Dipenhydramine or Diphenhydramine Hydrochloride is a first-generation antihistamine used to treat allergies. Like any other first-generation antihistamine, Diphenhydramine brings drowsiness to those who take it therefore sometimes used as a non-prescription sleep aid and a mild anxiolytic. Common brand names are Alerace, Allerin, Benadryl, Benaxil, Caladryl lotion, Dramelin, Insomed, and Tusicon. Diphenhydramine is classified as an Ethanolamine, Antihistamine, Anticholinergic, Antipruritic, Antitussive, Antiemetic, and Antidyskinetic.
Indication for Diphenhydramine
Diphenhydramine is used to treat allergic reactions and parkinsonism. It is also used in the prevention and treatment of nausea, vomiting, and vertigo due to motion sickness. Diphenhydramine is also an antitussive and can be used as a short term treatment of insomnia. A topical form of Diphenhydramine can be used to relieve pruritus, insect bites, and skin irritations.
Routes and Dosage of Diphenhydramine
Moderate to Severe Allergic Reaction, Dystonic Reaction
PO/IM/IV: ADULTS, ELDERLY: 25-50mg every 4 hours. Maximum: 400mg per day. CHILDREN: 5mg/kg/day in divided doses every 6-8 hours. Maximum: 300mg per day.
Motion Sickness, Minor Allergic Rhinitis
PO/IM/IV: ADULTS, ELDERLY, CHILDREN >12 YEARS: 25-50mg every 4-6 hours. Maximum: 300mg per day. CHILDREN: 6-12 years: 12.5-25mg every 4-6 hours. Maximum: 150mg per day. CHILDREN 2-6 YEARS: 6.25mg every 4-6 hours Maximum: 37.5mg per day.
Antitussive
PO: ADULTS, ELDERLY, CHILDREN >12 YEARS: 25mg every 4 hours. Maximum: 150mg per day. CHILDREN 6-12 YEARS: 12.5mg every 4 hours. Maximum: 75mg per day. CHILDREN 2-6 YEARS: 6.25mg every 4 hours. Maximum: 37.5mg per day.
Nighttime Sleep Aid
PO: ADULTS, ELDERLY, CHILDREN >12 YEARS: 50mg at bed time. CHILDREN 2-12 YEARS: 1 mg/kg/dose. Maximum: 50mg.
Pruritus Relief
TOPICAL: ADULTS, ELDERLY, CHILDREN >12 YEARS: 1% or 2% STRENGTH: Apply 3-4 times a day. CHILDREN 2-12 YEARS: 1% STRENGTH: Apply 3-4 times a day.
Action of Diphenhydramine
Diphenhydramine competes with histamine at histamine receptor sites. It inhibits central acetylcholine. It results in anticholinergic, antipruritic, antitussive, and antiemetic effect. Diphenhydramine produces antidyskinetic and sedative effect.
Side Effects and Adverse Reactions of Diphehydramine
Side Effects of Diphenhydramine
- Drowsiness
- Dizziness
- Muscular weakness
- Hypotension
- Dry mouth, nose, throat, or lips
- Urinary retention
- thicknening of bronchial secretions
- Sedation
- Epigastric distress
- Flushing
- Visual or hearing disturbances
- Paresthesia
- Diaphoresis
- Chills
Adverse Reactions of Diphenhydramine
- Dominant paradoxical reactions (restlessness, insomnia, euphoria, nervousness, and tremors)
- Hallucinations
- Seizures
- Hypersensitivity reactions (eczema, pruritus, rash, cardiac disturbances, and photosensitivity)
- CNS depression (sedation, apnea, hypotension, cardiovascular collapse, and death)
Nursing Considerations for Clients Taking Diphenhydramine
- Give without regards to meals.
- Scored tablets may be crushed. Do not crush capsules or film-coated tablets.
- If patient is having acute allergic reactions, obtain history of recently ingested food, drugs, environmental exposure, and recent emotional stress.
- Monitor rate, depth, rhythm, and type of respiration.
- Monitor rate, depth, rhythm, and quality or rate of pulse.
- Assess lung sounds for rhonchi, wheezing, rales.
- Monitor blood pressure especially in elderly.
- Monitor children closely for paradoxical reaction.
Patient Teachings for Clients Taking Diphenhydramine
- Tolerance to antihistamine effect generally does not occur; tolerance to sedative effect may occur.
- Avoid tasks that require alertness and motor skills until response to drug is established.
- Dry mouth, drowsiness, and dizziness may be an expected response of drug.
- Avoid alcoholic beverages.
