Cetirizine
Cetirizine is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria (hives). It is taken by mouth. Effects generally begin within thirty minutes and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation antihistamine.
| Clinical data | |
|---|---|
| Pronunciation | /sɛˈtɪrɪziːn/ |
| Trade names | Allacan, Piriteze, Zyrtec, others |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a698026 |
| License data |
|
| Pregnancy category |
|
| Routes of administration | By mouth |
| ATC code | |
| Legal status | |
| Legal status |
|
| Pharmacokinetic data | |
| Bioavailability | Well-absorbed (>70%) |
| Protein binding | 88–96% |
| Metabolism | Minimal (non-cytochrome P450-mediated) |
| Onset of action | 20–42 minutes |
| Elimination half-life | Mean: 8.3 hours Range: 6.5–10 hours |
| Duration of action | ≥24 hours |
| Excretion | Urine: 70–85% Feces: 10–13% |
| Identifiers | |
| |
| CAS Number | |
| PubChem CID | |
| IUPHAR/BPS | |
| DrugBank | |
| ChemSpider | |
| UNII | |
| KEGG | |
| ChEBI | |
| ChEMBL | |
| CompTox Dashboard (EPA) | |
| ECHA InfoCard | 100.223.545 |
| Chemical and physical data | |
| Formula | C21H25ClN2O3 |
| Molar mass | 388.89 g·mol−1 |
| 3D model (JSmol) | |
SMILES
| |
| |
| (verify) | |
Common side effects include sleepiness, dry mouth, headache, and abdominal pain. The degree of sleepiness that occurs is generally less than with first-generation antihistamines because second-generation antihistamines are more selective for the H1 receptor. Compared to other second-generation anti-histamines, cetirizine can cause drowsiness. Second-generation antihistamines that do not cause drowsiness are fexofenadine, and loratadine.
Use in pregnancy appears safe, but use during breastfeeding is not recommended. The medication works by blocking histamine H1 receptors, mostly outside the brain.
Cetirizine can be used for paediatric patients. The main side effect to be cautious about is somnolence.
It was patented in 1983 and came into medical use in 1987. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2021, it was the 49th most commonly prescribed medication in the United States, with more than 13 million prescriptions.