Cetirizine

Trade Names:
Zyrtec
- Tablets 5 mg
- Tablets 10 mg
- Tablets, chewable 5 mg
- Tablets, chewable 10 mg
- Syrup 5 mg per 5 mL

Pharmacology

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Competitively antagonizes histamine at the H ₁ -receptor site.

Pharmacokinetics

Absorption

Rapidly absorbed. T _max is about 1 h. C _max is 311 ng/mL.

T _max is delayed 1.7 h, and C _max is decreased 23%.

Distribution

93% protein bound.

Metabolism

Cetirizine has a low degree of first-pass metabolism. It also is metabolized by oxidative O-dealkylation to an inactive metabolite.

Elimination

70% is excreted in the urine (50% as unchanged drug) and 10% in the feces. The elimination half-life is 8.3 h. Cl is about 53 mL/min.

Onset

20 to 60 min.

Duration

At least 24 h.

Special Populations

The half-life is increased 3-fold, and Cl is decreased 70%. Dosage adjustment is recommended in those with moderate or severe impairment.

The half-life is increased 50%, and Cl is decreased 40%. Dosage adjustment is recommended.

The half-life is prolonged 50%, and Cl is 40% lower. Dosage adjustment is recommended.

Cl is increased, and half-life is decreased.

Indications and Usage

Symptomatic relief of symptoms (eg, nasal, nonnasal) associated with seasonal and perennial allergic rhinitis; treatment of uncomplicated skin manifestations of chronic idiopathic urticaria.

Unlabeled Uses

Bronchial asthma.

Contraindications

Hypersensitivity to any components of the product or to hydroxyzine.

Dosage and Administration

PO 5 or 10 mg/day.

PO 2.5 mg once daily (max, 5 mg/day as 5 mg once daily or 2.5 mg every 12 h).

PO 2.5 mg once daily. The dose in 12 to 23 mo of age may be increased to a max dosage of 5 mg once daily or 2.5 mg every 12 h.

PO 5 mg/day.

PO 5 mg/day. Do not administer to children younger than 6 yr of age with hepatic function impairment.

PO 5 mg/day. Do not administer to children younger than 6 yr of age with renal function impairment.

General Advice

• Administer prescribed dose without regard to meals. Administer with food if GI upset occurs.
• Administer chewable tablets with or without water.
• Measure and administer prescribed dose of syrup using dosing spoon, syringe, or cup.
• Syrup is recommended for children younger than 2 yr of age.

Storage/Stability

Store tablets, chewable tablets, and syrup at controlled room temperature (59° to 86°F). Syrup also can be stored in refrigerator (36° to 46°F). Keep container tightly closed.

Drug Interactions

None well documented.

Laboratory Test Interactions

May prevent or diminish otherwise positive reactions to skin tests.

Adverse Reactions

Cardiovascular

Cardiac failure, hypertension, palpitation, syncope, tachycardia (less than 2%); severe hypotension (postmarketing).

CNS

Headache, somnolence (14%); fatigue (6%); dizziness (2%); aggressive reactions, convulsions, hallucinations, orofacial dyskinesia, suicidal ideation (postmarketing).

EENT

Pharyngitis (6%); epistaxis (4%).

GI

Abdominal pain (6%); dry mouth (5%); diarrhea, nausea, vomiting (3%).

Genitourinary

Glomerulonephritis (postmarketing).

Hematologic-Lymphatic

Hemolytic anemia, thrombocytopenia (postmarketing).

Hepatic

Cholestasis, hepatitis (postmarketing).

Hypersensitivity

Anaphylaxis (postmarketing).

Respiratory

Coughing (4%); bronchospasm (3%).

Miscellaneous

Stillbirth, suicide (postmarketing).

Precautions

Pregnancy

Category B .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established in children younger than 6 mo of age.

Elderly

No differences in safety were observed in patients 65 yr of age and older compared with younger patients. Studies did not include sufficient numbers of patients aged 65 yr and older to determine whether efficacy is different from younger patients.

Renal Function

Dosage adjustment may be needed.

Hepatic Function

Dosage adjustment may be needed.

Overdosage

Symptoms

Drowsiness, irritability, restlessness, somnolence.

Patient Information

• Advise patient to take each dose without regard to meals but to take with food if stomach upset occurs.
• Advise patient or caregiver using syrup to measure and administer each dose using a dosing spoon, syringe, or cup.
• Advise patient using chewable tablet that tablet may be taken with or without water.
• Advise patient that if allergy symptoms are not controlled not to increase the dose of medication or frequency of use but to inform health care provider. Inform patient that larger doses or more frequent dosing does not increase effectiveness and may cause excessive drowsiness or other adverse reactions.
• Caution patient not to take any OTC antihistamines while taking this medication unless advised by health care provider.
• Caution patient to avoid alcohol and other CNS depressants (eg, sedatives) while using this medication.
• Caution patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
• Advise patient that medication may cause sensitivity to sunlight and to avoid unnecessary exposure to UV light (sunlight, tanning booths), and to use sunscreen and wear protective clothing until tolerance is determined.
• Advise patient to take frequent sips of water, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs.
• Advise patient having allergy skin testing not to take cetirizine for at least 4 days before the skin testing.

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