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Record Information
StatusExpected but not Quantified
Creation Date2012-09-06 15:16:50 UTC
Update Date2020-02-26 21:40:10 UTC
Secondary Accession Numbers
  • HMDB14697
Metabolite Identification
Common NameHydroxyzine
DescriptionHydroxyzine, also known as hidroxizina or hychotine, belongs to the class of organic compounds known as diphenylmethanes. Diphenylmethanes are compounds containing a diphenylmethane moiety, which consists of a methane wherein two hydrogen atoms are replaced by two phenyl groups. Hydroxyzine is a drug which is used for symptomatic relief of anxiety and tension associated with psychoneurosis and as an adjunct in organic disease states in which anxiety is manifested. useful in the management of pruritus due to allergic conditions such as chronic urticaria. Hydroxyzine is a very strong basic compound (based on its pKa). In humans, hydroxyzine is involved in hydroxyzine h1-antihistamine action. A histamine H1 receptor antagonist that is effective in the treatment of chronic urticaria, dermatitis, and histamine-mediated pruritus. Hydroxyzine is a potentially toxic compound. It is also effective as an antiemetic, for relief of anxiety and tension, and as a sedative. Hydroxyzine competes with histamine for binding at H1-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The sedative properties of hydroxyzine occur at the subcortical level of the CNS. There is no specific antidote.
Hydroxyzine baseHMDB
Hydroxyzine pamoateHMDB
Hydroxyzine hydrochlorideHMDB
Hydroxyzine dihydrochlorideHMDB
Pamoate, hydroxyzineHMDB
Chemical FormulaC21H27ClN2O2
Average Molecular Weight374.904
Monoisotopic Molecular Weight374.176105825
IUPAC Name2-(2-{4-[(4-chlorophenyl)(phenyl)methyl]piperazin-1-yl}ethoxy)ethan-1-ol
Traditional Namehydroxyzine
CAS Registry Number68-88-2
InChI Identifier
Chemical Taxonomy
Description belongs to the class of organic compounds known as diphenylmethanes. Diphenylmethanes are compounds containing a diphenylmethane moiety, which consists of a methane wherein two hydrogen atoms are replaced by two phenyl groups.
KingdomOrganic compounds
Super ClassBenzenoids
ClassBenzene and substituted derivatives
Sub ClassDiphenylmethanes
Direct ParentDiphenylmethanes
Alternative Parents
  • Diphenylmethane
  • Chlorobenzene
  • Aralkylamine
  • Halobenzene
  • N-alkylpiperazine
  • Aryl chloride
  • Aryl halide
  • 1,4-diazinane
  • Piperazine
  • Tertiary aliphatic amine
  • Tertiary amine
  • Dialkyl ether
  • Azacycle
  • Ether
  • Organoheterocyclic compound
  • Organohalogen compound
  • Organic nitrogen compound
  • Amine
  • Hydrocarbon derivative
  • Alcohol
  • Organopnictogen compound
  • Organic oxygen compound
  • Organochloride
  • Organonitrogen compound
  • Organooxygen compound
  • Primary alcohol
  • Aromatic heteromonocyclic compound
Molecular FrameworkAromatic heteromonocyclic compounds
External Descriptors

Route of exposure:

Biological location:


Naturally occurring process:


Industrial application:

Physical Properties
Experimental Properties
Melting Point190 °CNot Available
Boiling PointNot AvailableNot Available
Water Solubility0.091 g/LNot Available
LogP2.7Not Available
Predicted Properties
Water Solubility0.091 g/LALOGPS
pKa (Strongest Acidic)15.12ChemAxon
pKa (Strongest Basic)7.82ChemAxon
Physiological Charge1ChemAxon
Hydrogen Acceptor Count4ChemAxon
Hydrogen Donor Count1ChemAxon
Polar Surface Area35.94 ŲChemAxon
Rotatable Bond Count8ChemAxon
Refractivity107.07 m³·mol⁻¹ChemAxon
Polarizability41.99 ųChemAxon
Number of Rings3ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleYesChemAxon
Spectrum TypeDescriptionSplash KeyView
GC-MSGC-MS Spectrum - EI-B (Non-derivatized)splash10-0udi-6491000000-95c46c16c2b29900f4d9Spectrum
GC-MSGC-MS Spectrum - EI-B (Non-derivatized)splash10-0udi-6491000000-95c46c16c2b29900f4d9Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (Non-derivatized) - 70eV, Positivesplash10-0udj-4291000000-5750700bc5e75e581102Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (1 TMS) - 70eV, Positivesplash10-0udr-6589100000-8c29584ceed777207042Spectrum
LC-MS/MSLC-MS/MS Spectrum - , positivesplash10-0udi-0593000000-f20d2328497a3a80239bSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Positivesplash10-004i-0019000000-f6d89e75a6d7e8af9001Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Positivesplash10-0w4i-3179000000-af704769cca5c3dc8e6eSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Positivesplash10-0udj-5292000000-d581a3d2a57e2fa067fdSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Negativesplash10-00di-1009000000-753db826ff35e907de51Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Negativesplash10-00di-2029000000-b8ad29be99c096f6967aSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Negativesplash10-01ox-9061000000-5b2e7de6b58b52c40177Spectrum
MSMass Spectrum (Electron Ionization)splash10-0uxr-4591000000-d2e3424c44feae8a5d9cSpectrum
Biological Properties
Cellular Locations
  • Membrane
Biospecimen Locations
  • Blood
  • Urine
Tissue LocationsNot Available
Normal Concentrations
BloodExpected but not QuantifiedNot QuantifiedNot AvailableNot AvailableTaking drug identified by DrugBank entry DB00557 details
UrineExpected but not QuantifiedNot QuantifiedNot AvailableNot AvailableTaking drug identified by DrugBank entry DB00557 details
Abnormal Concentrations
Not Available
Predicted Concentrations
BiospecimenValueOriginal ageOriginal sexOriginal conditionComments
Blood0.000 uMAdult (>18 years old)BothNormalPredicted based on drug qualities
Blood0.000 umol/mmol creatinineAdult (>18 years old)BothNormalPredicted based on drug qualities
Associated Disorders and Diseases
Disease ReferencesNone
Associated OMIM IDsNone
DrugBank IDDB00557
Phenol Explorer Compound IDNot Available
FooDB IDNot Available
KNApSAcK IDNot Available
Chemspider ID3531
KEGG Compound IDC07045
BioCyc IDNot Available
BiGG IDNot Available
Wikipedia LinkHydroxyzine
METLIN IDNot Available
PubChem Compound3658
PDB IDNot Available
ChEBI ID5818
Food Biomarker OntologyNot Available
VMH IDNot Available
MarkerDB ID
Synthesis ReferenceNot Available
Material Safety Data Sheet (MSDS)Not Available
General References
  1. Clark BG, Araki M, Brown HW: Hydroxyzine-associated tardive dyskinesia. Ann Neurol. 1982 Apr;11(4):435. [PubMed:7103423 ]
  2. HUTCHEON DE, MORRIS DL, SCRIABINE A: Cardiovascular action of hydroxyzine (atarax). J Pharmacol Exp Ther. 1956 Dec;118(4):451-60. [PubMed:13385806 ]
  3. DOLAN CM: Management of emotional disturbances; use of hydroxyzine (atarax) in general practice. Calif Med. 1958 Jun;88(6):443-4. [PubMed:13536863 ]


General function:
Involved in monooxygenase 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 antidepressants.
Gene Name:
Uniprot ID:
Molecular weight:
  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. Preissner S, Kroll K, Dunkel M, Senger C, Goldsobel G, Kuzman D, Guenther S, Winnenburg R, Schroeder M, Preissner R: SuperCYP: a comprehensive database on Cytochrome P450 enzymes including a tool for analysis of CYP-drug interactions. Nucleic Acids Res. 2010 Jan;38(Database issue):D237-43. doi: 10.1093/nar/gkp970. Epub 2009 Nov 24. [PubMed:19934256 ]
General function:
Involved in G-protein coupled receptor protein signaling pathway
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 catecholamine release from adrenal medulla, as well as mediating neurotransmission in the central nervous system
Gene Name:
Uniprot ID:
Molecular weight:
  1. Chen X, Ji ZL, Chen YZ: TTD: Therapeutic Target Database. Nucleic Acids Res. 2002 Jan 1;30(1):412-5. [PubMed:11752352 ]
  2. Spahr L, Coeytaux A, Giostra E, Hadengue A, Annoni JM: Histamine H1 blocker hydroxyzine improves sleep in patients with cirrhosis and minimal hepatic encephalopathy: a randomized controlled pilot trial. Am J Gastroenterol. 2007 Apr;102(4):744-53. Epub 2007 Jan 11. [PubMed:17222324 ]
  3. Sakaguchi T, Itoh H, Ding WG, Tsuji K, Nagaoka I, Oka Y, Ashihara T, Ito M, Yumoto Y, Zenda N, Higashi Y, Takeyama Y, Matsuura H, Horie M: Hydroxyzine, a first generation H(1)-receptor antagonist, inhibits human ether-a-go-go-related gene (HERG) current and causes syncope in a patient with the HERG mutation. J Pharmacol Sci. 2008 Dec;108(4):462-71. Epub 2008 Dec 5. [PubMed:19057127 ]
  4. Chen C: Physicochemical, pharmacological and pharmacokinetic properties of the zwitterionic antihistamines cetirizine and levocetirizine. Curr Med Chem. 2008;15(21):2173-91. [PubMed:18781943 ]
  5. Snowman AM, Snyder SH: Cetirizine: actions on neurotransmitter receptors. J Allergy Clin Immunol. 1990 Dec;86(6 Pt 2):1025-8. [PubMed:1979798 ]