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Clinical data
Trade namesBenadryl, Unisom, Nytol, others
License data
  • AU: A
Very low[1]
Routes of
By mouth, intramuscular, intravenous, topical, rectal
ATC code
Legal status
Legal status
Pharmacokinetic data
Protein binding98–99%
MetabolismLiver (CYP2D6, others)[2][3]
Elimination half-lifeRange: 2.4–13.5 h[5][4][6]
ExcretionUrine: 94%[7]
Feces: 6%[7]
  • 2-(diphenylmethoxy)-N,N-dimethylethanamine
CAS Number
PubChem CID
ECHA InfoCard100.000.360 Edit this at Wikidata
Chemical and physical data
Molar mass255.36 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
 ☒NcheckY (what is this?)  (verify)

Diphenhydramine (DPH) is an antihistamine medication. It is mainly used to treat allergies.[8] It can also be used to treat insomnia, the common cold, tremor in parkinsonism, and nausea.[8] It is taken by mouth, injected into a vein, injected into a muscle, or put on the skin.[8] It works best two hours after taking, and works for up to seven hours.[8]

Common side effects include sleepiness, bad balance and a bad stomach.[8] It should not be used in young children or the elderly.[8][9] It can be used while pregnant, but not when breastfeeding.[10] It works by blocking some effects of histamine from working at the H1 receptor.[8] Diphenhydramine is also an anticholinergic, and is a deliriant at high doses.[11]

Diphenhydramine was first made by George Rieveschl and was first used in 1946.[12][13] It is available as a generic medication.[8] It is also sold under the brand name Benadryl, as well as others.[8] It was the 241st most commoly prescribed medication in the United States in 2017.[14][15]

References[change | change source]

  1. Hubbard, John R.; Martin, Peter R. (2001). Substance Abuse in the Mentally and Physically Disabled. CRC Press. p. 26. ISBN 9780824744977.
  2. Krystal AD (August 2009). "A compendium of placebo-controlled trials of the risks/benefits of pharmacological treatments for insomnia: the empirical basis for U.S. clinical practice". Sleep Med Rev. 13 (4): 265–74. doi:10.1016/j.smrv.2008.08.001. PMID 19153052.
  3. "Showing Diphenhydramine (DB01075)". DrugBank. Archived from the original on 31 August 2009. Retrieved 5 September 2009.
  4. 4.0 4.1 Paton DM, Webster DR (1985). "Clinical pharmacokinetics of H1-receptor antagonists (the antihistamines)". Clinical Pharmacokinetics. 10 (6): 477–97. doi:10.2165/00003088-198510060-00002. PMID 2866055. S2CID 33541001.
  5. AHFS Drug Information. Published by authority of the Board of Directors of the American Society of Hospital Pharmacists. 1990.
  6. Simons KJ, Watson WT, Martin TJ, Chen XY, Simons FE (July 1990). "Diphenhydramine: pharmacokinetics and pharmacodynamics in elderly adults, young adults, and children". Journal of Clinical Pharmacology. 30 (7): 665–71. doi:10.1002/j.1552-4604.1990.tb01871.x. PMID 2391399. S2CID 25452263.
  7. 7.0 7.1 Garnett WR (February 1986). "Diphenhydramine". American Pharmacy. NS26 (2): 35–40. doi:10.1016/s0095-9561(16)38634-0. PMID 3962845.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 "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.
  9. Schroeck JL, Ford J, Conway EL, Kurtzhalts KE, Gee ME, Vollmer KA, Mergenhagen KA (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.
  10. "Diphenhydramine Pregnancy and Breastfeeding Warnings". Drugs.com. Archived from the original on 2 October 2016. Retrieved 28 September 2016.
  11. Ayd, Frank J. (2000). Lexicon of Psychiatry, Neurology, and the Neurosciences. Lippincott Williams & Wilkins. p. 332. ISBN 978-0-7817-2468-5.
  12. Dörwald, Florencio Zaragoza (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.
  13. "Benadryl". Ohio History Central. Archived from the original on 17 October 2016. Retrieved 28 September 2016.
  14. "The Top 300 of 2020". ClinCalc. Retrieved 11 April 2020.
  15. "Diphenhydramine Hydrochloride - Drug Usage Statistics". ClinCalc. Archived from the original on 29 April 2017. Retrieved 11 April 2020.