Bronchodilator Pregnancy: Animal studies do not indicate harmful effects on pregnancy or embryonal/foetal development; limited data from available pregnancy databases do not suggest a causal relationship with malformations (limb defects rarely reported post-marketing). Montelukast may be used during pregnancy only if it is considered to be clearly essential. Breast-feeding: it is unknown whether montelukast/metabolites are excreted in human milk (excreted in milk in rats) - may be used in breast-feeding only if considered clearly essential.

Montelukast

Brand names: Singulair

Montelukast is an oral leukotriene receptor antagonist used as add-on preventer therapy in asthma and for exercise-induced bronchoconstriction and allergic rhinitis. It is taken once daily, usually in the evening.

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: One 10 mg tablet daily

Route: Oral

Frequency: Once daily, to be taken in the evening

Recommended dose for adults and adolescents 15 years of age and older with asthma, or with asthma and concomitant seasonal allergic rhinitis. May be taken with or without food. The therapeutic effect on parameters of asthma control occurs within one day. Patients should continue taking montelukast even if their asthma is under control, and during periods of worsening asthma. Must not be used concomitantly with other products containing montelukast. Can be added to an existing treatment regimen - may be used as add-on therapy when inhaled corticosteroids plus as-needed short-acting beta-agonists give inadequate clinical control, but must NOT be abruptly substituted for inhaled or oral corticosteroids. Never to be used to treat acute asthma attacks - patients must keep their usual rescue medication (a short-acting inhaled beta-agonist) available. Discontinue treatment if neuropsychiatric symptoms (behavioural changes, depression, suicidality, reported in all age groups) occur. The dosage is the same for male and female patients. Paediatric: this source is the 10 mg film-coated tablet SPC, which states montelukast 10 mg must not be given to children less than 15 years of age (safety and efficacy not established below 15 years); it notes that 5 mg chewable tablets are available for paediatric patients 6 to 14 years, 4 mg chewable tablets for 2 to 5 years, and 4 mg granules for 6 months to 5 years - those are separate products with their own SPCs and were not the source fetched here. No per-kg paediatric dose is stated; verify paediatric dosing against a children's formulary. Contains lactose and less than 1 mmol sodium per tablet.

Dose adjustments

Renal

No dosage adjustment is necessary for patients with renal insufficiency, nor for the elderly, nor for mild to moderate hepatic impairment. There are no data on patients with severe hepatic impairment (section 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.

Contraindications

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1
Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicinal product (contains lactose) - section 4.4

Side effects

Common (adults 15 years and older): headache
Common: abdominal pain
Very common: upper respiratory infection
Uncommon: hypersensitivity reactions including anaphylaxis
Psychiatric (post-marketing): dream abnormalities including nightmares, insomnia, somnambulism, anxiety, agitation including aggressive behaviour or hostility - the section 4.8 table was truncated at the source-fetch limit. Also reported: eczematous dermatitis, rash, thirst; rare increased bleeding tendency; very rare thrombocytopenia and hepatic eosinophilic infiltration

Interactions

Montelukast may be administered with other therapies routinely used in the prophylaxis and chronic treatment of asthma
At the recommended clinical dose montelukast did not have clinically important effects on the pharmacokinetics of theophylline, prednisone, prednisolone, oral contraceptives (ethinyl estradiol/norethindrone 35/1), terfenadine, digoxin or warfarin
The AUC for montelukast was decreased by approximately 40% when co-administered with an interacting medicine - the eMC section 4.5 text was truncated at the source-fetch limit before naming it; check the SPC
US labelling (cross-check only): no dose adjustment is needed when co-administered with theophylline, prednisone, prednisolone, oral contraceptives, terfenadine, digoxin, warfarin, gemfibrozil, itraconazole, thyroid hormones, sedative hypnotics, NSAIDs, benzodiazepines, decongestants and cytochrome P450 enzyme inducers

Clinical monograph

How it works

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

Prescribing in practice

Warn patients and carers about neuropsychiatric reactions including sleep disturbance, mood change, agitation and suicidal thoughts, which are the subject of an MHRA warning, and stop if they occur.
It is a preventer and does not relieve acute attacks, so reliever therapy must continue.
Reassess benefit periodically and stop if there is no clear improvement in asthma control.

Monitoring

Monitor asthma control and remain alert for any new or worsening behavioural, mood or sleep changes throughout treatment.

Counselling the patient

Stop the tablet and seek advice if you or your child notice changes in mood, sleep or behaviour.
Take it every evening as a preventer, not for sudden symptoms.
Keep using your other asthma inhalers as prescribed.

Evidence & guidelines

UK guidance supports montelukast as an add-on option in asthma, with an MHRA reminder about neuropsychiatric adverse effects.

Reference: NICE NG80 Asthma; MHRA Montelukast Safety Alert 2022; 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

Pediatric Asthma Severity Score (PASS) · Paediatric Respiratory

Drugs

Pathways