MONTELUKAST SODIUM
Clinical safety rating: safe
Phenobarbital may decrease levels Can cause neuropsychiatric events including agitation and depression.
Selective leukotriene receptor antagonist that inhibits the actions of leukotriene D4 at the CysLT1 receptor, reducing bronchoconstriction, eosinophilic infiltration, mucus production, and airway remodeling.
| Metabolism | Hepatic metabolism primarily via CYP3A4 and CYP2C9; also metabolized by CYP2C8. |
| Excretion | Fecal (86%) and renal (<0.2% as unchanged drug); primarily biliary excretion of metabolites. |
| Half-life | 2.7–5.5 hours in healthy adults; prolonged to 7.4 hours in hepatic impairment (Child-Pugh score 5–9). |
| Protein binding | >99% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 10–11 L (approximately 0.15 L/kg in adults), indicating distribution mainly into extracellular fluid. |
| Bioavailability | Oral: 63–73% (10 mg tablet); 73% (5 mg chewable tablet); 58–66% (4 mg chewable tablet). |
| Onset of Action | Oral: 1–3 hours for bronchodilation; maximal effect by 3–4 hours. |
| Duration of Action | 24 hours (once-daily dosing); clinical efficacy maintained over 24 hours for asthma and allergic rhinitis. |
| Molecular Weight | 608.67 |
10 mg orally once daily in the evening.
| Dosage form | TABLET, CHEWABLE |
| Renal impairment | No dose adjustment required for any degree of 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 available; use with caution. |
| Pediatric use | 6 months to 5 years: 4 mg orally once daily (granules or chewable tablet). 6 to 14 years: 5 mg orally once daily (chewable tablet). 15 years and older: 10 mg orally once daily. |
| Geriatric use | No specific dose adjustment; plasma half-life may be slightly prolonged but no dose change required. Monitor for adverse effects. |
| 1st trimester | Use only if clearly needed; limited human data, animal studies show no direct harm at therapeutic doses. |
| 2nd trimester | Use only if clearly needed; no known increased risk in second trimester. |
| 3rd trimester | Avoid near term due to theoretical risk of constriction of ductus arteriosus (not substantiated for montelukast, but class effect concern). |
Clinical note
Phenobarbital may decrease levels Can cause neuropsychiatric events including agitation and depression.
| FDA category | Animal |
| Placental transfer | Montelukast crosses the placenta in rats and humans; fetal plasma concentrations are approximately 50% of maternal concentrations. |
| Breastfeeding |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | allergic rhinitis |
| Serious Effects |
Hypersensitivity to montelukast sodium or any component of the formulationPhenylketonuria (for chewable tablets containing aspartame)
| Precautions | Neuropsychiatric events including agitation, depression, suicidal ideation, and behavior, Eosinophilic conditions including eosinophilic granulomatosis with polyangiitis, Acute asthma attacks: not for rescue therapy, Aspirin sensitivity: alternative anti-inflammatory therapy may be needed, Phenylketonuria: chewable tablets contain aspartame |
| Food/Dietary | No significant food interactions. Montelukast may be taken with or without food. For patients with aspirin-sensitive asthma, avoid foods containing salicylates (e.g., certain fruits, spices) as they may trigger asthma symptoms. |
Loading safety data…
| Montelukast is excreted into breast milk in low amounts. The estimated infant daily dose is <0.2% of the maternal weight-adjusted dose. No adverse effects reported in breastfed infants. Caution in preterm infants or neonates due to immature hepatic metabolism. |
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Montelukast is classified as Pregnancy Category B by the FDA. Animal studies have not demonstrated teratogenic effects, and adequate, well-controlled studies in pregnant women are lacking. There is no evidence of increased risk of major birth defects based on available data from the Merck Pregnancy Registry and observational studies. However, caution is advised, and use only if clearly needed. First trimester: No substantial evidence of harm. Second and third trimesters: Limited data; potential risk cannot be excluded. Overall, the risk is considered low, but definitive safety data are insufficient. |
| Fetal Monitoring | No specific monitoring is routinely required but may include clinical assessment of asthma control and fetal growth (ultrasound) if asthma exacerbations occur. In high-risk pregnancies, serial growth scans may be considered. No drug level monitoring is needed. |
| Fertility Effects | Montelukast has no known adverse effects on fertility in humans. Animal studies at high doses showed no impairment of fertility. In vitro and preclinical data suggest no significant reproductive toxicity. Therefore, no specific fertility monitoring is needed. |
| Clinical Pearls | Montelukast is a leukotriene receptor antagonist used primarily for asthma and allergic rhinitis. Monitor for neuropsychiatric events (e.g., agitation, depression, suicidal ideation). Not effective for acute asthma attacks; use as maintenance therapy. Administer once daily in the evening for asthma; for allergic rhinitis, timing can be adjusted. Dose adjustment not needed in renal impairment; use caution in hepatic impairment. |
| Patient Advice | Take montelukast once daily in the evening for asthma; may be taken anytime for allergic rhinitis. · Do not use montelukast for relief of acute asthma attacks; have a rescue inhaler available. · Report any unusual changes in mood, behavior, or thoughts of suicide immediately. · Continue taking montelukast even if you feel well, unless advised by your doctor. · Chewable tablets must be chewed; oral granules can be taken directly or mixed with soft foods. · Avoid foods high in salicylates if you have aspirin-sensitive asthma. |