Zafirlukast Maximum Dose
The maximum recommended dose of zafirlukast is 40 mg daily (20 mg twice daily) for patients 12 years and older, and 20 mg daily (10 mg twice daily) for children aged 7-11 years. 1
Age-Specific Maximum Dosing
Adults and Adolescents (≥12 years)
- Maximum dose: 40 mg daily, administered as 20 mg twice daily 1
- This represents the standard therapeutic dose for this age group 1
Children (7-11 years)
- Maximum dose: 20 mg daily, administered as 10 mg twice daily 1
- Zafirlukast is not approved for children under 7 years of age 1
Critical Safety Considerations
Hepatotoxicity Risk at Higher Doses
- Doses exceeding 40 mg twice daily (80 mg total daily) are contraindicated due to reports of elevated liver enzymes 2, 3, 4
- Asymptomatic elevations of serum liver enzymes have been documented with high dosages of 80 mg twice daily, which returned to normal after drug cessation 1
- Postmarketing surveillance has reported cases of reversible hepatitis and, rarely, irreversible hepatic failure resulting in death and liver transplantation 1
Administration Requirements
- Must be taken at least 1 hour before or 2 hours after meals, as food decreases bioavailability by approximately 40% 1, 5
- Administered twice daily dosing schedule 1
Drug Interactions Requiring Monitoring
- Zafirlukast is a microsomal P450 enzyme inhibitor that can inhibit the metabolism of warfarin 1
- Monitor hepatic enzymes (ALT) and warn patients to discontinue use if they experience signs and symptoms of liver dysfunction 1
- Doses of warfarin should be monitored accordingly when co-administered 1
Important Clinical Caveat
The maximum dose should never exceed 40 mg daily in any patient population, as higher doses (80 mg twice daily) have been associated with significant hepatotoxicity without demonstrated additional clinical benefit 2, 3, 4.