ZYRTEC HIVES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZYRTEC HIVES (ZYRTEC HIVES).
Selective histamine H1-receptor antagonist. Inhibits histamine-mediated vasodilation, capillary permeability, and smooth muscle contraction.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2D6; also via metabolism to cetirizine (active); less than 1% excreted unchanged in urine. |
| Excretion | Cetirizine is primarily excreted renally as unchanged drug (approximately 70%). Fecal excretion accounts for about 10%. The remainder undergoes hepatic metabolism to inactive metabolites, which are also renally eliminated. |
| Half-life | The terminal elimination half-life is approximately 8.3 hours in healthy adults. In patients with renal impairment (CrCl < 40 mL/min), half-life can extend to 18–21 hours, necessitating dose adjustment. |
| Protein binding | Protein binding: 93% bound, primarily to albumin. |
| Volume of Distribution | Volume of distribution: 0.5–0.8 L/kg, indicating distribution into total body water and some tissue binding. |
| Bioavailability | Oral bioavailability: Approximately 70% (range 60–80%), due to incomplete absorption. Food does not significantly affect the extent of absorption. |
| Onset of Action | Oral administration: Onset of action for symptom relief (e.g., wheal and flare suppression) occurs within 1 hour, with peak effect at 6–8 hours. |
| Duration of Action | Duration of action is approximately 24 hours, allowing once-daily dosing. Suppression of histamine-induced wheal and flare persists for at least 24 hours. Clinical efficacy for allergic rhinitis and urticaria is maintained throughout the dosing interval. |
For chronic idiopathic urticaria, adults: 10 mg orally once daily. For intermittent symptoms, up to 10 mg once daily as needed.
| Dosage form | TABLET |
| Renal impairment | For GFR 30-50 mL/min: reduce dose to 5 mg once daily. For GFR <30 mL/min or end-stage renal disease: contraindicated. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B or C: reduce dose to 5 mg once daily. |
| Pediatric use | Children 6-12 years: 5 mg orally once daily; children 2-5 years: 2.5 mg orally once daily; children 6 months to <2 years: 2.5 mg orally once daily. |
| Geriatric use | Elderly patients (≥65 years) with normal renal function: no adjustment; may start at 5 mg once daily if sensitivity is a concern. Monitor for dizziness and sedation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZYRTEC HIVES (ZYRTEC HIVES).
| Breastfeeding | Cetirizine is excreted in human breast milk at low concentrations. The milk-to-plasma ratio is approximately 0.25-0.43. Doses up to 10 mg daily are considered compatible with breastfeeding. Monitor infant for drowsiness or irritability. |
| Teratogenic Risk | Cetirizine is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. First trimester: No evidence of teratogenicity in human data. Second and third trimesters: No specific fetal risks identified, but use only if clearly needed. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to levocetirizine, cetirizine, or any excipient. End-stage renal disease (CrCl < 10 mL/min) or patients on dialysis. Avoiding use in pregnancy unless clearly needed (category B; limited human data).
| Precautions | Somnolence may occur; caution when driving or operating machinery. Avoid concurrent use with alcohol or CNS depressants. Dose adjustment in renal impairment (CrCl < 31 mL/min). Caution in elderly due to increased sensitivity/sedation. May cause urinary retention in patients with prostatic hyperplasia or bladder obstruction. |
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| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for maternal adverse effects such as drowsiness, dry mouth, or urinary retention. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at doses up to 20 times the maximum recommended human daily dose. |