Diphenhydramine (Benadryl) Overview
Diphenhydramine hydrochloride, known by the brand name Benadryl, is a widely used first-generation antihistamine. Its primary function is to alleviate allergy symptoms such as sneezing, itching, and runny nose. Additionally, it serves multiple other roles including treating motion sickness, and Parkinsonism, providing a nighttime sleep aid, and acting as an antitussive (cough suppressant).
Contents
This medication works by blocking acetylcholine and H-1 receptors, leading to its sedative, anticholinergic, and antiemetic effects.
Generic Name:
Diphenhydramine hydrochloride
Brand Name:
Benadryl
Classification:
Antihistamine, first-generation, ethanolamine
Uses
- Treatment of hypersensitivity reactions
- Treatment of motion sickness
- Treatment of Parkinsonism
- Nighttime sleep aid
- Antitussive
- Adjunctive therapy for anaphylactic reactions
Actions
- Exhibits sedative, anticholinergic, and antiemetic effects
- Blocks the action of acetylcholine
- Blocks H-1 receptors on effector cells of the GI tract, blood vessels, and respiratory tract
Contraindications
- Use with other products containing diphenhydramine
- Hypersensitivity to antihistamines
- Newborns and premature infants
Special Concerns:
- Elderly: Increases the risk of cognitive decline
- Use with caution in clients with:
- Increased intraocular pressure
- Closed-angle glaucoma
- Chronic constipation
- Hypertension
- Stenosing peptic ulcer
- Bladder obstruction
- Enlarged prostate
- Overactive thyroid
- Asthma
Side Effects
- Drowsiness
- Constipation
- Diarrhea
- Dizziness
- Dry mouth/nose/throat
- Headache
- Anorexia
- Nausea & Vomiting
- Anxiety
- Gastrointestinal upset
- Weakness (Asthenia)
- Blurred vision
- Fatigue
Dosage:
- Oral: 25-50 mg TID-QID
- IV: 10-50 mg, up to 100 mg/IV
Nursing Considerations
- Administer full prophylactic dose 30 minutes prior to travel if used as prophylaxis for motion sickness
- Take similar doses with meals and at bedtime
- Do not use for more than 2 weeks to treat insomnia
- For IV, may give undiluted
- Do not exceed the IV rate of 25 mg/minute
- The drug causes drowsiness; avoid activities requiring mental alertness
- Use sun protection as it may cause photosensitivity
- Use sugarless candy/gum to diminish dry mouth effects
- Avoid alcohol and other CNS depressants
- Discontinue therapy 72-96 hours before skin testing. Report adverse effects and lack of response
- Monitor for signs of anticholinergic effects such as dry mouth, urinary retention, and increased intraocular pressure
- Educate patients on potential interactions with other medications, including MAO inhibitors
References
- World Health Organization. (2020). WHO model list of essential medicines. Retrieved from https://www.who.int/publications/i/item/WHO-MHP-20.10
- Centers for Disease Control and Prevention. (2020). Diphenhydramine information. Retrieved from https://www.cdc.gov/ncbddd/medications/diphenhydramine.html
- MedlinePlus. (2020). Diphenhydramine. Retrieved from https://medlineplus.gov/druginfo/meds/a682539.html
- Mayo Clinic. (2020). Diphenhydramine (oral route). Retrieved from https://www.mayoclinic.org/drugs-supplements/diphenhydramine-oral-route/proper-use/drg-20068588
- Drugs.com. (2020). Diphenhydramine. Retrieved from https://www.drugs.com/diphenhydramine.html
