Generic name: Cyproheptadine hydrochloride.

Periactin is an antihistamine. Antihistamines block the effects of histamine, a body chemical that causes swelling and itching. 

Quick Facts About Periactin


Used to relieve cold and allergy symptoms such as hay fever, nasal inflammation, stuffy nose, red and inflamed eyes, hives, and swelling. Also used to treat anaphylaxis, a life-threatening allergic reaction. Also prescribed for cluster headaches, and to stimulate appetite in underweight people.

Periactin Dosage

Take exactly as prescribed.

  • Usual adult dose: 4 milligrams (1 tablet or 2 teaspoonfuls) 3 times per day, initially. Ongoing dose — ranges from 12 to 16 milligrams per day.
  • Usual child dose: 4 milligrams (1 tablet or 2 teaspoonfuls) 3 times per day, initially. Ongoing dose — ranges from 12 to 16 milligrams per day.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose; go back to regular schedule. Do not double doses.

Periactin Side Effects

Overdose symptoms:

dilated pupils, dry mouth, extreme excitement and agitation, fever, flushing, stomach or bowel distress, stupor or coma. If you suspect an overdose, immediately seek medical attention.

More common side effects: anaphylaxis (life-threatening allergic reaction); anemia; appetite loss; chest congestion or tightness; chills; confusion; constipation; convulsions; diarrhea; difficulty urinating; dizziness; dry mouth, nose, or throat; earlier-than-expected menstrual period; exaggerated feeling of well-being; excessive perspiration; excitement; faintness; fatigue; fluttery or throbbing heartbeat; frequent urination; hallucinations; headache; hives; hysteria; inability to urinate; insomnia; irritability; lack of coordination; light sensitivity; low blood pressure; nausea; nervousness; rapid heartbeat; rash and swelling; restlessness; ringing in ears; sleepiness; stomach pain; stuffy nose; tingling or pins and needles; tremor; vertigo; vision problems; vomiting; weight gain; wheezing; yellow eyes and skin.

No known less common or rare Periactin side effects.


Inform your doctor before combining Periactin with:

sedatives such as Nembutal and Seconal, tranquilizers such as Librium and Valium. Do not take with MAO inhibitors such as Nardil and Parnate.

Avoid alcohol while taking Periactin. 

Special Cautions

Should not be used during pregnancy or breastfeeding due to possible harm to the fetus or newborn.

Seniors may develop dizziness or drowsiness, or low blood pressure.

May cause hallucinations or convulsions in children.

  • Do not take if sensitive to or allergic to this or similar medications.
  • Do not take if you have: angle-closure glaucoma, peptic ulcer, enlarged prostate, obstruction of neck and bladder, or obstruction of outlet of the stomach.
  • May cause drowsiness and impair your ability to drive a car or operate machinery. Do not take part in any activity that requires alertness.
  • Use with caution if you have: overactive thyroid, high blood pressure, heart disease, or circulatory problems.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Periactin side effects, please contact your healthcare provider