Clinical safety rating: caution
Animal studies have demonstrated safety
Selective leukotriene receptor antagonist that inhibits the cysteinyl leukotriene (CysLT1) receptor, thereby reducing airway edema, smooth muscle contraction, and inflammatory cell infiltration.
| Metabolism | Extensively metabolized by cytochrome P450 (CYP) isoenzymes 3A4, 2C8, and 2C9; negligible metabolism by CYP2D6 and CYP2A6. |
| Excretion | Primarily hepatic metabolism (CYP3A4, 2C8, 2C9); excreted in bile and feces (~86%), renal excretion of parent drug and metabolites is minimal (<0.2% unchanged). |
| Half-life | Terminal elimination half-life is 2.7–5.5 hours in healthy adults. No significant accumulation with once-daily dosing. |
| Protein binding | >99% bound primarily to albumin. |
| Volume of Distribution | 10–12 L (approx. 0.14–0.17 L/kg in 70 kg adult). Distribution is limited, mainly to extracellular fluid. |
| Bioavailability | Oral bioavailability is 64% (10 mg tablet) with food reducing absorption by up to 20% (no dosage adjustment required). |
| Onset of Action | Oral: Onset of clinical effect occurs within 1–3 hours for exercise-induced bronchoconstriction; asthma control benefit noted after first dose with maximal effect in 1–2 weeks. |
| Duration of Action | Duration of action for leukotriene receptor blockade is ~24 hours, supporting once-daily dosing. Symptom control persists throughout the dosing interval. |
| Molecular Weight | 586.2 |
10 mg orally once daily in the evening.
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | Mild-to-moderate hepatic impairment (Child-Pugh A or B): no dose adjustment. Severe hepatic impairment (Child-Pugh C): no data, use with caution. |
| Pediatric use | 6 months to 5 years: 4 mg orally once daily in the evening (granules or chewable tablet); 6 to 14 years: 5 mg chewable tablet once daily in the evening; 15 years and older: 10 mg tablet once daily in the evening. |
| Geriatric use | No specific dose adjustment recommended; monitor for adverse effects due to potential age-related changes in renal function. |
| 1st trimester | Montelukast is not associated with an increased risk of major birth defects; limited data suggest no significant teratogenic risk. |
| 2nd trimester | Based on available human data, no increased risk of adverse fetal outcomes; use if clearly needed. |
| 3rd trimester | No reported adverse effects on pregnancy or fetus; may be used with caution. |
Clinical note
Used for asthma and allergic rhinitis. Human pregnancy data are limited but reassuring — no consistent increase in malformations in available cohort studies. The FDA added a boxed warning in 2020 regarding neuropsychiatric events (not pregnancy-specific). Inhaled corticosteroids and beta-agonists remain first-line for asthma in pregnancy; montelukast may be continued if the patient was well-controlled on it prior to pregnancy.
| Placental transfer | Montelukast crosses the placenta; based on animal studies and limited human data, transfer is low to moderate. |
| Breastfeeding |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to montelukast or any component of the formulationPhenylketonuria (chewable tablets contain aspartame)
| Precautions | Neuropsychiatric events (e.g., agitation, depression, suicidal behavior), eosinophilic conditions (e.g., Churg-Strauss syndrome), systemic corticosteroid withdrawal, hepatic effects (elevated liver enzymes), aspiration in patients with aspirin-sensitive asthma. |
| Food/Dietary | Montelukast has no significant food interactions except that grapefruit juice may increase plasma concentrations (minor clinical relevance). No dietary restrictions required. |
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| Montelukast is excreted into human breast milk in low amounts. Infant serum levels are negligible; unlikely to cause adverse effects in breastfed infants. Caution is advised, but it is generally considered compatible with breastfeeding. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Pregnancy category B. No evidence of teratogenicity in animal studies; limited human data show no increased risk of major malformations. However, risk cannot be ruled out; use only if clearly needed. |
| Fetal Monitoring | No specific monitoring required beyond standard prenatal care. Monitor maternal asthma control and adjust therapy as needed. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |
| Clinical Pearls |
| Montelukast is not effective for acute asthma attacks; it is for maintenance therapy. Neuropsychiatric events (e.g., agitation, depression, suicidal thoughts) have been reported, especially in children and adolescents. Monitor for behavioral changes. It is a leukotriene receptor antagonist that can be used for exercise-induced bronchoconstriction and allergic rhinitis. Onset of action is 2–4 hours; maximal benefit may take weeks. Consider drug interactions with CYP3A4 inducers (e.g., rifampin) and inhibitors (e.g., gemfibrozil). |
| Patient Advice | Take this medication daily as prescribed, even if you have no symptoms. · Do not use montelukast to treat an acute asthma attack; have a rescue inhaler available. · Report any unusual mood changes, agitation, or suicidal thoughts immediately to your healthcare provider. · For exercise-induced bronchoconstriction, take at least 2 hours before exercise. · Store tablets at room temperature; chewable tablets should be chewed completely. · Avoid grapefruit and grapefruit juice as they may increase side effects. |