Leukotriene Receptor Antagonist — Allergic Rhinitis Pregnancy: Animal studies do not indicate harmful effects on pregnancy or embryonal/foetal development and limited pregnancy-database data do not suggest a causal relationship with malformations; montelukast may be used during pregnancy only if considered clearly essential. It is unknown whether montelukast/metabolites are excreted in human milk — may be used in breast-feeding only if considered clearly essential (§4.6).

Montelukast

Brand names: Singulair

Used in: Asthma

Montelukast is a leukotriene receptor antagonist used as add-on preventer therapy in asthma and for allergic rhinitis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 10 mg (one film-coated tablet)

Route: Oral

Frequency: Once daily, taken in the evening

Adults and adolescents 15 years of age and older with asthma, or with asthma and concomitant seasonal allergic rhinitis: one 10 mg tablet daily to be taken in the evening (§4.2). May be taken with or without food. The therapeutic effect on asthma control parameters occurs within one day; patients should continue taking montelukast even when asthma is controlled and during periods of worsening asthma. Can be added to an existing regimen (e.g. as add-on when inhaled corticosteroids plus as-needed short-acting beta-agonists give inadequate control) but must not be abruptly substituted for inhaled or oral corticosteroids, and must never be used to treat acute asthma attacks. Do not use concomitantly with other montelukast-containing products. No dosage adjustment for the elderly, renal insufficiency, or mild to moderate hepatic impairment; there are no data in severe hepatic impairment. Paediatric (fixed strengths by age, not per kg): do not give this 10 mg tablet to children under 15 years — 5 mg chewable tablets are available for 6 to 14 years, 4 mg chewable tablets for 2 to 5 years, and 4 mg granules for 6 months to 5 years. Discontinue treatment if neuropsychiatric symptoms (behavioural changes, depression, suicidality) occur (§4.4). Source product: Montelukast 10 mg Film Coated Tablets (UK SPC). US labelling (cross-check only) additionally covers exercise-induced bronchoconstriction — a single dose at least 2 hours before exercise, not within 24 hours of a previous dose — and perennial allergic rhinitis.

Dose adjustments

Renal

No dosage adjustment is necessary for patients with renal insufficiency (§4.2).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Administration (by indications): • 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. Dosage (by age) ( 2 ): • 15 years and older: one 10-mg tablet. • 6 to 14 years: one 5-mg chewable tablet. • 2 to 5 years: one 4-mg chewable tablet. Patients with both asthma and allergic rhinitis should take only one dose daily in the evening ( 2.4 ). 2.1 Asthma Montelukast sodium should be taken once daily …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-03-05. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to the active substance or to any of the excipients (§4.3)

Side effects

Headache — common in adults 15 years and older (§4.8)
Abdominal pain — common (§4.8)
Upper respiratory infection — very common (§4.8)
Neuropsychiatric events: dream abnormalities including nightmares, insomnia, somnambulism, anxiety, agitation including aggressive behaviour or hostility (post-marketing, §4.8); behavioural changes, depression and suicidality reported in all age groups (§4.4)
Hypersensitivity reactions including anaphylaxis — uncommon (§4.8)
Increased bleeding tendency — rare; thrombocytopenia — very rare (§4.8)

Interactions

At the recommended clinical dose montelukast had no clinically important effect on the pharmacokinetics of theophylline, prednisone, prednisolone, oral contraceptives (ethinylestradiol/norethindrone 35/1), terfenadine, digoxin or warfarin (§4.5)
The AUC for montelukast was decreased by approximately 40% when co-administered with an interacting agent — the SPC §4.5 text is truncated in this bundle at that point; the clinician must check the full §4.5 for the drug(s) named
Aspirin/NSAIDs: treatment with montelukast does not alter the need for patients with aspirin-sensitive asthma to avoid aspirin and other NSAIDs (§4.4)

Clinical monograph

How it works

It blocks cysteinyl leukotriene receptors, reducing airway inflammation, bronchoconstriction and mucus.

Prescribing in practice

It is a regular preventer taken in the evening, not a reliever.
Neuropsychiatric reactions (sleep disturbance, mood and behaviour change, rarely suicidal thoughts) are recognised — counsel patients and carers to report them (MHRA alert).
It is an add-on, not a replacement for inhaled corticosteroids in most asthma.

Monitoring

Review asthma control and ask specifically about mood, sleep and behaviour changes.

Counselling the patient

Take it regularly in the evening to prevent symptoms — it is not for sudden attacks.
Report any new mood, sleep or behaviour changes, including in children.
Continue your inhalers as prescribed.

Evidence & guidelines

An add-on option in asthma and for allergic rhinitis (NICE NG80), with an MHRA warning on neuropsychiatric effects.

Reference: MHRA Drug Safety Update (2019 and 2020) Montelukast; BSACI Rhinitis Guidelines 2017; 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).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Myasthenia Gravis Activities of Daily Living (MG-ADL) Scale · Neuromuscular

Pathways