Clinical safety rating: safe
Animal studies have demonstrated safety
Cetirizine is a selective second-generation H1-receptor antagonist that inhibits histamine release from mast cells and basophils, thereby reducing allergic symptoms.
| Metabolism | Cetirizine undergoes limited hepatic metabolism; primarily excreted unchanged in urine. Minor metabolism via oxidative pathways; not significantly metabolized by CYP450 enzymes. |
| Excretion | Primarily renal (60% unchanged in urine); minor biliary/fecal (10%) |
| Half-life | Terminal elimination half-life is approximately 8.3 hours in healthy adults; extended to 20 hours in elderly and patients with renal impairment |
| Protein binding | Approximately 93% bound to plasma proteins (primarily albumin) |
| Volume of Distribution | 0.5-0.8 L/kg, indicating distribution into total body water |
| Bioavailability | Oral: approximately 70% (range 50-85%) with minimal first-pass metabolism |
| Onset of Action | Oral: within 1 hour; peak effect at 1-2 hours |
| Duration of Action | Approximately 24 hours, supporting once-daily dosing for allergic rhinitis and urticaria |
| Molecular Weight | 388.9 |
| Action Class | H1 Antihistaminics (second Generation) |
| Brand Substitutes | Dio 1 10mg Tablet, Leecet Tablet, Okacet Tablet, Cetcip Tablet, Mast 1 Tablet |
10 mg orally once daily; 5 mg orally once daily for mild symptoms
| Renal impairment | GFR 10-50 mL/min: 5 mg orally once daily; GFR <10 mL/min or hemodialysis: 5 mg orally every other day |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B or C: 5 mg orally once daily |
| Pediatric use | 6-12 months: 2.5 mg orally once daily; 12-24 months: 2.5 mg orally twice daily; 2-5 years: 2.5 mg orally once daily (up to 5 mg/day); 6-11 years: 5-10 mg orally once daily |
| Geriatric use | Initial 5 mg orally once daily; consider increasing to 10 mg once daily if response inadequate and well tolerated |
| 1st trimester | Limited human data; animal studies show no teratogenic effects. Use only if clearly needed. |
| 2nd trimester | Generally considered safe; no known fetal risk. Use cautiously. |
| 3rd trimester | May cause uterine contractions or withdrawal symptoms in neonates if used near term; avoid high doses. |
Clinical note
Second-generation (non-sedating) antihistamine used for allergic rhinitis, urticaria, and pruritic conditions in pregnancy. Preferred over first-generation antihistamines due to minimal sedation and CNS penetration. Large registry data shows no significant increase in birth defects.
| Placental transfer | Crosses placenta; limited data suggests low transfer. |
| Breastfeeding | Small amounts excreted into breast milk; monitor infant for drowsiness or irritability. Consider benefit vs risk. |
■ FDA Black Box Warning
None.
| Serious Effects | Anaphylaxis, Angioedema, Severe hypotension, Tachycardia, Seizures, Acute urinary retention, Hepatotoxicity (rare) |
Hypersensitivity to cetirizine or hydroxyzineSevere renal impairment (CrCl <10 mL/min)End-stage renal disease requiring dialysis
| Precautions | Use with caution in patients with renal impairment (dose adjustment required)., May cause drowsiness; avoid driving or operating machinery until response is known., Avoid concurrent use of alcohol or other CNS depressants., Not recommended during pregnancy unless clearly needed; caution during lactation. |
| Food/Dietary | No significant food interactions; absorption is not affected by food. Avoid concurrent use with alcohol due to additive sedation. |
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| Lactation Rating |
| L2 |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies. In humans, large cohort studies show no increased risk of major malformations with first-trimester exposure. Fetal risk cannot be ruled out in third trimester due to potential for histamine receptor blockade; however, cetirizine is generally considered low risk. |
| Fetal Monitoring | No specific fetal monitoring required beyond routine prenatal care. Monitor maternal blood pressure and heart rate if using high doses due to potential anticholinergic effects. Assess for maternal sedation, particularly when combined with other CNS depressants. |
| Fertility Effects | No significant adverse effects on fertility in human studies. Animal studies show no impairment of fertility at doses up to 10 mg/kg/day. However, antihistamines may theoretically affect implantation via histamine receptor modulation; no conclusive human data. |
| Clinical Pearls | Cetirizine is a second-generation antihistamine with minimal anticholinergic effects; it is less sedating than first-generation agents but may cause somnolence in some patients. It is renally eliminated (60% unchanged in urine), requiring dose adjustment for creatinine clearance <30 mL/min. Onset of action is within 1 hour; peak effect at 4-8 hours. It is superior to loratadine for urticaria but similar for allergic rhinitis. |
| Patient Advice | Take once daily as directed; may cause drowsiness, avoid driving if affected. · Do not exceed recommended dose; skip dose if missed and do not double. · Avoid alcohol as it may increase drowsiness. · Consult doctor if symptoms persist beyond 3 days or if you have kidney disease. · Store at room temperature, away from moisture and heat. |