Diphenhydramine

What is Diphenhydramine?

• Diphenhydramine is a first generation antihistamine used to relieve red, irritated, itchy, watery eyes; sneezing; and runny nose caused by hay fever, allergies, or the common cold.
• It can also be used for insomnia, symptoms of the common cold, tremor in parkinsonism, and nausea.

Diphenhydramine

Diphenhydramine ball-and-stick animation

Diphenhydramine 3D ball

What are the uses of this medicine?

• Diphenhydramine is used to relieve red, irritated, itchy, watery eyes; sneezing; and runny nose caused by hay fever, allergies, or the common cold.
• Diphenhydramine is used for allergic conjunctivitis due to foods; mild, uncomplicated allergic skin manifestations of urticaria and angioedema; amelioration of allergic reactions to blood or plasma; dermatographism; as therapy for anaphylactic reactions adjunctive to epinephrine and other standard measures after the acute manifestations have been controlled.
• Diphenhydramine is used for active and prophylactic treatment of motion sickness.
• Diphenhydramine is also used to control abnormal movements in people who have early stage parkinsonian syndrome (a disorder of the nervous system that causes difficulties with movement, muscle control, and balance) or who are experiencing movement problems as a side effect of a medication.
• Diphenhydramine is also used as nighttime sleep-aid.

How does this medicine work?

• Diphenhydramine (dye" fen hye' dra meen) is a first generation antihistamine that is used widely in the therapy of the symptoms of allergic rhinitis and the common cold, including sneezing, cough, runny note, watery eyes and itching.
• Because of its sedating side effects, it is also used as a mild sleeping aid.
• In intravenous forms, diphenhydramine is used in the treatment of severe allergic reactions and anaphylaxis.
• Diphenhydramine belongs to the ethanolamine class of antihistamines (with clemastine and dimenhydrinate) and in 1946 became the first antihistamine approved for use in the United States.
• It is still widely used today and is available in multiple generic forms as tablets, capsules, liquid oral and intravenous solutions, creams and syrups, many of which are available without prescription.

Who Should Not Use this medicine ?

This medicine cannot be used in:

• neonates or premature infants.
• nursing mothers
• Patients with hypersensitivity to diphenhydramine hydrochloride and other antihistamines of similar chemical structure.

What drug interactions can this medicine cause?

• Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Be sure to mention the medications listed below:

• other diphenhydramine products (even those that are used on the skin)
• other medications for colds, hay fever, or allergies
• medications for anxiety, depression, or seizures
• muscle relaxants
• narcotic medications for pain
• sedatives
• sleeping pills
• tranquilizers

Is this medicine FDA approved?

• Diphenhydramine was first made by George Rieveschl and came into commercial use in 1946.
• It is available as a generic medication.
• It is sold under the brand name Benadryl, among others.
• In 2017, it was the 241st most commonly prescribed medication in the United States, with more than two million prescriptions.

How should this medicine be used?

Recommended dosage: Adults:

• 25 to 50 mg three to four times daily.
• The nightime sleep aid dosage is 50 mg at bedtime.

Pediatric Patients (over 20 lbs.):

• 12.5 to 25 mg three or four times daily. Maximum daily dosage not to exceed 300 mg.
• The recommended dosage is 5 mg/kg/24 hours or 150 mg/m2/24 hours.

• Data are not available on the use of diphenhydramine hydrochloride as a nighttime sleep-aid in children under 12 years.

• In motion sickness, full dosage is recommended for prophylactic use, the first dose to be given 30 minutes before exposure to motion.

Administration:

• Diphenhydramine comes as a tablet, a rapidly disintegrating (dissolving) tablet, a capsule, a liquid-filled capsule, a dissolving strip, powder, and a liquid to take by mouth.
• When diphenhydramine is used for the relief of allergies, cold, and cough symptoms, it is usually taken every 4 to 6 hours.
• When diphenhydramine is used to treat motion sickness, it is usually taken 30 minutes before departure and, if needed, before meals and at bedtime. When diphenhydramine is used to treat insomnia it is taken at bedtime (30 minutes before planned sleep). When diphenhydramine is used to treat abnormal movements, it is usually taken three times a day at first and then taken 4 times a day.
• Nonprescription cough and cold combination products, including products that contain diphenhydramine, can cause serious side effects or death in young children. Do not give these products to children younger than 4 years of age. If you give these products to children 4 to 11 years of age, use caution and follow the package directions carefully.
• If you are taking the liquid, do not use a household spoon to measure your dose. Use the measuring spoon or cup that came with the medication or use a spoon made especially for measuring medication.
• If you are taking the dissolving strips, place the strips on your tongue one at a time and swallow after they melt.
• If you are taking the rapidly dissolving tablets, place a tablet on your tongue and close your mouth. The tablet will quickly dissolve and can be swallowed with or without water.
• If you are taking the capsules, swallow them whole. Do not try to break the capsules.

What are the dosage forms and brand names of this medicine?

This medicine is available in fallowing doasage form:

• As as a tablet, a rapidly disintegrating (dissolving) tablet, a capsule, a liquid-filled capsule, a dissolving strip, powder, and a liquid

This medicine is available in fallowing brand namesː

• Aler-Dryl
• Allergia-C
• Allermax
• Altaryl
• Banophen
• Ben Tann
• Benadryl
• Bromanate AF
• Compoz Nighttime Sleep Aid
• Dicopanol
• Diphedryl
• Diphen
• Diphenadryl
• Diphenhist
• Diphenylin
• Dytan
• Hydramine
• Nytol
• Pardryl
• PediaCare Children's Allergy
• Siladryl
• Silphen
• Sominex
• Unisom

What side effects can this medication cause?

The most common side effects of this medicine include:

• dry mouth, nose, and throat
• drowsiness
• dizziness
• nausea
• vomiting
• loss of appetite
• constipation
• increased chest congestion
• headache
• muscle weakness
• excitement (especially in children)
• nervousness
• sedation
• impairment of motor function
• confusion
• blurred vision
• palpitations
• tachycardia
• abdominal distress
• constipation
• headache

• Antihistamines can worsen urinary retention and glaucoma

What special precautions should I follow?

• Antihistamines should be used with considerable caution in patients with narrow-angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, or bladder-neck obstruction.
• In pediatric patients, especially, antihistamines in overdosage may cause hallucinations, convulsions, or death. As in adults, antihistamines may diminish mental alertness in pediatric patients. In the young pediatric patient, particularly, they may produce excitation.
• Antihistamines are most likely to cause dizziness, sedation, and hypotension in elderly patients.
• Diphenhydramine hydrochloride has an atropine-like action and therefore, should be used with caution in patients with a history of bronchial asthma, increased intraocular pressure, hyperthyroidism, cardiovascular disease or hypertension.
• Patients taking diphenhydramine hydrochloride should be advised that this drug may cause drowsiness and has an additive effect with alcohol. Patients should be warned about engaging in activities requiring mental alertness such as driving a car or operating appliances, machinery, etc.
• Avoid alcoholic beverages while you are taking this medication.
• If you have phenylketonuria (PKU, an inherited condition in which a special diet must be followed to prevent damage to your brain that can cause severe intellectual disability), you should know that some brands of chewable tablets and rapidly disintegrating tablets that contain diphenhydramine may be sweetened with aspartame, a source of phenylalanine.
• Diphenhydramine has not been linked to instances of clinically apparent acute liver injury.

What to do in case of emergency/overdose?

Symptoms of overdose may include:

• dry mouth
• fixed
• dilated pupils
• flushing
• gastrointestinal symptoms

Management of overdosage:

• If vomiting has not occurred spontaneously, the patient should be induced to vomit.
• This is best done by having him drink a glass of water or milk after which he should be made to gag.
• If vomiting is unsuccessful, gastric lavage is indicated within 3 hours after ingestion and even later if large amounts of milk or cream were given beforehand.
• Isotonic or 1/2 isotonic saline is the lavage solution of choice.
• Saline cathartics, as milk of magnesia, by osmosis draw water into the bowel and therefore are valuable for their action in rapid dilution of bowel content.
• Stimulants should not be used.
• Vasopressors may be used to treat hypotension.

Can this medicine be used in pregnancy?

• Pregnancy Category B.
• There are, however, no adequate and well-controlled studies in pregnant women.
• This drug should be used during pregnancy only if clearly needed.

Can this medicine be used in children?

• Diphenhydramine hydrochloride should not be used in neonates and premature infants.
• Diphenhydramine hydrochloride may diminish mental alertness, or, in the young pediatric patient, cause excitation.
• Overdosage may cause hallucinations, convulsions, or death.

What are the active and inactive ingredients in this medicine?

Active ingredients:

• diphenhydramine hydrochloride

Inactive Ingredients:

• alcohol
• anhydrous citric acid
• d&c red no. 33
• fd&c red no. 40
• water
• sodium citrate
• sucrose

Who manufactures and distributes this medicine?

• Pharmaceutical Associates, Inc.
• Greenville, SC

What should I know about storage and disposal of this medication?

• Store it at room temperature and away from excess heat and moisture (not in the bathroom).
• Store at 20° to 25°C (68° to 77°F).

• Dailymed label info on Diphenhydramine
• FDA Diphenhydramine

Diphenhydramine Resources
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