Accession Number

Diphenhydramine - perhaps known most commonly as its brand name formulation Benadryl - is a first-generation H1 receptor antihistamine that is used extensively for the treatment of seasonal allergies, insect bites and stings, and rashes 9,10,11,16. However, it also has antiemetic, antitussive, hypnotic, and antiparkinson properties 11,15. As histamine receptors exist both peripherally and in the central nervous system, diphenhydramine has been shown to cause sedation due to its competitive antagonism of histamine H1 receptors within the central nervous system 9,10,11,16,5. While its use in allergy therapy can sometimes fall out of favor due to its sedative effect, diphenhydramine has been repurposed for use within many non-prescription over-the-counter sleep aids and cough-and-cold medications that have been marketed for "night time" use 9,12,13.

Diphenhydramine is also used in combination with 8-chlorotheophylline as the anti-nausea drug Dimenhydrinate where it is utilized primarily for its antagonism of H1 histamine receptors within the vestibular system 4.

Diphenhydramine has also been shown to be implicated in a number of neurotransmitter systems that affect behaviour including dopamine, norepinephrine, serotonin, acetylcholine, and opioid 3. As a result, diphenhydramine is being investigated for its anxiolytic and anti-depressant properties.

Small Molecule
Approved, Investigational
Average: 255.3547
Monoisotopic: 255.162314299
Chemical Formula
  • 2-(benzhydryloxy)-N,N-dimethylethylamine
  • 2-diphenylmethoxy-N,N-demthylethanamine
  • Difenhidramina
  • Diphenhydramine
  • Diphenhydraminum
  • N-(2-(diphenylmethoxy)ethyl)-N,N-dimethylamine
  • O-benzhydryldimethylaminoethanol
  • α-(2-dimethylaminoethoxy)diphenylmethane
  • β-dimethylaminoethanol diphenylmethyl ether
  • β-dimethylaminoethyl benzhydryl ether



Diphenhydramine is a first-generation histamine H1 receptor antagonist (H1 antihistamine) that is widely available as a non-prescription, over-the-counter (OTC) medication. As an OTC medication, diphenhydramine is typically formulated as tablets and creams indicated for use in treating sneezing, runny nose, itchy/watery eyes, itching of nose or throat, insomnia, pruritis, urticaria, insect bites/stings, allergic rashes, and nausea 9,10,11,16,5.

Additionally, when the use of oral diphenhydramine is impractical, there are also prescription-only formulations such as diphenhydramine injection products that are effective in adults and pediatric patients (other than premature infants and neonates) for: i) the amelioration of allergic reactions to blood or plasma, in anaphylaxis as an adjunct to epinephrine and other standard measures after acute allergic reaction symptoms have been controlled, and for other uncomplicated allergic conditions of the immediate type when oral therapy is impossible or contraindicated 15; ii) the active treatment of motion sickness 15; and iii) use in parkinsonism when oral therapy is impossible or contraindicated, as follows: parkinsonism in the elderly who are unable to tolerate more potent agents; mild cases of parkinsonism in other age groups, and in other cases of parkinsonism in combination with centrally acting anticholinergic agents 15.

Associated Conditions
Contraindications & Blackbox Warnings
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Diphenhydramine has anti-histaminic (H1-receptor), anti-emetic, anti-vertigo and sedative and hypnotic properties 12. The anti-histamine action occurs by blocking the spasmogenic and congestive effects of histamine by competing with histamine for H1 receptor sites on effector cells, preventing but not reversing responses mediated by histamine alone 12. Such receptor sites may be found in the gut, uterus, large blood vessels, bronchial muscles, and elsewhere 12. Anti-emetic action is by inhibition at the medullary chemoreceptor trigger zone 12. Anti-vertigo action is by a central antimuscarinic effect on the vestibular apparatus and the integrative vomiting center and medullary chemoreceptor trigger zone of the midbrain 12.

Mechanism of action

Diphenhydramine predominantly works via the antagonism of H1 (Histamine 1) receptors 9,10,11,16,5. Such H1 receptors are located on respiratory smooth muscles, vascular endothelial cells, the gastrointestinal tract (GIT), cardiac tissue, immune cells, the uterus, and the central nervous system (CNS) neurons 9,10,11,16,5. When the H1 receptor is stimulated in these tissues it produces a variety of actions including increased vascular permeability, promotion of vasodilation causing flushing, decreased atrioventricular (AV) node conduction time, stimulation of sensory nerves of airways producing coughing, smooth muscle contraction of bronchi and the GIT, and eosinophilic chemotaxis that promotes the allergic immune response 9,10,11,16,5.

Ultimately, diphenhydramine functions as an inverse agonist at H1 receptors, and subsequently reverses effects of histamine on capillaries, reducing allergic reaction symptoms 9,10,11,16,5. Moreover, since diphenhydramine is a first-generation antihistamine, it readily crosses the blood-brain barrier and inversely agonizes the H1 CNS receptors, resulting in drowsiness, and suppressing the medullary cough center 9,10,11,16,5.

Furthermore, H1 receptors are similar to muscarinic receptors 9,10,11,16,5. Consequently, diphenhydramine also acts as an antimuscarinic 9,10,11,16,5. It does so by behaving as a competitive antagonist of muscarinic acetylcholine receptors, resulting in its use as an antiparkinson medication 9,10,11,16,5.

Lastly, diphenhydramine has also demonstrated activity as an intracellular sodium channel blocker, resulting in possible local anesthetic properties 9.

AHistamine H1 receptor
UMuscarinic acetylcholine receptor M2

Diphenhydramine is quickly absorbed after oral administration with maximum activity occurring in approximately one hour 6,13. The oral bioavailability of diphenhydramine has been documented in the range of 40% to 60%, and peak plasma concentration occurs about 2 to 3 hours after administration 6,13.

Volume of distribution

Diphenhydramine is widely distributed throughout the body, including the CNS 17. Following a 50 mg oral dose of diphenhydramine, the volume of distribution is in the range of 3.3 - 6.8 l/kg 17.

Protein binding

Some prescribing information records the protein binding of diphenhydramine as approximately 78% 17 while others have suggested the medication is about 80 to 85% 13 bound to plasma proteins.


Diphenhydramine undergoes rapid and extensive first-pass metabolism 17,13,8. In particular, two successive N-demethylations occur wherein diphenhydramine is demethylated to N-desmethyldiphenhydramine (the N-desmethyl metabolite) and then this metabolite is itself demethylated to N,N-didesmethyldiphenhydramine (the N,N-didesmethyl metabolite) 17,8. Subsequently, acetyl metabolites like N-acetyl-N-desmethyldiphenhydramine are generated via the amine moiety of the N,N-didesmethyl metabolite 8. Additionally, the N,N-didesmethyl metabolite also undergoes some oxidation to generate the diphenylmethoxyacetic acid metabolite as well 17,13,8. The remaining percentage of a dose of administered diphenhydramine is excreted unchanged 17,13,8. The metabolites are further conjugated with glycine and glutamine and excreted in urine 13.

Moreover, studies have determined that a variety of cytochrome P450 isoenzymes are involved in the N-demethylation that characterizes the primary metabolic pathway of diphenhydramine, including CYP2D6, CYP1A2, CYP2C9, and CYP2C19 7. In particular, CYP2D6 demonstrates higher affinity catalysis with the diphenhydramine substrate than the other isoenzymes identified 7. Consequently, inducers or inhibitors of these such CYP enzymes may potentially affect the serum concentration and incidence and/or severity of adverse effects associated with exposure to diphenhydramine 7.

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Route of elimination

The metabolites of diphenhydramine are conjugated with glycine and glutamine and excreted in urine 12,13. Only about 1% of a single dose is excreted unchanged in urine 12,13. The medication is ultimately eliminated by the kidneys slowly, mainly as inactive metabolites 12,13.


The elimination half-life ranges from 2.4-9.3 hours in healthy adults 17,13. The terminal elimination half-life is prolonged in liver cirrhosis 13.


Values for plasma clearance of a 50 mg oral dose of diphenhydramine has been documented as lying in the range of 600-1300 ml/min 17.

Adverse Effects
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Overdose is expected to result in effects similar to the adverse effects that are ordinarily associated with the use of diphenhydramine, including drowsiness, hyperpyrexia, and anticholinergic effects, among others 10,11,12,13,17. Additional symptoms during overdose may include mydriasis, fever, flushing, agitation, tremor, dystonic reactions, hallucinations and ECG changes 13. Large overdose may cause rhabdomyolysis, convulsions, delirium, toxic psychosis, arrhythmias, coma and cardiovascular collapse 13. Moreover, with higher doses, and particularly in children, symptoms of CNS excitation including hallucinations and convulsions may appear; with massive doses, coma or cardiovascular collapse may follow 17.

Although diphenhydramine has been in widespread use for many years without ill consequence, it is known to cross the placenta and has been detected in breast milk 17. This medication should therefore only be used when the potential benefit of treatment to the mother exceeds any possible hazards to the developing fetus or suckling infant 17.

Pharmacokinetic studies indicate no major differences in the distribution or elimination of diphenhydramine compared to younger adults 17. Nevertheless, diphenhydramine should be used with caution in the elderly, who are more likely to experience adverse effects 13. Avoid use in elderly patients with confusion 13.

The results of a review on the use of diphenhydramine in renal failure suggest that in moderate to severe renal failure, the dose interval should be extended by a period dependent on Glomerular filtration rate (GFR) 17.

After intravenous administration of 0.8 mg/kg diphenhydramine, a prolonged half-life was noted in patients with chronic liver disease which correlated with the severity of the disease 17. However, the mean plasma clearance and apparent volume of distribution were not significantly affected 17.

LD50=500 mg/kg (orally in rats). Considerable overdosage can lead to myocardial infarction (heart attack), serious ventricular dysrhythmias, coma and death.

Affected organisms
  • Humans and other mammals
Diphenhydramine H1-Antihistamine ActionDrug action
Pharmacogenomic Effects/ADRs
Not Available


Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
AbataceptThe metabolism of Diphenhydramine can be increased when combined with Abatacept.
AbirateroneThe metabolism of Diphenhydramine can be decreased when combined with Abiraterone.
AcebutololThe metabolism of Acebutolol can be decreased when combined with Diphenhydramine.
AcenocoumarolThe metabolism of Acenocoumarol can be decreased when combined with Diphenhydramine.
AcetazolamideThe risk or severity of adverse effects can be increased when Acetazolamide is combined with Diphenhydramine.
AcetohexamideThe metabolism of Diphenhydramine can be decreased when combined with Acetohexamide.
AcetophenazineThe risk or severity of adverse effects can be increased when Acetophenazine is combined with Diphenhydramine.
Acetyl sulfisoxazoleThe metabolism of Diphenhydramine can be decreased when combined with Acetyl sulfisoxazole.
AclidiniumThe risk or severity of adverse effects can be increased when Diphenhydramine is combined with Aclidinium.
AcrivastineThe risk or severity of QTc prolongation can be increased when Diphenhydramine is combined with Acrivastine.
Additional Data Available
  • Extended Description
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  • Severity

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  • Evidence Level
    Evidence Level

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Food Interactions
  • Avoid alcohol.
  • Take before a meal. Take 30 minutes before a meal or 30 minutes before departure for motion sickness.


Product Ingredients
IngredientUNIICASInChI Key
Diphenhydramine citrate4OD433S20988637-37-0SPCKHVPPRJWQRZ-UHFFFAOYSA-N
Diphenhydramine hydrochlorideTC2D6JAD40147-24-0PCHPORCSPXIHLZ-UHFFFAOYSA-N
Diphenhydramine methylbromideUJO67AO8YI31065-89-1BDQPXVWYFLTETB-UHFFFAOYSA-M
Diphenhydramine salicylate707L3YC54L7491-10-3RTSZUSOHOIFYSY-UHFFFAOYSA-N
Active Moieties
Product Images
International/Other Brands
Aleryl / Alledryl / Allerdryl (Valeant) / Belix / Benylan (Biogen) / Dermodrin (Montavit) / Desentol (Meda) / Dibondrin (Montavit) / Dimedrol (Zdorovie) / Diphen (Wockhardt) / Dormarex 2 / Genahist / Histaxin (Meda) / Hyrexin (Hyrex) / Nytol Quickgels (GlaxoSmithKline) / Restamin (Kowa Souyaku) / Siladryl / Silphen Cough
Brand Name Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
BenadrylInjection, solution50 mg/1mLIntramuscular; IntravenousPhysicians Total Care, Inc.1994-06-012010-12-29US flag
BenadrylInjection, solution50 mg/1mLIntramuscular; IntravenousParke Davis Div Of Pfizer Inc1957-12-302007-01-31US flag
BenadrylInjection, solution50 mg/1mLIntramuscular; IntravenousPhysicians Total Care, Inc.2006-01-132010-12-29US flag
BenadrylInjection, solution50 mg/1mLIntramuscular; IntravenousParke Davis Div Of Pfizer Inc1947-03-062008-01-31US flag
Benadryl Inj. 50mg/mlLiquidIntramuscular; IntravenousWarner Lambert Canada Inc.1994-12-312000-11-27Canada flag
DicopanolKit0.86 g/0.86gOralCalifornia Pharmaceuticals, Llc2016-01-01Not applicableUS flag
DicopanolKit0.75 g/0.75gOralFusion Pharmaceuticals LLC2010-02-08Not applicableUS flag
Diphenhydramine HCl Inj USP 50mg/mlLiquidIntravenousInternational Medication Systems, Limited1974-12-311997-08-15Canada flag
Diphenhydramine HCl Injection, USPSolutionIntramuscular; IntravenousSterimax Inc1994-12-31Not applicableCanada flag
Diphenhydramine Hydrochloride InjectionSolutionIntramuscular; IntravenousFresenius Kabi2012-02-17Not applicableCanada flag
Additional Data Available
  • Application Number
    Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Generic Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
Di-phenSolution12.5 mg/5mLOralTriVue Pharmaceuticals, Inc.2020-10-02Not applicableUS flag
DiphenSolution12.5 mg/5mLOralFoxland Pharmaceuticals, Inc.2019-09-11Not applicableUS flag
Diphendydramine HydrochlorideCapsule25 mg/1OralRemedy Repack2010-12-172017-04-24US flag66424 0020 01 nlmimage10 1a038d6c
DiphenhydramineInjection, solution50 mg/1mLIntramuscular; IntravenousMicro Labs Limited2019-12-10Not applicableUS flag
DiphenhydramineInjection, solution50 mg/1mLIntramuscular; IntravenousFresenius Kabi USA, LLC2002-08-01Not applicableUS flag
DiphenhydramineInjection, solution50 mg/1mLIntravenousRemedy Repack2013-11-182017-01-20US flag
DiphenhydramineInjection, solution50 mg/1mLIntramuscular; IntravenousMicro Labs Limited2018-12-04Not applicableUS flag
Diphenhydramine HciInjection, solution50 mg/1mLIntramuscular; IntravenousHF Acquisition Co LLC, DBA HealthFirst2018-11-19Not applicableUS flag
Diphenhydramine HydrochlorideInjection, solution50 mg/1mLIntramuscular; IntravenousCardinal Health1988-11-202018-03-31US flag
Diphenhydramine HydrochlorideCapsule50 mg/1OralContract Pharmacy Services Pa2010-08-05Not applicableUS flag00555 0059 02 nlmimage10 a62dd30e
Additional Data Available
  • Application Number
    Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Over the Counter Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
7 Select AllergyTablet25 mg/1Oral7-Eleven2014-04-222021-02-28US flag
7 Select Allergy ChildrensSolution12.5 mg/5mLOral7-Eleven2014-08-052021-04-30US flag
7 Select Night Time Sleep AidSolution50 mg/30mLOral7-Eleven2014-04-222021-05-31US flag
Adult AllergySolution50 mg/20mLOralChain Drug Consortium, LLC2015-05-04Not applicableUS flag
Adult Allergy ReliefSolution50 mg/20mLOralWal-Mart Stores, Inc.2017-05-03Not applicableUS flag
Adult Allergy Relief Dye FreeSolution25 mg/10mLOralWalgreen Company2020-01-30Not applicableUS flag
After Bite OutdoorGel20 mg/1gTopicalTender Corporation2018-03-012020-09-30US flag
After Bite OutdoorGel20 mg/1mLTopicalTender Corporation2016-11-012018-03-01US flag
After Bite OutdoorGel20 mg/1gTopicalAdventure Ready Brands2020-09-01Not applicableUS flag
After Bite PlusGel20 mg/1gTopicalTender Corporation2018-03-012020-09-30US flag
Additional Data Available
  • Application Number
    Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code

    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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Mixture Products
NameIngredientsDosageRouteLabellerMarketing StartMarketing EndRegionImage
7 Select Ibuprofen PMDiphenhydramine citrate (38 mg/1) + Ibuprofen (200 mg/1)Tablet, film coatedOral7-Eleven2014-08-052020-11-30US flag
7 Select Night Time Severe Cold Cough and FluDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (650 mg/1) + Phenylephrine hydrochloride (10 mg/1)Powder, for solutionOral7-Eleven2016-01-252021-01-01US flag
7 Select Night Time severe cold, cough and fluDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (650 mg/1) + Phenylephrine hydrochloride (10 mg/1)Powder, for solutionOral7 Eleven2015-11-122017-08-01US flag
7 Select Pain Relief PMDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (500 mg/1)Tablet, film coatedOral7 Eleven2014-09-042016-07-22US flag
7-Select Advil PMDiphenhydramine citrate (38 mg/1) + Ibuprofen (200 mg/1)Tablet, coatedOralLil' Drug Store Products, Inc.2011-06-012017-12-31US flag
Acedif PLUSDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (500 mg/1)TabletOralPlus Distributors LLC2019-02-01Not applicableUS flag
Aceta-gesicDiphenhydramine hydrochloride (12.5 mg/1) + Acetaminophen (325 mg/1)Tablet, coatedOralRUGBY LABORATORIES2014-06-302018-12-31US flag
Aceta-gesicDiphenhydramine hydrochloride (12.5 mg/1) + Acetaminophen (325 mg/1)Tablet, coatedOralREMEDYREPACK INC.2014-08-082017-12-11US flag
AcetadrylDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (500 mg/1)Tablet, film coatedOralAidarex Pharmaceuticals LLC2011-07-21Not applicableUS flag
AcetadrylDiphenhydramine hydrochloride (25 mg/1) + Acetaminophen (500 mg/1)Tablet, film coatedOralPhysicians Science & Nature Inc.2011-07-212016-05-31US flag
Unapproved/Other Products
NameIngredientsDosageRouteLabellerMarketing StartMarketing EndRegionImage
AiracofDiphenhydramine hydrochloride (12.5 mg/5mL) + Codeine phosphate hemihydrate (7.5 mg/5mL) + Phenylephrine hydrochloride (7.5 mg/5mL)LiquidOralCenturion Labs2010-01-082016-05-02US flag
Antiphlamine Coin PlasterDiphenhydramine (0.246 mg/0.2832g) + Levomenthol (2.769 mg/0.2832g) + Synthetic camphor (1.108 mg/0.2832g)PatchTopicalHanul Trading Co., Ltd.2016-10-102017-04-14US flag
Antiphlamine Coin PlasterDiphenhydramine (0.246 mg/0.2832g) + DL-alpha-Tocopherol (0.308 mg/0.2832g) + Levomenthol (2.769 mg/0.2832g) + Methyl salicylate (5.541 mg/0.2832g) + Nonivamide (0.046 mg/0.2832g) + Peppermint oil (0.693 mg/0.2832g) + Synthetic camphor (1.108 mg/0.2832g)PatchTopicalHanul Trading Co., Ltd.2016-10-10Not applicableUS flag
BenadrylDiphenhydramine hydrochloride (50 mg/1mL)Injection, solutionIntramuscular; IntravenousPhysicians Total Care, Inc.2006-01-132010-12-29US flag
BenadrylDiphenhydramine hydrochloride (50 mg/1mL)Injection, solutionIntramuscular; IntravenousPhysicians Total Care, Inc.1994-06-012010-12-29US flag
Childrens Dimetapp Multi-Symptom Cold and FluDiphenhydramine hydrochloride (12.5 mg/10mL) + Acetaminophen (320 mg/10mL) + Phenylephrine hydrochloride (5 mg/10mL)LiquidOralWyeth Consumer Healthcare Llc2020-01-01Not applicableUS flag
Contrast Allergy PreMed PackDiphenhydramine hydrochloride (50 mg/50mg) + Prednisone (50 mg/50mg)KitOralShertech Laboratories, Llc2016-09-13Not applicableUS flag
CoreTex Professional Outdoor Skin Protection WalletDiphenhydramine hydrochloride (2 g/100mL) + Avobenzone (1 g/100mL) + Avobenzone (1 g/100g) + Avobenzone (3 g/100mL) + Benzocaine (6 g/100mL) + Ethanol (62.5 mL/100mL) + Homosalate (5 g/100mL) + Homosalate (5 g/100g) + Homosalate (7.5 g/100mL) + Octinoxate (7.5 g/100mL) + Octinoxate (7.5 g/100g) + Octisalate (5 g/100mL) + Octisalate (5 g/100g) + Octisalate (5 g/100mL) + Octocrylene (2.5 g/100mL) + Oxybenzone (6 g/100mL) + Oxybenzone (6 g/100g) + Oxybenzone (6 g/100mL) + Synthetic camphor (0.1 g/100mL) + Zinc acetate dihydrate (1 g/100mL)TopicalCoreTex Products2019-11-27Not applicableUS flag
DermagesicDiphenhydramine hydrochloride (1 mg/100mL) + Phenol (1.4 mg/100mL)LiquidTopicalLlorens Pharmaceuticals International Division2009-02-012014-01-20US flag
DicopanolDiphenhydramine hydrochloride (0.75 g/0.75g)KitOralFusion Pharmaceuticals LLC2010-02-08Not applicableUS flag


ATC Codes
D04AA32 — DiphenhydramineR06AA02 — DiphenhydramineD04AA33 — Diphenhydramine methylbromideR06AA52 — Diphenhydramine, combinations
Drug Categories
Chemical TaxonomyProvided by Classyfire
This compound belongs to the class of organic compounds known as diphenylmethanes. These are compounds containing a diphenylmethane moiety, which consists of a methane wherein two hydrogen atoms are replaced by two phenyl groups.
Organic compounds
Super Class
Benzene and substituted derivatives
Sub Class
Direct Parent
Alternative Parents
Benzylethers / Trialkylamines / Dialkyl ethers / Organopnictogen compounds / Hydrocarbon derivatives
Amine / Aromatic homomonocyclic compound / Benzylether / Dialkyl ether / Diphenylmethane / Ether / Hydrocarbon derivative / Organic nitrogen compound / Organic oxygen compound / Organonitrogen compound
Molecular Framework
Aromatic homomonocyclic compounds
External Descriptors
tertiary amino compound, ether (CHEBI:4636) / a small molecule (CPD-10890)

Chemical Identifiers

CAS number
InChI Key


Synthesis Reference

Alison B. Lukacsko, Joseph J. Piala, "Effect of a combination of a terbutaline, diphenhydramine and ranitidine composition on gastrointestinal injury produced by nonsteroidal anti-inflammatory compositions." U.S. Patent US5260333, issued December, 1983.

General References
  1. Raphael GD, Angello JT, Wu MM, Druce HM: Efficacy of diphenhydramine vs desloratadine and placebo in patients with moderate-to-severe seasonal allergic rhinitis. Ann Allergy Asthma Immunol. 2006 Apr;96(4):606-14. [PubMed:16680933]
  2. Abdi A, Rose E, Levine M: Diphenhydramine overdose with intraventricular conduction delay treated with hypertonic sodium bicarbonate and i.v. lipid emulsion. West J Emerg Med. 2014 Nov;15(7):855-8. doi: 10.5811/westjem.2014.8.23407. Epub 2014 Sep 19. [PubMed:25493135]
  3. Halpert AG, Olmstead MC, Beninger RJ: Mechanisms and abuse liability of the anti-histamine dimenhydrinate. Neurosci Biobehav Rev. 2002 Jan;26(1):61-7. [PubMed:11835984]
  4. Jaju BP, Wang SC: Effects of diphenhydramine and dimenhydrinate on vestibular neuronal activity of cat: a search for the locus of their antimotion sickness action. J Pharmacol Exp Ther. 1971 Mar;176(3):718-24. [PubMed:4329456]
  5. Flake ZA, Scalley RD, Bailey AG: Practical selection of antiemetics. Am Fam Physician. 2004 Mar 1;69(5):1169-74. [PubMed:15023018]
  6. Paton DM, Webster DR: Clinical pharmacokinetics of H1-receptor antagonists (the antihistamines). Clin Pharmacokinet. 1985 Nov-Dec;10(6):477-97. [PubMed:2866055]
  7. Akutsu T, Kobayashi K, Sakurada K, Ikegaya H, Furihata T, Chiba K: Identification of human cytochrome p450 isozymes involved in diphenhydramine N-demethylation. Drug Metab Dispos. 2007 Jan;35(1):72-8. doi: 10.1124/dmd.106.012088. Epub 2006 Oct 4. [PubMed:17020955]
  8. Rodrigues WC, Castro C, Catbagan P, Moore C, Wang G: Immunoassay screening of diphenhydramine (Benadryl(R)) in urine and blood using a newly developed assay. J Anal Toxicol. 2012 Mar;36(2):123-9. doi: 10.1093/jat/bkr015. [PubMed:22337782]
  9. StatPearls [Internet]: Diphenhydramine [Link]
  10. Electronic Medicines Compendium: Histergan (diphenhydramine hydrochloride) Tablets Patient Information [Link]
  11. Electronic Medicines Compendium: Histergan (diphenhydramine hydrochloride) Cream Monograph [Link]
  12. Electronic Medicines Compendium: Boots Sleepeaze (diphenhydramine hydrochloride) 50mg Tablets Monograph [Link]
  13. Electronic Medicines Compendium: Nytol One-A-Night (diphenhydramine hydrochloride) Monograph [Link]
  14. DailyMed: Ibuprofen PM (ibuprofen/diphenhydramine) product information [Link]
  15. Diphenhydramine Hydrochloride Injection, USP FDA Label [File]
  16. DIPHENHYDRAMINE- diphenhydramine hcl tablet, coated DailyMed FDA Label [File]
  17. Benylin Chesty Coughs UK MHRA Product Information [File]
Human Metabolome Database
KEGG Compound
PubChem Compound
PubChem Substance
Therapeutic Targets Database
Guide to Pharmacology
GtP Drug Page
PDBe Ligand
RxList Drug Page Drug Page
AHFS Codes
  • 04:04.04 — Ethanolamine Derivatives
  • 04:04.00 — First Generation Antihistamines
PDB Entries
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Clinical Trials

Clinical Trials
4CompletedPreventionHypnotic / Specified Sedative1
4CompletedSupportive CareAdjunct Anesthesia Medication / Colonoscopy1
4CompletedTreatmentBacterial Infections1
4CompletedTreatmentExtra-pyramidal symptoms / Nausea1
4CompletedTreatmentMigraine / Nausea / Restlessness1
4CompletedTreatmentNasal Congestion1
4CompletedTreatmentOccasional Sleeplessness1


Not Available
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  • Martin Surgical Supply
  • McNeil Laboratories
  • Medique Products
  • Medtech Labs
  • Merit Pharmaceuticals
  • Midlothian Labs
  • Mississippi State Dept Health
  • Murfreesboro Pharmaceutical Nursing Supply
  • Nexgen Pharma Inc.
  • North Safety Products
  • Nucare Pharmaceuticals Inc.
  • Patient First Corp.
  • PD-Rx Pharmaceuticals Inc.
  • Perrigo Co.
  • Pfizer Inc.
  • Pharmaceutical Association
  • Pharmedix
  • Physicians Total Care Inc.
  • Poly Pharmaceuticals Inc.
  • Preferred Pharmaceuticals Inc.
  • Prepackage Specialists
  • Prepak Systems Inc.
  • Prescript Pharmaceuticals
  • Procter & Gamble
  • Provident Pharmaceuticals LLC
  • Remedy Repack
  • Rite Aid Corp.
  • River's Edge Pharmaceuticals
  • Rugby Laboratories
  • Sandhills Packaging Inc.
  • Scientific Laboratories Inc.
  • Silarx Pharmaceuticals
  • Southwood Pharmaceuticals
  • St Mary's Medical Park Pharmacy
  • Tya Pharmaceuticals
  • UDL Laboratories
  • United Research Laboratories Inc.
  • Vangard Labs Inc.
  • Walgreen Co.
Dosage Forms
Tablet, effervescentOral
Capsule; kitOral
CreamTopical20 mg/1mL
CreamTopical2.0 mL/100mL
Injection, solutionIntravenous20 mg/2ml
LiquidOral12.5 mg
LiquidOral12.5 mg/5mL
Capsule, gelatin coatedOral
PowderOral25 mg/1
SyrupOral10 mg/4mL
GelTopical2 g/100g
CreamTopical2 %
Capsule15 mg
Syrup100 mg/5mL
SolutionOral125 mg/5mL
Syrup125 mg/5mL
Injection, solutionIntramuscular; Intravenous50 mg/1mL
Syrup150 mg/5mL
SolutionOral12.5 mg
TabletOral25 mg
Tablet, coatedOral25 mg/1
StripOral25 mg/1
Solution / dropsOral135 mg/5mL
Syrup12.5 mg/5mL
GelTopical20 mg/1mL
TabletOral25 mg/250mg
Syrup135 mg
Solution20 mg
Capsule, gelatin coated25 mg
Syrup135 mg/5mL
SolutionOral4 mg/5mL
Syrup7.5 mg/5mL
SolutionOral131.5 mg/5mL
Tablet, orally disintegratingOral
Tablet, chewableOral
TabletOral12.5 mg/1
Tablet, chewableOral12.5 mg/1
LiquidOral12.5 mg/237mL
LiquidOral6.25 mg/1mL
Syrup137 mg/5mL
Syrup107.5 mg/5mL
Kit; tabletOral
SyrupOral25 mg/10ml
KitOral0.75 g/0.75g
KitOral0.86 g/0.86g
Capsule, coatedOral50 mg
SyrupOral250 mg
SolutionIntramuscular; Intravenous10 mg
GelTopical1.2 %
Tablet50 MG
Tablet50 mg/1
Capsule, coatedOral25 mg/1
Cream200 mg/100g
Injection, solutionIntravenous50 mg/1mL
Syrup250 mg/100mL
Tablet, coatedOral25 mg/ 11
Capsule, liquid filledOral20 mg/1
Injection, solution50 mg/1mL
TabletOral50 mg/1
Capsule, gelatin coatedOral25 mg/1
Capsule25 mg/1
Capsule50 mg/1
CapsuleOral25 mg/1
CapsuleOral50 mg/1
Capsule, liquid filledOral50 mg/1
InjectionIntramuscular50 mg/1mL
InjectionIntramuscular; Intravenous50 mg/1mL
InjectionParenteral50 mg/1mL
SolutionOral25 mg/10mL
SolutionOral50 mg/20mL
Tablet, film coatedOral25 mg/1
Tablet, film coatedOral50 mg/1
Tablet, orally disintegratingOral25 mg/1
Syrup25 mg/5mL
LiquidIntramuscular; Intravenous
Tablet, chewableOral
LotionTopical15 g/100ml
TabletOral500 mg
LotionTopical2 g/120g
SolutionOral50 mg/30mL
GelTopical2 mg/100mL
Capsule, liquid filledOral25 mg/1
SyrupOral14 mg/5ml
GelTopical2 %
Cream50 g
SolutionOral50 mg/40mL
Bar, chewableOral12.5 mg/1
SyrupOral10 mg
Aerosol, sprayTopical
TabletOral25 mg/1
Tablet25 mg
Syrup50 mg/5mL
Solution / dropsOral125 mg/5mL
SyrupOral135 mg
Capsule, liquid filledOral
Tablet, chewableOral; Topical
LiquidTopical20.3 g/1L
SprayTopical2 g/100mL
GelTopical2.03 g/100g
Syrup5 mg/5mL
Syrup110 mg/5mL
LotionTopical16 g
Lotion100 ml
Tablet, orally disintegratingOral12.5 mg/1
Syrup15 mg/5mL
LiquidOral50 mg/20mL
Capsule, gelatin coatedOral50 mg/1
LiquidTopical200 mg/100mL
Solution / dropsOral100 mg/5mL
KitOral; Topical
Capsule, liquid filledOral25 mg
CapsuleOral25 mg
LiquidOral50 mg/30mL
SolutionOral50 mg
LiquidOral50 mg
Capsule, liquid filledOral50 mg/21
Tablet, sugar coatedOral50 mg
GranuleOral500 mg
PowderOral500 mg
Granule, for solutionOral
Tablet, coatedOral
Syrup100 ml
SolutionOral12.5 mg/5mL
SyrupOral12.5 mg/5mL
GelTopical20.5 mg/1mL
SolutionIntramuscular; Intravenous
GelTopical2 g/100mL
GelTopical.2 g/10mL
TabletOral50 mg
Tablet, coatedOral50 mg/1
LotionTopical100 ml
Tablet, multilayerOral
Tablet, multilayer, extended releaseOral
GelTopical20 mg/1g
SprayTopical20 mg/1mL
Capsule, coatedOral
Tablet, film coatedOral
Tablet, delayed releaseOral
SolutionOral325 mg/15ml
Tablet, chewableOral25 mg/1
Powder, for solutionOral
Tablet, film coatedOral
Tablet, coatedOral25 mg
LiquidOral25 mg/10mL
Capsule, gelatin coatedOral50 mg/21
Capsule25 MG
Capsule50 MG
CapsuleOral0.05 g
Gum, chewingOral25 MG
Tablet0.05 G
Capsule, liquid filledOral250 mg
Unit descriptionCostUnit
DiphenhydrAMINE HCl 100 50 mg capsule Bottle13.99USD bottle
Diphenhydramine 50 mg/ml3.94USD ml
Diphenhydramine 50 mg/ml vial1.69USD ml
DiphenhydrAMINE HCl 50 mg/ml vial1.44USD vial
Dytan 25 mg tablet chewable1.37USD tablet
Benadryl 50 mg/ml vial1.36USD ml
Diphenmax 25 mg tablet1.24USD tablet
Benadryl allergy 25 mg strips0.45USD strip
Unisom sleep aid tablet0.34USD tablet
Sleep-eze 3 tablet0.29USD tablet
Compoz 50 mg tablet0.27USD tablet
Sominex max str 50 mg caplet0.27USD caplet
Benadryl allergy fastmelt tablet0.26USD tablet
Unisom 25 mg sleeptabs0.25USD tablet
Unisom 50 mg sleepgels0.25USD each
Unisom sleepmelts 25 mg tablet0.24USD tablet
Nytol 25 mg tablet0.23USD tablet
Benadryl allergy-sinus caplet0.22USD caplet
Compoz 25 mg gelcap0.2USD capsule
Benadryl allergy 25 mg softgel0.19USD softgel capsule
Benadryl allergy 25 mg ultratab0.19USD tablet
Benadryl allergy-cold kapgels0.19USD each
Benadryl allergy-sinus kapgels0.19USD each
Benadryl-d allergy-sinus ultratab0.19USD tablet
Diphenhydramine hcl powder0.17USD g
Eql allergy 25 mg tablet0.17USD tablet
Nighttime sleep aid 25 mg cplt0.17USD caplet
Banophen anti-itch 2% cream0.16USD g
Benadryl itch relief stick0.16USD ml
Sominex 25 mg tablet0.16USD tablet
Benadryl allergy 25 mg kapgels0.15USD each
Allergy 25 mg tablet0.14USD tablet
Benadryl 25 mg kapseals0.14USD each
Benadryl itch stopping crm0.14USD g
DiphenhydrAMINE HCl 25 mg capsule0.13USD capsule
Diphenhist with zinc cream0.12USD g
Ra allergy 25 mg tablet0.12USD tablet
CVS Pharmacy allergy 25 mg tablet0.11USD tablet
Diphenhydramine 25 mg minitab0.11USD tablet
Simply sleep 25 mg caplet0.11USD caplet
Sleep ii tablet0.11USD tablet
Diphenhydramine 50 mg capsule0.1USD capsule
Benadryl 2% spray0.09USD ml
Diphenhist 50 mg tablet0.09USD tablet
Genahist 25 mg tablet0.09USD tablet
Ra sleep tablet0.09USD tablet
Banophen 25 mg tablet0.08USD tablet
Wal-dryl anti-itch spray0.08USD ml
CVS Pharmacy allergy 25 mg caplet0.07USD caplet
Nighttime sleep aid 25 mg caplet0.07USD caplet
CVS Pharmacy itch relief spray0.06USD ml
Diphen 25 mg capsule0.06USD capsule
Diphenhist 25 mg caplet0.06USD caplet
Benadryl anti-itch 0.45% gel0.05USD g
Diphenhydramine 50 mg caplet0.05USD caplet
Benadryl itch stopping gel0.04USD g
Child benadryl-d aller-sin liquid0.04USD ml
Diphenhydramine 25 mg capsule0.04USD capsule
Vicks 44d cough & head liquid0.03USD ml
Vicks 44e cough & chest liquid0.03USD ml
Banophen allergy liquid0.02USD ml
Diphenhydramine 25 mg tablet0.02USD tablet
Ra anti-tussive dm syrup0.02USD ml
Siladryl 12.5 mg/5 ml liquid0.02USD ml
Silphen cough syrup0.02USD ml
Silphen dm cough syrup0.02USD ml
DrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only.
Patent NumberPediatric ExtensionApprovedExpires (estimated)Region
US8883849No2014-11-112022-01-17US flag
US9155718No2015-10-132022-01-17US flag
US8263647No2012-09-112022-05-30US flag
Additional Data Available
  • Filed On
    Filed On

    The date on which a patent was filed with the relevant government.

    Learn more


Experimental Properties
melting point (°C)161-162Martin, H., Hafliger, F.,Gatzi, K.and Grob, A.; U.S. Patent 2,397,799; April 2,1946; assigned to J.R. Geigy AG, Switzerland. Rieveschl, G. Jr.; U.S. Patent 2,421,714; June 3,1947; assigned to Parke, Davis & Co. Rieveschl, G. Jr.; U.S. Patent 2,427,878; September 23,1947; assigned to Parke, Davis & Company.
boiling point (°C)150-165 °C at 2.00E+00 mm HgPhysProp
water solubility3060 mg/L (at 37 °C)BEILSTEIN
logP3.27HANSCH,C ET AL. (1995)
pKa8.98SANGSTER (1994)
Predicted Properties
Water Solubility0.0752 mg/mLALOGPS
pKa (Strongest Basic)8.87ChemAxon
Physiological Charge1ChemAxon
Hydrogen Acceptor Count2ChemAxon
Hydrogen Donor Count0ChemAxon
Polar Surface Area12.47 Å2ChemAxon
Rotatable Bond Count6ChemAxon
Refractivity79.93 m3·mol-1ChemAxon
Polarizability29.86 Å3ChemAxon
Number of Rings2ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleNoChemAxon
Predicted ADMET Features
Human Intestinal Absorption+0.9898
Blood Brain Barrier+0.9381
Caco-2 permeable+0.8744
P-glycoprotein substrateSubstrate0.6211
P-glycoprotein inhibitor INon-inhibitor0.6632
P-glycoprotein inhibitor IINon-inhibitor0.8381
Renal organic cation transporterInhibitor0.7752
CYP450 2C9 substrateNon-substrate0.7897
CYP450 2D6 substrateSubstrate0.8919
CYP450 3A4 substrateSubstrate0.6173
CYP450 1A2 substrateInhibitor0.8306
CYP450 2C9 inhibitorNon-inhibitor0.9144
CYP450 2D6 inhibitorInhibitor0.8932
CYP450 2C19 inhibitorNon-inhibitor0.9039
CYP450 3A4 inhibitorNon-inhibitor0.934
CYP450 inhibitory promiscuityLow CYP Inhibitory Promiscuity0.7293
Ames testNon AMES toxic0.9132
BiodegradationNot ready biodegradable0.9253
Rat acute toxicity2.7846 LD50, mol/kg Not applicable
hERG inhibition (predictor I)Weak inhibitor0.536
hERG inhibition (predictor II)Inhibitor0.6318
ADMET data is predicted using admetSAR, a free tool for evaluating chemical ADMET properties. (23092397)


Mass Spec (NIST)
Not Available
SpectrumSpectrum TypeSplash Key
Predicted GC-MS Spectrum - GC-MSPredicted GC-MSNot Available
GC-MS Spectrum - EI-BGC-MSsplash10-0a4i-9100000000-7b9eb1f702c76f6b6062
Mass Spectrum (Electron Ionization)MSsplash10-0a4i-9200000000-b9014c8fc8ccbba24163
MS/MS Spectrum - Quattro_QQQ 10V, N/ALC-MS/MSsplash10-0006-0090000000-a71e531b49571f09ab25
MS/MS Spectrum - Quattro_QQQ 25V, N/ALC-MS/MSsplash10-00kk-0980000000-cce91896f34562beeffa
MS/MS Spectrum - Quattro_QQQ 40V, N/ALC-MS/MSsplash10-001i-1900000000-4c29bd5e0eab94596eaa
MS/MS Spectrum - EI-B (Unknown) , PositiveLC-MS/MSsplash10-0a4i-9100000000-ab642e8f86de11af896c
Predicted MS/MS Spectrum - 10V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 20V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 40V, Positive (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 10V, Negative (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 20V, Negative (Annotated)Predicted LC-MS/MSNot Available
Predicted MS/MS Spectrum - 40V, Negative (Annotated)Predicted LC-MS/MSNot Available
LC-MS/MS Spectrum - LC-ESI-QFT , negativeLC-MS/MSsplash10-000t-0910000000-3576ca5ec77ab87354ec
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-0ccd6de9ca58593fd490
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-3568aae4c27ffe333c0e
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-22e0c745355c836f1535
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-6bb69a66a343440c64f8
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-1b87d83415d22bb17f1b
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0gb9-0900000000-50251362d768cd1b1c4f
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0gb9-0900000000-9f37a733a05f5b01d313
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-014i-0900000000-7d73b95ed09ea2d72260
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0gb9-2900000000-1666a8ab5a6d81c0bd01
LC-MS/MS Spectrum - LC-ESI-ITFT , positiveLC-MS/MSsplash10-014i-0900000000-3f31841d858381760f03
LC-MS/MS Spectrum - LC-ESI-ITFT , positiveLC-MS/MSsplash10-014i-0900000000-de872e048c7e12cef490
LC-MS/MS Spectrum - LC-ESI-ITFT , positiveLC-MS/MSsplash10-014i-0900000000-de872e048c7e12cef490
MS/MS Spectrum - , positiveLC-MS/MSsplash10-014i-0900000000-789a4a3fe118d5bf2456
MS/MS Spectrum - , positiveLC-MS/MSsplash10-014i-2900000000-8ef94659f614b9ff24ca
LC-MS/MS Spectrum - LC-ESI-QFT , positiveLC-MS/MSsplash10-0002-2950000000-7c7a9841f2f0b6428d69
1H NMR Spectrum1D NMRNot Applicable
[1H,13C] 2D NMR Spectrum2D NMRNot Applicable


1. Histamine H1 receptor
Pharmacological action
General Function
Histamine receptor activity
Specific Function
In peripheral tissues, the H1 subclass of histamine receptors mediates the contraction of smooth muscles, increase in capillary permeability due to contraction of terminal venules, and catecholamin...
Gene Name
Uniprot ID
Uniprot Name
Histamine H1 receptor
Molecular Weight
55783.61 Da
  1. Chen X, Ji ZL, Chen YZ: TTD: Therapeutic Target Database. Nucleic Acids Res. 2002 Jan 1;30(1):412-5. [PubMed:11752352]
  2. Piao H, Nagai S, Tsurumaki T, Niki T, Higuchi H: Potentiation by neuropeptide Y of histamine H1 receptor-mediated contraction in rat blood vessels. Vascul Pharmacol. 2007 Apr;46(4):260-70. Epub 2006 Oct 27. [PubMed:17169617]
  3. Kesiova M, Alexandrova A, Yordanova N, Kirkova M, Todorov S: Effects of diphenhydramine and famotidine on lipid peroxidation and activities of antioxidant enzymes in different rat tissues. Pharmacol Rep. 2006 Mar-Apr;58(2):221-8. [PubMed:16702624]
  4. Hasala H, Moilanen E, Janka-Junttila M, Giembycz MA, Kankaanranta H: First-generation antihistamines diphenhydramine and chlorpheniramine reverse cytokine-afforded eosinophil survival by enhancing apoptosis. Allergy Asthma Proc. 2007 Jan-Feb;28(1):79-86. [PubMed:17390763]
  5. Wang Z, Woolverton WL: Self-administration of cocaine-antihistamine combinations: super-additive reinforcing effects. Eur J Pharmacol. 2007 Feb 28;557(2-3):159-60. Epub 2006 Dec 1. [PubMed:17196194]
  6. Ishikawa T, Takechi K, Rahman A, Ago J, Matsumoto N, Murakami A, Kamei C: Influences of histamine H1 receptor antagonists on maximal electroshock seizure in infant rats. Biol Pharm Bull. 2007 Mar;30(3):477-80. [PubMed:17329841]
  7. Havas TE, Cole P, Parker L, Oprysk D, Ayiomamitis A: The effects of combined H1 and H2 histamine antagonists on alterations in nasal airflow resistance induced by topical histamine provocation. J Allergy Clin Immunol. 1986 Nov;78(5 Pt 1):856-60. [PubMed:2878016]
Pharmacological action
General Function
G-protein coupled acetylcholine receptor activity
Specific Function
The muscarinic acetylcholine receptor mediates various cellular responses, including inhibition of adenylate cyclase, breakdown of phosphoinositides and modulation of potassium channels through the...
Gene Name
Uniprot ID
Uniprot Name
Muscarinic acetylcholine receptor M2
Molecular Weight
51714.605 Da
  1. Liu H, Zheng Q, Farley JM: Antimuscarinic actions of antihistamines on the heart. J Biomed Sci. 2006 May;13(3):395-401. [PubMed:16453179]


Pharmacological action
General Function
Steroid hydroxylase activity
Specific Function
Responsible for the metabolism of many drugs and environmental chemicals that it oxidizes. It is involved in the metabolism of drugs such as antiarrhythmics, adrenoceptor antagonists, and tricyclic...
Gene Name
Uniprot ID
Uniprot Name
Cytochrome P450 2D6
Molecular Weight
55768.94 Da
  1. Hamelin BA, Bouayad A, Drolet B, Gravel A, Turgeon J: In vitro characterization of cytochrome P450 2D6 inhibition by classic histamine H1 receptor antagonists. Drug Metab Dispos. 1998 Jun;26(6):536-9. [PubMed:9616188]
  2. Akutsu T, Kobayashi K, Sakurada K, Ikegaya H, Furihata T, Chiba K: Identification of human cytochrome p450 isozymes involved in diphenhydramine N-demethylation. Drug Metab Dispos. 2007 Jan;35(1):72-8. doi: 10.1124/dmd.106.012088. Epub 2006 Oct 4. [PubMed:17020955]
  3. Lessard E, Yessine MA, Hamelin BA, Gauvin C, Labbe L, O'Hara G, LeBlanc J, Turgeon J: Diphenhydramine alters the disposition of venlafaxine through inhibition of CYP2D6 activity in humans. J Clin Psychopharmacol. 2001 Apr;21(2):175-84. [PubMed:11270914]
  4. Flockhart Table of Drug Interactions [Link]
Pharmacological action
General Function
Steroid hydroxylase activity
Specific Function
Cytochromes P450 are a group of heme-thiolate monooxygenases. In liver microsomes, this enzyme is involved in an NADPH-dependent electron transport pathway. It oxidizes a variety of structurally un...
Gene Name
Uniprot ID
Uniprot Name
Cytochrome P450 2C9
Molecular Weight
55627.365 Da
  1. Zhou SF, Zhou ZW, Yang LP, Cai JP: Substrates, inducers, inhibitors and structure-activity relationships of human Cytochrome P450 2C9 and implications in drug development. Curr Med Chem. 2009;16(27):3480-675. Epub 2009 Sep 1. [PubMed:19515014]
  2. Connecticut's Official State Website: CYP Chart [File]
Pharmacological action
General Function
Steroid hydroxylase activity
Specific Function
Responsible for the metabolism of a number of therapeutic agents such as the anticonvulsant drug S-mephenytoin, omeprazole, proguanil, certain barbiturates, diazepam, propranolol, citalopram and im...
Gene Name
Uniprot ID
Uniprot Name
Cytochrome P450 2C19
Molecular Weight
55930.545 Da
  1. Zhou SF, Zhou ZW, Yang LP, Cai JP: Substrates, inducers, inhibitors and structure-activity relationships of human Cytochrome P450 2C9 and implications in drug development. Curr Med Chem. 2009;16(27):3480-675. Epub 2009 Sep 1. [PubMed:19515014]
Pharmacological action
General Function
Prostaglandin-endoperoxide synthase activity
Specific Function
Converts arachidonate to prostaglandin H2 (PGH2), a committed step in prostanoid synthesis. Involved in the constitutive production of prostanoids in particular in the stomach and platelets. In gas...
Gene Name
Uniprot ID
Uniprot Name
Prostaglandin G/H synthase 1
Molecular Weight
68685.82 Da
  1. Zhou SF, Zhou ZW, Yang LP, Cai JP: Substrates, inducers, inhibitors and structure-activity relationships of human Cytochrome P450 2C9 and implications in drug development. Curr Med Chem. 2009;16(27):3480-675. Epub 2009 Sep 1. [PubMed:19515014]


Pharmacological action
General Function
Quaternary ammonium group transmembrane transporter activity
Specific Function
Mediates tubular uptake of organic compounds from circulation. Mediates the influx of agmatine, dopamine, noradrenaline (norepinephrine), serotonin, choline, famotidine, ranitidine, histamin, creat...
Gene Name
Uniprot ID
Uniprot Name
Solute carrier family 22 member 2
Molecular Weight
62579.99 Da
  1. Urakami Y, Okuda M, Masuda S, Akazawa M, Saito H, Inui K: Distinct characteristics of organic cation transporters, OCT1 and OCT2, in the basolateral membrane of renal tubules. Pharm Res. 2001 Nov;18(11):1528-34. [PubMed:11758759]
Pharmacological action
General Function
Symporter activity
Specific Function
Sodium-ion dependent, high affinity carnitine transporter. Involved in the active cellular uptake of carnitine. Transports one sodium ion with one molecule of carnitine. Also transports organic cat...
Gene Name
Uniprot ID
Uniprot Name
Solute carrier family 22 member 5
Molecular Weight
62751.08 Da
  1. Ohashi R, Tamai I, Nezu Ji J, Nikaido H, Hashimoto N, Oku A, Sai Y, Shimane M, Tsuji A: Molecular and physiological evidence for multifunctionality of carnitine/organic cation transporter OCTN2. Mol Pharmacol. 2001 Feb;59(2):358-66. [PubMed:11160873]

Drug created on June 13, 2005 07:24 / Updated on October 19, 2020 07:46

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