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Boxed warning

Because of the risk of severe side effects, the US Food and Drug Administration (FDA) has issued a boxed warning for montelukast and recommended that it not be used if any other medications effectively treat the condition.

The boxed warning includes the following statement: “Serious neuropsychiatric events have been reported with the use of montelukast sodium. The types of events reported were highly variable, and included, but were not limited to, agitation, aggression, depression, sleep disturbances, suicidal thoughts and behavior (including suicide).”¹

Prescribers are asked to discuss the risks and benefits with patients before they begin treatment with montelukast. In addition, they are to provide information about how to monitor for changes in behavior, what to look for, and what to do if they occur.

The US FDA has also required a patient medication guide be included to provide more information for those taking montelukast.²


What is montelukast?

Montelukast is a highly selective leukotriene receptor antagonist. It works by preventing specific leukotrienes from connecting with their receptors. When these leukotrienes bind to the receptors, they trigger the inflammatory process that leads to the symptoms of asthma and allergic rhinitis. By blocking the receptors, montelukast prevents inflammation, reducing the symptoms of asthma, bronchoconstriction, and allergies.³

What is montelukast used to treat?

This medication has been approved by the US FDA to treat the following conditions in adults and children:⁴

Dosage forms and strengths

Montelukast is taken orally, and it's available as a film-coated tablet, chewable tablet, and granules in the following strengths:⁵

  • Tablets: 10mg

  • Chewable tablets: 4mg, 5mg

  • Granules: 4mg/packet

How do you take montelukast?

You can take this medication with or without food.

Dosage instructions vary by condition and age. Typical recommended doses are detailed below. However, your doctor may prescribe outside the usual range, depending on your condition and personal characteristics.⁶

Chronic asthma

  • Use daily for maintenance therapy (not acute asthma episodes)

  • Best results if used in the evening

  • Adult and adolescent patients 15 years and older: 10mg

  • Children 6–14 years: 5mg (chewable)

  • Children 2–5 years: 4mg (chewable tablet or granule packet)

  • Children 12–23 months: 4mg (granule packet)

Exercise-induced bronchoconstriction

  • Use at least two hours before planned exercise

  • Adult and adolescent patients 15 years and older: 10mg

  • Children 6–14 years: 5mg (chewable)

  • Not recommended for this indication in children five and under

Allergic rhinitis

  • Use daily during allergy season

  • May be taken either morning or evening

  • Adult and adolescent patients 15 years and older: 10mg

  • Children 6–14 years: 5mg

  • Children 2–5 years: 4mg (chewable or granule packet)

  • Children 6–23 months (for year-round indoor allergic rhinitis only): 4mg (granule packet)

How long does it take to see results?

Montelukast starts reducing leukotriene levels immediately. However, it may take about a week to effectively combat the symptoms of chronic asthma and allergies. 

Taking montelukast two hours before exercising typically provides noticeable results for patients with bronchoconstriction during exercise.

In a 2014 review of the clinical data, montelukast significantly improved the targeted symptoms for both children and adults, even in adults who smoke.⁷

Who should not take montelukast?

Those with a past adverse or allergic reaction to the medication should not take montelukast. Additionally, people with phenylketonuria should note that the chewable tablet form contains phenylalanine.⁸ ⁹

Potential side effects of montelukast

Side effects have been reported when using montelukast, some of which are seen more frequently than others. The most significant concern is the risk of serious neuropsychiatric events.¹⁰

Common side effects of montelukast include the following:

  • Headache (most common)

  • Cough, wheezing

  • Diarrhea

  • Ear pain, ear infection

  • Fatigue

  • Fever

  • Rash, hives

  • Runny nose

  • Sinus infection

  • Sore throat

  • Stomach pain

  • Upper respiratory infection

Rare side effects include the following:

  • Bruising or rash

  • Cramps

  • Dizziness

  • Drowsiness

  • Heart palpitations

  • Inflammation of the pancreas or liver

  • Joint or muscle pain

  • Low blood platelet count, leading to increased bleeding

  • Nose bleed or stuffy nose

  • Pins and needles or numbness

  • Seizures

Montelukast has a US FDA boxed warning because it carries a risk of serious neurologic symptoms and psychiatric events, including the following:¹¹

  • Aggressive behavior

  • Agitation, irritability

  • Anxiety, restlessness

  • Stuttering

  • Depression

  • Disorientation, confusion

  • Hallucinations

  • Irritability

  • Sleep problems, nightmares, and sleepwalking

  • Memory problems

  • Obsessive-compulsive symptoms

  • Problems with attention

  • Suicidal thoughts and actions

  • Tremor, shaking, and uncontrolled muscle movements

These adverse effects have been seen even in patients who do not have a history of psychiatric disorders. Therefore, patients taking montelukast must be monitored closely for changes in behavior or mood, especially thoughts of suicide. If any of these occur, seek emergency medical care and discontinue using the medication.

Overdose

High doses of montelukast have been used in clinical studies without serious adverse effects. There have been cases of overdose when children or adults accidentally took doses up to 1,000mg. Signs of an overdose include any of the above symptoms and the following:¹²

  • Vomiting

  • Hyperactivity

  • Sleepiness

  • Abdominal pain

  • Headaches

  • Thirst

In cases of suspected montelukast overdose, discontinue the medication, call the National Poison Control helpline, and seek emergency medical care.

Allergy information

Serious allergic reactions to montelukast are rare. If you experience any combination of the following symptoms of an allergic reaction after taking it, seek emergency medical care.¹³

  • Hives or blisters

  • Trouble breathing

  • Extreme itchiness

  • Swelling of the lips, face, tongue, or throat

  • Vomiting

  • Loss of consciousness

Long-term use of montelukast

Montelukast is intended to be taken over a long period and is considered safe for long-term use. The drug is not suitable for the treatment of acute episodes.¹⁴

Pregnancy category

The FDA has designated montelukast as a pregnancy category B medication. Animal studies have shown no evidence of risk with large doses, but there have not been sufficient well-controlled human studies to determine its safety.¹⁵

Montelukast in pregnancy and breastfeeding

Studies in humans have not shown an increase in congenital disorders when montelukast has been used during pregnancy, but the trials were not well-controlled. Thus, the risk for the human fetus has not yet been determined.¹⁶

Small amounts of montelukast pass through and get into breastmilk. However, these levels are low and have not been shown to cause harm to the infant.¹⁷

Doctors should discuss the benefits and potential risks with their patients before starting or continuing montelukast during pregnancy and lactation.

Missed doses

If you miss a dose of montelukast, skip it and take your next dose as scheduled. Do not take two doses to make up for the missed one.

Drug interactions

A variety of medications interact with montelukast. The interactions range from minor to severe.

Caution is advised when taking the following medications alongside montelukast:¹⁸

  • Apalutamide (Erleada)

  • Butalbital (often used in combination products for headaches, such as Fioricet)

  • Carbamazepine (Tegretol)

  • Enzalutamide (Xtandi)

  • Fosphenytoin (Cerebyx)

  • Ivosidenib (Tibsovo)

  • Lumacaftor/ivacaftor (Orkambi)

  • Mitotane (Lysodren)

  • Pentobarbital (Nembutal)

  • Phenobarbital (Solfoton, Luminal)

  • Phenytoin (Dilantin)

  • Primidone (Mysoline)

  • Rifabutin (Mycobutin)

  • Rifampin (Rifadin, Rimactane)

  • St. John’s wort

Can I drink alcohol while taking montelukast?

There are no known restrictions for drinking alcohol while taking montelukast.

What to discuss with your doctor before starting montelukast

Montelukast is available by prescription only, so you’ll need to meet with your doctor before you start taking it. At your appointment, you should discuss the following:

  • All medications, supplements, or herbs you take regularly or occasionally

  • Any allergies or allergic reactions you’ve had to medicines

  • Any personal or family history of mental illness

  • If you have phenylketonuria

  • Any other medical conditions you have, such as liver disease

  • If you are pregnant or plan to become pregnant

  • If you are breastfeeding or plan to breastfeed

Stopping montelukast

In general, patients should continue taking montelukast until a doctor advises them to stop. However, there are no expected withdrawal concerns with discontinuing use.

If you experience mood or behavior changes while taking montelukast, stop using it immediately and consult your prescriber.

Drug approval history¹⁹

1998: The US FDA grants initial approval

2007: The manufacturer adds a warning to the drug’s prescribing information to address the risk of psychiatric issues

2020: The US FDA requires a boxed warning regarding the potential for adverse psychiatric effects

Tips for taking montelukast

  • Do not stop using a rescue inhaler when needed if you are taking montelukast for asthma. It is exclusively preventative and is not an appropriate treatment for acute asthma attacks.

  • When giving granules to children, don’t open the packet until it is time to give the dose. You can pour them directly into the child’s mouth or place them on a spoon. Additionally, and particularly for infants, you may mix them with a teaspoon of formula, applesauce, or breast milk. Dispose of any unused, opened portions.²⁰

  • If you experience any psychiatric symptoms, discontinue use immediately and contact your doctor or seek emergency medical care.

Frequently asked questions

Does montelukast make you sleepy?

Some people may feel tired after taking montelukast. Avoid driving or operating heavy machinery until you know how the drug affects you.

Do the side effects from montelukast go away?

Some of the mild side effects from the medication may resolve without intervention. However, if you or the people close to you notice changes in your mood or behavior, don’t wait to see if these side effects will improve. Instead, stop using the medication immediately and see your doctor.

Is montelukast a high-risk medication?

Although serious side effects are uncommon, the US FDA considers some of them so severe that it issued a boxed warning. Because of these dangers, it's recommended that montelukast be taken only if no other medication is tolerated or provides adequate symptom relief.

  1. Montelukast- montelukast tablet, film coated | NIH DailyMed

  2. FDA requires boxed warning about serious mental health side effects for asthma and allergy drug montelukast (Singulair); Advises restricting use for allergic rhinitis | U.S. Food and Drug Administration

  3. Montelukast (2022)

  4. (As above)

  5. Singulair (montelukast sodium) tablet label (2012)

  6. Montelukast sodium granule montelukast sodium tablet, chewable montelukast sodium- montelukast tablet, chewable montelukast sodium tablet, coated | NIH DailyMed

  7. Clinical effectiveness and safety of montelukast in asthma. What are the conclusions from clinical trials and meta-analyses? (2014)

  8. Singulair (montelukast sodium) tablet label (2012)

  9. Phenylketonuria | NIH MedlinePlus

  10. Singulair (montelukast sodium) tablet label (2012)

  11. FDA requires boxed warning about serious mental health side effects for asthma and allergy drug montelukast (singulair); advises restricting use for allergic rhinitis | U.S. Food & Drug Administration

  12. Montelukast | NIH MedlinePlus

  13. Singulair (montelukast sodium) tablet label (2012)

  14. Clinical effectiveness and safety of montelukast in asthma. What are the conclusions from clinical trials and meta-analyses? (2014)

  15. Pregnancy medications (2022)

  16. Montelukast sodium granule montelukast sodium tablet, chewable montelukast sodium- montelukast tablet, chewable montelukast sodium tablet, coated | NIH DailyMed

  17. Montelukast (Rx) | Medscape

  18. (As above)

  19. FDA requires stronger warning about risk of neuropsychiatric events associated with asthma and allergy medication singulair and generic montelukast | U.S. Food & Drug Administration

  20. Montelukast | NIH MedlinePlus

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Disclaimer

Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.