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Cetirizine

 

1. Generic Name & Brand Names

  • Generic Name: Cetirizine

  • Common Brand Names:

    • Zyrtec® (Global)

    • Reactine® (Canada)

    • Cetrizet® (India)

    • Aller-Tec® (US generic)

    • Piriteze® (UK)

2. Dosage Forms

  • Oral:

    • Tablets (5 mg, 10 mg)

    • Chewable tablets (5 mg, 10 mg)

    • Liquid syrup (1 mg/mL)

  • No injectable/topical forms

3. Drug Class

  • Second-Generation H₁ Antihistamine

  • Non-sedating (low CNS penetration)

  • Anti-allergic, antipruritic (anti-itch)

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

5. Side Effects

Common (≥1%)Rare but Serious
Drowsiness (10-15%)*Tachycardia (fast heartbeat)
Dry mouthSevere allergic reactions
HeadacheSeizures (very rare)
FatigueDifficulty urinating
*Less sedating than 1st-gen antihistaminesLiver problems (jaundice)

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

7. How to Take It

Age GroupStandard DoseMax Daily
Adults/≥12 yrs10 mg once daily10 mg
6-11 years5-10 mg once daily10 mg
2-5 years2.5-5 mg once daily5 mg

  • Key Tips:

    • Take with/without food

    • Evening dosing reduces daytime drowsiness

    • Do NOT crush chewable tablets (swallow whole)

8. Missed Dose

  • Take ASAP if <12 hours late

  • Skip if >12 hours; resume next day

  • Never double dose

9. Overdose

  • Symptoms:

    Drowsiness, agitation, dilated pupils, rapid heartbeat

  • Action:

    • Seek medical help immediately

    • Activated charcoal may be used

10. Drug Interactions

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

11. Storage

  • Temperature: 20-25°C (68-77°F)

  • Liquid: Discard after 6 months of opening

  • Keep away from children (sweet syrup risk)

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.


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