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Montelukast
(Singulair, Merck)
Classification: Respiratory Agents; Miscellaneous Respiratory Agents
Description: Singular® may be confused with Sinequan®
Pharmacology:
The cysteinyl leukotriene type-1 (CysLT1) receptor is found in the human airway (including airway
smooth muscle cells and airway macrophages) and on other pro- inflammatory cells (including
eosinophils and certain myeloid stem cells). Montelukast binds with high affinity and selectivity to the
CysLT1 receptor inhibiting the physiologic actions of LTD4 without any agonist activity. ). In asthma,
leukotriene- mediated effects include airway edema, smooth muscle contraction, and altered cellular
activity associated with the inflammatory process. In allergic rhinitis, CysLTs are released from the
nasal mucosa after allergen exposure during both early and late- phase reactions and are associated
with symptoms of allergic rhinitis.
Pharmacokinetics:
Absorption:
Rapidly absorbed with a mean oral bioavailability of 64%.
Distribution:
more than 99% bound to plasma proteins
Metabolism:
Extensively metabolized by CYP450 3A4 and 2C9
Elimination:
Montelukast and its metabolites are excreted almost exclusively via the bile.
Indications:
Montelukast is indicated for the prophylaxis and chronic treatment of asthma in adults and pediatric
patients 12 months of age and older and for the relief of symptoms of seasonal allergic rhinitis in
adults and pediatric patients 2 years of age and older.
Dosage:
Montelukast should be taken once daily. For asthma, the dose should be taken in the evening. For
seasonal allergic rhinitis, the time of administration may be individualized to suit patient needs.
Patients with both asthma and seasonal allergic rhinitis should take only 1 tablet daily in the evening.
Contraindications and Precautions:
 Pregnancy category B
 Phenylketonurics: the chewable tablets contain phenylalanine
 Montelukast can not be used for the reversal of acute bronchospasm
 Use has been associated with eosinophilic vasculitis (Churg-Strauss syndrome)
Interactions:
Montelukast is a major substrate for CYP 2C8/9 and 3A4. It weakly inhibits CYP 2C8/9.
The effects of Montelukast may be decreased by Carbamazepine, Phenobarbital, Phenytoin,
Rifampin, secobarbital and St. John’s wart.
Adverse Reactions:
The most common adverse reactions (>10%) include headache. Less common adverse effects (1%
to 10%) include: dizziness, fatigue, fever, rash, dyspepsia, dental pain, gastroenteritits, abdominal
pain, weakness, cough, nasal congestion and flu-like syndrome.
Costs and Monitoring:
Routine monitoring should include the signs and symptoms of the treated condition (asthma/allergic
rhinitis).
The cost of therapy is $2.55 per day.
Product Identification:
Tablet, chewable: 4 mg
Tablet: 10 mg
Efficacy:
Asthma: Overall, the use of montelukast has been shown to reduced the use of “as needed” betaagonist use, decrease the incidence of nocturnal awakenings. When compared to placebo,
montelukast decreased the incidence of asthma attacks requiring medical intervention, reduced the
need for oral corticosteroid use and decrease the number of days with asthma exacerbations.
Allergic rhinitis: Montelukast has been shown to reduce daytime nasal symptoms as measured by the
average of individual scores of nasal congestion, rhinorrhea, nasal itching, sneezing.
Conclusions:
Montelukast is an effective and well-tolerated preventative treatment for asthma and allergic rhinitis in
adults and children. There are no well designed head-to-head trials between Montelukast and
Zafirlukast. However, with the similar cost of therapy and the once daily dosing (verses the twice daily
dosing of Zafirlukast), Montelukast would be an advantageous addition to the treatment options for
asthma.
Recommendation: Add to formulary.
References:
1. Montelukast Monograph. Mosby’s Drug Consult. Mosby’s Inc., St. Louis Mo. 2005.
2. Montelukast Monograph. Facts and Comparisons. Facts and Comparisons. St. Louis. 2002.
Prepared by:
Sharon M. Tramonte, Pharm.D.
Clinical Pharmacologist
San Antonio State School
1 August 2017
Montelukast
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