Cetirizine: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Cetirizine
Brand Name(s):
- Pakistan: Zyrtec, Virlix
- India: Okacet, Zyrtec
- United States: Zyrtec
- United Kingdom: Zirtek, Benadryl Allergy One A Day Relief
2. Pharmacological Class
Class: Antihistamine
Subclass: Second-generation H1 antagonist
3. Mechanism of Action
Cetirizine works by selectively inhibiting peripheral H1 receptors, which blocks the action of histamine, a substance in the body that causes allergic symptoms. This helps to reduce the symptoms of allergic reactions such as sneezing, itching, and runny nose.
4. Indications
Primary Indications:
- Allergic rhinitis (seasonal and perennial)
- Chronic idiopathic urticaria (hives)
Off-label Uses:
- Allergic conjunctivitis
- Pruritus (itching) due to other causes
5. Dosage and Administration
Standard Dosage:
- Adults and children 6 years and older: 10 mg once daily.
- Children 2-5 years: 5 mg once daily or 2.5 mg twice daily.
Route of Administration: Oral (tablets, syrup, disintegrating tablets).
Special Populations:
- Pediatric: Dose adjustment required for children under 6 years.
- Geriatric: Use with caution, start at a lower dose due to potential for decreased renal function.
6. Pharmacokinetics
Absorption: Rapidly absorbed after oral administration, with peak plasma concentrations occurring in about 1 hour.
Distribution: Widely distributed in the body, 93% bound to plasma proteins.
Metabolism: Minimal hepatic metabolism, primarily excreted unchanged.
Excretion: Excreted mainly in urine.
Half-life: Approximately 8-9 hours.
7. Contraindications
Cetirizine is contraindicated in patients with a known hypersensitivity to cetirizine, hydroxyzine, or any of its components. It is also contraindicated in patients with severe renal impairment.
8. Warnings and Precautions
Use with caution in patients with renal impairment or hepatic impairment. Although cetirizine is less sedating than first-generation antihistamines, it may still cause drowsiness in some patients. Avoid engaging in activities requiring mental alertness until you know how cetirizine affects you.
9. Side Effects
Common Side Effects: Drowsiness, fatigue, dry mouth, headache.
Serious Side Effects: Severe allergic reactions including rash, itching, swelling, and difficulty breathing. Seek immediate medical attention if these occur.
10. Drug Interactions
Major Interactions: Concurrent use with alcohol or other CNS depressants may enhance sedative effects.
Moderate Interactions: May interact with theophylline, leading to increased levels of cetirizine.
Minor Interactions: Minimal interactions with food or other drugs.
11. Pregnancy and Lactation
Pregnancy Category: Category B - No proven risk in humans, but use only if clearly needed.
Breastfeeding Considerations: Cetirizine is excreted in breast milk, use with caution. Consult your doctor before use.
12. Patient Counseling Information
Key Points for Patients:
- Take cetirizine exactly as directed. Do not exceed the recommended dose.
- Avoid alcohol and other sedatives while taking cetirizine.
- Inform your doctor about any other medications you are taking to avoid potential interactions.
Administration Tips:
- Take with or without food.
- If using disintegrating tablets, allow them to dissolve on the tongue without water.