Montelukast
Is It Right for You?
A complete guide to Montelukast — what it treats, how it works, dosages, side effects, and when a clinician may prescribe it following an online consultation.
What Is Montelukast?
Montelukast is an orally administered leukotriene receptor antagonist (LTRA) used in the management of asthma and allergic rhinitis. It is available generically and previously under the brand name Singulair (now discontinued in the UK). Montelukast is supplied as 4 mg chewable tablets (for children aged 2–5 years), 5 mg chewable tablets (for children aged 6–14 years), and 10 mg film-coated tablets (for adults and adolescents aged 15 years and over). A 4 mg oral granule sachet formulation is also available for children aged 6 months to 5 years.
Montelukast was first approved in 1998 and has been extensively prescribed in both adults and children for over two decades. It has a distinct mechanism of action from both inhaled corticosteroids and beta-2 agonists, targeting the leukotriene inflammatory pathway rather than the corticosteroid-responsive or adrenergic pathways. This makes it useful as an add-on therapy when standard treatments provide insufficient control, and as an alternative in patients who cannot or will not use inhaled preparations.
In 2020, the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK and the FDA in the USA issued strengthened warnings regarding neuropsychiatric side effects associated with montelukast. Prescribers are now required to discuss these risks with patients before initiating treatment, and the benefit-risk balance must be carefully considered, particularly in patients with a personal or family history of psychiatric conditions.
What Conditions Does Montelukast Treat?
Montelukast is prescribed for:
Montelukast is licensed as add-on therapy for the prophylaxis (prevention) and treatment of asthma in adults and children aged 6 months and over whose asthma is not adequately controlled on inhaled corticosteroids (ICS) alone and who require additional controller therapy. In NICE's stepwise asthma management framework, montelukast can be added at Step 2–3 alongside inhaled corticosteroids as an alternative to or in addition to long-acting beta-2 agonists (LABAs). It is particularly useful in:
- Patients with concurrent allergic rhinitis and asthma (dual-indication treatment)
- Children with viral-induced wheeze
- Exercise-induced bronchoconstriction
- Aspirin/NSAID-exacerbated respiratory disease (AERD) — where aspirin sensitivity contributes to both asthma and nasal polyposis
- Patients unable to use or reluctant to use inhaled therapy
Montelukast is licensed for the relief of symptoms of seasonal allergic rhinitis (hayfever) in patients aged 2 years and over, and of perennial allergic rhinitis in patients aged 6 months and over. It is particularly effective for nasal congestion — a symptom that oral antihistamines address poorly — and may be used as monotherapy or in combination with an antihistamine for hayfever. For allergic rhinitis, it is less effective than intranasal corticosteroids for most patients, but its oral formulation makes it a useful option in those who dislike or cannot tolerate nasal sprays.
A single 10 mg dose of montelukast taken at least 2 hours before exercise can prevent exercise-induced bronchoconstriction. This is particularly useful in patients whose asthma is predominantly exercise-triggered and in athletes who wish to avoid the stigma of using a reliever inhaler.
Patients with AERD have asthma triggered or worsened by aspirin and NSAIDs due to the diversion of arachidonic acid metabolism towards the leukotriene pathway when cyclo-oxygenase enzymes are inhibited. Leukotriene overproduction is a central pathophysiological mechanism in AERD, and montelukast directly targets this pathway, providing meaningful clinical benefit.
While Montelukast is effective for managing asthma and allergic rhinitis, it should be used cautiously in patients with a history of psychiatric conditions due to potential neuropsychiatric side effects.
How Does Montelukast Work?
Leukotrienes are potent inflammatory lipid mediators derived from arachidonic acid via the 5-lipoxygenase (5-LOX) pathway. In allergic and asthmatic conditions, mast cells, eosinophils, basophils, and macrophages produce cysteinyl leukotrienes (LTC4, LTD4, LTE4) in response to allergen exposure, exercise, cold air, aspirin, and other triggers.
Cysteinyl leukotrienes exert their effects by binding to CysLT1 and CysLT2 receptors on airway smooth muscle, bronchial epithelium, nasal mucosa, and inflammatory cells. The physiological consequences are profound: bronchial smooth muscle contraction (bronchoconstriction), increased vascular permeability (mucosal oedema), enhanced mucus secretion, and recruitment of eosinophils and other inflammatory cells into the airway mucosa. Leukotrienes are up to 1,000 times more potent as bronchoconstrictors than histamine on a molar basis.
Montelukast selectively and competitively binds to the CysLT1 receptor, blocking the binding of cysteinyl leukotrienes and preventing their pro-inflammatory and bronchoconstrictive effects. This reduces airway oedema and mucus secretion, decreases bronchospasm, reduces eosinophilic airway inflammation, and in the nasal passages, reduces congestion, rhinorrhoea, and sneezing. Unlike inhaled corticosteroids, montelukast does not produce systemic corticosteroid effects and does not require an inhalation device.
Dosages & Administration
The correct dose depends on the type and severity of infection, age, weight, and kidney function. Always follow your clinician's instructions. The table below is for general reference only.
Administration Tips
Montelukast tablets can be taken with or without food. The once-daily dose for asthma should be taken in the evening, as leukotriene levels in the airways are highest overnight and in the early morning hours — correlating with the nocturnal and early-morning dip in lung function that characterises asthma. For allergic rhinitis alone, the time of day is less critical.
Chewable tablets should be chewed thoroughly before swallowing and not swallowed whole. Granule sachets should be emptied directly into the mouth or mixed with a small amount of soft food or cold liquid; they should not be stored in food or liquid and should be taken immediately after mixing.
Side Effects of Montelukast
Montelukast is generally well tolerated, but some side effects may occur.
- Headache
- Abdominal pain
- Cough or upper respiratory symptoms
- Diarrhoea
- Fever (more common in children)
- Neuropsychiatric effects — agitation, anxiety, depression, sleep disturbances, suicidal thoughts
- Severe allergic reaction — swelling of face, lips, or throat, difficulty breathing
- Churg-Strauss syndrome (rare) — worsening asthma, rash, nerve pain, flu-like symptoms
- Liver problems (rare) — yellowing of skin/eyes, dark urine, fatigue
Patients should be informed about the risk of neuropsychiatric side effects and the importance of reporting any unusual changes in behavior or mood to their clinician.
Drug Interactions
Inform your clinician about all medications you are taking, as some drugs may interact with Montelukast and affect its efficacy.
Important Warnings
Montelukast has been associated with serious neuropsychiatric events including depression, suicidal ideation, sleep disturbances, aggression, and hallucinations. These can occur in patients of any age. Contact your clinician immediately and consider stopping montelukast if you or your child experiences any behavioural changes, mood disturbances, sleep problems, or suicidal thoughts. The MHRA patient alert card should be read carefully before starting treatment.
Montelukast is a preventer and controller medication. It will not relieve an acute asthma attack or acute allergic reaction. Always carry your reliever inhaler (salbutamol) and seek emergency help if you experience severe or life-threatening breathing difficulty.
Stopping montelukast abruptly may lead to worsening asthma or allergic rhinitis symptoms. Discuss any planned changes to your treatment with your clinician.
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The treatment you need, when you need it.
Montelukast FAQs
For asthma management, leukotriene production in the airways is highest overnight and in the early morning hours, contributing to the nocturnal and early-morning worsening of asthma symptoms that many patients experience. Taking montelukast in the evening ensures peak plasma drug levels coincide with the period of greatest leukotriene activity. For isolated allergic rhinitis, the timing is less critical, but evening dosing is conventionally maintained for simplicity.
Yes. Montelukast is licensed for seasonal allergic rhinitis (hayfever) from the age of 2 years and for perennial allergic rhinitis from 6 months. It is particularly useful in children who struggle with nasal sprays or who have both asthma and hayfever, as a single tablet addresses both conditions. Parents must be fully informed of the neuropsychiatric side effect risk and must know to seek help promptly if behavioural or sleep changes occur.
Some improvement in allergic rhinitis symptoms may be noticed within a few days of starting montelukast. For asthma control, the clinical benefit develops gradually over 2 to 4 weeks. The full benefit for both conditions is typically apparent after several weeks of consistent use.
Sleep disturbances including vivid dreams, nightmares, and sleepwalking are well-recognised neuropsychiatric side effects of montelukast. If your child experiences these, contact your GP promptly. Stopping montelukast typically results in resolution of sleep disturbances within a few days. Do not simply continue and hope the symptoms resolve — these side effects require clinical assessment. Alternatives to montelukast are available and should be discussed.
No. Montelukast is a leukotriene receptor antagonist — it is completely unrelated to steroids. It does not cause any of the steroid-related side effects (weight gain, growth suppression, adrenal suppression, bone thinning) associated with corticosteroids.
In very mild asthma, montelukast monotherapy may be considered as an alternative to low-dose inhaled corticosteroids when patients are unable or unwilling to use an inhaler. However, inhaled corticosteroids remain the preferred and most evidence-based preventer therapy for asthma at all ages. Montelukast is most commonly used as add-on therapy alongside an ICS. The appropriateness of monotherapy should be determined by a clinician based on the individual patient's asthma severity and control.