Diphenhydramine Capsules or Tablets

Diphenhydramine is an antihistamine medication that treats the symptoms of allergies and allergic reactions. It also prevents and treats motion sickness or symptoms of Parkinson’s disease.

What is this medication?

DIPHENHYDRAMINE (dye fen HYE dra meen) treats the symptoms of allergies and allergic reactions. It may also be used to prevent and treat motion sickness or symptoms of Parkinson disease. It works by blocking histamine, a substance released by the body during an allergic reaction. It belongs to a group of medications called antihistamines.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

COMMON BRAND NAME(S): Alka-Seltzer Plus Allergy, Aller-G-Time, Banophen, Benadryl Allergy, Benadryl Allergy Dye Free, Benadryl Allergy Kapgel, Benadryl Allergy Ultratab, Diphedryl, Diphenhist, Genahist, Geri-Dryl, PHARBEDRYL, Q-Dryl, Sleepinal, Valu-Dryl, Vicks ZzzQuil Nightime Sleep-Aid

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What should I tell my care team before I take this medication?

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 medications foods, dyes, or preservatives such as sulfites
  • Pregnant or trying to get pregnant
  • Breast-feeding

How should I use this medication?

Take this medication 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 medication more often than directed. To prevent motion sickness start taking this medication 30 to 60 minutes before you leave.

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

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

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

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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 medication?

Do not take this medication with any of the following:

  • MAOIs like Carbex, Eldepryl, Marplan, Nardil, and Parnate

This medication may also interact with the following:

  • Alcohol
  • Barbiturates, like phenobarbital
  • Medications for bladder spasm like oxybutynin, tolterodine
  • Medications for blood pressure
  • Medications for depression, anxiety, or psychotic disturbances
  • Medications for movement abnormalities or Parkinson's disease
  • Medications for sleep
  • Other medications for cold, cough or allergy
  • Some medications for the stomach like chlordiazepoxide, dicyclomine

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

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What should I watch for while using this medication?

Visit your care team for regular check-ups. Tell your care team 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 care team if the problem does not go away or is severe.

This medication 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 medication 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 medication. Avoid alcoholic drinks.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

  • Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
  • Sudden eye pain or change in vision such as blurry vision, seeing halos around lights, vision loss
  • Trouble passing urine

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

  • Constipation
  • Drowsiness
  • Dry mouth
  • Headache
  • Upset stomach

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medication?

Keep out of the reach of children and pets. This medication can be abused. Keep your medication in a safe place.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Keep container closed tightly. Throw away any unused medication after the expiration date.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.

Copyright ©2024 Elsevier Inc. All Rights Reserved.

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Note: Introduction and Additional Common Questions written and medically approved by Cleveland Clinic professionals.

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