Cyproheptadine is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.

Cyproheptadine is used to treat sneezing, runny nose, itching, red or watery eyes, and other symptoms of seasonal allergies (hay fever). Cyproheptadine is also used to treat other conditions such as eczema or skin reactions to insect bites.

Cyproheptadine is sometimes used to treat certain types of headaches, including migraines.

Cyproheptadine may also be used for purposes not listed in this medication guide.

You should not use cyproheptadine if you are allergic to it, or if:

• you have narrow-angle glaucoma;
• you have a stomach ulcer or obstruction;
• you have an enlarged prostate or urination problems;
• you are breast-feeding a baby;
• you are having an asthma attack; or
• you are elderly or have a debilitating disease.

Do not give this medicine to a newborn or premature baby. Cyproheptadine is not approved for use by anyone younger than 2 years old.

To make sure cyproheptadine is safe for you, tell your doctor if you have:

• glaucoma;
• a history of asthma;
• high blood pressure;
• heart disease; or
• an overactive thyroid.

Cyproheptadine is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine.

It is not known whether cyproheptadine passes into breast milk or if it could harm a nursing baby. Antihistamines may slow breast milk production. You should not breast-feed while using this medicine.

Use Periactin (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using cyproheptadine and call your doctor at once if you have:

• a light-headed feeling, like you might pass out;
• tremor, seizure (convulsions);
• confusion, hallucinations;
• little or no urination;
• fast or pounding heartbeats;
• easy bruising or bleeding;
• ringing in your ears; or
• pale or yellowed skin, dark colored urine, fever, weakness.

Common side effects may include:

• drowsiness, dizziness;
• dry mouth, nose, or throat;
• constipation;
• blurred vision; or
• feeling restless or excited (especially in children).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

This medicine may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Drinking alcohol with this medicine can cause side effects.