1. How it works

• Montelukast may be used for the treatment of asthma or allergic rhinitis. It inhibits bronchoconstriction, which is the narrowing of the airways resulting in breathing difficulties.
• 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 12 months.
• 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 allergic rhinitis in adults and children over the age of two and perennial allergic rhinitis in those over the age of 6 months.
• Has a preference for inhibiting CysLT-1 receptors over other receptors (such as prostanoid, cholinergic, or beta-adrenergic receptors).
• Available as tablets, chewable tablets, and oral granules. Granules may be dissolved in baby formula or breast milk for administration to children older than 12 months.
• No dosage adjustment is needed in people with kidney disease.
• Appears to have few significant drug interactions.
• Taken once a day.
• May be taken with or without food.
• 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.
• Although no association between montelukast use during pregnancy and birth defects has been reported, weigh up the benefits versus risks before using during pregnancy. Montelukast has been shown to pass into breastmilk and the data available do not suggest any significant risk of adverse effects to the infant.

Note: 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. View complete list of side effects

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. Available as tablets, chewable tablets, and oral granules. The granules can be administered directly into the mouth or dissolved in a teaspoonful of breast milk or formula, or soft food such as applesauce, carrots, rice, or ice cream. Once the packet is opened, the contents should be taken within 15 minutes. Discard any unused portion.
• Take once daily in the evening when used as a preventative treatment for asthma. Take montelukast daily as prescribed, even if you have no symptoms of asthma. Do not take another dose of montelukast within 24 hours of a previous dose. Do not increase or decrease the dose of montelukast without your doctor's permission and continue to take all other asthma medications as prescribed.
• 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.
• If you miss a dose, take it as soon as possible. But if it is almost time for your next dose, just skip that dose. Do not double up on doses.
• 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. Also, tell your doctor if you develop any symptoms of an allergic reaction including a rash or breathing problems; or side effects such as an abnormal heartbeat, unusual bruising, yellowing of the skin or eye, trouble sleeping, or a tingling or twitching in your fingers and toes.
• Avoid driving or operating machinery if montelukast makes you drowsy or dizzy.
• 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.
• Tell your doctor if you are breastfeeding, pregnant, or intending to become pregnant because they will need to discuss the risks versus benefits of using montelukast while pregnant or breastfeeding.

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.