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

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

If you have any of these other conditions, you may need a dose adjustment or special tests to safely use this medication:

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

FDA pregnancy category B. Periactin is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. It is not known whether Periactin passes into breast milk, but if it does it could harm a nursing baby. Do not use this medication while you are breast-feeding a baby. Do not give Periactin to a child younger 2 years. Older adults may be more likely to have side effects from Periactin.

Important safety information:

• Periactin can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.
• Avoid drinking alcohol. It can increase some of the side effects of Periactin.

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

Stop taking Periactin and call your doctor at once if you have a serious side effect such as:

• confusion, hallucinations, unusual thoughts or behavior;
• seizure (convulsions);
• ringing in your ears;
• feeling like you might pass out;
• fast or pounding heartbeats;
• easy bruising or bleeding;
• urinating less than usual or not at all; or
• pale or yellowed skin, dark colored urine, fever, or unusual weakness.

Less serious side effects may include:

• mild drowsiness, dizziness, or spinning sensation;
• restlessness or excitability (especially in children);
• sleep problems (insomnia), tired feeling;
• numbness or tingly feeling;
• increased sweating or urination;
• blurred vision;
• appetite changes;
• dry mouth or nose, upset stomach; or
• nausea, diarrhea, constipation.

This is not a complete list of side effects and others may occur.