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Leukotriene Receptor Antagonist — Asthma Prophylaxis / Allergic Rhinitis Pregnancy: UK §4.6, verbatim. Pregnancy: 'Animal studies do not indicate harmful effects with respect to effects on pregnancy or embryonal/foetal development. Available data from published prospective and retrospective cohort studies with montelukast use in pregnant women evaluating major birth defects have not established a drug-associated risk. Available studies have methodologic limitations, including small sample size, in some cases retrospective data collection, and inconsistent comparator groups. Singulair may be used during pregnancy only if it is considered to be clearly essential.' Breast-feeding: 'Studies in rats have shown that montelukast is excreted in milk. It is unknown whether montelukast/metabolites are excreted in human milk. Singulair may be used in breast-feeding only if it is considered to be clearly essential.' US §8.1 adds the disease-risk framing, verbatim: 'Poorly or moderately controlled asthma in pregnancy increases the maternal risk of perinatal adverse outcomes such as preeclampsia and infant prematurity, low birth weight, and small for gestational age.'

Montelukast (Paediatric)

Brand names: Singulair

Montelukast (paediatric) is an oral leukotriene receptor antagonist used as add-on preventer therapy for asthma in children and for exercise-induced bronchoconstriction, available as chewable tablets and granules. This page covers its use in the paediatric population.

Adult dose

Dose: 10 mg (one 10 mg film-coated tablet) once daily in the evening.
Route: Oral. §4.2 Method of administration, verbatim: 'Oral use.' §4.2 adds: 'Singulair may be taken with or without food.'
Frequency: Once daily in the evening. UK §4.2, verbatim: 'one 10 mg tablet daily to be taken in the evening.'
Max: Maximum one 10 mg dose in any 24 hours. UK §4.2, verbatim: 'Singulair should not be used concomitantly with other products containing the same active ingredient, montelukast.' US §2.4, verbatim: 'Patients with both asthma and allergic rhinitis should take only one dose daily in the evening'; US §2.1: 'Patients who miss a dose should take the next dose at their regular time and should not take 2 doses at the same time'; US §2.2 (EIB): 'An additional dose of montelukast sodium should not be taken within 24 hours of a previous dose. Patients already taking montelukast sodium daily for another indication (including chronic asthma) should not take an additional dose to prevent EIB.' No higher dose is authorised for any indication in either label.
SCOPE: the adult figure is included as the page's own 'adult reference' band — on this paediatric page it is the dose for adolescents 15 years and over, which the UK SPC treats as the adult dose. UK §4.2, verbatim: 'The recommended dose for adults and adolescents 15 years of age and older with asthma, or with asthma and concomitant seasonal allergic rhinitis, is one 10 mg tablet daily to be taken in the evening.' The 10 mg strength is pinned by the product name (Singulair 10 mg film-coated tablets) and the dose is stated in milligrams. || INDICATION COVERAGE: this bundle doses the page's primary indications — asthma prophylaxis, allergic rhinitis (seasonal and perennial) and prevention of exercise-induced bronchoconstriction. US §2, verbatim: 'Asthma (2.1): Once daily in the evening for patients 2 years and older. Acute prevention of EIB (2.2): One tablet at least 2 hours before exercise for patients 6 years of age and older. Seasonal allergic rhinitis (2.3): Once daily for patients 2 years and older. Perennial allergic rhinitis (2.3): Once daily for patients 2 years and older.' For allergic rhinitis the US label adds: 'Efficacy was demonstrated for seasonal allergic rhinitis when montelukast was administered in the morning or the evening without regard to time of food ingestion. The time of administration may be individualized to suit patient needs.' || NOT A RELIEVER, UK §4.4 verbatim: 'Patients should be advised never to use oral montelukast to treat acute asthma attacks and to keep their usual appropriate rescue medication for this purpose readily available. If an acute attack occurs, a short-acting inhaled β-agonist should be used.' || ADD-ON POSITION, UK §4.2 verbatim: 'Treatment with Singulair can be used as add-on therapy in patients when inhaled corticosteroids plus "as needed" short acting β-agonists provide inadequate clinical control. Singulair should not be abruptly substituted for inhaled corticosteroids.' And: 'Patients should be advised to continue taking Singulair even if their asthma is under control, as well as during periods of worsening asthma.' 'The therapeutic effect of Singulair on parameters of asthma control occurs within one day.' || ELDERLY: UK §4.2 — 'No dosage adjustment is necessary for the elderly'; US §8.5 — 'No dosage adjustment in the elderly is required.'

Paediatric dose

Route: Oral. The UK SPC names the paediatric presentations, verbatim: '5 mg chewable tablets are available for paediatric patients 6 to 14 years of age. 4 mg chewable tablets are available for paediatric patients 2 to 5 years of age. 4 mg granules are available for paediatric patients 6 months to 5 years of age.'
Frequency: Asthma: once daily in the evening. Allergic rhinitis: once daily, timing individualised. Prevention of exercise-induced bronchoconstriction (6 years and over): a single dose at least 2 hours before exercise, and not in addition to a regular daily dose.
Max: Maximum one dose in any 24 hours, at the age-band strength: 4 mg (2–5 years), 5 mg (6–14 years), 10 mg (15 years and over). US §2.1, verbatim: 'Patients who miss a dose should take the next dose at their regular time and should not take 2 doses at the same time.' US §2.4: 'Patients with both asthma and allergic rhinitis should take only one dose daily in the evening.' US §2.2: 'An additional dose of montelukast sodium should not be taken within 24 hours of a previous dose.' UK §4.2: 'Singulair should not be used concomitantly with other products containing the same active ingredient, montelukast.'
WEIGHT CALCULATOR DELIBERATELY LEFT UNSET (dosePerKg null): montelukast is dosed by AGE BAND as a fixed strength, and neither label contains a per-kg figure of any kind, so nothing here can drive a weight-based calculation. || THE AGE BANDS, US §2.1 (asthma) verbatim: 'Montelukast sodium should be taken once daily in the evening. The following doses are recommended: For adults and adolescents 15 years of age and older: one 10-mg tablet. For pediatric patients 6 to 14 years of age: one 5-mg chewable tablet. For pediatric patients 2 to 5 years of age: one 4-mg chewable tablet.' The same three bands are repeated verbatim in §2.3 for both seasonal and perennial allergic rhinitis, and in §2.2 for EIB down to 6 years ('For pediatric patients 6 to 14 years of age: one 5-mg chewable tablet'). Each count is quantified because the strength is in the product name and is confirmed in US §3: 'Chewable tablets: 4 mg and 5 mg.' The UK SPC independently confirms the same strengths and bands for the UK market (5 mg chewable 6–14 years; 4 mg chewable 2–5 years; 4 mg granules 6 months–5 years). || EIB, US §2.2 verbatim: 'For prevention of EIB, a single dose of montelukast sodium should be taken at least 2 hours before exercise... All patients should have available for rescue a short-acting β-agonist. Safety and efficacy in patients younger than 6 years of age have not been established. Daily administration of montelukast sodium for the chronic treatment of asthma has not been established to prevent acute episodes of EIB.' || AGE BARS AND LIMITS OF EVIDENCE — UK §4.2, verbatim: 'Do not give Singulair 10 mg film-coated tablets to children less than 15 years of age. The safety and efficacy of Singulair 10 mg film-coated tablets in children less than 15 years has not been established.' US: 'Safety and effectiveness in pediatric patients less than 12 months of age with asthma have not been established'; 'Safety and effectiveness in pediatric patients younger than 2 years of age with seasonal allergic rhinitis have not been established'; 'Safety and effectiveness in pediatric patients younger than 6 months of age with perennial allergic rhinitis have not been established.' US §8.4 adds that efficacy in the 2–5 year asthma band is extrapolated: 'The safety of montelukast sodium 4-mg chewable tablets in pediatric patients 2 to 5 years of age with asthma has been demonstrated by adequate and well-controlled data. Efficacy of montelukast sodium in this age group is extrapolated from the demonstrated efficacy in patients 6 years of age and older with asthma.' || The 4 mg granule presentation is named by the UK SPC for 6 months to 5 years, but neither label in this bundle states a granule regimen, so no dose is drafted for it here. || PHENYLKETONURIA, US §5.6: 'Inform patients with phenylketonuria that the 4-mg and 5-mg chewable tablets contain phenylalanine.' || Verify the paediatric dose against a children's formulary before prescribing. || NEUROPSYCHIATRIC COUNSELLING APPLIES TO CHILDREN, UK §4.4 verbatim: 'Neuropsychiatric events have been reported in adults, adolescents, and children taking Singulair. Patients and physicians should be alert for neuropsychiatric events. Patients and/or caregivers should be instructed to notify their physician if these changes occur.'

Dose adjustments

Renal

UK §4.2, verbatim: 'No dosage adjustment is necessary for the elderly, or for patients with renal insufficiency, or mild to moderate hepatic impairment.' No eGFR thresholds are given and no separate paediatric renal statement appears in either label.

Hepatic

UK §4.2, verbatim: 'No dosage adjustment is necessary for the elderly, or for patients with renal insufficiency, or mild to moderate hepatic impairment. There are no data on patients with severe hepatic impairment.' No Child-Pugh banding is given. §4.8 lists 'elevated levels of serum transaminases (ALT, AST)' as common and hepatitis (cholestatic, hepatocellular and mixed-pattern liver injury) as very rare.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • UK §4.3, verbatim and complete — the only contraindication stated: 'Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.' US §4 states the same: 'Hypersensitivity to any component of this product.'
  • Not a contraindication but the §4.2 age bar for the presentation this SPC covers: 'Do not give Singulair 10 mg film-coated tablets to children less than 15 years of age. The safety and efficacy of Singulair 10 mg film-coated tablets in children less than 15 years has not been established.'
  • Not a contraindication but a §4.4 restriction on use: 'Patients should be advised never to use oral montelukast to treat acute asthma attacks and to keep their usual appropriate rescue medication for this purpose readily available.'
  • Not a contraindication but a §4.4 restriction: 'Montelukast should not be substituted abruptly for inhaled or oral corticosteroids. There are no data demonstrating that oral corticosteroids can be reduced when montelukast is given concomitantly.'
  • Not a contraindication but a §4.4 excipient restriction for the 10 mg tablet: 'Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.' The US label's parallel excipient warning for the paediatric presentations is §5.6: 'Inform patients with phenylketonuria that the 4-mg and 5-mg chewable tablets contain phenylalanine.'
  • Not a contraindication but a §4.4 caution: 'Treatment with montelukast does not alter the need for patients with aspirin-sensitive asthma to avoid taking aspirin and other non-steroidal anti-inflammatory drugs.'
  • Not a contraindication but a §4.5 interaction caution, verbatim: 'Since montelukast is metabolised by CYP 3A4, 2C8, and 2C9, caution should be exercised, particularly in children, when montelukast is co-administered with inducers of CYP 3A4, 2C8, and 2C9, such as phenytoin' — the list is cut at the source-fetch limit. §4.5 also records that 'The area under the plasma concentration curve (AUC) for montelukast was decreased approximately 40% in subjects with co-administration of phenobarbital.'

Side effects

  • US §5.1 Neuropsychiatric Events, verbatim: 'Serious neuropsychiatric (NP) events have been reported with of montelukast sodium. These postmarketing reports have been highly variable and included, but were not limited to, agitation, aggressive behavior or hostility, , depression, disorientation, disturbance in attention, dream abnormalities, dysphemia (stuttering), hallucinations, insomnia, irritability, memory impairment, -compulsive symptoms, restlessness, somnambulism, suicidal thoughts and behavior (including suicide), tic, and tremor.'
  • Very common (≥1/10): upper respiratory infection
  • Common (≥1/100 to <1/10): headache; abdominal pain — these were the drug-related reactions reported commonly in clinical studies both in adults/adolescents 15 years and older and in paediatric patients 6 to 14 years of age; also diarrhoea, nausea, vomiting; rash; elevated levels of serum transaminases (ALT, AST)
  • Uncommon (≥1/1,000 to <1/100) — psychiatric: 'dream abnormalities including nightmares, insomnia, somnambulism, anxiety, agitation including aggressive behaviour or hostility, depression, psychomotor hyperactivity (including irritability, restlessness, tremor)'
  • Uncommon (≥1/1,000 to <1/100) — other: hypersensitivity reactions including anaphylaxis; dizziness, drowsiness, paraesthesia/hypoesthesia, seizure; epistaxis; dry mouth, dyspepsia; bruising, urticaria, pruritus
  • Rare (≥1/10,000 to <1/1,000): increased bleeding tendency; disturbance in attention, memory impairment, tic; palpitations; angiooedema
  • Very rare (<1/10,000): thrombocytopenia; hepatic eosinophilic infiltration; 'hallucinations, disorientation, suicidal thinking and behaviour (suicidality), obsessive-compulsive symptoms, dysphemia'; Churg-Strauss Syndrome; pulmonary eosinophilia; hepatitis (including cholestatic, hepatocellular, and mixed-pattern liver injury); erythema nodosum, erythema multiforme
  • Also listed: arthralgia, myalgia (the §4.8 table is cut at the source-fetch limit at this point)
  • UK §4.4 Churg-Strauss context, verbatim: 'In rare cases, patients on therapy with anti-asthma agents including montelukast may present with systemic eosinophilia, sometimes presenting with clinical features of vasculitis consistent with Churg-Strauss syndrome... These cases have been sometimes associated with the reduction or withdrawal of oral corticosteroid therapy.'
  • UK §4.8 duration note, verbatim: 'With prolonged treatment in clinical trials with a limited number of patients for up to 2 years for adults, and up to 12 months for paediatric patients 6 to 14 years of age, the safety profile did not change.'
  • This side-effect list may be incomplete — check the full SPC.

Monitoring

  • UK §4.4 neuropsychiatric events, verbatim: 'Neuropsychiatric events have been reported in adults, adolescents, and children taking Singulair. Patients and physicians should be alert for neuropsychiatric events. Patients and/or caregivers should be instructed to notify their physician if these changes occur. Prescribers should carefully evaluate the risks and benefits of continuing treatment with Singulair if such events occur.'
  • UK §4.4 Churg-Strauss vigilance, verbatim: 'physicians should be alert to eosinophilia, vasculitic rash, worsening pulmonary symptoms, cardiac complications, and/or neuropathy presenting in their patients. Patients who develop these symptoms should be reassessed and their treatment regimens evaluated.'
  • UK §4.4 asthma control, verbatim: 'Patients should seek their doctors' advice as soon as possible if they need more inhalations of short-acting β-agonists than usual.'
  • UK §4.2 adherence, verbatim: 'Patients should be advised to continue taking Singulair even if their asthma is under control, as well as during periods of worsening asthma.'
  • US §2.2 (EIB): all patients 'should have available for rescue a short-acting β-agonist.'

Clinical monograph

How it works

It selectively blocks the cysteinyl leukotriene CysLT1 receptor, reducing leukotriene-driven airway inflammation, bronchoconstriction and mucus secretion.

Prescribing in practice

  • The most important paediatric concern is the risk of neuropsychiatric reactions (including sleep disturbance, nightmares, agitation, depression and behavioural change), which the MHRA has highlighted; families should be warned to watch for these and stop the drug if they occur.
  • It is a preventer, not a reliever, and does not treat acute attacks, so reliever inhaler use must continue.
  • It is given once daily, usually in the evening, with formulation (granules/chewable) chosen to suit the child's age.

Monitoring

Monitor asthma control and, importantly, for any new behavioural or mood changes and sleep disturbance.

Counselling the patient

  • Tell the team about any nightmares, sleep problems, mood changes, agitation or unusual behaviour.
  • This is a daily preventer and will not relieve a sudden attack; keep using the reliever inhaler.
  • Granules can be given directly or mixed with a small amount of soft food for younger children.

Evidence & guidelines

The MHRA has issued reminders about the risk of neuropsychiatric reactions with montelukast, and NICE asthma guidance positions it as add-on preventer therapy.

Reference: MHRA Drug Safety Update 2020 (Montelukast Neuropsychiatric); NICE NG80 (Asthma); BTS/SIGN Asthma Guideline 2023; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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