Cetirizine (Reactine)

1. Health Canada Product Monograph — Cetirizine

• In adults and children 12 years and older, provides fast relief of nasal and non-nasal symptoms of seasonal and perennial allergic rhinitis, such as sneezing, runny nose, nasal congestion, and itchy or watery eyes, and relief of chronic idiopathic urticaria including itching and hives.
• In children 2 to 12 years, indicated for relief of seasonal allergic rhinitis symptoms and for fast, long-lasting relief of itching from allergic skin reactions such as hives; nasal congestion, itchy throat, perennial rhinitis, and chronic urticaria have not been adequately studied in this age group.

• Should not be used during pregnancy unless directed by a physician; animal studies at doses far exceeding the human dose showed no teratogenic effects, but there are no adequate, well-controlled studies in pregnant women.

• Use in nursing mothers is not recommended unless directed by a physician; a small percentage of the dose is known to pass into milk in animal studies, though the extent of excretion into human milk is unknown.

• Generally well tolerated in patients 65 years and older, but clearance is reduced in proportion to declining kidney function, so a starting dose of 5 mg once daily is recommended; patients unsure about dosing should consult a doctor.

• Should not be given to children under 2 years of age unless directed by a physician, and use beyond 14 days in children should also be physician-directed.
• Dosing varies by age and formulation, ranging from 2.5 mL of syrup twice daily in young children to standard adult dosing in adolescents 12 and older.

• The usual starting dose is 5 to 10 mg once daily depending on symptom severity, taken with or without food; the dose may be increased under medical direction up to a maximum of 20 mg daily if the non-prescription strengths are insufficient.
• Use a reduced starting dose of 5 mg daily in patients with moderate hepatic or renal impairment or in adults 65 years and older.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Overdose is mainly associated with central nervous system effects such as drowsiness, sedation, confusion, or stupor.
• Anticholinergic-type effects can also occur, including dry mouth, dilated pupils, urinary retention, or restlessness.
• A fast heart rate and elevated blood pressure have been reported with overdose.
• Children may show hyperactivity or unusually severe lethargy after an overdose.
• There is no specific antidote for cetirizine, and dialysis does not effectively remove it from the body.
• Emptying the stomach may be considered if the overdose is recognized within the first few hours.

• Cetirizine may cause drowsiness (somnolence), which is more likely at higher doses.
• Dry mouth may occur.
• Headache may occur.
• Fatigue may occur.
• Nausea may occur.
• Sore throat (pharyngitis) may occur, particularly in children.
• Abdominal pain may occur, particularly in children.
• Cough may occur, particularly in children.
• Nosebleed (epistaxis) may occur, particularly in children.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Rare but serious skin reactions, including acute generalized exanthematous pustulosis, can occur.
• Severe hypotension has been reported rarely.
• Anaphylaxis has been reported rarely.
• Seizures (convulsions) have been reported rarely.
• Liver problems, including hepatitis and drug-induced liver injury, have been reported rarely.
• Blood disorders such as hemolytic anemia or thrombocytopenia have been reported rarely.
• Kidney inflammation (glomerulonephritis) has been reported rarely.
• Urinary retention has been reported.
• Involuntary movements (dyskinesia, dystonia) and hallucinations have been reported rarely.
• Seek immediate medical attention for signs of a severe allergic reaction such as facial or throat swelling, difficulty breathing, a widespread rash, fainting, or seizures.

• Use with caution in patients with pre-existing liver disease or renal impairment, where a reduced dose is recommended.
• Because drowsiness can occur, especially at higher doses, exercise caution with driving or operating machinery and avoid combining cetirizine with other sedating substances.

• Contraindicated in patients with known hypersensitivity to cetirizine or any ingredient in the formulation.
• Contraindicated in patients with known hypersensitivity to hydroxyzine, the parent compound of cetirizine.
• Contraindicated in patients with known hypersensitivity to piperazine derivatives.
• Contraindicated in patients with severe renal impairment (creatinine clearance below 10 mL/min).

• No clinically significant interaction has been found with theophylline.
• No clinically significant interaction has been found with pseudoephedrine.
• No clinically significant interaction has been found with cimetidine.
• No clinically significant interaction has been found with erythromycin, and cetirizine is considered unlikely to interact significantly with other macrolides such as clarithromycin.
• No clinically significant interaction has been found with ketoconazole, and cetirizine is considered unlikely to interact significantly with other imidazole antifungals such as itraconazole.
• Alcohol and other sedating substances, including anti-anxiety medications, sleep aids, other antihistamines, antidepressants, muscle relaxants, or prescription analgesics, can add to cetirizine's sedative effect and should generally be avoided together.
• Cetirizine has been safely combined with beta-agonists, NSAIDs, oral contraceptives, narcotic analgesics, corticosteroids, H2-antagonists, cephalosporins, penicillins, thyroid hormones, and thiazide diuretics in clinical trials.

• Interactions with food have not been formally established; cetirizine can be taken with or without food, though food may modestly delay the time to peak blood levels for some formulations.

• Usually taken once daily at a consistent time, with or without food; some products allow a twice-daily divided-dose schedule.

• Store all dosage formats between 15 and 30 degrees C; liquid gel capsules should also avoid high humidity and excessive heat above 40 degrees C and be protected from light.

• Cetirizine is a second-generation antihistamine used to relieve allergy symptoms such as sneezing, runny nose, itchy or watery eyes, and hives.
• Take it once daily at a consistent time; the usual starting dose is 5 to 10 mg, up to a maximum of 20 mg daily if directed by a doctor.
• Common side effects include drowsiness, dry mouth, headache, and fatigue.
• Contact your doctor's office if you develop a severe rash, facial or throat swelling, difficulty breathing, or fainting, since these can signal a serious allergic reaction.
• It can be taken with or without food and at any convenient time of day, though staying consistent helps maintain steady symptom control.
• Store at room temperature away from excess heat, humidity, and light, and avoid driving or operating machinery until you know how it affects you.