Cetirizine

 

1. Generic Name & Brand Names

• Generic Name: Cetirizine

• Common Brand Names:

  • Zyrtec® (Global)

  • Reactine® (Canada)

  • Cetrizet® (India)

  • Aller-Tec® (US generic)

  • Piriteze® (UK)

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2. Dosage Forms

• Oral:

  • Tablets (5 mg, 10 mg)

  • Chewable tablets (5 mg, 10 mg)

  • Liquid syrup (1 mg/mL)

• No injectable/topical forms

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3. Drug Class

• Second-Generation H₁ Antihistamine

• Non-sedating (low CNS penetration)

• Anti-allergic, antipruritic (anti-itch)

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4. Uses

• Allergic Rhinitis:

  • Seasonal (pollen) & perennial (dust mites, pets)

• Urticaria (Hives):

  • Acute/chronic idiopathic urticaria

• Allergic Conjunctivitis (eye itching)

• Itch Relief:

  • Insect bites, eczema-related itching

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5. Side Effects

Common (≥1%)	Rare but Serious
Drowsiness (10-15%)*	Tachycardia (fast heartbeat)
Dry mouth	Severe allergic reactions
Headache	Seizures (very rare)
Fatigue	Difficulty urinating
*Less sedating than 1st-gen antihistamines	Liver problems (jaundice)

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6. Key Warnings

• Renal Impairment:

  • ↓ Dose if eGFR <30 mL/min (e.g., 5 mg daily)

• Pregnancy/Lactation:

  • Category B: Use only if clearly needed

  • Excreted in breast milk (caution advised)

• Avoid with:

  • Alcohol (↑ drowsiness)

  • CNS depressants (benzodiazepines, opioids)

• Not for Acute Asthma/Anaphylaxis:

  • Does NOT replace epinephrine in emergencies

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7. How to Take It

Age Group	Standard Dose	Max Daily
Adults/≥12 yrs	10 mg once daily	10 mg
6-11 years	5-10 mg once daily	10 mg
2-5 years	2.5-5 mg once daily	5 mg

• Key Tips:

  • Take with/without food

  • Evening dosing reduces daytime drowsiness

  • Do NOT crush chewable tablets (swallow whole)

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8. Missed Dose

• Take ASAP if <12 hours late

• Skip if >12 hours; resume next day

• Never double dose

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9. Overdose

• Symptoms:

  Drowsiness, agitation, dilated pupils, rapid heartbeat

• Action:

  • Seek medical help immediately

  • Activated charcoal may be used

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10. Drug Interactions

Medication	Risk
Theophylline	↑ Cetirizine levels
CNS Depressants	↑ Drowsiness (alcohol, opioids)
Ritonavir	↑ Cetirizine concentration

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11. Storage

• Temperature: 20-25°C (68-77°F)

• Liquid: Discard after 6 months of opening

• Keep away from children (sweet syrup risk)

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Critical Safety Notes:

⚠️ Driving Alert:

10-15% experience drowsiness - avoid operating machinery until tolerance confirmed.

⚠️ Chronic Urticaria:

Maximum 4 weeks continuous use without medical review.

⚠️ False Allergy Tests:

Stop 72 hours before skin prick/IgE tests (antihistamines mask results).

⚠️ Kidney Patients:

Halve dose (5 mg daily) if creatinine clearance <30 mL/min.

OTC Availability:

Approved for non-prescription use in most countries for ages 6+.

Duration of Action:

24-hour coverage with single daily dose.