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 may also be used to treat asthma symptoms caused by exercise (exercise-induced bronchoconstriction). 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. It may be taken alone or in addition to other asthma medications. 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.

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, 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.

Chewable Tablet

5 mg
Each round, pink-to-slightly-speckled-pink, chewable tablet with odour of cherry, embossed "5" on one side, contains 5 mg of montelukast as montelukast sodium. Nonmedicinal ingredients: aspartame, cellulose microcrystalline, cherry flavour (acacia gum, allura red, fatty acids, flavouring substances, maize maltodextrin, silicon dioxide, sugar), croscarmellose sodium, hydroxypropyl cellulose, magnesium stearate, mannitol, and red ferric oxide.

Tablets

10 mg
Each beige, round, film-coated tablet, contains 10 mg of montelukast as montelukast sodium. Nonmedicinal ingredients: cellulose microcrystalline, croscarmellose sodium, hydroxypropylcellulose, polyvinyl alcohol, iron oxide red, iron oxide yellow, lactose monohydrate, macrogol, magnesium stearate, titanium dioxide, and talc.

Do not take this medication if you are allergic to montelukast or any ingredients of the 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
• abnormal dreams
• bedwetting (for children)
• diarrhea
• dizziness
• drowsiness
• fatigue
• fever
• headache
• joint pain
• muscle aches or cramps
• scaly and itchy skin
• skin rash
• symptoms of a cold (i.e., sore throat, runny nose, nasal congestion)
• thirst
• trouble sleeping
• 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)
• asthma symptoms
• behaviour changes (e.g., anxiety, irritability, aggressiveness, hostility)
• disorientation (not knowing time of day, location)
• hyperactivity
• memory problems
• pins and needles sensation
• pounding, fast, or irregular heartbeat
• red lumps under the skin, most commonly on the shins
• respiratory tract infection
• restlessness
• seeing or hearing things that are not there (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)
• sleepwalking
• stuttering
• swelling
• tremor
• trouble paying attention
• uncontrolled muscle movement

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)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• symptoms of Churg-Strauss syndrome (e.g., persistent or worsening flu-like symptoms, rash, pins and needles, numbness of the arms or legs, joint pain, and severe sinusitis)
• thoughts of self-harm or suicide

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.

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, decreased memory, sleep disturbances, or suicidal thoughts and behaviour. 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: The chewable tablet form of this medication contains aspartame, an artificial sweetener which contains phenylalanine. The 4 mg chewable tablet contains 0.674 mg of phenylalanine, and the 5 mg chewable tablet contains 0.842 mg. People with phenylketonuria are unable to break phenylalanine down to get rid of it. If you have phenylketonuria, talk to your doctor about other alternatives.

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 breast-feeding and 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 for children aged 2 years and older and to treat seasonal allergies for adolescents 15 years and older.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other 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.

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.