Levocetirizine, sold under the brand name Xyzal, among others, is a second-generation antihistamine used for the treatment of allergic rhinitis (hay fever) and long-term hives of unclear cause.^[3] It is less sedating than older antihistamines.^[4] It is taken by mouth.^[3]

Quick Facts Clinical data, Trade names ...

Levocetirizine

Clinical data
Trade names	Xyzal, Levazyr, others
Other names	Levocetirizine dihydrochloride
AHFS/Drugs.com	Monograph
MedlinePlus	a607056
License data	US DailyMed: Levocetirizine
Routes of administration	By mouth
Drug class	Second generation antihistamines
ATC code	R06AE09 (WHO)
Legal status
Legal status	UK: POM (Prescription only) US: OTC / Rx-only[1][2]
Pharmacokinetic data
Bioavailability	High
Protein binding	91–92%[2]
Metabolism	Minimal (less than 14%, primarily CYP3A4)[2]
Elimination half-life	8 to 9 hours[2]
Excretion	Urine: 85%[2] Feces: 12.9%[2]
Identifiers
IUPAC name 2-(2-{4-[(R)-(4-Chlorophenyl)(phenyl)methyl]piperazin-1-yl}ethoxy)acetic acid
CAS Number	130018-77-8 N
PubChem CID	1549000
IUPHAR/BPS	1214
DrugBank	DB06282 Y
ChemSpider	1266001 Y
UNII	6U5EA9RT2O
KEGG	D07402 Y as salt: D08118 Y
ChEBI	CHEBI:94559
ChEMBL	ChEMBL1201191 N
PDB ligand	LCR (PDBe, RCSB PDB)
CompTox Dashboard (EPA)	DTXSID60156294
Chemical and physical data
Formula	C21H25ClN2O3
Molar mass	388.89 g·mol−1
3D model (JSmol)	Interactive image
SMILES Clc1ccc(cc1)[C@H](N2CCN(CCOCC(=O)O)CC2)c3ccccc3
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)/t21-/m1/s1 Y Key:ZKLPARSLTMPFCP-OAQYLSRUSA-N Y
NY (what is this?)  (verify)

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Common side effects include sleepiness, dry mouth, cough, vomiting, and diarrhea.^[3] Use in pregnancy appears safe but has not been well studied and use when breastfeeding is of unclear safety.^[5] It is classified as a second-generation antihistamine and works by blocking histamine H₁-receptors.^[6][3]

Levocetirizine was approved for medical use in the United States in 2007.^[3] It is available as a generic medication.^[4] In 2021, it was the 190th most commonly prescribed medication in the United States, with more than 2 million prescriptions.^[7][8]

Levocetirizine is used for allergic rhinitis.^[9] This includes allergy symptoms such as watery eyes, runny nose, sneezing, hives, and itching.^[10]

Levocetirizine is referred to as a non-sedating antihistamine as it does not enter the brain in significant amounts and is therefore unlikely to cause drowsiness. Cardiac safety with repolarization may be better than some other antihistamines, as levocetirizine does not significantly prolong the QT interval in healthy individuals.^[11][12][13] However, some people may still experience some slight sleepiness, headache, mouth dryness, lightheadedness, vision problems (mainly blurred vision), palpitations and fatigue.^[14]

Levocetirizine is an antihistamine. It acts as an inverse agonist that decreases activity at histamine H1 receptors. This in turn prevents the release of other allergy chemicals and increases the blood supply to the area, providing relief from the typical symptoms of hay fever. Levocetirizine, (R)-(-)-cetirizine, is essentially a chiral switch of (±)-cetirizine. This enantiomer, the eutomer, is more selective and the (S)-counterpart, the distomer, is inactive.^[15][16]

Chemically, levocetirizine is the active levorotary enantiomer of cetirizine, also called the l-enantiomer of cetirizine. It is a member of the diphenylmethylpiperazine group of antihistamines.^{[citation needed]}

Levocetirizine was first launched in 2001 by the Belgian pharmaceutical company UCB (Union Chimique Belge).^{[citation needed]}