Hydroxyzine
Also called Ataraxoid, Atarazoid, Hychotine and Hydroxizinum.
An older antihistamine used both for itching and, because it is sedating, for anxiety and sleep. Cetirizine is what the body turns it into.
Sources and notes
- The introductionfrom sourceMoleculeFinder curated
- Other namesfrom sourcePubChem / Wikidata
- Formula and weightcomputedPubChem
- 2D drawingcomputedPubChem structure, drawn by RDKit
- 3D modelfrom sourcePubChem 3D conformerLoaded after the page has painted, and on a phone only when you ask for it; the 2D drawing shows until it arrives.
Where you encounter it
Dispensed on prescription, not sold on a shelf.
Sources and notes
- The line abovefrom sourceMoleculeFinder curatedFrom the group the molecule belongs to.
Explore its structure
Choose a part to light it up.
A nitrogen bonded to three carbons, with no hydrogen of its own. Its spare pair of electrons can still pick up a hydrogen ion, so a tertiary amine is a base.
From: standard chemistry.
An O-H on a carbon that is not part of an aromatic ring, the group that makes a molecule an alcohol. It both gives and accepts hydrogen bonds, which helps the molecule mix with water.
From: standard chemistry.
An oxygen bridging two carbons, written C-O-C. It accepts hydrogen bonds but has no hydrogen to give, and it is slow to react.
From: standard chemistry.
Sources and notes
- The drawingcomputedPubChem structure, drawn by RDKitThe page's one shipped drawing, with the chosen part lit in amber under it.
- The partscomputedFound by ruleEach part is found by a chemical pattern, never picked by hand atom by atom; its words say where they come from.
Compare a related molecule
Hydroxyzine
Diphenhydramine
Hydroxyzine and diphenhydramine, sold as Benadryl, both cause drowsiness, but hydroxyzine lasts longer, is prescription only and also treats anxiety.
Hydroxyzine vs Diphenhydramine, side by sideSources and notes
- The sentencefrom sourceMoleculeFinder comparison notesThe pair's answer line.
- The two drawingscomputedPubChem structures, drawn by RDKitThe two drawings side by side.
Properties and sources
Calculated by PubChem
- Molecular formula
- C21H27ClN2O2
- Molecular weight
- 374.9 g/mol
- XLogP3octanol/water, log units
- 3.7
- Polar surface areatopological
- 35.9 Ų
- H-bond donors
- 1
- H-bond acceptors
- 4
- Rotatable bonds
- 8
- Complexity
- 376
Measured LD50, HSDB via PubChem
840 mg/kg pure hydroxyzine, rat, oral
An LD50 is an animal study measurement, not a dose for a person.
Reported Hazard label (GHS), ECHA via PubChem
Danger Irritant pictogram (GHS07) and Health hazard pictogram (GHS08); hazard statements H302, H334, H336, H360, H372
Reported Licence
The US Food and Drug Administration licenses Hydroxyzine for human use (ANDA 087408, authorized August 27, 1981). Drugs@FDA
Groups it belongs to
- Category
- Prescription medicine
- Family
- Antihistamines
- Chemical groups
- Alcohols, Aromatics, Ethers, Halogenated
- Hazard classes
- Irritant, Health hazard, GHS Danger
C1CN(CCN1CCOCCO)C(C2=CC=CC=C2)C3=CC=C(C=C3)ClPubChem CID 3658 · Wikidata Q421937 · InChIKey ZQDWXGKKHFNSQK-UHFFFAOYSA-N · Data refreshed
Questions
- What is Hydroxyzine?
- An older antihistamine used both for itching and, because it is sedating, for anxiety and sleep. Cetirizine is what the body turns it into.
- How toxic is Hydroxyzine?
- The reported LD50 of Hydroxyzine is 840 mg/kg (rat, oral). An LD50 is an animal study measurement, not a dose for a person. Its GHS hazard label carries the signal word Danger and the hazard pictograms Irritant and Health hazard. from sourcefrom source
- What kind of molecule is Hydroxyzine?
- Hydroxyzine has the formula C21H27ClN2O2 and a molecular weight of 374.9 g/mol. MoleculeFinder files it under antihistamines, in the prescription medicine group. from sourcefrom sourcefrom sourcefrom source
- Who licenses Hydroxyzine as a medicine?
- The US Food and Drug Administration licenses Hydroxyzine for human use (ANDA 087408, authorized August 27, 1981). from source
Sources and notes
- Calculated valuescomputedPubChemComputed from the structure, so no laboratory conditions apply; complexity is PubChem's own structural score.
- LD50from sourceHSDB via PubChemOther values the sources report: mouse, oral, 480 mg/kg; rat, intravenous, 45 mg/kg; rat, another route, 160 mg/kg. The page shows the one LD50 the site uses everywhere.
- Hazard labelfrom sourceECHA via PubChemThe label combines these classifications.
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Licencefrom sourceDrugs@FDARead 2026-10-21.
- Data refreshedfrom sourceMoleculeFinder2026-11-09
Keep exploring
More related molecules
- Cyclizine Both carry an aromatic ring.
- Quetiapine Both carry an alcohol and an ether group.
Sources and notes
- Compared side by sidefrom sourceMoleculeFinder comparison notesA molecule we compare it with on its own page.
- The same kind of moleculefrom sourceMoleculeFinder curated groupsA structural neighbour in the same family or type group; the line names the group in its own words.
- Similar in shapecomputedRDKit Morgan/TanimotoNeighbours by structural fingerprint; the sentence names the chemical groups the two share.
- The drawingscomputedPubChem structures, drawn by RDKit