Montelukast may cause serious or life-threatening mental health changes while you are taking this medication or after treatment has stopped. Tell your doctor if you have or have ever had any type of mental illness. However, you should know that it is possible to develop these changes in mental health and behavior even if you have never had any mental health problems in the past. You should call your doctor right away and stop taking montelukast if you experience any of the following symptoms: agitation, aggressive behavior, anxiety, irritability, difficulty paying attention, memory loss or forgetfulness, confusion, unusual dreams, hallucinations (seeing things or hearing voices that do not exist), repeating thoughts that you cannot control, depression, difficulty falling asleep or staying asleep, restlessness, sleep walking, suicidal thoughts or actions (thinking about harming or killing yourself or planning or trying to do so), or tremor (uncontrollable shaking of a part of the body). Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.

Montelukast is used to prevent wheezing, difficulty breathing, chest tightness, and coughing caused by asthma in adults and children 12 months of age and older. Montelukast is also used to prevent bronchospasm (breathing difficulties) during exercise in adults and children 6 years of age and older. Montelukast is also used to treat the symptoms of seasonal (occurs only at certain times of the year), allergic rhinitis (a condition associated with sneezing and stuffy, runny or itchy nose) in adults and children 2 years of age and older, and perennial (occurs all year round) allergic rhinitis in adults and children 6 months of age and older. Montelukast should be used to treat seasonal or perennial allergic rhinitis only in adults and children who cannot be treated with other medications. Montelukast is in a class of medications called leukotriene receptor antagonists (LTRAs). It works by blocking the action of substances in the body that cause the symptoms of asthma and allergic rhinitis.

Montelukast comes as a tablet, a chewable tablet, and granules to take by mouth. Montelukast is usually taken once a day with or without food. When montelukast is used to treat asthma, it should be taken in the evening. When montelukast is used to prevent breathing difficulties during exercise, it should be taken at least 2 hours before exercise. If you are taking montelukast once a day on a regular basis, or if you have taken a dose of montelukast within the past 24 hours, you should not take an additional dose before exercising. When montelukast is used to treat allergic rhinitis, it may be taken at any time of day. Take montelukast at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take montelukast exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you are giving the granules to your child, you should not open the foil pouch until your child is ready to take the medication. There are several ways that you can give the granules to your child, so choose the one that works best for you and your child. You may pour all of the granules directly from the packet into your child’s mouth to be swallowed immediately. You may also pour the entire packet of granules onto a clean spoon and place the spoonful of medication in your child’s mouth. If you prefer, you may mix the entire packet of granules in 1 teaspoon (5 mL) of cold or room temperature baby formula, breast milk, applesauce, soft carrots, ice cream, or rice. You should not mix the granules with any other foods or liquids, but your child may drink any liquid right after he or she takes the granules. If you mix the granules with one of the allowed foods or drinks, use the mixtures within 15 minutes. Do not store unused mixtures of food, formula, or breast milk and the medication.

Do not use montelukast to treat a sudden attack of asthma symptoms. Your doctor will prescribe a short-acting inhaler to use during attacks. Talk to your doctor about how to treat symptoms of a sudden asthma attack. If your asthma symptoms get worse or if you have asthma attacks more often, be sure to call your doctor.

If you are taking montelukast to treat asthma, continue to take or use all other medications that your doctor has prescribed to treat your asthma. Do not stop taking any of your medications or change the doses of any of your medications unless your doctor tells you that you should. If your asthma is made worse by aspirin, do not take aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) during your treatment with montelukast.

Montelukast controls the symptoms of asthma and allergic rhinitis but does not cure these conditions. Continue to take montelukast even if you feel well. Do not stop taking montelukast without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking montelukast,

• Tell your doctor and pharmacist if you are allergic to montelukast or any other medications, or any of the ingredients in montelukast tablet, chewable tablet, or granules.
• Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention gemfibrozil (Lopid), phenobarbital and rifampin (Rifadin, Rimactane, in Rifamate, Rifater). Your doctor may need to change the doses of your medications or monitor you more carefully for side effects.
• Tell your doctor if you have or have ever had liver disease.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking montelukast, call your doctor.
• If you have phenylketonuria (PKU, an inherited condition in which a special diet must be followed to prevent damage to your brain that can cause severe intellectual disability), you should know that the chewable tablets contain aspartame that forms phenylalanine.

Unless your doctor tells you otherwise, continue your normal diet.

Skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one. Do not take more than one dose of montelukast in a 24 hour period.

Montelukast may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Headache
• Heartburn
• Stomach pain
• Tiredness
• Diarrhea

Some side effects can be serious. If you experience any of the following symptoms or those listed in the IMPORTANT WARNINGS or SPECIAL PRECAUTIONS section, call your doctor immediately:

• Difficulty breathing or swallowing; swelling of the face, throat, tongue, lips, or eyes; hoarseness; itching; rash; hives
• Blistering, peeling, or shedding skin
• Flu-like symptoms, rash, pins and needles or numbness in the arms or legs, pain and swelling of the sinuses
• Ear pain, fever (in children)

Montelukast may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from light and excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

• Stomach pain
• Sleepiness
• Thirst
• Headache
• Vomiting
• Restlessness or agitation

Keep all appointments with your doctor.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.