Diphenhydramine is an antihistamine sometimes used as a sleep aid. Magnesium salicylate is a nonsteroidal anti-inflammatory drug (NSAID) in a group of drugs called salicylates (sa-LIS-il-ates).

Diphenhydramine and magnesium salicylate is a combination medicine that is used to treat back pain that keeps you awake during your normal sleeping hours.

Diphenhydramine and magnesium salicylate may also be used for purposes not listed in this medication guide.

You should not use this medicine if you are allergic to aspirin or other salicylates.

Do not give this medicine to a child or teenager with a fever, flu symptoms, or chickenpox. Salicylates can cause Reye's syndrome, a serious and sometimes fatal condition in children. Ask a doctor before giving the medicine to a child younger than 12 years old.

Magnesium salicylate may cause stomach or intestinal bleeding, which can be fatal. These conditions can occur without warning while you are using magnesium salicylate, especially in older adults.

Ask a doctor or pharmacist if this medicine is safe to use if you have ever had:

• bleeding problems;
• heartburn, stomach ulcer, or stomach bleeding;
• an enlarged prostate or urination problems;
• asthma or COPD, cough with mucus, or cough caused by smoking, emphysema, or chronic bronchitis;
• heart disease, high blood pressure;
• liver disease, cirrhosis, or if you drink more than 3 alcoholic beverages per day;
• kidney disease;
• arthritis, gout;
• diabetes;
• glaucoma; or
• a thyroid disorder.

Ask a doctor before using this medicine if you are pregnant or breastfeeding.

Taking this medicine during the last 20 weeks of pregnancy may cause serious kidney problems in the unborn baby, or bleeding in the mother or the baby during delivery.

Use Diphenhydramine And Magnesium Salicylate (Doans PM) 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; wheezing, difficult breathing; feeling light-headed; swelling of your face, lips, tongue, or throat.

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

• severe drowsiness;
• painful or difficult urination;
• ringing in your ears, hearing loss;
• confusion; or
• signs of stomach bleeding--feeling light-headed, ongoing stomach pain, bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds.

Common side effects may include:

• drowsiness;
• dry eyes, blurred vision;
• dry mouth, nose, or throat;
• decreased urination;
• heartburn, nausea, vomiting, gas;
• constipation;
• feeling restless or excited (especially in children); or
• day-time drowsiness or "hangover" feeling after night-time use.

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.

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Also ask a doctor or pharmacist before using any other medicine that may contain diphenhydramine or ingredients similar to magnesium salicylate (such as aspirin or other salicylates). This includes medicines for pain, fever, swelling, sleep, cold/allergy symptoms, or anti-itch medicine used on the skin. Using too much diphenhydramine may lead to a fatal overdose.

Avoid alcohol. Heavy drinking can increase your risk of stomach bleeding.