ZzzQuil

Diphenhydramine

Clinical data
Pronunciation	/ˌdaɪfɛnˈhaɪdrəmiːn/
Trade names	Benadryl, Unisom, Sominex, others
AHFS/Drugs.com	Monograph
MedlinePlus	a682539
Pregnancy category	AU: A US: B (No risk in non-human studies)
Dependence liability	Very low
Routes of administration	By mouth, IM, IV, topical and rectal
ATC code	D04AA32 (WHO) D04AA33 (WHO), R06AA02 (WHO)
Legal status
Legal status	AU: S2 (Pharmacy only) US: OTC
Pharmacokinetic data
Bioavailability	40–60%
Protein binding	98–99%
Metabolism	Various liver enzymes: CYP2D6 (80%), 3A4 (10%)
Biological half-life	7 hours (children) 12 hours (adults) 17 hours (elderly)
Excretion	94% through the urine, 6% through feces
Identifiers
IUPAC name 2-(diphenylmethoxy)-N,N-dimethylethanamine
CAS Number	58-73-1 Y
PubChem CID	3100
IUPHAR/BPS	1224
DrugBank	DB01075 Y
ChemSpider	2989 Y
UNII	8GTS82S83M
KEGG	D00669 N
ChEBI	CHEBI:4636 Y
ChEMBL	CHEMBL657 Y
ECHA InfoCard	100.000.360
Chemical and physical data
Formula	C17H21NO
Molar mass	255.355 g/mol
3D model (Jmol)	Interactive image
SMILES O(CCN(C)C)C(c1ccccc1)c2ccccc2
InChI 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 Y Key:ZZVUWRFHKOJYTH-UHFFFAOYSA-N Y
NY (what is this?)

Diphenhydramine is an antihistamine mainly used to treat allergies. It is also used for insomnia, symptoms of the common cold, tremor in parkinsonism, and nausea. It is used by mouth, injection into a vein, and injection into a muscle. Maximal effect is typically around two hours after a dose and effects can last for up to seven hours.

Common side effects include sleepiness, poor coordination, and an upset stomach. Its use is not recommended in babies. There is no clear risk of harm when used during pregnancy; however, use during breastfeeding is not recommended. It is a first generation H1-antihistamine and works by blocking certain effects of histamine.

Diphenhydramine was made by George Rieveschl and came into commercial use in 1946. It is available as a generic medication. The wholesale price in the developing world as of 2014 is about US$0.01 per dose. In the United States, it costs less than US$25 for a typical month supply. It is sold under the trade name Benadryl among others.

Diphenhydramine is a first-generation antihistamine used to treat a number of conditions including allergic symptoms and itchiness, the common cold, insomnia, motion sickness, and extrapyramidal symptoms. Diphenhydramine also has local anesthetic properties, and has been used as such in people allergic to common local anesthetics such as lidocaine.