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  1. LTRA's
    • Zafirlukast(LTRA)
    • Montelukast(LTRA)
    • Zileuton(synthesis inhibitor) – still available
  2. MoA
    • Cysteinyl leukotrienes (cys-LTs); B4 (LTB4), C4 (LTC4), D4 (LTD4), and E4 (LTE4), are potent
    • bronchial smooth muscle constrictors, and mediators of inflammation
    • They exert their action through receptors cys-LT1 and cys-LT2
    • Zafirlukast and Montelukast are competitive antagonists for the cys-LT1 receptor
    • Zileuton has the potential advantage of blocking synthesis of leukotrienes from arachidonic acid via the 5-lipoxygenase pathway, by inhibiting 5-lipoxygenase activity. This would prevent other effects of cys-LTs that occur via cys-LT2 receptors (not substantiated in practice)
  3. Effects
    • Bronchodilation
    • Anti-inflammatory
  4. SEs
    • Zileuton: hepatotoxicity, must monitor liver function tests q4-6wks, Headaches.
    • Montelukast: eosinophilia and Churg-Strauss syndrome very rare.
    • Zafirlukast: hepatotoxicity (much lower than Zileuton), eosinophilia and Churg-Strauss syndrome very rare, and increased incidence of infections, rare.
  5. Contra
    • Zileuton: elevated liver enzymes 3 times normal.
    • Zafirlukast: elevated liver enzymes 3 times normal,eosinophilia and vasculitis symptoms.
    • Montelukast: eosinophilia and vasculitis symptoms
  6. Drug Interactions
    • Zileuton: increases levels of coumadin, theophylline, and propanolol.
    • Zafirlukast: aspirin increases levels of zafirlukast, erythromycin and theophylline reduce levels of zafirlukast, effect of coumadin increased. Drugs that effect CYP2C9.
    • Montelukast: drugs that effect CYP2C9.
Card Set:
2011-11-30 08:13:49
Ashtma COPD

Leukotriene receptor antagonists/leukotriene synthesis inhibitors
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