Drugs A - Z

Diphenhydramine Hydrochloride Oral tablet

It is used to treat the symptoms of an allergic reaction

Generic Name: diphenhydrAMINE  |  Brand Name: Hydramine

There is an FDA Alert for this drug. Click here to view it.

What is this medicine?

DIPHENHYDRAMINE (dye fen HYE dra meen) is an antihistamine. It is used to treat the symptoms of an allergic reaction. It is also used to treat Parkinson's disease. This medicine is also used to prevent and to treat motion sickness and as a nighttime sleep aid.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
  • asthma or lung disease
  • glaucoma
  • high blood pressure or heart disease
  • liver disease
  • pain or difficulty passing urine
  • prostate trouble
  • ulcers or other stomach problems
  • an unusual or allergic reaction to diphenhydramine, other medicines foods, dyes, or preservatives such as sulfites
  • pregnant or trying to get pregnant
  • breast-feeding

How should I use this medicine?

Take this medicine by mouth with a full glass of water. Follow the directions on the prescription label. Take your doses at regular intervals. Do not take your medicine more often than directed. To prevent motion sickness start taking this medicine 30 to 60 minutes before you leave.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

Patients over 65 years old may have a stronger reaction and need a smaller dose.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

Do not take this medicine with any of the following medications:
  • MAOIs like Carbex, Eldepryl, Marplan, Nardil, and Parnate

This medicine may also interact with the following medications:

  • alcohol
  • barbiturates, like phenobarbital
  • medicines for bladder spasm like oxybutynin, tolterodine
  • medicines for blood pressure
  • medicines for depression, anxiety, or psychotic disturbances
  • medicines for movement abnormalities or Parkinson's disease
  • medicines for sleep
  • other medicines for cold, cough or allergy
  • some medicines for the stomach like chlordiazepoxide, dicyclomine

What should I watch for while using this medicine?

Visit your doctor or health care professional for regular check ups. Tell your doctor if your symptoms do not improve or if they get worse.

Your mouth may get dry. Chewing sugarless gum or sucking hard candy, and drinking plenty of water may help. Contact your doctor if the problem does not go away or is severe.

This medicine may cause dry eyes and blurred vision. If you wear contact lenses you may feel some discomfort. Lubricating drops may help. See your eye doctor if the problem does not go away or is severe.

You may get drowsy or dizzy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. Do not stand or sit up quickly, especially if you are an older patient. This reduces the risk of dizzy or fainting spells. Alcohol may interfere with the effect of this medicine. Avoid alcoholic drinks.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:
  • allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
  • changes in vision
  • confused, agitated, nervous
  • irregular or fast heartbeat
  • tremor
  • trouble passing urine
  • unusual bleeding or bruising
  • unusually weak or tired

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):

  • constipation, diarrhea
  • drowsy
  • headache
  • loss of appetite
  • stomach upset, vomiting
  • thick mucous


Last Updated: April 06, 2009
Licensed from
The Healthline Site, its content, such as text, graphics, images, search results, HealthMaps, Trust Marks, and other material contained on the Healthline Site ("Content"), its services, and any information or material posted on the Healthline Site by third parties are provided for informational purposes only. None of the foregoing is a substitute for professional medical advice, examination, diagnosis, or treatment. Always seek the advice of a physician or other qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on the Healthline Site. If you think you may have a medical emergency, call your doctor or 911 immediately. Please read the Terms of Service for more information regarding use of the Healthline Site.
Advertisement