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What is cyproheptadine?

Cyproheptadine (also called Periactin®) is an antihistamine medicine. It is used to stimulate the appetite and promote weight gain. It is also used to relieve symptoms of seasonal allergies, such as, skin rash, itchy or watery eyes, and runny nose. It is available as a white 4 mg tablet and as a yellow liquid to be taken by mouth.

How to take cyproheptadine

  • Cyproheptadine may be taken with or without food. Take with food if stomach upset occurs.
  • Use an oral syringe to measure liquid doses carefully.
  • If ordered for weight gain, follow the instructions closely on when to give this medicine in regards to meals.

Possible side effects of cyproheptadine

  • Feeling sleepy or dizzy
  • Belly pain
  • Dry Mouth
  • Excitement (especially in children)
  • Skin more sensitive to the sun
  • Headache
  • Blurred eyesight

These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

In case of a severe side effect or reaction, call the doctor, nurse, or pharmacist at 901-595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.

Special instructions for cyproheptadine

  • Store tablets and liquid at room temperature and keep dry. Protect from light.
  • Keep this and all medicine out of the reach of children and pets.
  • This medicine may cause you to feel dizzy and drowsy. Do not operate heavy equipment or drive a car until you see how this medicine affects you. Children should avoid tasks that call for alertness (such as riding a bicycle, or using scissors) until it is known how this medicine affects them.
  • Cyproheptadine can make your skin sensitive to sunlight. You should wear sunscreen and clothing that protects your skin when you are outside during the daylight hours.
  • Avoid alcohol while you are taking this medicine. Alcohol is found in many over-the-counter cold medicines.
  • Cyproheptadine may affect the way other medicines work. Always give a complete list of medicines you are taking to your doctor or pharmacist. Check with your doctor or pharmacist before starting any new vitamins, herbals, or other medicines.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).