Zafirlukast

1. Introduction

Zafirlukast is a leukotriene receptor antagonist (LTRA) used for the long-term management of asthma. It works by inhibiting the action of leukotrienes, which are inflammatory mediators involved in bronchoconstriction and airway inflammation. Zafirlukast helps improve breathing and reduce asthma symptoms, but it is not intended for acute asthma attacks.

2. Indications

  • Long-term management and prophylaxis of asthma
  • Prevention of exercise-induced bronchoconstriction (off-label use)

3. Dosage

Adults and Children (≥12 years):

  • Standard dose: 20 mg orally twice daily, preferably on an empty stomach (1 hour before or 2 hours after meals).

Children (5–11 years):

  • Standard dose: 10 mg orally twice daily, preferably on an empty stomach.

Elderly:

  • Use the standard adult dose; no specific dose adjustments required, but monitor for hepatic function and side effects.

4. Administration

  • Take zafirlukast at least 1 hour before or 2 hours after meals to ensure proper absorption.
  • Consistent dosing times improve therapeutic effects.

5. Forms Available

  • Tablets: 10 mg, 20 mg

6. Side Effects

6.1 Common Side Effects:

  • Headache
  • Nausea
  • Diarrhoea
  • Abdominal pain

6.2 Less Common Side Effects:

  • Dizziness
  • Weakness or fatigue
  • Rash

6.3 Rare but Serious Side Effects:

  • Hepatotoxicity (liver injury, elevated liver enzymes)
  • Churg-Strauss syndrome (eosinophilic granulomatosis with polyangiitis)
  • Severe hypersensitivity reactions (e.g., angioedema)

7. Warnings

  • Hepatotoxicity: Rare but serious liver injury has been reported. Monitor liver enzymes regularly, particularly during the initial months of therapy.
  • Churg-Strauss Syndrome: This rare condition may occur when corticosteroid doses are tapered in asthma patients. Be vigilant for symptoms such as eosinophilia, vasculitic rash, or worsening pulmonary symptoms.
  • Not for Acute Use: Zafirlukast is not a rescue medication and should not be used to treat acute asthma attacks.

8. Precautions

  • Use cautiously in patients with pre-existing liver disease or a history of alcohol abuse.
  • Monitor patients for unusual mood or behavioural changes, including agitation or depression.
  • Avoid abrupt discontinuation in patients using corticosteroids concurrently.

9. Interactions

  • Warfarin: May increase INR levels and the risk of bleeding. Monitor INR closely.
  • Aspirin: May increase zafirlukast levels, potentially leading to toxicity.
  • Erythromycin and Rifampin: May reduce zafirlukast levels and effectiveness.
  • Theophylline: Reduced efficacy of both drugs when used concurrently.

10. Monitoring Parameters

  • Liver function tests (ALT, AST) periodically, especially during the first 3 months of therapy.
  • Assess for symptom control and reduction in the frequency of asthma exacerbations.
  • Monitor for signs of hypersensitivity or Churg-Strauss syndrome.

11. Use in Children

  • Approved for children aged 5 years and older.
  • Use the lower dose (10 mg twice daily) for children aged 5–11 years.

12. Use in Pregnancy

  • Category B: Animal studies show no harm to the foetus, but human data are limited. Use only if the potential benefit outweighs the risks.

13. Use in Elderly

  • Safe for use in elderly patients at standard doses. Monitor for potential liver-related side effects.

14. Use in Kidney Disease

  • No dose adjustments are required for renal impairment.

15. Use in Liver Disease

  • Avoid use in patients with active liver disease or unexplained elevated liver enzymes. Monitor liver function regularly if use is necessary.

16. Patient Counselling Points

  • Take zafirlukast on an empty stomach for optimal absorption.
  • This medication is for long-term asthma management and will not provide immediate relief for asthma attacks. Always carry a rescue inhaler for acute symptoms.
  • Report symptoms such as yellowing of the skin or eyes, dark urine, or persistent abdominal pain, which may indicate liver problems.
  • Do not stop taking zafirlukast without consulting your doctor, even if your asthma symptoms improve.
  • Inform your doctor of any new or worsening symptoms, including unusual mood changes or behavioural issues.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
AccolateAstraZeneca20 mg Tablet$120 (60 tablets)
Generic ZafirlukastVarious20 mg Tablet$40 (60 tablets)

18. 15 FAQs (Frequently Asked Questions)

1. What is Zafirlukast used for?
Zafirlukast is used for long-term management of asthma and prevention of asthma symptoms.

2. How does Zafirlukast work?
It blocks leukotriene receptors, reducing airway inflammation, bronchoconstriction, and mucus production.

3. Can Zafirlukast be used for acute asthma attacks?
No, it is not a rescue medication and should not be used for acute asthma symptoms.

4. How should I take Zafirlukast?
Take it on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption.

5. Can Zafirlukast cause liver problems?
Yes, though rare, zafirlukast may cause liver injury. Monitor liver function tests regularly.

6. Can children take Zafirlukast?
Yes, it is approved for children aged 5 years and older.

7. How long does it take for Zafirlukast to work?
Improvement in asthma symptoms may be noticeable within a few days, but maximum benefit may take several weeks.

8. Can I stop Zafirlukast if my asthma improves?
No, continue taking zafirlukast as prescribed to maintain control of asthma symptoms.

9. Can Zafirlukast be used during pregnancy?
Yes, but only if the benefits outweigh the risks. Consult your doctor.

10. Does Zafirlukast interact with other medications?
Yes, it interacts with warfarin, aspirin, theophylline, and erythromycin.

11. Can Zafirlukast cause behavioural changes?
Yes, mood changes, including agitation or depression, have been reported.

12. Can I drink alcohol while taking Zafirlukast?
Avoid alcohol, as it may increase the risk of liver-related side effects.

13. Does Zafirlukast affect exercise-induced asthma?
It may help prevent exercise-induced asthma symptoms (off-label use).

14. How should Zafirlukast be stored?
Store at room temperature, away from moisture and heat.

15. What should I do if I miss a dose of Zafirlukast?
Take the missed dose as soon as you remember, unless it is close to the next scheduled dose. Do not double the dose.