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Revised: May 29, 2023
Published: April 25, 2005

(For veterinary information only)

The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you use drugs on your pet without your veterinarian's advice. 

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

Brand Name: Ciplactin®, Cyheptine®, Cyprogin®, Cyprono®, Cyprosian®, Klarivitina®, Nuran®, Periactine®, Periactinol®, Periatin®, Peritol®, Polytab®, Practin®, Preptin®, Supersan®, Trimetabol®

Available in 4 mg tablets and oral syrup


Cyproheptadine is an antihistamine, in many ways similar to other antihistamines with which we are more familiar, but it is rarely used for its antihistamine effects. Cyproheptadine is mostly used because of its strong appetite-stimulating side effect, though it also is used in inflammatory conditions which involve histamine. Cyproheptadine is also used (rarely and not very reliably) in the treatment of Cushing's disease, the hormone imbalance involving excess cortisone production in the body.

In addition to blocking H1 histamine receptors and thereby blocking the effects of histamine, cypropheptadine interferes with serotonin, an important neurotransmitter in the brain. It is through this effect that appetite stimulation occurs.

How this Medication is Used

Cyproheptadine has two main uses:

  • appetite stimulation;
  • treatment for serotonin syndrome (see below).

Cyproheptadine is usually given twice daily, either with or without food. If a dose is skipped, the next dose should not be doubled, and dosing is picked up where it was left off. 

Side Effects

Common side effects of cyproheptadine stem from its antihistamine nature. Drowsiness is probably the most common side effect though some cats will have a paradoxical reaction and become excited.

Antihistamines, in general, also produce what are called anticholinergic effects at higher doses or in overdoses, and cyproheptadine is no different. These anticholinergic 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.

More seriously, hemolytic anemia has been reported, although rarely.

Interactions with Other Drugs

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

Cyproheptadine interferes with the activity of several anti-anxiety medications, including clomipramine and fluoxetine.    

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 may interfere with the effectiveness of tramadol, a pain reliever.

Concerns and Cautions

Cyproheptadine is best avoided in patients with glaucoma, recovering from urinary blockage, seizure disorders, hyperthyroidism, and/or heart failure patients.

Cyproheptadine should not be used in nursing mothers as it may interfere with milk production.

Tablets should be stored at room temperature and protected from light. The syrup can be refrigerated but does not have to be.

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The information contained here is for general purposes only and is not a substitute for advice from your veterinarian. Any reliance you place on such information is strictly at your own risk.

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