Fexofenadine

1. Introduction

Fexofenadine is a non-drowsy antihistamine used to treat allergies. It works by selectively blocking histamine H1 receptors, reducing allergy symptoms such as runny nose, sneezing, itching, and hives. Fexofenadine is less likely to cause sedation compared to older antihistamines, making it suitable for daytime use.

2. Indications

  • Approved Indications:
    • Seasonal allergic rhinitis (hay fever).
    • Chronic idiopathic urticaria (hives).
  • Off-Label Uses:
    • Perennial allergic rhinitis.

3. Dosage

  • Adults and Children (≥12 years):
    • Seasonal allergic rhinitis: 120 mg once daily.
    • Chronic idiopathic urticaria: 180 mg once daily.
  • Children (6–11 years):
    • Seasonal allergic rhinitis and urticaria: 30 mg twice daily.
  • Children (2–5 years):
    • Seasonal allergic rhinitis and urticaria: 15 mg twice daily (using oral suspension).
  • Elderly:
    • No specific dose adjustment, but start with the lowest effective dose due to potential reduced renal function.

4. Administration

  • Take orally with water.
  • Take on an empty stomach for better absorption. Avoid taking with fruit juices (e.g., orange or grapefruit), as they can reduce effectiveness.

5. Forms Available

  • Tablets: 30 mg, 60 mg, 120 mg, 180 mg.
  • Oral suspension: 6 mg/mL (for paediatric use).

6. Side Effects

6.1. Common Side Effects

  • Headache.
  • Drowsiness (less common compared to older antihistamines).
  • Nausea.
  • Dizziness.

6.2. Less Common Side Effects

  • Fatigue.
  • Dry mouth.
  • Insomnia.

6.3. Rare but Serious Side Effects

  • Hypersensitivity reactions (e.g., rash, itching, swelling).
  • Anaphylaxis (extremely rare).

7. Warnings

  • Renal Impairment: Dose adjustment may be needed in patients with reduced kidney function.
  • Severe Allergies: Fexofenadine is not suitable for severe allergic reactions like anaphylaxis; use adrenaline (epinephrine) and seek emergency care instead.

8. Precautions

  • Avoid alcohol, as it may worsen drowsiness in some individuals.
  • Use cautiously in patients with a history of drug allergies.

9. Interactions

  • Drug-Drug Interactions:
    • Antacids containing aluminium or magnesium: Reduce absorption of fexofenadine; take at least 2 hours apart.
    • Erythromycin and ketoconazole: May increase fexofenadine plasma levels but without clinical significance.
  • Drug-Food Interactions:
    • Fruit juices (e.g., orange, grapefruit, apple): Reduce absorption; avoid drinking fruit juice within 4 hours of taking fexofenadine.

10. Monitoring Parameters

  • Symptom improvement in allergic rhinitis or urticaria.
  • Watch for signs of hypersensitivity reactions, particularly during initial use.

11. Use in Children

  • Approved for children aged 2 years and older for seasonal allergic rhinitis and chronic idiopathic urticaria. Dose adjustments are based on age and weight.

12. Use in Pregnancy

  • Category C: Use only if the potential benefits outweigh the risks. Limited human data is available.

13. Use in Elderly

  • No specific dose adjustment is required, but renal function should be considered due to potential drug accumulation.

14. Use in Kidney Disease

  • Use with caution in patients with renal impairment. Reduce dose if necessary (e.g., 60 mg once daily for adults with renal impairment).

15. Use in Liver Disease

  • No dose adjustment required, as fexofenadine is minimally metabolised in the liver.

16. Patient Counselling Points

  • Take fexofenadine as prescribed, preferably on an empty stomach with water. Avoid fruit juices for better absorption.
  • It is less likely to cause drowsiness, but be cautious during activities requiring alertness if drowsiness occurs.
  • Inform your doctor if symptoms do not improve or if you experience severe side effects like swelling or rash.
  • For children, use the appropriate paediatric formulation and dose.
  • Do not use fexofenadine as a substitute for adrenaline in severe allergic reactions.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
AllegraSanofi$20–40 (30 tablets, 180 mg)
TelfastSanofi$25–50 (30 tablets, 180 mg)
Generic FexofenadineVarious$10–25 (30 tablets, 180 mg)

18. FAQs (15 Questions)

  1. What is fexofenadine used for?
    It is used to treat seasonal allergic rhinitis (hay fever) and chronic idiopathic urticaria (hives).
  2. How does fexofenadine work?
    It blocks histamine H1 receptors, reducing allergy symptoms like sneezing, itching, and runny nose.
  3. How long does fexofenadine take to work?
    Symptom relief usually begins within 1 hour and lasts for 24 hours.
  4. What are the common side effects of fexofenadine?
    Common side effects include headache, nausea, and occasional drowsiness.
  5. Can fexofenadine cause drowsiness?
    It is less likely to cause drowsiness compared to older antihistamines, but some people may still feel sleepy.
  6. Can children take fexofenadine?
    Yes, it is approved for use in children aged 2 years and older, with appropriate paediatric doses.
  7. Is fexofenadine safe during pregnancy?
    It should only be used if the benefits outweigh the risks. Consult your doctor before use.
  8. Does fexofenadine interact with other medications?
    Yes, antacids and certain antibiotics (e.g., erythromycin) can interact with fexofenadine. Avoid taking antacids 2 hours before or after.
  9. Can I drink fruit juice while taking fexofenadine?
    Avoid fruit juices (e.g., orange, grapefruit) as they can reduce the absorption of the medication.
  10. What should I do if I miss a dose of fexofenadine?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double the dose.
  11. Can fexofenadine treat severe allergic reactions?
    No, it is not suitable for severe allergic reactions like anaphylaxis. Use adrenaline and seek emergency care instead.
  12. How should fexofenadine be stored?
    Store at room temperature, away from moisture and heat.
  13. Can fexofenadine be taken long-term?
    Yes, it can be taken long-term under medical supervision for chronic allergies or urticaria.
  14. Is fexofenadine available over-the-counter?
    In many countries, fexofenadine is available without a prescription for treating mild allergies.
  15. Can I drink alcohol while taking fexofenadine?
    It is best to avoid alcohol, as it may enhance drowsiness in some individuals.