Drugs >  Diphenhydramine
Diphenhydramine
Pronunciation
Brand Names
Foreign Brand Names
Therapeutic Categories
Reasons not to take this medicine
What is this medicine used for?
How does it work?
How is it best taken?
What do I do if I miss a dose?
What are the precautions when taking this medicine?
What are the common side effects of this medicine?
What should I monitor?
Reasons to call healthcare provider immediately
How should I store this medicine?
General statements

Pronunciation
(dye fen HYE dra meen)

Brand Names
AllerMax® Oral [OTC]; Banophen® Oral [OTC]; Benadryl® Injection; Benadryl® Oral [OTC]; Benadryl® Topical; Bydramine® Cough Syrup [OTC]; Compoz® Gel Caps [OTC]; Compoz® Nighttime Sleep Aid [OTC]; Dihydrex® Injection; Diphenacen-50® Injection; Diphen® Cough [OTC]; Diphenhist [OTC]; Dormin® Oral [OTC]; Genahist® Oral; Hyrexin-50® Injection; Maximum Strength Nytol®[OTC]; Miles Nervine® Caplets [OTC]; Nordryl® Injection; Nordryl® Oral; Nytol® Oral [OTC]; Siladryl® Oral [OTC]; Silphen® Cough [OTC]; Sleep-eze 3® Oral [OTC]; Sleepinal®[OTC]; Sleepwell 2-nite®[OTC]; Sominex® Oral [OTC]; Tusstat® Syrup; Twilite® Oral [OTC]; Uni-Bent® Cough Syrup; 40 Winks®[OTC]

Foreign Brand Names
Allerdryl® (Canada); Allernix® (Canada)

Therapeutic Categories
Antihistamine

Reasons not to take this medicine

  • If you have an allergy to diphenhydramine or any other part of the medicine.
  • If you have an asthma attack.
  • Do not give to newborns.


What is this medicine used for?

  • This medicine relieves symptoms (runny nose; sneezing; throat irritation and itching; watery, irritated, itchy, red eyes) from allergies.
  • It is used for the treatment of hives and angioedema.
  • It is also used for motion sickness, sleep disturbance, Parkinson's disease, cough (colds/allergy), drug-induced extrapyramidal reactions, and skin disorders causing itching.


How does it work?

  • Diphenhydramine, if taken before coming in contact with the material that causes the allergy, blocks the allergic reaction by minimizing/preventing the body's reaction to the allergen.
  • For motion sickness, it interferes with messages between the vomiting center in the brain and other control centers.
  • One of its side effects is drowsiness which aids in sleep.
  • In Parkinson's disease, it helps balance a chemical problem.


How is it best taken?

  • Oral:
    • Take with or without food. Take with food if this medicine causes an upset stomach.
    • A liquid (elixir, syrup) is available if you cannot swallow pills. Those who have feeding tubes can also use the liquid. Flush the feeding tube before and after medicine is given.
    • If you are taking this medicine for motion sickness, take 30 minutes before travel.
    • If you are taking this medicine for an allergy, it is most effective if started before contact with the allergen. Take at least 1-3 hours before.
    • Diphenhydramine needs to be taken an hour before going to bed if you are taking this medicine to help you sleep.
  • Skin:
    • Do not take by mouth. For skin only. Keep out of mouth, nose, and eyes (may burn).
    • Clean affected area before use.
    • Use in a small amount over the area affected as a light film. Rub in gently.


What do I do if I miss a dose?

  • Take a missed dose as soon as possible.
  • If it is almost time for the next dose, skip the missed one. Return to your regular schedule.
  • Do not take a double dose or extra doses.


What are the precautions when taking this medicine?

  • Tell healthcare provider if you are allergic to any medicine. Make sure to tell about the allergy and how it affected you. This includes telling about rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, throat; or any other symptoms involved. pregnant.
  • Do not use if you are breast-feeding.
  • Tell healthcare provider if you are pregnant or plan on getting
  • Oral:
    • If you are 65 or older, you may have more side effects. You could feel sleepy, confused, constipated, or be unable to pass urine.
    • Avoid alcohol (includes wine, beer, and liquor) and other medicines and herbs that slow your actions and reactions. This includes sedatives, tranquilizers, mood stabilizers, or pain medicine. Talk with healthcare provider.
    • Increased activity or inability to sleep may be seen in children.
  • Skin:
    • Use caution on skin where a large area is involved or where there are open wounds. The medicine can get into your system and cause side effects.


What are the common side effects of this medicine?

  • Oral:
    • Feeling sleepy, tired, dizzy, or unable to think clearly. Avoid driving, doing other tasks or activities that require you to be alert until you see how this medicine affects you.
    • Constipation. More liquid, regular exercise, or a fiber-containing diet may help. Talk with healthcare provider about a stool softener or laxative.
    • Dry mouth. Frequent mouth care, sucking hard candy, or chewing gum may help.
    • Unable to pass urine. Go to the bathroom before taking medicine. Talk with healthcare provider if it becomes a problem.
  • Skin:
    • Burning, itching, redness.


What should I monitor?

  • Watch for effectiveness of medicine in preventing and treating symptoms.


Reasons to call healthcare provider immediately

  • Signs of a life-threatening reaction. These include wheezing; tightness in the chest; fever; itching; bad cough; blue skin color; fits; swelling of face, lips, tongue, or throat.
  • Too tired or sleepy.
  • Any rash.
  • No improvement in condition or feeling worse.


How should I store this medicine?

  • Store in a tight container at room temperature.


General statements

  • Do not share your medicine with others and do not take anyone else's medicine.
  • Keep all medicine out of the reach of children and pets.
  • Keep a list of all your medicines (prescription, herbal/supplements, vitamins, over-the-counter) with you. Give this list to healthcare provider (doctor, nurse, pharmacist, physician assistant).
  • Talk with healthcare provider before starting any new medicine, including over-the-counter or natural products (herbs, vitamins).


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