cyproheptadine can interfere with the activity of serotonin reuptake inhibitors which would typically be used for anxiety. Examples of serotonin reuptake inhibitors would include fluoxetine, sertraline, and paroxitine.
Cyproheptadine can also be used to reverse serotonin syndrome caused by excessive use of mirtazapine or other medications that increase brain levels of serotonin. Serotonin syndrome is a reaction that occurs when brain levels of serotonin get too high. Elevated heart rate, tremors/shivering, dilated pupils, difficulty breathing, elevated body temperature, or high blood pressure can all be signs of serotonin syndrome. Cyproheptadine acts by reducing brain serotonin levels and can be used to reverse serotonin syndrome.
Cyproheptadine is best avoided in patients with glaucoma, recovering from urinary blockage, and heart failure patients.
Page last updated: 6/19/2013