How does this medication work? What will it do for me?

Montelukast belongs to a group of medications known as leukotriene receptor antagonists. It is used to prevent and manage asthma symptoms and to relieve the symptoms of seasonal allergies, also known as seasonal allergic rhinitis or hay fever. It works by blocking the effects of leukotrienes, a substance produced by the body in response to certain "triggers" that cause narrowing and swelling of airways in the lungs. Montelukast usually starts to work within one day.

When used to prevent and manage asthma, it is important to understand that montelukast should not be used to relieve an asthma attack once it has started. People with asthma should always have their fast-acting asthma relief medication on hand to treat an asthma attack.

Your doctor may have suggested this medication for conditions other than the ones listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Chewable Tablets

4 mg
Each pink, oval, bi-convex chewable tablet, engraved with "APO" on one side and "M 4" on the other side, contains 4 mg of montelukast. Nonmedicinal ingredients: aspartame, croscarmellose sodium, magnesium stearate, mannitol, microcrystalline cellulose, red Iron oxide, and cherry flavour (artificial).

5 mg
Each pink, round, bi-convex chewable tablet, engraved with "APO" on one side and "M 5" on the other side, contains 5 mg of montelukast. Nonmedicinal ingredients: aspartame, croscarmellose sodium, magnesium stearate, mannitol, microcrystalline cellulose, red Iron oxide, and cherry flavour (artificial).

Tablets

10 mg
Each beige, rounded, square-shaped, biconvex, film-coated tablet, engraved with "APO" on one side and "M10" on the other side, contains 10 mg montelukast as montelukast sodium. Nonmedicinal ingredients: anhydrous lactose, colloidal silicon dioxide, croscarmellose sodium, magnesium stearate, microcrystalline cellulose, hydroxypropyl methylcellulose, hydroxypropyl cellulose, red ferric oxide, titanium dioxide, and yellow ferric oxide.

How should I use this medication?

For seasonal allergic rhinitis, the recommended dose of montelukast for adults and adolescents 15 years and older is one 10 mg tablet taken once a day in the evening.

For asthma, the recommended dose of montelukast for adults and adolescents 15 years and older is one 10 mg tablet taken once a day in the evening. For children 6 to 14 years old, the recommended dose is one chewable 5 mg tablet taken once a day in the evening. For children 2 to 5 years old, the recommended dose is one chewable 4 mg tablet or one packet of 4 mg granules taken in the evening.

Montelukast can be taken with or without food.

The oral granules can be given either directly in the mouth, or mixed with a spoonful of cold or room temperature soft food (e.g., apple sauce). The packet should not be opened until ready to use. After opening the packet, the full dose of oral granules must be given within 15 minutes. Do not store any oral granule and food mixture for later use. Do not mix the oral granules in liquid. Children may drink liquids after swallowing the oral granules.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you are allergic to montelukast or any ingredients of the medication.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal or stomach pain
  • diarrhea
  • dizziness
  • fever
  • headache
  • scaly and itchy skin
  • skin rash
  • thirst
  • weakness or unusual tiredness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • aggressive behaviour (such as temper tantrums in children)
  • hyperactivity
  • pounding, fast, or irregular heartbeat
  • persistent or worsening flu-like symptoms, rash, pins and needles, numbness of the arms or legs, joint pain, and severe sinusitis
  • seeing things that are not there (visual hallucinations)
  • signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
  • signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • tremor

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • breathing problems that continue to get worse
  • seizures
  • signs of a severe allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Asthma attacks and asthma control: The effectiveness of montelukast in treating acute asthma attacks has not been established. You should not use it to treat an acute asthma attack - have your rescue medication ready in case of an acute attack. Do not stop taking montelukast without consulting your doctor. For this medication to be effective, it is important to take it regularly on a daily basis, even if you feel your asthma is under control, unless otherwise directed by your doctor.

If you feel your asthma symptoms are not improving or are getting worse while taking this medication, contact your doctor. If your asthma is made worse by acetylsalicylic acid (ASA), do not take ASA or other nonsteroidal anti-inflammatory medications (NSAIDS; e.g., ibuprofen, ketoprofen, naproxen). If your asthma is made worse by exercise, continue to use the medications your doctor has prescribed before exercise.

Behaviour changes: Some people have reported changes in behaviour associated with taking montelukast. There have been occasional reports of aggressive behaviour or hostility, anxiousness, disorientation or decreased memory. If you experience any of these effects or notice them in a family member who is taking this medication contact your doctor as soon as possible.

Depression: Montelukast has been associated with mood swings and symptoms of depression. If you have depression or a history of depression, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience symptoms of depression such as poor concentration, changes in weight, changes in sleep, decreased interest in activities, or notice them in a family member who is taking this medication contact your doctor as soon as possible.

Phenylketonuria: People with phenylketonuria (a condition where the body cannot break down phenylalanine) should know that the chewable tablet form of this medication contains aspartame. The 4 mg chewable tablet contains 0.674 mg of phenylalanine, and the 5 mg chewable tablet contains 0.842 mg.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. The safety of using montelukast for people with severely reduced liver function has not been established. If you have reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if montelukast passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of montelukast have not been established for children under 2 years old. Montelukast can be used to treat asthma in children aged 2 years and older and to treat seasonal allergies in adolescents 15 years and older.

What other drugs could interact with this medication?

There may be an interaction between montelukast and any of the following:

  • amiodarone
  • aprepitant
  • "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
  • barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
  • bosentan
  • capecitabine
  • carbamazepine
  • dabrafenib
  • defirasirox
  • dexamethasone
  • fenofibric acid
  • fluconazole
  • fluorouracil
  • fluvastatin
  • gemfibrozil
  • HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delaviridine, efavirenz, etravirine, nevirapine)
  • irbesartan
  • leflunomide
  • losartan
  • mifepristone
  • milk thistle
  • mitotane
  • omeprazole
  • oxcarbazepine
  • peginterferon Alfa-2b
  • phenytoin
  • primidone
  • quinine
  • rifabutin
  • rifampin
  • St. John's wort
  • sorafenib
  • sulfonamide antibiotics (e.g., sulfadiazine, sulfamethoxazole, sulfisoxazole)
  • ticagrelor
  • tocilizumab
  • tolbutamide
  • trimethoprim
  • zafirlukast

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.