XYZAL ALLERGY 24HR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).

How it works

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.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).

Breastfeeding	Levocetirizine is excreted in human breast milk. The milk-to-plasma ratio is not reported. Caution is advised; consider the benefits of breastfeeding and the potential for adverse effects in the infant, such as drowsiness or irritability.
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

Warnings & precautions

■ FDA Black Box Warning

None.

Side Effect Profile

Common Effects	Sleepiness Fatigue Dryness in mouth Headache Vomiting Nasopharyngitis inflammation of the throat and nasal passages
Serious Effects

Absolute Contraindications

Hypersensitivity to levocetirizine, cetirizine, or any component of the formulation. End-stage renal disease (CrCl < 10 mL/min) or patients undergoing hemodialysis.

Clinical Precautions

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.

Clinical Tips & Counseling

Drug interactions

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XYZAL ALLERGY 24HR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).

How it works

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for XYZAL ALLERGY 24HR (XYZAL ALLERGY 24HR).

Breastfeeding	Levocetirizine is excreted in human breast milk. The milk-to-plasma ratio is not reported. Caution is advised; consider the benefits of breastfeeding and the potential for adverse effects in the infant, such as drowsiness or irritability.
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

Warnings & precautions

■ FDA Black Box Warning

None.

Side Effect Profile

Common Effects	Sleepiness Fatigue Dryness in mouth Headache Vomiting Nasopharyngitis inflammation of the throat and nasal passages
Serious Effects

Absolute Contraindications

Hypersensitivity to levocetirizine, cetirizine, or any component of the formulation. End-stage renal disease (CrCl < 10 mL/min) or patients undergoing hemodialysis.