Cetirizine
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| Pronunciation | /sɛˈtɪrɪziːn/ ⓘ |
| Trade names | Zyrtec, others |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a698026 |
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| Routes of administration | By mouth |
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| 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% |
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| ECHA InfoCard | 100.223.545 |
| Chemical and physical data | |
| Formula | C21H25ClN2O3 |
| Molar mass | 388.89 g·mol−1 |
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Cetirizine is a second-generation Peripherally selective 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.
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 antihistamines, cetirizine can cause drowsiness. Among second-generation antihistamines, cetirizine is more likely than fexofenadine and loratadine to cause drowsiness.
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 2022, it was the 43rd most commonly prescribed medication in the United States, with more than 13 million prescriptions.