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Diphenhydramine

Brand Names: Benadryl, Benadryl Allergy Dye-Free LiquiGels, Children's Benadryl Allergy, Children's Triaminic Thin Strips Allergy, Alka-Seltzer Plus Allergy, Nytol, PediaCare Children's Allergy, Simply Sleep, Sominex, QlearQuil Nighttime Allergy Relief, Tranquil Nighttime Sleep Aid, Unisom SleepGels, Unisom SleepMelts, ZzzQuil

Generic Name: Diphenhydramine

Drug Class: Antihistamines, 1st Generation; Antiemetic Agents

What Is Diphenhydramine and How Does It Work?

Diphenhydramine is an antihistamine which can be obtained both via a prescription and over-the-counter (OTC). Diphenhydramine can be used to treat allergic reactions, insomnia, cough, motion sickness and Parkinsonism.

Diphenhydramine is available under the following different brand names: Benadryl, Benadryl Allergy Dye-Free LiquiGels, Children's Benadryl Allergy, Children's Triaminic Thin Strips Allergy, Alka-Seltzer Plus Allergy, Nytol, PediaCare Children's Allergy, Simply Sleep, Sominex, QlearQuil Nighttime Allergy Relief, Tranquil Nighttime Sleep Aid, Unisom SleepGels, Unisom SleepMelts, and ZzzQuil.

Dosages of Diphenhydramine:

Oral liquid/solution

  • 12.5 mg/5 ml (Benadryl Allergy Childrens, PediCare Children's Allergy, Allergy Relief Childrens)
  • 50 mg/30 ml (ZzzQuil)

Elixir

  • 12.5 mg/ml (Altaryl)

Syrup

  • 12.5 mg/ml (Altaryl, Quenalin, Silphen Cough)

Tablet

  • 25 mg (Benadryl, Nytol, Simply Sleep, Sominex, Simply Allergy, Tetra-Formula Nighttime Sleep)
  • 50 mg (Aler-Dryl, Nytol Maximum Strength)

Capsule

  • 25 mg (Benadryl Allergy Dye-Free Allergy, Anti-Hist Allergy, Allergy Relief, Diphenhist, Geri-Dryl)
  • 50 mg (Banophen, Pharbedryl)

Chewable Tablet

  • 12.5 mg (Benadryl Allergy Childrens)

Dispersible Tablets

  • 25 mg (Unisom SleepMelts)

Strip

Injectable solution

  • 50 mg/ml

Dosage Considerations – Should be Given as Follows:

Allergic Reaction

Adult

  • 25-50 mg orally every 6-8 hours, not to exceed 300 mg/day
  • 10-50 mg (no more than 100 mg) intravenously or intramuscular every 4-6 hours, not to exceed 400 mg/day

Children

  • Children 2-6 years: 6.25 mg every 4-6 hours, not to exceed 37.5 mg/day
  • Children 6-12 years: 12.5-25 mg orally every 4-6 hours, not to exceed 150 mg/day
  • Children 12 years and older: 25-50 mg orally every 4-6 hours, not to exceed 300 mg/day

Geriatric

  • 25 mg orally/intravenously/intermuscular every 8-12 hours, use only for emergency allergic reactions at smallest effective dose
  • Non-anticholinergic antihistamines should be considered first for treatment of allergic reaction (Beers criteria); use of diphenhydramine in acute treatment of severe allergic reaction may be appropriate

Insomnia

Adult

  • 50 mg orally 30 minutes before bedtime

Children

  • Children under 12 years (off-label): 1 mg/kg; not to exceed 50 mg; 30 min before bedtime
  • Children 12 years or older: 50 mg orally 30 minutes before bedtime

Cough

Adult

  • 25-50 mg orally every 4 hours as needed (syrup preferred), not to exceed 150 mg/day

Children

  • Children under 12 years: Safety and efficacy not established
  • Children 12 years or older: 25-50 mg orally every 4-6 hours, not to exceed 300 mg/day

Geriatric

  • 25 mg orally every 8-12 hours, avoid in elderly if possible

Motion Sickness

Adult

  • Treatment or as a prophylaxis: 25-50 mg orally every 6-8 hours.
  • Alternatively, 10-50 mg/dose for treatment; may use up to 100 mg if needed; not to exceed 400 mg

Children

  • Administer 30 min before motion, 12.5-25 mg orally every 6-8 hours or 150 mg/m² ; not to exceed 300 mg/day

Geriatric

  • 25 mg orally/intravenously/intramuscular every 8-12 hours

Parkinsonism

  • 25 mg orally every 8 hours initially, then 50 mg orally every 6 hours, not to exceed 300 mg/day
  • Alternatively, 10-50 mg intravenously at a rate not to exceed 25 mg/min; not to exceed 400 mg/day; may also administer 100 mg intramuscular as required

Dystonic Reaction

  • 50 mg intravenously/intramuscular, may be repeated in 20-30 minutes if necessary

Geriatric Dosing Modifications

Advanced age is associated with reduced clearance of drug and greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity; if used, consider lower doses.

In patients with Parkinsonism who are unable to tolerate more potent agents, use at lowest effective dose.

What Are Side Effects Associated with Using Diphenhydramine?

Common side effects include:

What Other Drugs Interact with Diphenhydramine?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

Severe Interactions of Diphenhydramine include:

  • eliglustat

Serious Interactions of Diphenhydramine include

  • eluxadoline
  • isocarboxazid
  • mefloquine
  • pramlintide
  • quinidine
  • sodium oxybate
  • thioridazine
  • tranylcypromine

Diphenhydramine has moderate interactions with at least 275 different drugs.

Diphenhydramine has mild interactions with at least 37 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Diphenhydramine?

Warnings

  • Elderly patients: Considered high-risk medication for this age group because it may increase risk of falls and has high incidence of anticholinergic effects; it may exacerbate existing lower urinary tract conditions or benign prostatic hyperplasia; use in special situations may be appropriate; diphenhydramine is not recommended for treatment of insomnia, because tolerance develops and risk of anticholinergic effects increases
  • This medication contains diphenhydramine. Do not take Benadryl, Benadryl Allergy Dye-Free LiquiGels, Children's Benadryl Allergy, Children's Triaminic Thin Strips Allergy, Alka-Seltzer Plus Allergy, Nytol, PediaCare Children's Allergy, Simply Sleep, Sominex, QlearQuil Nighttime Allergy Relief, Tranquil Nighttime Sleep Aid, Unisom SleepGels, Unisom SleepMelts, or ZzzQuil if you are allergic to diphenhydramine or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

  • Documented hypersensitivity
  • Lower respiratory tract disease, such as acute asthma (controversial)
  • Premature infants or neonates
  • Nursing mothers
  • Use as local anesthetic
  • To make children under 6 years old sleep, when used for self-medication

Effects of Drug Abuse

  • Patients may develop a tolerance for diphenhydramine

Short-Term Effects

  • May cause central nervous system depression, which can impair driving or operating heavy machinery. May increase the effects of sedatives such as alcohol
  • See "What Are Side Effects Associated with Using Diphenhydramine?"

Long-Term Effects

  • Diphenhydramine is not recommended for treatment of insomnia in elderly patients, because tolerance develops and risk of anticholinergic effects increases.
  • See "What Are Side Effects Associated with Using Diphenhydramine?"

Cautions

  • May cause central nervous system depression, which can impair driving or operating heavy machinery
  • May potentiate effects of sedatives such as alcohol
  • Use caution in patients with angle-closure glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, and thyroid dysfunction
  • Elderly patients: Considered high-risk medication for this age group because it may increase risk of falls and has high incidence of anticholinergic effects; may exacerbate existing lower urinary tract conditions or benign prostatic hyperplasia; use in special situations may be appropriate; not recommended for treatment of insomnia, because tolerance develops and risk of anticholinergic effects increases
    • Pregnancy and Lactation

      • Diphenhydramine use in pregnancy may be acceptable
      • Either animal studies show no risk but human studies are not available, or animal studies showed minor risks and human studies were done and showed no risk
      • Diphenhydramine enters into breast milk, therefore do not use diphenhydramine when lactating
Reviewed on 4/14/2017


SOURCE:
Medscape. Diphenhydramine.
https://reference.medscape.com/drug/benadryl-nytol-diphenhydramine-343392#0

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