Diphenhydramine (/ˌdaɪfɛnˈhaɪdrəmiːn/; abbreviated DPH, sometimes DHM) is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms. The drug has a strong hypnotic effect and is FDA-approved as a nonprescription sleep aid, especially in the form of diphenhydramine citrate. It is produced and marketed under the trade name Benadryl by McNeil Consumer Healthcare in the U.S., Canada, and South Africa (trade names in other countries include Dimedrol, Daedalon, and Nytol). It is also available as a generic or store brand medication.
Starting at
2-(diphenylmethoxy)-N,N-dimethylethanamine |
Trade names | Benadryl, Unisom, Sominex, ZzzQuil |
AHFS/Drugs.com | monograph |
MedlinePlus | a682539 |
Pregnancy category |
AU: A US: B (No risk in non-human studies) |
Legal status |
AU: S2 (Pharmacy only) US: Over-the-counter |
Dependence liability |
Very low |
Routes of administration |
Oral, IM, IV, topical and suppository |
Bioavailability | 40–60%[1] |
Protein binding | 98–99% |
Metabolism | Various cytochrome P450 liver enzymes: CYP2D6 (80%), 3A4 (10%)[2] |
Biological half-life | 7 hours (children)[3] 12 hours (adults)[3] 17 hours (elderly)[3] |
Excretion | 94% through the urine, 6% through feces[4] |
CAS Number | 58-73-1 |
ATC code | D04AA32 D04AA33, R06AA02 |
PubChem | CID: 3100 |
IUPHAR/BPS | 1224 |
DrugBank | DB01075 |
ChemSpider | 2989 |
UNII | 8GTS82S83M |
KEGG | D00669 |
ChEBI | CHEBI:4636 |
ChEMBL | CHEMBL657 |
Formula | C17H21NO |
Molecular mass | 255.355 g/mol |
SMILES[show] | |
InChI[show] |