(Periactin® is another name for this medication.)

Use: Cyproheptadine is an antihistamine used to stop itching in dogs and cats. Cyproheptadine can also be used to stimulate appetite in cats. Cyproheptadine is sometimes used to help other asthma medications work better in cats. It is not usually helpful by itself for asthma.

Side Effects: Typically, cyproheptadine will cause sedation, dry mouth, and constipation. It also causes appetite stimulation in cats and is used for this effect in some instances. Cats and horses may be stimulated by cyproheptadine. Large doses can cause severe effects such as very rapid heartbeat, inability to urinate, fever and possibly seizures and death. 

Precautions: Cyproheptadine has effects on the smooth muscles of the body. It should be used with caution in pets with prostate problems, glaucoma, problems with urination, bladder stones, heart problems and obstructions in the intestinal tract.

Directions: Dogs: Dogs usually receive cyproheptadine orally two or three times daily.
Cats: Cats usually receive cyproheptadine once or twice daily.

Remember: All cyproheptadine products should be protected from light and moisture and should not be frozen. Some compounded solutions may require refrigeration.

If you miss a dose of this medication you should give it as soon as you remember it, but if it is within a few hours of the regularly scheduled dose, wait and give it at the regular time. Do not double a dose as this can be toxic to your pet.