Montelukast tablets side effects: A detailed guide

This article describes possible side effects of montelukast tablets. You can explore this overview article to learn more about montelukast, including the drug’s uses, dosage, ways to save on cost, and more.

Montelukast tablets are generic versions of the brand-name drug Singulair. Montelukast comes as an oral tablet and a chewable tablet. It also comes as granules that you’ll take by mouth, but this form isn’t described in this article. To learn more about the granules, talk with your doctor.

Boxed warning: Risk of serious behavior or mood changes

Montelukast tablets have a boxed warning for the risk of serious behavior and mood changes. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

For details, see the “Side effects of montelukast in detail” section below.

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More common side effects of montelukast

Montelukast tablets may cause mild or serious side effects. Below are some of the more common side effects of this medication.

Commonly reported side effects of montelukast tablets include:

• abdominal pain
• diarrhea
• dizziness
• headache
• indigestion

Mild side effects of montelukast

Montelukast may cause certain mild side effects. Usually, mild side effects are temporary and can be easily managed. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.

Mild side effects reported with montelukast tablets include:

• abdominal pain
• cough
• diarrhea
• dizziness
• earache or ear infection
• fatigue
• fever
• headache
• indigestion
• runny nose
• sinusitis (pain or swelling in the sinuses)
• sore throat
• upper respiratory infection
• mild low platelet count*
• mild allergic reaction†

* This side effect wasn’t reported in studies of the drug. But it has occurred in people after the drug was approved for use. To learn more about this side effect, see the “Side effects of montelukast in detail” section below.
† An allergic reaction is possible with montelukast tablets. But it’s unclear whether it occurred in the drug’s studies. To learn more about this side effect, see the “Side effects of montelukast in detail” section below.

Montelukast tablets may cause more mild side effects than those listed above. For details, see the drug’s prescribing information.

Serious side effects of montelukast

Montelukast may cause certain serious side effects. If you have any serious side effects from montelukast tablets, call your doctor right away. But if you think you’re having a medical emergency or your side effects feel life threatening, take immediate action. Call 911 or a local emergency number, or go to the nearest emergency room.

After the FDA approves a drug, it tracks and reviews side effects of the medication. Visit MedWatch’s website if you’d like to notify the FDA about a side effect you’ve had with montelukast.

Serious side effects reported with montelukast tablets include:

• high liver enzyme levels, which can be a sign of liver problems
• risk of serious behavior or mood changes*†
• increased eosinophil count†
• severe low platelet count†
• severe allergic reaction‡

* Montelukast tablets have a boxed warning for this side effect. A boxed warning is the most serious warning from the FDA. To learn more, see the “Side effects of montelukast in detail” section below.
† This side effect wasn’t reported in studies of the drug. But it has occurred in people after the drug was approved for use. To learn more about this side effect, see the “Side effects of montelukast in detail” section below.
‡ An allergic reaction is possible with montelukast tablets. But it’s unclear whether it occurred in the drug’s studies. To learn more about this side effect, see the “Side effects of montelukast in detail” section below.

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Common questions about side effects of montelukast

Here are answers to some common questions about side effects of montelukast tablets. If you have other questions, talk with your doctor or pharmacist.

Does montelukast cause long-term side effects?

Long-term side effects aren’t expected with montelukast tablets. In studies, specific side effects weren’t seen in people who had taken the drug for a long time. And long-lasting side effects after treatment ended weren’t reported.

Talk with your doctor if you have more questions about possible long-term side effects with montelukast.

How do side effects of montelukast compare with those seen with levocetirizine?

The side effects of montelukast tablets are different than those seen with levocetirizine. Both drugs can be used to treat allergies. But levocetirizine is an antihistamine, not a leukotriene receptor antagonist like montelukast.

Common side effects of levocetirizine include dry mouth, fatigue, and sleepiness. Serious side effects that are possible with levocetirizine include severe fatigue, severe sleepiness, and urinary retention (not being able to empty your bladder fully).

You can learn more about how these two drugs compare by talking with your doctor or pharmacist.

Side effects of montelukast in detail

Below you’ll find details on some of the side effects of montelukast tablets.

Risk of serious behavior or mood changes

Montelukast tablets have a boxed warning for the risk of serious behavior and mood changes. A boxed warning is the most serious warning from the FDA.

Mental health problems, such as serious behavior or mood changes, can occur while taking montelukast tablets or after stopping treatment. This side effect wasn’t reported in studies of the drug. But it has occurred in people after the drug was approved for use. It has happened in people of all ages and in those with and without previous mental health problems.

Reports of serious behavior or mood changes include:

• aggressive or hostile behavior
• anxiety
• attention problems
• bad or vivid dreams
• confusion
• depression
• feeling irritable or restless
• hallucinations (seeing or hearing things that aren’t real)
• memory problems
• obsessive-compulsive disorder symptoms (reoccurring and uncontrollable thoughts or behaviors)
• sleep problems
• sleepwalking
• stuttering
• tremors (shaking) or uncontrollable muscle movements
• suicidal thoughts or actions

Ways to manage

If you develop any of the above behaviors, stop taking montelukast tablets and tell your doctor right away. They’ll likely have you stop treatment with the drug.

To learn more about this warning, talk with your doctor or pharmacist.

Suicide prevention

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

• Call the 988 Suicide and Crisis Lifeline at 988.
• Text HOME to the Crisis Text Line at 741741.
• Not in the United States? Find a helpline in your country with Befrienders Worldwide.
• Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Increased eosinophil count

Eosinophilia (increased eosinophil count) can happen while taking montelukast tablets and may be serious. (Eosinophils are a type of white blood cell.) This side effect wasn’t reported in studies of the drug. But it has occurred in people after the drug was approved for use.

With eosinophilia, high white blood cell counts can cause problems in the body’s tissues, including:

• heart problems
• lung problems
• nerve damage
• systemic vasculitis (inflamed blood vessels throughout the body) and rash

Ways to manage

If you experience symptoms of eosinophilia, tell your doctor. They may recommend treatment with corticosteroids.

Low platelet count

Low platelet count can happen while taking montelukast tablets. This side effect wasn’t reported in studies of the drug. But it has occurred in people after the drug was approved for use. Low platelet count is usually mild but may be serious in some cases.

Having low platelet levels can increase the risk of bleeding. This can lead to nosebleeds, bleeding gums, or cuts that bleed longer than usual. Serious bleeding may also occur.

Ways to manage

If you notice that you bleed longer or more easily than usual, tell your doctor. They can determine the most likely cause and recommend ways to manage it.

Allergic reaction

For some people, montelukast tablets can cause an allergic reaction. But it’s not clear whether this side effect occurred in the drug’s studies.

Symptoms can be mild or serious, and they may include:

• itchiness
• skin rash
• severe skin rashes that may blister and peel
• swelling under the skin, usually affecting eyelids, lips, hands, or feet
• swelling of the mouth, tongue, or throat, which can make it hard to breathe
• flushing (temporary warmth, redness, or deepening of skin color)

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to montelukast tablets, your doctor may recommend taking a different medication instead.

Warnings for montelukast

Below are some factors you may want to discuss with your doctor before taking montelukast tablets.

Boxed warning: Risk of serious behavior or mood changes

Montelukast has a boxed warning for the risk of serious behavior or mood changes. A boxed warning is the most serious warning from the FDA.

For details, see the “Side effects of montelukast in detail” section above.

Other warnings

It may not be safe for you to take montelukast tablets if you have specific health conditions. These are sometimes called drug-condition interactions. Other things may also affect whether montelukast tablets are safe treatment options for you.

Before taking montelukast tablets, tell your doctor about your health and medications you take. Things to consider include:

• current or past mental health problems
• liver disease
• phenylketonuria
• past allergic reaction to montelukast or aspirin

Montelukast and pregnancy

In general, montelukast tablets are considered safe to take during pregnancy. That said, check with your doctor about whether they feel it’s safe for you specifically.

Montelukast and breastfeeding

In general, montelukast tablets are considered safe to take while breastfeeding. That said, check with your doctor about whether they feel it’s safe for you specifically.

Montelukast and alcohol

Montelukast tablets are not known to interact with alcohol.

But drinking alcohol while taking montelukast tablets may increase the risk of liver problems.

If you drink alcohol, talk with your doctor about whether it’s safe to consume it during your treatment with montelukast tablets.

What to ask your doctor

This article describes common and serious side effects of montelukast tablets. If your doctor prescribes this medication, they can discuss possible side effects with you. Let your doctor know if you have concerns or questions about treatment with this medication.

Here’s a list of questions you may want to ask your doctor:

• Do any of the other medications I take increase my risk of side effects?
• How can I manage the most common side effects of montelukast tablets?
• How do the side effects of montelukast tablets compare with other drugs that could treat my condition?

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.