Fexofenadine: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Fexofenadine
Brand Name(s):
- Pakistan: Telfast
- India: Allegra
- United States: Allegra
- United Kingdom: Telfast
2. Pharmacological Class
Class: Antihistamine
Subclass: Second-generation H1 antagonist
3. Mechanism of Action
Fexofenadine 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 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 12 years and older: 60 mg twice daily or 180 mg once daily.
- Children 6-11 years: 30 mg twice daily.
Route of Administration: Oral (tablets, suspension).
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 1-2 hours.
Distribution: Widely distributed in the body, 60-70% bound to plasma proteins.
Metabolism: Minimal hepatic metabolism, primarily excreted unchanged.
Excretion: Excreted mainly in feces, with a smaller amount excreted in urine.
Half-life: Approximately 14.4 hours.
7. Contraindications
Fexofenadine is contraindicated in patients with a known hypersensitivity to fexofenadine 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 fexofenadine 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 fexofenadine affects you.
9. Side Effects
Common Side Effects: Drowsiness, headache, fatigue, dry mouth.
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 ketoconazole or erythromycin may increase levels of fexofenadine.
Moderate Interactions: May interact with antacids containing aluminum or magnesium, reducing the absorption of fexofenadine.
Minor Interactions: Minimal interactions with food or other drugs.
11. Pregnancy and Lactation
Pregnancy Category: Category C - Risk cannot be ruled out. Use only if clearly needed and the potential benefits justify the potential risk to the fetus.
Breastfeeding Considerations: Fexofenadine is excreted in breast milk, use with caution. Consult your doctor before use.
12. Patient Counseling Information
Key Points for Patients:
- Take fexofenadine exactly as directed. Do not exceed the recommended dose.
- Avoid alcohol and other sedatives while taking fexofenadine.
- Inform your doctor about any other medications you are taking to avoid potential interactions.
Administration Tips:
- Take with water. Avoid taking with fruit juices as they can reduce the absorption of fexofenadine.
- If using suspension, shake well before use and measure the dose with a special measuring spoon or device.