SINGULAIR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SINGULAIR (SINGULAIR).
Selective leukotriene receptor antagonist; inhibits cysteinyl leukotriene (LTC4, LTD4, LTE4) at the CysLT1 receptor, reducing bronchoconstriction, mucus secretion, and eosinophilic inflammation.
| Metabolism | Primarily metabolized by CYP2C8 and CYP3A4; minor contribution from CYP2C9. Metabolites are excreted in bile. |
| Excretion | Primarily hepatic metabolism; 86% eliminated in feces via bile, <0.2% unchanged in urine. Minor renal excretion of metabolites. |
| Half-life | 2.7-5.5 hours (mean 3-4 hours). No significant accumulation with once-daily dosing; extended effect due to receptor binding kinetics. |
| Protein binding | >99% bound primarily to albumin; minor binding to other plasma proteins. |
| Volume of Distribution | 10-20 L (approximately 0.14-0.29 L/kg). Indicates extensive tissue distribution, consistent with intracellular target (cysteinyl leukotriene receptor). |
| Bioavailability | Oral: 64% (10 mg tablet). Food reduces rate and extent of absorption; administered without regard to meals. |
| Onset of Action | Oral: 3-4 hours for detectable improvement in FEV1; maximal bronchodilation observed within 24 hours of first dose. |
| Duration of Action | 24 hours for clinical effect (once-daily dosing). Note: Duration exceeds plasma half-life due to sustained receptor occupancy; continuous coverage over 24 hours. |
| Molecular Weight | 608.8 |
| Action Class | Leukotriene antagonists |
| Brand Substitutes | Vitamont 10mg Tablet, Solukast 10mg Tablet, Ebmont 10mg Tablet, Lasma 10 Tablet, Symkast DX 10mg Tablet |
10 mg orally once daily in the evening, with or without food.
| Dosage form | GRANULE |
| Renal impairment | No dosage adjustment required for renal impairment, including end-stage renal disease. |
| Liver impairment | No dosage adjustment required for mild-to-moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | 6 to 23 months: 4 mg (chewable tablet or oral granules) once daily; 2 to 5 years: 4 mg (chewable tablet) once daily; 6 to 14 years: 5 mg (chewable tablet) once daily; 15 years and older: 10 mg tablet once daily. |
| Geriatric use | No specific dose adjustment; use with caution due to potential age-related renal or hepatic function decline. |
| 1st trimester | Limited human data; animal studies show no teratogenic effects. Use only if clearly needed. |
| 2nd trimester | Limited human data; no known fetal risk. Use cautiously. |
| 3rd trimester | Limited human data; no known fetal risk. Use cautiously near term. |
Clinical note
Comprehensive clinical and safety monograph for SINGULAIR (SINGULAIR).
| Placental transfer | Montelukast crosses the placenta in animals; human data not extensive but likely crosses due to low molecular weight. |
| Breastfeeding | Montelukast is excreted into breast milk in low amounts. Doses up to 10 mg daily produce low levels in milk, unlikely to cause adverse effects in infants. Consider monitoring for gastrointestinal upset. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to montelukast or any component
| Precautions | Neuropsychiatric events (agitation, depression, suicidal behavior), Eosinophilic conditions (Churg-Strauss syndrome), Acute asthma attacks (not for reversal of bronchospasm), Aspirin sensitivity (avoid in aspirin-sensitive patients) |
| Food/Dietary | No significant food interactions. Take with or without food. Avoid grapefruit juice? No known interaction with montelukast. No dietary restrictions specific to Singulair. |
| Clinical Pearls |
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| L2 |
| Teratogenic Risk | Montelukast is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal harm, and there are no adequate and well-controlled studies in pregnant women. Use only if clearly needed. No known risk of major birth defects or miscarriage based on limited human data; first trimester exposure not associated with increased risk of congenital anomalies in large cohort studies. Second and third trimester: no specific risks identified. However, monitor as part of routine prenatal care. |
| Fetal Monitoring | No specific fetal monitoring required beyond routine obstetric care. Monitor maternal asthma control and adjust therapy as needed. Evaluate for potential adverse effects including neuropsychiatric events (e.g., mood changes, agitation) which may indicate need dose adjustment or discontinuation. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies showed no impairment of fertility at clinically relevant doses. No specific monitoring required. |
| Montelukast (Singulair) is a leukotriene receptor antagonist used for prophylaxis and chronic treatment of asthma, and for relief of symptoms of allergic rhinitis. It is not indicated for acute asthma attacks. It may be less effective than inhaled corticosteroids for asthma control. Neuropsychiatric events (e.g., agitation, depression, suicidal thoughts) have been reported, especially in children; monitor mood and behavior. Tablet formulations contain phenylalanine (aspartame contraindicating in phenylketonuria). Once-daily dosing (evening for asthma). |
| Patient Advice | Take Singulair exactly as prescribed, usually once daily in the evening for asthma. · Do not use Singulair to treat sudden asthma attacks; always carry a rescue inhaler. · Report any mood changes, agitation, aggression, depression, or suicidal thoughts to your doctor immediately. · If you have phenylketonuria (PKU), avoid the chewable tablets due to aspartame content. · Inform your doctor if you have liver disease or are breastfeeding. · Store at room temperature away from moisture and heat. |