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Generic Name: diphenhydramine

It is used to treat the symptoms of an allergic reaction
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What is this medicine?

DIPHENHYDRAMINE (dye fen HYE dra meen) is an antihistamine. It is used to treat the symptoms of an allergic reaction.

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

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

How should I use this medicine?

Take this medicine by mouth. Chew it completely before swallowing. Follow the directions on the prescription label. Take your doses at regular intervals. Do not take your medicine more often than directed.

Talk to your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for children as young as 6 years old for selected conditions, precautions do apply.

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 or healthcare professional if your symptoms do not start to get better 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

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All visitors to AARP.org should seek expert medical care and consult their own physicians for any specific health issues. Read this disclaimer in its entirety.
Note: This information is not intended to cover all possible uses, precautions, interactions, or adverse effects for this drug. If you have question about the drug(s) you are taking, check with your health care professional.
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