Montelukast (Singulair)
Leukotriene receptor antagonist for asthma and allergic rhinitis
📊 Quick facts about Montelukast
💡 Key takeaways about Montelukast
- Blocks leukotrienes: Montelukast works by blocking substances called leukotrienes that cause airway constriction, swelling, and mucus production in asthma and allergies
- Once-daily evening dose: Take one 10 mg tablet each evening for adults and adolescents aged 15 and older — it can be taken with or without food
- Not for acute attacks: Montelukast does not replace rescue inhalers — always have your quick-relief bronchodilator available for sudden asthma attacks
- Neuropsychiatric warning: The FDA has issued a boxed warning about mood and behavioral changes including depression, agitation, and suicidal thoughts — report any changes to your doctor immediately
- Also treats allergic rhinitis: Effective for seasonal allergies (hay fever) including nasal congestion, runny nose, sneezing, and itchy eyes when used alongside asthma treatment
What Is Montelukast and What Is It Used For?
Montelukast is a leukotriene receptor antagonist (LTRA) that blocks inflammatory substances called leukotrienes in the airways. It is prescribed for the long-term management of asthma, prevention of exercise-induced bronchoconstriction, and treatment of seasonal allergic rhinitis (hay fever) in adults and children.
Montelukast belongs to a class of medicines known as leukotriene receptor antagonists. Leukotrienes are potent chemical mediators produced by the immune system that play a central role in the inflammatory cascade underlying asthma and allergic conditions. When released from mast cells and eosinophils, leukotrienes cause the airways to narrow and swell, increase mucus production, and recruit inflammatory cells to the lungs. By selectively blocking the cysteinyl leukotriene type 1 (CysLT1) receptor, montelukast prevents these effects and helps control both the symptoms and the underlying inflammation of asthma.
Montelukast is used to treat asthma in adults and adolescents aged 15 years and older who have not achieved adequate control with their existing asthma medication and who therefore need add-on therapy. It works to prevent asthma symptoms during the day and at night. The medication is also effective in preventing exercise-induced bronchoconstriction — the sudden narrowing of the airways that some people experience during or after physical activity.
In addition to asthma, montelukast is approved for the treatment of seasonal allergic rhinitis (hay fever) in patients who also have asthma. Seasonal allergic rhinitis is an allergic reaction typically triggered by airborne pollen from trees, grasses, or weeds. Symptoms include a stuffy, runny, and itchy nose; sneezing; and watery, swollen, red, and itchy eyes. By blocking leukotrienes, montelukast helps reduce both nasal and ocular symptoms of hay fever.
How does montelukast work in the body?
The mechanism of action of montelukast centers on selective antagonism of the CysLT1 receptor. Cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are derived from arachidonic acid through the 5-lipoxygenase pathway and are among the most potent known bronchoconstrictor agents — approximately 1,000 times more potent than histamine in causing airway narrowing. By binding to the CysLT1 receptor with high affinity, montelukast blocks the action of these leukotrienes and thereby:
- Reduces bronchoconstriction — preventing the airway smooth muscle from tightening
- Decreases airway inflammation — reducing swelling of the airway lining
- Reduces mucus secretion — decreasing excess mucus that blocks airways
- Decreases vascular permeability — reducing tissue swelling
- Reduces eosinophil recruitment — limiting the influx of inflammatory cells
Montelukast reaches peak plasma concentration approximately 3 to 4 hours after oral ingestion of the 10 mg film-coated tablet. Its bioavailability is approximately 64%. The drug is extensively metabolized in the liver, primarily by CYP3A4 and CYP2C9, and has a mean plasma half-life of approximately 2.7 to 5.5 hours in healthy adults. It is excreted almost exclusively via bile.
Asthma is a chronic inflammatory disease of the airways characterized by recurrent episodes of wheezing, breathlessness, chest tightness, and coughing. The airways of a person with asthma are hypersensitive to triggers such as cigarette smoke, pollen, cold air, and exercise. During an asthma episode, the airway lining swells, the surrounding muscles contract, and excessive mucus is produced, making it difficult to breathe. Montelukast addresses one important pathway of this inflammation but does not treat all pathways, which is why it is typically used alongside other asthma medications.
What Should You Know Before Taking Montelukast?
Do not take montelukast if you are allergic to montelukast or any of its inactive ingredients. Tell your doctor about all medical conditions, medications, and supplements before starting treatment. Montelukast is not for treating acute asthma attacks — always keep your rescue inhaler available.
Before starting treatment with montelukast, it is essential to have an open discussion with your prescribing physician about your complete medical history, any allergies, and all other medications you are taking. While montelukast is generally well tolerated, there are important safety considerations that every patient should understand.
Contraindications
You should not take montelukast if you have a known allergy (hypersensitivity) to montelukast sodium or any of the other ingredients in the tablets. Hypersensitivity reactions to montelukast, although rare, have included anaphylaxis, angioedema, and urticaria. If you have experienced any allergic reaction to this medication in the past, inform your doctor immediately and do not take it again.
Warnings and precautions
Several important warnings apply to the use of montelukast. Patients and caregivers should be aware of the following:
- Not for acute asthma attacks: Montelukast is a preventive (controller) medication and should not be used to treat a sudden asthma attack. If an asthma attack occurs, follow the instructions your doctor has given you for these situations. Always carry your rescue inhaled bronchodilator for acute symptoms.
- Do not stop other asthma medications: Continue taking all other asthma medications as prescribed by your doctor. Montelukast is intended as add-on therapy and should not replace inhaled corticosteroids or other controller medications unless specifically directed by your physician.
- Aspirin sensitivity: If you know that your asthma worsens with aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), do not use these medications while taking montelukast. While montelukast may provide some benefit in aspirin-sensitive asthma, it does not completely prevent aspirin-induced reactions.
- Eosinophilic conditions: In rare cases, patients treated with asthma medications including montelukast have developed a combination of symptoms such as flu-like illness, tingling or numbness of the arms or legs, worsening respiratory symptoms, and skin rash, which may be consistent with eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome). If you develop any combination of these symptoms, contact your doctor immediately.
In March 2020, the U.S. Food and Drug Administration (FDA) strengthened an existing warning about serious neuropsychiatric events associated with montelukast. These include agitation, aggression, depression, sleep disturbances (including nightmares and insomnia), hallucinations, obsessive-compulsive symptoms, and suicidal thinking and behavior. These events have been reported in patients of all ages. The FDA advises healthcare professionals to discuss the risks and benefits of montelukast with patients and to consider alternative treatments when appropriate. If you or someone in your care develops any mood or behavioral changes while taking montelukast, contact your doctor immediately.
Pregnancy and breastfeeding
If you are pregnant, planning to become pregnant, or breastfeeding, you should discuss the use of montelukast with your doctor before starting treatment. The available data on montelukast use during pregnancy are limited. Animal reproduction studies have not demonstrated harmful effects on the fetus, but there are no well-controlled studies in pregnant women. Your doctor will assess whether the potential benefits of treatment justify any potential risks to the developing baby.
It is not known whether montelukast is excreted in human breast milk. Because many drugs are excreted in breast milk, caution should be exercised when montelukast is given to breastfeeding mothers. Consult your healthcare provider to discuss the benefits of breastfeeding, the benefit of montelukast therapy for you, and any potential adverse effects on the nursing infant.
Driving and operating machinery
Montelukast is not expected to affect your ability to drive or operate machinery under normal circumstances. However, individual responses to medication can vary, and dizziness and drowsiness have been reported in some patients. You are responsible for assessing whether you are in a suitable condition to drive or perform activities requiring alertness. If you experience dizziness or drowsiness while taking montelukast, avoid driving until these effects resolve.
Montelukast 10 mg film-coated tablets contain lactose monohydrate. If you have been told by your doctor that you have an intolerance to certain sugars, consult your doctor before taking this medicine. The tablets also contain less than 1 mmol (23 mg) sodium per tablet, meaning they are essentially sodium-free.
How Does Montelukast Interact with Other Drugs?
Montelukast has relatively few clinically significant drug interactions. CYP450 enzyme inducers such as phenobarbital, phenytoin, and rifampicin can reduce montelukast blood levels by up to 40%. Gemfibrozil can increase montelukast concentrations. Montelukast is safe to use alongside inhaled corticosteroids and beta-agonists.
Drug interactions are an important consideration with any medication. Montelukast is metabolized in the liver, primarily by the cytochrome P450 enzymes CYP3A4 and CYP2C9. While montelukast has a relatively favorable drug interaction profile compared to many other medications, certain drugs can affect how it works, and montelukast may also affect other drugs. Always inform your doctor about all medications you are taking, including over-the-counter drugs, herbal supplements, and vitamins.
Major interactions
The following medications can significantly reduce the effectiveness of montelukast by inducing the liver enzymes that metabolize it:
| Drug | Type | Effect | Clinical Significance |
|---|---|---|---|
| Phenobarbital | CYP3A4 inducer | Reduces montelukast AUC by ~40% | May reduce efficacy; monitor asthma control |
| Phenytoin | CYP3A4 inducer | Reduces montelukast AUC by ~40% | May reduce efficacy; monitor asthma control |
| Rifampicin | Potent CYP3A4 inducer | Reduces montelukast AUC by ~40% | May reduce efficacy; consider dose adjustment |
| Gemfibrozil | CYP2C8 inhibitor | Increases montelukast AUC by ~4.4-fold | Increased exposure; monitor for side effects |
Safe co-administration
Montelukast can be safely taken alongside many commonly prescribed medications. Clinical studies have demonstrated that montelukast does not significantly interact with the following drug classes:
- Inhaled corticosteroids (e.g., budesonide, fluticasone) — the primary combination used in asthma management
- Short-acting beta-agonists (e.g., salbutamol/albuterol) — rescue inhalers
- Long-acting beta-agonists (e.g., salmeterol, formoterol)
- Oral corticosteroids (e.g., prednisolone, prednisone)
- Antihistamines (e.g., loratadine, cetirizine, desloratadine)
- Oral contraceptives — no interaction demonstrated
- Theophylline — no clinically significant interaction
- Warfarin — montelukast does not significantly alter INR, but prothrombin time should still be monitored
- Digoxin — no pharmacokinetic interaction observed
Despite the relatively favorable interaction profile, always provide your doctor or pharmacist with a complete list of all medications and supplements you take. New interactions may be identified as more data become available from post-marketing surveillance.
What Is the Correct Dosage of Montelukast?
Adults and adolescents aged 15 years and older: one 10 mg film-coated tablet taken once daily in the evening. Children aged 6–14: one 5 mg chewable tablet daily. Children aged 2–5: one 4 mg chewable tablet or 4 mg granules daily. Always take as directed by your doctor.
The dosage of montelukast depends on the patient's age, the condition being treated, and the prescribing physician's clinical judgment. It is essential to take this medication exactly as prescribed. Do not take more or less than directed, and do not stop taking it without consulting your doctor, even if you feel well.
Adults and adolescents (15 years and older)
Standard dose
The recommended dose is one 10 mg film-coated tablet taken once daily in the evening. The tablet can be taken with or without food. Taking montelukast in the evening is recommended because leukotriene-mediated inflammation tends to be most active during the nighttime hours, and evening dosing has shown optimal clinical benefit in controlled trials.
Children (6 to 14 years)
Pediatric dose (6–14 years)
The recommended dose is one 5 mg chewable tablet once daily in the evening. The chewable tablet should be chewed before swallowing. No dose adjustment is needed within this age group.
Children (2 to 5 years)
Pediatric dose (2–5 years)
The recommended dose is one 4 mg chewable tablet or one sachet of 4 mg oral granules once daily in the evening. The granules can be given directly in the mouth, dissolved in a spoonful of soft food (e.g., applesauce), or mixed with a spoonful of cold or room-temperature liquid.
Elderly patients
No dose adjustment is necessary for elderly patients. Montelukast has been studied in elderly patients and the pharmacokinetic profile and safety are similar to those observed in younger adults. Standard adult dosing (10 mg once daily) is appropriate for this population.
| Age Group | Dose | Form | Timing |
|---|---|---|---|
| Adults & adolescents ≥15 years | 10 mg | Film-coated tablet | Once daily in the evening |
| Children 6–14 years | 5 mg | Chewable tablet | Once daily in the evening |
| Children 2–5 years | 4 mg | Chewable tablet or granules | Once daily in the evening |
| Children 6 months–2 years | 4 mg | Oral granules | Once daily in the evening |
Missed dose
If you miss a dose of montelukast, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your regular schedule. Do not take a double dose to make up for a forgotten one. Consistency is important for maintaining asthma control, so try to take your medication at the same time each evening.
Overdose
In the event of an overdose, seek medical attention immediately by contacting your doctor, hospital emergency department, or poison control center. In the majority of reported overdose cases, no adverse effects have been reported. The most commonly reported symptoms after overdose in adults and children include abdominal pain, drowsiness, thirst, headache, vomiting, and hyperactivity. There is no specific antidote for montelukast overdose; treatment is supportive and symptomatic.
Montelukast only works to control your asthma if you continue to take it regularly. It is important to keep taking it both during symptom-free periods and during asthma flare-ups. Do not stop taking montelukast without speaking to your doctor first, as discontinuation may lead to worsening of asthma control. Do not use montelukast together with any other product containing the same active ingredient (montelukast).
What Are the Side Effects of Montelukast?
Common side effects include headache and abdominal pain. Serious but uncommon effects include allergic reactions, neuropsychiatric events (mood changes, depression, suicidal thinking), and Churg-Strauss syndrome. The FDA has a boxed warning for neuropsychiatric events. Report any mood or behavioral changes to your doctor immediately.
Like all medications, montelukast can cause side effects, although not everyone will experience them. In clinical trials, the most commonly reported side effects with montelukast 10 mg film-coated tablets were headache and abdominal pain, both of which were generally mild and occurred at a somewhat higher rate in patients treated with montelukast compared to those receiving placebo.
Understanding the frequency and severity of possible side effects will help you make informed decisions about your treatment and know when to seek medical attention. The side effects reported with montelukast are categorized below by how commonly they occur.
Very Common
- Upper respiratory tract infection
Common
- Headache
- Abdominal pain
- Diarrhea, nausea, vomiting
- Skin rash
- Fever (pyrexia)
- Elevated liver enzymes (transaminases)
Uncommon
- Allergic reactions including facial swelling, lip/tongue/throat swelling
- Behavioral and mood changes: agitation, aggression, hostility, depression
- Abnormal dreams including nightmares, insomnia, sleepwalking
- Irritability, anxiety, restlessness
- Dizziness, drowsiness, numbness and tingling
- Nosebleeds
- Dry mouth, indigestion
- Bruising, itching, urticaria (hives)
- Joint or muscle pain, muscle cramps
- Bedwetting in children
- Weakness, fatigue, general malaise, swelling
- Seizures
Rare to Very Rare
- Increased bleeding tendency
- Tremor, palpitations
- Attention disturbance, memory impairment, involuntary muscle movements
- Hallucinations, disorientation, suicidal thoughts and actions
- Obsessive-compulsive symptoms, stuttering
- Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
- Decreased platelet count
- Pulmonary inflammation (pulmonary eosinophilia)
- Severe skin reactions (erythema multiforme, erythema nodosum)
- Hepatitis (liver inflammation)
Serious side effects requiring immediate medical attention
Contact your doctor immediately or seek emergency care if you experience any of the following:
- Allergic reactions: Swelling of the face, lips, tongue, or throat that may cause difficulty breathing or swallowing
- Neuropsychiatric events: Unusual mood or behavioral changes, agitation, depression, or thoughts of self-harm
- Churg-Strauss-like symptoms: A combination of flu-like illness, tingling or numbness in limbs, worsening respiratory symptoms, and/or skin rash
- Severe skin reactions: Widespread rash, blistering, or painful red areas appearing without warning
Patients and caregivers should be vigilant for any behavioral or mood changes during treatment with montelukast. If you notice agitation, aggression, depression, sleep disturbances, hallucinations, or any thoughts of self-harm, stop taking montelukast and contact your healthcare provider immediately. These symptoms can occur at any time during treatment and may persist after discontinuation in some cases.
How Should You Store Montelukast?
Store montelukast in its original packaging at room temperature, protected from light and moisture. Keep out of reach of children. Do not use after the expiration date printed on the packaging. Dispose of unused medication properly through a pharmacy take-back program.
Proper storage of medication is essential to maintain its effectiveness and safety. Montelukast should be stored according to the following guidelines:
- Keep in original packaging: Store the tablets in their original blister packaging to protect them from light and moisture
- Room temperature: Store at normal room temperature (below 25°C / 77°F). Do not refrigerate or freeze
- Protect from light: Montelukast is light-sensitive; do not store outside of its original packaging
- Protect from moisture: Keep the medication in a dry place; do not store in the bathroom
- Keep out of reach of children: Store all medications where children cannot see or reach them
- Expiration date: Do not use montelukast after the expiration date printed on the blister and carton (EXP). The expiration date refers to the last day of that month
Do not dispose of medications in the household trash or down the drain. Return unused or expired medicines to your local pharmacy for safe disposal. These measures help protect the environment and prevent accidental ingestion.
What Does Montelukast Contain?
The active ingredient is montelukast (as montelukast sodium). Each 10 mg film-coated tablet contains montelukast sodium equivalent to 10 mg montelukast. Inactive ingredients include lactose monohydrate, microcrystalline cellulose, croscarmellose sodium, hydroxypropylcellulose, and magnesium stearate.
Active ingredient
Each film-coated tablet contains montelukast sodium equivalent to 10 mg montelukast as the active substance. Montelukast sodium is a white to off-white, hygroscopic powder that is freely soluble in ethanol, methanol, and water.
Inactive ingredients (excipients)
The following excipients are present in the 10 mg film-coated tablet formulation:
- Tablet core: Lactose monohydrate (89.3 mg), microcrystalline cellulose, croscarmellose sodium, hydroxypropylcellulose (E463), and magnesium stearate
- Film coating: Hypromellose, hydroxypropylcellulose (E463), titanium dioxide (E171), red and yellow iron oxide (E172), and carnauba wax
Appearance and pack sizes
Montelukast 10 mg film-coated tablets are beige, rounded square in shape. In the branded Singulair formulation, they are marked with “SINGULAIR” on one side and “MSD 117” on the other. Generic formulations may differ in appearance. The tablets are available in blister packs in a variety of sizes, including 7, 10, 14, 20, 28, 30, 50, 56, 84, 90, 98, and 100 tablets. Not all pack sizes may be marketed in all countries.
Each 10 mg film-coated tablet contains approximately 89.3 mg of lactose monohydrate. Patients with rare hereditary problems of galactose intolerance, total lactase deficiency, or glucose-galactose malabsorption should not take this medication. The sodium content per tablet is less than 1 mmol (23 mg), making it essentially sodium-free.
Frequently Asked Questions About Montelukast
Medical References and Sources
This article is based on current medical research, regulatory documents, and international guidelines. All claims are supported by scientific evidence from peer-reviewed and authoritative sources.
- European Medicines Agency (EMA). "Singulair – Summary of Product Characteristics (SmPC)." EMA – Singulair European regulatory documentation for montelukast, including full prescribing information.
- U.S. Food and Drug Administration (FDA) (2020). "FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast (Singulair)." FDA Drug Safety Communication FDA safety communication regarding neuropsychiatric events with montelukast.
- Global Initiative for Asthma (GINA) (2024). "Global Strategy for Asthma Management and Prevention." GINA Reports International guidelines for asthma management, including role of leukotriene modifiers.
- British National Formulary (BNF). "Montelukast – Drug Monograph." BNF – Montelukast UK clinical guidance on montelukast dosing, interactions, and side effects.
- World Health Organization (WHO). "WHO Model List of Essential Medicines – 23rd List (2023)." WHO Essential Medicines WHO’s list of essential medicines for global health systems.
- Bousquet J, et al. (2020). "ARIA 2019 – Care pathways for allergic rhinitis." Allergy. 75(10):2596–2610. International guidelines for allergic rhinitis management, including role of leukotriene antagonists.
- Haarman MG, et al. (2021). "Neuropsychiatric adverse effects of montelukast in children: a systematic review." European Respiratory Journal. 58(3):2100536. Systematic review of neuropsychiatric events in pediatric patients. Evidence level: 1A.
Evidence grading: This article uses the GRADE framework (Grading of Recommendations Assessment, Development and Evaluation) for evidence-based medicine. Evidence level 1A represents the highest quality of evidence, based on systematic reviews of randomized controlled trials. Drug information has been cross-referenced with regulatory agency databases (EMA, FDA, BNF).
iMedic Medical Editorial Team
Specialists in pharmacology, respiratory medicine, and allergy
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iMedic's medical content is produced by a team of licensed specialist physicians and medical experts with solid academic background and clinical experience. Our editorial team includes:
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