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Cetirizine

Athanor · official

C21H25ClN2O3 · 388.9 g/mol

IUPAC name: 2-[2-[4-[(4-chlorophenyl)-phenylmethyl]piperazin-1-yl]ethoxy]acetic acid

Also called Zyrtec, antihistamine

DrugsRings
Open in Athanor
The structure of Cetirizine
Drawn from its SMILES with RDKit
Harmful or irritantWarningHarmful if swallowed

Names and identifiers

IUPAC name
2-[2-[4-[(4-chlorophenyl)-phenylmethyl]piperazin-1-yl]ethoxy]acetic acid
Synonyms
Zyrtec, antihistamine, Cetirizina
+ 37 more

Virlix, Ziptek, Cetryn, Setir, Cetirizinum, Cetirizin, Hitrizin Film Tablet, Cetiderm, Reactine, 2-(2-{4-[(4-chlorophenyl)(phenyl)methyl]piperazin-1-yl}ethoxy)acetic acid, 2-[2-[4-[(4-chlorophenyl)-phenylmethyl]piperazin-1-yl]ethoxy]acetic acid, 2-(2-(4-((4-Chlorophenyl)(phenyl)methyl)piperazin-1-yl)ethoxy)acetic acid, YO7261ME24, (2-(4-((4-Chlorophenyl)phenylmethyl)-1-piperazinyl)ethoxy)acetic acid, CHEBI:3561, DTXSID4022787, Acetic acid, (2-(4-((4-chlorophenyl)phenylmethyl)-1-piperazinyl)ethoxy)-, Acetic acid, [2-[4-[(4-chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]-, [2-[4-[(4-chlorophenyl)phenylmethyl]-1-piperazinyl]ethoxy]acetic acid, 2-(2-(4-((4-chlorophenyl)-phenylmethyl)piperazin-1-yl)ethoxy)acetic acid, 2-[2-[4-[(4-Chlorophenyl)(phenyl)methyl]piperazin-1-yl]ethoxy]acetic Acid, RefChem:5658, DTXCID802787, R06AE07, Zirtek, AC-170, Cetrizine, Cetirizine (INN), Prestwick1_000503, 2-[2-[4-[(4-chlorophenyl)-phenyl-methyl]piperazin-1-yl]ethoxy]acetic acid dihydrichloride, MFCD00800721, SCHEMBL4176, CHEMBL1000, Cetirizinum [Latin], Cetirizina [Spanish], Cetirizine (dihydrochloride), HMS3370I19

Molecular formula
C21H25ClN2O3
Empirical formula
C21H25ClN2O3
Molecular weight
388.9 g/mol
Exact mass
388.15537
CAS number
83881-51-0
PubChem CID
2678
Canonical SMILES
C1CN(CCN1CCOCC(=O)O)C(C2=CC=CC=C2)C3=CC=C(C=C3)Cl
Isomeric SMILES
C1CN(CCN1CCOCC(=O)O)C(C2=CC=CC=C2)C3=CC=C(C=C3)Cl
InChI
InChI=1S/C21H25ClN2O3/c22-19-8-6-18(7-9-19)21(17-4-2-1-3-5-17)24-12-10-23(11-13-24)14-15-27-16-20(25)26/h1-9,21H,10-16H2,(H,25,26)
InChIKey
ZKLPARSLTMPFCP-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

log P
log Kow = 1.70[1]

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms
27
Rings
3
Aromatic rings
2
Fraction sp³ carbons (Fsp3)
0.38
H-bond donors
1
H-bond acceptors
4 computed here · PubChem 5
Rotatable bonds
8
TPSA (Ų)
53
Formal charge
0
XLogP3
1.7 PubChem
Complexity
443 PubChem
Stereocenters
0 defined, 1 undefinedCIP: C14: undefined
Double-bond geometry
None specified
Point group
C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

  • C64.86%
  • H6.48%
  • Cl9.12%
  • N7.20%
  • O12.34%

Isotope pattern

100%388.15524%389.15935%390.1538.0%391.1561.1%392.159393.161

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P
3.15 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-4.04 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
2.48 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 388.9
  • log P ≤ 5 (Crippen): 3.15
  • H-bond donors ≤ 5: 1
  • H-bond acceptors ≤ 10: 4

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Warning

Most widely reported: 10 company reports to ECHA. Source [2].

  • Harmful or irritant
  • H302Harmful if swallowed

Precautionary statements: P264, P270, P301+P317, P330, P501

Storage

  • Store at 20-25 °C (68-77 °F); excursions permitted to 15-30 °C (59-86 °F)[1]

Safety data sheets on the supplier’s page: Amerigo Scientific, Protheragen, MolCore.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

  1. [1]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
  2. [2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
  3. [3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
  4. [4]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
  5. [5]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
  6. [6]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
  7. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  8. ·Literature on PubChem

Data last updated 2026-10-14.