Diphenhydramine

Not to be confused with dimenhydrinate.

Diphenhydramine
Clinical data
Pronunciation/ˌdaɪfɛnˈhaɪdrəmiːn/
Trade namesBenadryl, Unisom, Nytol, others
AHFS/Drugs.comMonograph
MedlinePlusa682539
License data
Pregnancy
category
  • AU: A
Dependence
liability		Low[1][2]
Routes of
administration		By mouth, intramuscular, intravenous, topical, rectal
Drug classFirst-generation antihistamine, antimuscarinic, hallucinogen (deliriant)
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only) / S2 (Pharmacy Medicine) / S3 (Pharmacist Only Medicine)
  • CA: OTC
  • UK: P (Pharmacy medicines)[3]
  • US: OTC / Rx-only[4]
  • UN: Unscheduled
Pharmacokinetic data
Bioavailability40–60%[5]
Protein binding98–99%
MetabolismLiver (CYP2D6, others)[9][10]
Elimination half-lifeRange: 2.4–13.5 h[6][5][7]
ExcretionUrine: 94%[8]
Feces: 6%[8]
Identifiers
  • 2-(diphenylmethoxy)-N,N-dimethylethanamine
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.360 Edit this at Wikidata
Chemical and physical data
FormulaC17H21NO
Molar mass255.361 g·mol−1
3D model (JSmol)
  • O(CCN(C)C)C(c1ccccc1)c2ccccc2
  • InChI=1S/C17H21NO/c1-18(2)13-14-19-17(15-9-5-3-6-10-15)16-11-7-4-8-12-16/h3-12,17H,13-14H2,1-2H3 checkY
  • Key:ZZVUWRFHKOJYTH-UHFFFAOYSA-N checkY
 ☒NcheckY (what is this?)  (verify)

Diphenhydramine (DPH) is an antihistamine and sedative first developed by George Rieveschl and put into commercial use in 1946.[11][12] It is available as a generic medication,[13] and also sold under the brand name Benadryl among others.[13] In 2021, it was the 242nd most commonly prescribed medication in the United States, with more than 1 million prescriptions.[14][15]

It is a first-generation H1-antihistamine and it works by blocking certain effects of histamine, which produces its antihistamine and sedative effects.[13][2] Diphenhydramine is also a potent anticholinergic, which means it also works as a deliriant at much higher than recommended doses as a result.[16]

It is mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremors in parkinsonism, and nausea.[13] It is taken by mouth, injected into a vein, injected into a muscle, or applied to the skin.[13] Maximal effect is typically around two hours after a dose, and effects can last for up to seven hours.[13]

Common side effects include sleepiness, poor coordination, and upset stomach.[13] Its use is not recommended in young children or the elderly.[13][17] There is no clear risk of harm when used during pregnancy; however, use during breastfeeding is not recommended.[18]

Its sedative and deliriant effects have led to some cases of recreational use.[19][2]

  1. ^ Hubbard JR, Martin PR (2001). Substance Abuse in the Mentally and Physically Disabled. CRC Press. p. 26. ISBN 978-0-8247-4497-7.
  2. ^ a b c Saran JS, Barbano RL, Schult R, Wiegand TJ, Selioutski O (October 2017). "Chronic diphenhydramine abuse and withdrawal: A diagnostic challenge". Neurology. Clinical Practice. 7 (5): 439–441. doi:10.1212/CPJ.0000000000000304. PMC 5874453. PMID 29620065.
  3. ^ "Benylin Chesty Coughs (Original) - Summary of Product Characteristics (SmPC)". (emc). 24 February 2022. Archived from the original on 30 December 2022. Retrieved 29 December 2022.
  4. ^ "Diphenhydramine- diphenhydramine hydrochloride injection, solution". DailyMed. 11 November 2019. Retrieved 18 May 2024.
  5. ^ a b Cite error: The named reference pmid2866055 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference AHFS was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference pmid2391399 was invoked but never defined (see the help page).
  8. ^ a b Garnett WR (February 1986). "Diphenhydramine". American Pharmacy. NS26 (2): 35–40. doi:10.1016/s0095-9561(16)38634-0. PMID 3962845.
  9. ^ Cite error: The named reference pmid19153052 was invoked but never defined (see the help page).
  10. ^ "Showing Diphenhydramine (DB01075)". DrugBank. Archived from the original on 31 August 2009. Retrieved 5 September 2009.
  11. ^ Dörwald FZ (2013). Lead Optimization for Medicinal Chemists: Pharmacokinetic Properties of Functional Groups and Organic Compounds. John Wiley & Sons. p. 225. ISBN 978-3-527-64565-7. Archived from the original on 2 October 2016.
  12. ^ "Benadryl". Ohio History Central. Archived from the original on 17 October 2016. Retrieved 28 September 2016.
  13. ^ a b c d e f g h "Diphenhydramine Hydrochloride". Drugs.com. American Society of Health-System Pharmacists. 6 September 2016. Archived from the original on 15 September 2016. Retrieved 28 September 2016.
  14. ^ "The Top 300 of 2021". ClinCalc. Archived from the original on 15 January 2024. Retrieved 14 January 2024.
  15. ^ "Diphenhydramine - Drug Usage Statistics". ClinCalc. Retrieved 14 January 2024.
  16. ^ Ayd FJ (2000). Lexicon of Psychiatry, Neurology, and the Neurosciences. Lippincott Williams & Wilkins. p. 332. ISBN 978-0-7817-2468-5. Archived from the original on 8 September 2017.
  17. ^ Schroeck JL, Ford J, Conway EL, Kurtzhalts KE, Gee ME, Vollmer KA, et al. (November 2016). "Review of Safety and Efficacy of Sleep Medicines in Older Adults". Clinical Therapeutics. 38 (11): 2340–2372. doi:10.1016/j.clinthera.2016.09.010. PMID 27751669.
  18. ^ "Diphenhydramine Pregnancy and Breastfeeding Warnings". Drugs.com. Archived from the original on 2 October 2016. Retrieved 28 September 2016.
  19. ^ Cite error: The named reference Thomas2008 was invoked but never defined (see the help page).