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Drug

Diphenhydramine

Pronounced

"dye-fen-HI-druh-meen"

Uses

Diphenhydramine injection is an antihistamine used to treat life-threatening allergic reactions (anaphylaxis) along with epinephrine and other treatments. It is also used to relieve symptoms of household allergies, hay fever and the common cold when medication cannot be given by mouth. Common allergy symptoms relieved by antihistamines include rash, itching, watery eyes, itchy eyes/nose/throat, cough, runny nose and sneezing.

It is also used to treat nausea, vomiting and dizziness caused by motion sickness when medication cannot be given by mouth. Diphenhydramine works by blocking a certain natural substance (histamine) that your body makes during an allergic reaction. Its drying effects on such symptoms as watery eyes and runny nose are caused by blocking another natural substance made by your body (acetylcholine).

Diphenhydramine should not be used in newborns or premature infants because of an increased risk of side effects. It should not be used for common cold symptoms in children less than 6 years of age due to the risk of serious side effects, such as slow/shallow breathing. Cough-and-cold products have not been shown to be safe or effective in children younger than 6.

Other Uses

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used for shaking (tremor) and muscle stiffness caused by Parkinson's disease when medication cannot be given by mouth. It may also be used for side effects of certain psychiatric drugs such as involuntary movements and muscle stiffness (such as EPS).

How to Use This Medication

This medication is given by injection into a vein or into a muscle as directed by your doctor. The dosage is based on your medical condition and response to treatment. Do not use this medication more often than prescribed.

Do not inject this medication into the skin or just under the skin because it can destroy the skin and tissues around the injection site (necrosis).

If you are giving this medication to yourself at home, learn all preparation and usage instructions from your health care professional. Before using, check this product for particles or discoloration. If either is present, do not use the liquid. Learn how to store and discard medical supplies safely.

Tell your doctor if your condition does not get better or if it gets worse.

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Drug information is selected from data included with permission and copyrighted by First DataBank, Inc. This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your healthcare professional. Always seek the advice of your healthcare professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your healthcare professional. This information does not contain any assurances that this product is safe, effective or appropriate for you.

This information is intended only for residents of the United States. Products sold under the same brand names in other countries may contain different ingredients.

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Information expires December 2025.