====== Montelukast ======

===== Classification =====
  * Leukotriene Receptor Antagonist (CysLT1 blocker)

Parent class:
  * [[respiratory:drug_classes:leukotriene_modifiers|Leukotriene Modifiers]]

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===== Mechanism of Action =====

Montelukast selectively blocks the CysLT1 receptor.

Leukotrienes (LTC4, LTD4, LTE4) normally cause:

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

By blocking the receptor:

  * ↓ Bronchospasm
  * ↓ Airway inflammation
  * ↓ Mucus production

Does NOT block leukotriene synthesis — only receptor binding.

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===== Pharmacokinetics =====

  * Oral administration
  * Once daily dosing
  * Hepatic metabolism (CYP3A4, CYP2C9)
  * Eliminated via bile

No routine lab monitoring required.

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===== Indications =====

  * [[respiratory:clinical:asthma|Asthma]] (mild persistent or add-on therapy)
  * Exercise-induced bronchospasm
  * [[allergy:clinical:allergic_rhinitis|Allergic Rhinitis]]
  * Aspirin-exacerbated respiratory disease (AERD)

Not first-line for moderate or severe asthma.

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===== Dosing (Adult) =====

  * 10 mg PO once daily (evening preferred)

Pediatric dosing based on age (chewable formulations available).

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===== Adverse Effects =====

Common:
  * Headache
  * GI upset

Serious:
  * Neuropsychiatric effects (boxed warning)
      - Agitation
      - Depression
      - Sleep disturbances
      - Suicidal ideation (rare)

FDA recommends reserving for patients who cannot tolerate alternative therapy in allergic rhinitis.

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===== Contraindications / Cautions =====

  * Use caution in patients with history of depression or psychiatric illness
  * Not effective for acute asthma attacks

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===== Clinical Role in Asthma =====

Montelukast:

  * Less effective than inhaled corticosteroids
  * Useful as add-on therapy
  * Helpful in aspirin-sensitive asthma
  * Useful in patients with both asthma and allergic rhinitis

See:
  * [[respiratory:clinical:asthma|Asthma Management]]

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===== Clinical Role in Allergic Rhinitis =====

  * Inferior to intranasal corticosteroids
  * Consider if antihistamines not tolerated
  * Consider if coexisting asthma

See:
  * [[allergy:clinical:allergic_rhinitis|Allergic Rhinitis]]

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===== Comparison Within Class =====

^ Drug ^ Mechanism ^ Major Risk ^
| [[respiratory:drugs:montelukast|Montelukast]] | CysLT1 receptor blocker | Neuropsychiatric effects |
| [[respiratory:drugs:zafirlukast|Zafirlukast]] | CysLT1 receptor blocker | Rare hepatotoxicity |
| [[respiratory:drugs:zileuton|Zileuton]] | 5-LO inhibitor | Hepatotoxicity |

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===== Clinical Pearls =====

  * Leukotrienes are potent bronchoconstrictors.
  * Useful in aspirin-exacerbated respiratory disease.
  * Not a rescue medication.
  * Discuss mental health risks before prescribing.
  * Often used in pediatric asthma due to oral formulation.

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===== Related Pages =====

  * [[respiratory:drug_classes:leukotriene_modifiers|Leukotriene Modifiers]]
  * [[endocrine:drug_classes:corticosteroids|Corticosteroids]]
  * [[allergy:histamine|Histamine & Antihistamines]]