Montelukast is used to control and prevent symptoms caused by asthma (such as wheezing and shortness of breath). It is also used before exercise to prevent breathing problems during exercise (bronchospasm). This medication can help decrease the number of times you need to use your quick relief inhaler.

Montelukast is also used to relieve symptoms of hay fever and allergic rhinitis (such as sneezing, stuffy/runny/itchy nose). Since there are other allergy medications that may be safer (see also Warning section), this medication should be used for this condition only when you cannot take other allergy medications or they do not work well.

This medication must be used regularly to be effective. It does not work right away and should not be used to relieve sudden asthma attacks or breathing problems. If an asthma attack or sudden shortness of breath occurs, use your quick-relief inhaler as prescribed.

This drug works by blocking certain natural substances (leukotrienes) that may cause or worsen asthma and allergies. It helps make breathing easier by reducing swelling (inflammation) in the airways.

Read the Medication Guide provided by your pharmacist before you start taking montelukast and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor. The dosage is based on your age and medical condition.

If you are using the chewable tablets, chew them thoroughly before swallowing. If your child cannot safely chew and swallow them, consult the doctor or pharmacist for advice.

Take this medication at the same time each day. If you are taking this medication for asthma or for both asthma and allergies, take your dose in the evening. If you are taking montelukast to prevent only allergies, take your dose either in the morning or the evening.

If you are taking this medication to prevent breathing problems during exercise, take your dose at least 2 hours before exercise. Do not take more than one dose in 24 hours. Do not take a dose before exercise if you are already taking this medication daily for asthma or allergies. Doing so may increase the risk of side effects.

Do not increase or decrease your dose or stop using this medication without consulting your doctor. Continue to use this medication regularly to keep your asthma under control, even during sudden asthma attacks or periods when you have no asthma symptoms. Continue to also take other medications for asthma as directed by your doctor. This medication works over time and is not meant to relieve sudden attacks of asthma. If an asthma attack or other breathing problem occurs, use your quick-relief inhaler as prescribed. You should always have a quick-relief inhaler with you. Consult your doctor or pharmacist for more details.

Get medical help right away if your asthma symptoms get worse and your quick-relief inhaler is not helping. Tell your doctor promptly if asthma symptoms, breathing problems, allergy symptoms, number of times you use your rescue inhaler last or get worse.

See also Warning section.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• numbness/tingling/shooting pain in the arms or legs
• sinus pain/swelling
• muscle weakness
• uncontrolled muscle movements
• stuttering

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking montelukast, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this drug, tell your doctor or pharmacist your medical history, especially of:

• liver disease
• mental/mood problems (such as anxiety, depression, thoughts of suicide)

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

The chewable tablets may contain aspartame. If you have phenylketonuria (PKU) or any other condition that requires you to limit/avoid aspartame (or phenylalanine) in your diet, ask your doctor or pharmacist about using this medication safely.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: thirst, drowsiness, inability to keep still, vomiting, or severe stomach pain.

Do not share this medication with others.

Lab and/or medical tests (such as lung function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up. Do not take more than 1 dose in 24 hours.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).