Diphenhydramine


Description

Diphenhydramine - perhaps known most commonly as its brand name formulation Benadryl - is a first-generation H1 receptor antihistamine that is used extensively for the treatment of seasonal allergies, insect bites and stings, and rashes [

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Pharmacology

Indication

Diphenhydramine is a first-generation histamine H1 receptor antagonist (H1 antihistamine) that is wi... Read more

Pharmacodynamic

Diphenhydramine has anti-histaminic (H1-receptor), anti-emetic, anti-vertigo and sedative and hypnot... Read more

Mechanismofaction

Diphenhydramine predominantly works via the antagonism of H1 (Histamine 1) receptors [ Read more

Absorption

Diphenhydramine is quickly absorbed after oral administration with maximum activity occurring in app... Read more

Proteinbinding

Some prescribing information records the protein binding of diphenhydramine as approximately 78% [ Read more

Volumeofdistribution

Diphenhydramine is widely distributed throughout the body, including the CNS [ Read more

Clearance

Values for plasma clearance of a 50 mg oral dose of diphenhydramine has been documented as lying in... Read more

Halflife

The elimination half-life ranges from 2.4-9.3 hours in healthy adults [ Read more

Routeofelimination

The metabolites of diphenhydramine are conjugated with glycine and glutamine and excreted in urine [... Read more

Toxicity

Overdose is expected to result in effects similar to the adverse effects that are ordinarily associa... Read more


Adverse Effects

Effect Regions Age Groups Incidences Evidence Type
Wheezing US
Varying Reports
Tightness of throat US
Varying Reports
Tightness of chest US
Varying Reports
Thickening of bronchial secretions US
Varying Reports
Early menses US
Varying Reports
Urinary Retention US
Varying Reports
Difficult urination US
Varying Reports
Urinary Frequency US
Varying Reports
Nasal Stuffiness US
Varying Reports
Tinnitus US
Varying Reports
Acute labyrinthitis US
Varying Reports
Diplopia US
Varying Reports
Vertigo US
Varying Reports
Paresthesia US
Varying Reports
Blurred vision US
Varying Reports
Insomnia US
Varying Reports
Euphoria US
Varying Reports
Diarrhea US
Varying Reports
Constipation US
Varying Reports
Nausea US
Varying Reports
Vomiting US
Varying Reports
Epigastric distress US
Varying Reports
Anorexia US
Varying Reports
Neuritis US
Varying Reports
Convulsions US
Varying Reports
Sedation US
Varying Reports
Agranulocytosis US
Varying Reports
Dizziness US
Varying Reports
Sleepiness US
Varying Reports
Extrasystoles US
Varying Reports
Tachycardia US
Varying Reports
Thrombocytopenia US
Varying Reports
Hemolytic Anemia US
Varying Reports
Nervousness US
Varying Reports
Excitation US
Varying Reports
Irritability US
Varying Reports
Tremor US
Varying Reports
Fatigue US
Varying Reports
Disturbed coordination US
Varying Reports
Restlessness US
Varying Reports
Confusion US
Varying Reports
Urticaria US
Varying Reports
Drug rash US
Varying Reports
Anaphylactic shock US
Varying Reports
Dryness of nose dryness of throat US
Varying Reports
Hypotension US
Varying Reports
Headache US
Varying Reports
Palpitations US
Varying Reports
Photosensitivity US
Varying Reports
Excessive perspiration US
Varying Reports

Contraindications

  • Route:
    • Intravenous
    • Intramuscular
  • Dose Form:
    • Injection
  • Regions: US
  • Patient Conditions:
      • Name: Use as a local anesthetic
      • Drugbank Id: DBCOND0108188
  • Route:
    • Intravenous
    • Intramuscular
  • Dose Form:
    • Injection
  • Regions: US
  • Patient Conditions:
      • Name: Nursing mothers
      • Drugbank Id: DBCOND0107390
  • Route:
    • Intravenous
    • Intramuscular
  • Dose Form:
    • Injection
  • Regions: US
  • Age Groups:
    • neonatal
    • premature infants

Food Interactions

  • Avoid alcohol.
  • Take with food.

Interactions

Type in a drug name to check for interaction with Diphenhydramine

The metabolism of (R)-warfarin can be decreased when combined with Diphenhydramine.
The metabolism of (S)-Warfarin can be decreased when combined with Diphenhydramine.
The therapeutic efficacy of Diphenhydramine can be decreased when used in combination with 1,10-Phenanthroline.
2,5-Dimethoxy-4-ethylamphetamine may decrease the sedative and stimulatory activities of Diphenhydramine.
2,5-Dimethoxy-4-ethylthioamphetamine may decrease the sedative and stimulatory activities of Diphenhydramine.
4-Bromo-2,5-dimethoxyamphetamine may decrease the sedative and stimulatory activities of Diphenhydramine.
4-Bromo-2,5-dimethoxyphenethylamine may increase the central nervous system depressant (CNS depressant) activities of Diphenhydramine.
The risk or severity of adverse effects can be increased when Diphenhydramine is combined with 4-Methoxyamphetamine.
The risk or severity of adverse effects can be increased when Diphenhydramine is combined with 5-methoxy-N,N-dimethyltryptamine.
The risk or severity of adverse effects can be increased when Diphenhydramine is combined with 7-Nitroindazole.
The risk or severity of adverse effects can be increased when 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline is combined with Diphenhydramine.
The metabolism of Diphenhydramine can be increased when combined with Abatacept.
The risk or severity of Tachycardia can be increased when Diphenhydramine is combined with Abediterol.
The risk or severity of QTc prolongation can be increased when Diphenhydramine is combined with Abexinostat.
The metabolism of Diphenhydramine can be decreased when combined with Abiraterone.
The metabolism of Acebutolol can be decreased when combined with Diphenhydramine.
The metabolism of Aceclofenac can be decreased when combined with Diphenhydramine.
The metabolism of Acenocoumarol can be decreased when combined with Diphenhydramine.
The risk or severity of adverse effects can be increased when Diphenhydramine is combined with Acepromazine.
The risk or severity of adverse effects can be increased when Diphenhydramine is combined with Aceprometazine.

References

  • 1 . Raphael GD, Angello JT, Wu MM, Druce HM: Efficacy of diphenhydramine vs desloratadine and placebo in patients with moderate-to-severe seasonal allergic rhinitis. Ann Allergy Asthma Immunol. 2006 Apr;96(4):606-14. [PubMed: 16680933]
  • 2 . Abdi A, Rose E, Levine M: Diphenhydramine overdose with intraventricular conduction delay treated with hypertonic sodium bicarbonate and i.v. lipid emulsion. West J Emerg Med. 2014 Nov;15(7):855-8. doi: 10.5811/westjem.2014.8.23407. Epub 2014 Sep 19. [PubMed: 25493135]
  • 3 . Halpert AG, Olmstead MC, Beninger RJ: Mechanisms and abuse liability of the anti-histamine dimenhydrinate. Neurosci Biobehav Rev. 2002 Jan;26(1):61-7. [PubMed: 11835984]
  • 4 . Jaju BP, Wang SC: Effects of diphenhydramine and dimenhydrinate on vestibular neuronal activity of cat: a search for the locus of their antimotion sickness action. J Pharmacol Exp Ther. 1971 Mar;176(3):718-24. [PubMed: 4329456]
  • 5 . Flake ZA, Scalley RD, Bailey AG: Practical selection of antiemetics. Am Fam Physician. 2004 Mar 1;69(5):1169-74. [PubMed: 15023018]
  • 6 . Paton DM, Webster DR: Clinical pharmacokinetics of H1-receptor antagonists (the antihistamines). Clin Pharmacokinet. 1985 Nov-Dec;10(6):477-97. [PubMed: 2866055]
  • 7 . Akutsu T, Kobayashi K, Sakurada K, Ikegaya H, Furihata T, Chiba K: Identification of human cytochrome p450 isozymes involved in diphenhydramine N-demethylation. Drug Metab Dispos. 2007 Jan;35(1):72-8. doi: 10.1124/dmd.106.012088. Epub 2006 Oct 4. [PubMed: 17020955]
  • 8 . Rodrigues WC, Castro C, Catbagan P, Moore C, Wang G: Immunoassay screening of diphenhydramine (Benadryl(R)) in urine and blood using a newly developed assay. J Anal Toxicol. 2012 Mar;36(2):123-9. doi: 10.1093/jat/bkr015. [PubMed: 22337782]
  • 9 . StatPearls [Internet]: Diphenhydramine [Link]
  • 10 . Electronic Medicines Compendium: Histergan (diphenhydramine hydrochloride) Tablets Patient Information [Link]
  • 11 . Electronic Medicines Compendium: Histergan (diphenhydramine hydrochloride) Cream Monograph [Link]
  • 12 . Electronic Medicines Compendium: Boots Sleepeaze (diphenhydramine hydrochloride) 50mg Tablets Monograph [Link]
  • 13 . Electronic Medicines Compendium: Nytol One-A-Night (diphenhydramine hydrochloride) Monograph [Link]
  • 14 . Diphenhydramine Hydrochloride Injection, USP FDA Label [File]
  • 15 . DIPHENHYDRAMINE- diphenhydramine hcl tablet, coated DailyMed FDA Label [File]
  • 16 . Benylin Chesty Coughs UK MHRA Product Information [File]

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