Leukotriene Antagonist
LEUKOTRIENE ANTAGONIST
- Are also referred as “Leukotriene Receptor Antagonists” (LTRA’s).
- Non-steroidal anti-inflammatory bronchoconstriction preventors.
- Work by blocking inflammatory reactions in airways.
MECHANISM OF ACTION:
Two main approaches to block leukotrienes actions:
Inhibition of 5-lipoxygenase pathway
- Drugs inhibiting 5-lipoxygenase enzyme will inhibit synthetic pathway of leukotriene metabolism
- MK-886 – Blocks 5-lipoxygenase activating protein (FLAP), inhibiting 5-lipoxygenase enzyme functioning & helps in treating atherosclerosis.
Antagonism of cysteinyl-leukotriene type 1 receptors
- Eg: Montelukast & Zafirlukast.
- Blocks cysteinyl leukotriene actions at CysLT1 receptor on bronchial smooth muscle via receptor antagonism.
- Helps improve asthma symptoms, reduce asthma exacerbation, limit inflammation markers such as eosinophil counts in peripheral blood & bronchoalveolar lavage fluid.
- Hence, are anti-inflammatory.
MONTELUKAST:
- A LTRA (Leukotriene receptor antagonist).
- Usually administered orally.
- More acceptable in children.
Mechanism of action:
CysLT1 antagonist:
- Blocks leukotriene D4 action on cysteinyl leukotriene receptor CysLT1 in lungs & bronchial tubes by binding to it.
- Hence, reduces bronchoconstriction & results in less inflammation.
Indications:
- Indicated for prophylactic therapy of mild to moderate asthma.
- As an alternative to inhaled glucocorticoids.
- Used in maintenance therapy of asthma & relief of seasonal allergies.
Contraindications:
- Not used in terminating asthma episodes.
- Not useful in treating acute asthma attacks.
- Due to its very specific action, it does not interact with other allergy medications like theophylline.
SIDE EFFECTS:
- Gastrointestinal disturbances
- Hypersensitivity reactions
- Sleep disorders
- Increased bleeding tendency
- Higher incidence of Churg-Strauss syndrome
Exam Question
- Montelukast mechanism of action is Competitive inhibition of leukotriene synthesis
- Montelukast is leukotriene antagonist
- The leukotriene receptor antagonist used in bronchial asthma is Zafirlukast
- Leukotrienes antagonists are effective in aspirin-induced asthma.
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