XYZAL ALLERGY 24HR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).
Levocetirizine is the active R-enantiomer of cetirizine, a second-generation antihistamine. It selectively inhibits peripheral H1 receptors, reducing histamine-mediated allergic responses such as itching, sneezing, and rhinorrhea.
| Metabolism | Approximately 14% of levocetirizine is metabolized via hepatic CYP3A4 to form a major metabolite (oxidation product). The majority (86%) is excreted unchanged in urine. |
| Excretion | Primarily renal excretion; approximately 85% of the dose is excreted unchanged in urine, with the remainder as metabolites (mainly the conjugate) in feces via biliary elimination (~10-13%). |
| Half-life | Terminal elimination half-life is approximately 8-9 hours in healthy adults. In patients with renal impairment (CrCl <30 mL/min), half-life may be prolonged to up to 21 hours. |
| Protein binding | ~91-92% bound primarily to human serum albumin, with minor binding to alpha-1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 1.1 L/kg, indicating extensive extravascular distribution. This reflects tissue binding and penetration into peripheral compartments. |
| Bioavailability | Oral bioavailability is approximately 70-80%. The absolute bioavailability based on a 5 mg oral dose is 78%. |
| Onset of Action | Oral (tablet): Onset of action occurs within 1 hour, with peak effect observed at 2-4 hours post-dose. |
| Duration of Action | Duration of action is approximately 24 hours, allowing once-daily dosing. Clinical effect lasts for the entire dosing interval due to sustained antihistaminic activity. |
| Molecular Weight | 388.89 |
5 mg (1 tablet) orally once daily, preferably in the evening.
| Dosage form | TABLET |
| Renal impairment | Creatinine clearance 30–50 mL/min: 5 mg every other day; <30 mL/min or end-stage renal disease: not recommended. |
| Liver impairment | No specific adjustment for mild-to-moderate hepatic impairment; severe impairment: not studied, use with caution. |
| Pediatric use | Children 6 months to <2 years: 1.25 mg (0.5 tsp) orally once daily; 2 to <6 years: 1.25 mg (0.5 tsp) orally once daily; 6 to 11 years: 2.5 mg (1 tsp) orally once daily; ≥12 years: 5 mg (1 tablet or 2 tsp) orally once daily. |
| Geriatric use | No specific adjustment, but monitor for sedation and dizziness; consider starting at lower dose (2.5 mg) in frail elderly. |
| 1st trimester | Use only if clearly needed. Animal studies show risk, but human data are limited. Levocetirizine is generally not recommended in first trimester unless benefits outweigh risks. |
| 2nd trimester | Generally considered safe with caution. No known teratogenic effects in second trimester, but use lowest effective dose for shortest duration. |
| 3rd trimester | Use with caution near term. May theoretically cause respiratory depression in newborns if used in high doses near delivery. Avoid late third trimester unless essential. |
Clinical note
Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).
| Placental transfer | Levocetirizine crosses the placenta. Animal studies show placental transfer. Human data limited but expected similar to cetirizine. |
| Breastfeeding | Levocetirizine is excreted into human breast milk in small amounts. The American Academy of Pediatrics considers cetirizine (parent drug) compatible with breastfeeding. Monitor infant for drowsiness, irritability, or feeding difficulties. Use lowest effective dose. |
■ FDA Black Box Warning
None.
| Common Effects | Sleepiness Fatigue Dryness in mouth Headache Vomiting Nasopharyngitis inflammation of the throat and nasal passages |
| Serious Effects |
Hypersensitivity to levocetirizine, cetirizine, or any excipientsSevere renal impairment (CrCl <10 mL/min)End-stage renal disease (ESRD) requiring dialysis
| Precautions | Use with caution in patients with renal impairment (dose adjustment required for CrCl < 50 mL/min). May cause somnolence; avoid driving or operating hazardous machinery. Caution in patients with urinary retention or prostatic hypertrophy. Avoid alcohol or other CNS depressants. |
| Food/Dietary | No significant food interactions. Alcohol may increase sedation and should be avoided. |
Loading safety data…
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | First trimester: No evidence of teratogenicity in animal studies; limited human data. Second and third trimesters: No known specific risks, but use only if clearly needed. Overall, classified as FDA Pregnancy Category B. |
| Fetal Monitoring | Monitor for maternal adverse effects including drowsiness, dizziness, and dry mouth. No specific fetal monitoring required; routine prenatal care is sufficient. |
| Fertility Effects | No significant effects on fertility have been reported in animal studies. Limited human data; no known impact on fertility. |
| Clinical Pearls | Levocetirizine is the active R-enantiomer of cetirizine with twice the potency and reduced sedation. Onset of action within 1 hour; duration 24 hours. Dosing adjustment required for renal impairment (CrCl <50 mL/min). Avoid in patients with history of urinary retention or narrow-angle glaucoma due to anticholinergic effects. |
| Patient Advice | Take once daily at the same time; may be taken with or without food. · Do not exceed one tablet in 24 hours. · May cause drowsiness; avoid driving or operating machinery until you know how you react. · Notify your doctor if you have kidney problems, as dose adjustment may be needed. · Store at room temperature away from moisture and heat. |