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Montelukast: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Mar 23, 2020.

1. How it works

  • Montelukast inhibits bronchoconstriction (which is the narrowing of the airways resulting in breathing difficulties) and may be used in the treatment of asthma or allergic rhinitis.
  • Montelukast inhibits specific receptors in the airways called cysteinyl leukotriene (CysLT) receptors, specifically CysLT-1. These receptors are affected by substances called cysteinyl leukotrienes (LTDs), which are released during inflammation and following exposure to an allergen. By blocking these receptors, montelukast inhibits the actions of LTD-4 and prevents the development of edema, smooth muscle constriction and inflammation. This relaxes the airways, relieves edema, and dampens down redness and irritation.
  • Montelukast belongs to the class of medicines known as leukotriene receptor antagonists (LTRAs).

2. Upsides

  • Used for the maintenance treatment of asthma in adults and children aged older than two years (chewable tablets).
  • May also be used to treat exercise-induced bronchospasm (EIB) (this is shortness of breath that occurs only during exercise) in adults and children aged six years and older.
  • Can help relieve symptoms of seasonal and perennial allergic rhinitis in adults and children over the age of two.
  • Has a preference for inhibiting CysLT-1 receptors over other receptors (such as prostanoid, cholinergic, or beta-adrenergic receptors).
  • No dosage adjustment is needed in people with kidney disease.
  • Appears to have few significant drug interactions.
  • Generic montelukast is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Infection in the upper airways, fever, headache, sore throat, cough, abdominal pain, diarrhea, otitis media, influenza and a runny nose are the most common side effects.
  • Will not help treat an acute asthma attack. Albuterol or another short-acting inhaled beta-agonist should be used for this purpose.
  • Will not effectively replace inhaled or oral corticosteroids.
  • May cause psychiatric-type effects including agitation, aggressive behavior, anxiety, depression, abnormal dreams, and hallucinations.
  • Other less common side effects include an increased bleeding tendency and liver enzyme changes.
  • May not be suitable for some people including those with severe liver disease or with a history of mental health disease.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

4. Bottom Line

Montelukast may be used on a daily basis for the maintenance treatment of asthma or allergic rhinitis. It will not relieve an acute asthma attack and some people may experience unwanted neuropsychiatric effects.

5. Tips

  • May be taken with or without food. For some indications (for example, allergic rhinitis), tablets may be taken once a day, morning or evening. For asthma, montelukast is recommended to be taken in the evening.
  • Take montelukast two hours before exercise when using to prevent exercise-induced bronchospasm (EIB). If you are already taking montelukast on a daily basis, you do not need to take an additional dose to prevent EIB.
  • Take exactly as prescribed when given for asthma, even if you are asymptomatic. Continue taking as prescribed even during an acute asthma attack.
  • Chewable tablets are typically taken once daily in the evening (although studies have not been conducted to evaluate if there is any difference in effectiveness with morning dosing). Chew the tablets thoroughly before swallowing.
  • If you are having an acute asthma attack, take your short acting bronchodilator medicine (for example, albuterol) as prescribed. Talk to your doctor if you regularly need to take more of your acute asthma treatment.
  • Notify your doctor if you experience any neuropsychiatric effects (such as aggression, anxiety, depression, or hallucinations) while taking montelukast.
  • If you know you are sensitive to aspirin or other NSAIDs, continue to avoid these while taking montelukast.
  • If you have phenylketonuria, be aware that the 4 and 5mg chewable tablets contain phenylalanine.

6. Response and Effectiveness

  • Peak concentrations of montelukast are reached two to four hours after oral administration.
  • It may take several weeks of regular use before the full effects on breathing measurements (such as Forced Expiratory Volume [FEV]) are apparent in people with asthma.

7. Interactions

Medicines that interact with montelukast may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with montelukast. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with montelukast include:

  • anticonvulsants, such as carbamazepine, divalproex, fosphenytoin, or phenytoin
  • antifungals, such as fluconazole, miconazole, or voriconazole
  • echinacea
  • fibrates, such as gemfibrozil
  • fluvoxamine
  • heart medications, such as amiodarone
  • HIV medications, such as efavirenz
  • isoniazid
  • metronidazole
  • nafcillin
  • phenobarbital
  • rifampin
  • St. John's wort
  • sulfamethoxazole
  • tamoxifen
  • trimethoprim
  • zafirlukast.

Note that this list is not all-inclusive and includes only common medications that may interact with montelukast. You should refer to the prescribing information for montelukast for a complete list of interactions.


Montelukast. Revised 10/2019.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use montelukast only for the indication prescribed.

Copyright 1996-2020 Revision date: April 10, 2020.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.