• Leukotriene Receptor Antagonist (CysLT1 blocker)

Parent class:

• Leukotriene Modifiers

Zafirlukast selectively blocks the CysLT1 receptor.

Leukotrienes (LTC4, LTD4, LTE4) normally cause:

• Bronchoconstriction
• Increased mucus secretion
• Increased vascular permeability
• Eosinophilic airway inflammation

By blocking CysLT1:

• ↓ Bronchospasm
• ↓ Airway inflammation
• ↓ Mucus production

Does NOT inhibit leukotriene synthesis.

• Oral administration
• Twice-daily dosing
• Hepatic metabolism (CYP2C9)
• Eliminated via bile

Absorption reduced by food — take on empty stomach.

• Asthma (maintenance therapy)

Not indicated for:

• Acute asthma exacerbations

Less commonly used than Montelukast.

• 20 mg PO twice daily
• Take 1 hour before or 2 hours after meals

Common:

• Headache
• GI upset

Serious:

• Hepatotoxicity (rare)
• Elevated liver enzymes

Monitor LFTs if clinically indicated.

• Inhibits CYP2C9
• May increase warfarin levels (monitor INR)
• Food reduces absorption

Fewer neuropsychiatric warnings compared to montelukast.

Compared to montelukast:

• Requires twice-daily dosing
• Food restrictions reduce convenience
• More drug interaction potential
• Less commonly prescribed

May be considered in:

• Patients who cannot tolerate montelukast
• Certain asthma phenotypes

See:

• Asthma Management

• Must be taken on empty stomach.
• Less convenient than montelukast.
• Can increase warfarin levels.
• Not effective for acute asthma attacks.
• Used far less commonly in current practice.

• Leukotriene Modifiers
• Montelukast
• Asthma