A histamine H1 antagonist used as an antiemetic, antitussive, for dermatoses and pruritus, for hypersensitivity reactions, as a hypnotic, an antiparkinson, and as an ingredient in common cold preparations. It has some undesired antimuscarinic and sedative effects.
Synonyms
2-(Benzhydryloxy)-N,N-dimethylethylamine
2-diphenylmethoxy-N,N-demthylethanamine
alpha-(2-Dimethylaminoethoxy)diphenylmethane
beta-Dimethylaminoethanol diphenylmethyl ether
beta-Dimethylaminoethyl benzhydryl ether
Difenhidramina
Diphenhydraminum
N-(2-(Diphenylmethoxy)ethyl)-N,N-dimethylamine
O-benzhydryldimethylaminoethanol
β-dimethylaminoethyl benzhydryl ether
Salts
Diphenhydramine citrate
Diphenhydramine Hydrochloride
Diphenhydramine Salicylate
Brand Names
7 Select Allergy
7 Select Allergy Childrens
7 Select Ibuprofen PM
7 Select Night Time Severe Cold, C
Affected Organism
Humans and other mammals
Indication
For the treatment of symptoms associated with Vertigo/Meniere's disease, nausea and vomiting, motion sickness and insect bite.
Pharmacology
Diphenhydramine is an antihistamine of the ethanolamine class. Ethanolamine antihistamines have significant antimuscarinic activity and produce marked sedation in most patients. In addition to the usual allergic symptoms, the drug also treats irritant cough and nausea, vomiting, and vertigo associated with motion sickness. It also is used commonly to treat drug-induced extrapyramidal symptoms as well as to treat mild cases of Parkinson's disease. Rather than preventing the release of histamine, as do cromolyn and nedocromil, diphenhydramine competes with free histamine for binding at HA-receptor sites. Diphenhydramine competitively antagonizes the effects of histamine on HA-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Ethanolamine derivatives have greater anticholinergic activity than do other antihistamines, which probably accounts for the antidyskinetic action of diphenhydramine. This anticholinergic action appears to be due to a central antimuscarinic effect, which also may be responsible for its antiemetic effects, although the exact mechanism is unknown.
Mechanism of action
Diphenhydramine competes with free histamine for binding at HA-receptor sites. This antagonizes the effects of histamine on HA-receptors, leading to a reduction of the negative symptoms brought on by histamine HA-receptor binding.
Route of administration
Intramuscular
Intramuscular; Intravenous
Intravenous
Oral
Oral; Topical
Topical
Categories
Amines
Aminoalkyl Ethers
Anesthetics
Anesthetics, Local
Anti-Allergic Agents
Antiemetics
Antihistamines for Systemic Use
Autonomic Agents
Benzene Derivatives
Benzhydryl Compounds
Central Nervous System Agents
Central Nervous System Depressants
Chemical Actions and Uses
Cytochrome P-450 CYP1A2 Substrates
Cytochrome P-450 CYP2B6 Substrates
Cytochrome P-450 CYP2C19 Substrates
Cytochrome P-450 CYP2C9 Substrates
Cytochrome P-450 CYP2D6 Inhibitors
Cytochrome P-450 CYP2D6 Inhibitors (moderate)
Cytochrome P-450 CYP2D6 Substrates
Ethylamines
Gastrointestinal Agents
Histamine Agents
Histamine Antagonists
Histamine H1 Antagonists
Hydrocarbons
Hydrocarbons, Aromatic
Hydrocarbons, Cyclic
Hypnotics and Sedatives
Molecular Mechanisms of Pharmacological Action
Neurotransmitter Agents
Organic Chemicals
Peripheral Nervous System Agents
Pharmacologic Actions
Physiological Effects of Drugs
QTc-Prolonging Agents (Indeterminate Risk and Risk Modifying)
Drug Info/Drug Targets: DrugBank 3.0: a comprehensive resource for 'omics' research on drugs. Knox C, Law V, Jewison
T, Liu P, Ly S, Frolkis A, Pon A, Banco K, Mak C, Neveu V, Djoumbou Y, Eisner R, Guo AC, Wishart DS.
Nucleic Acids Res. 2011 Jan; 39 (Database issue):D1035-41. | PMID:21059682
