Singular - General Information:

Singular is a leukotriene receptor antagonist (LTRA) used for the maintenance treatment of asthma and to relieve symptoms of seasonal allergies. It is usually administered orally. Singular blocks the action of leukotriene D4 on the cysteinyl leukotriene receptor CysLT1 in the lungs and bronchial tubes by binding to it. This reduces the bronchoconstriction otherwise caused by the leukotriene, and results in less inflammation. Because of its method of operation, it is not useful for the treatment of acute asthma attacks. Again because of its very specific locus of operation, it does not interact with other allergy medications such as theophylline.
Singular is marketed in United States and many other countries by Merck & Co. with the brand name Singulair®. It is available as oral tablets, chewable tablets, and oral granules. In India and other countries, it is also marketed under the brand name Montair®, produced by Indian company Cipla.

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SingulairGeneric Singulair (Montelukast) - 4mg 60 tabs for $73.80
Singulair (Montelukast) is used for the prevention and long-term treatment of asthma. It is also used to treat hay fever (seasonal allergic rhinitis). Montelukast works by blocking substances in the body called leukotrienes. Blocking leukotrienes improves asthma and seasonal allergic rhinitis symptoms.


Singular, like zafirlukast, is a leukotriene receptor antagonist used as an alternative to anti-inflammatory medications in the management and chronic treatment of asthma and exercise-induced bronchospasm (EIB). Unlike zafirlukast, montelukast does not inhibit CYP2C9 or CYP3A4 and is, therefore, not expected to affect the hepatic clearance of drugs metabolized by these enzymes.

Singular for patients


  • Patients should be advised to take montelukast daily as prescribed, even when they are asymptomatic, as well as during periods of worsening asthma, and to contact their physicians if their asthma is not well controlled.
  • Patients should be advised that oral tablets of montelukast are not for the treatment of acute asthma attacks. They should have appropriate short-acting inhaled b-agonist medication available to treat asthma exacerbations.
  • Patients should be advised that, while using montelukast, medical attention should be sought if short-acting inhaled bronchodilators are needed more often than usual, or if more than the maximum number of inhalations of short-acting bronchodilator treatment prescribed for 24-hour period are needed.
  • Patients receiving montelukast should be instructed not to decrease the dose or stop taking any other antiasthma medications unless instructed by a physician.
  • Patients who have exacerbations of asthma after exercise should be instructed to continue to use their usual regimen of inhaled b-agonists as prophylaxis unless otherwise instructed by their physician. All patients should have available for rescue a short-acting inhaled b-agonist.
  • Patients with known aspirin sensitivity should be advised to continue avoidance of aspirin or non-steroidal anti-inflammatory agents while taking montelukast.
Chewable Tablets:

Phenylketonurics: Phenylketonuric patients should be informed that the chewable tablet contains phenylalanine (a component of aspartame) 0.842 mg per 5-mg chewable tablet.

Singular Interactions

Montelukast at a Dose of 10 mg Once Daily Dosed to Pharmacokinetic Steady State

  • did not cause clinically significant changes in the kinetics of a single intravenous dose of theophylline (predominantly a cytochrome P450 1A2 substrate).
  • did not change the pharmacokinetic profile of warfarin (a substrate of cytochromes P450 2A6 and 2C9) or influence the effect of a single 30-mg oral dose of warfarin on prothrombin time or the INR (International Normalized Ratio).
  • did not change the pharmacokinetic profile or urinary excretion of immunoreactive digoxin.
  • did not change the plasma concentration profile of terfenadine (a substrate of cytochrome P450 3A4) or fexofenadine, its carboxylated metabolite, and did not prolong the QTc interval following co-administration with terfenadine 60 mg twice daily.
Montelukast at Doses of ³100 mg Daily Dosed to Pharmacokinetic Steady State:
  • did not significantly alter the plasma concentrations of either component of an oral contraceptive containing norethindrone 1 mg/ethinyl estradiol 35 mcg.
  • did not cause any clinically significant change in plasma profiles of prednisone or prednisolone following administration of either oral prednisone or intravenous prednisolone.

Phenobarbital, which induces hepatic metabolism, decreased the AUC of montelukast approximately 40% following a single 10-mg dose of montelukast. No dosage adjustment for montelukast is recommended. It is reasonable to employ appropriate clinical monitoring when potent cytochrome P450 enzyme inducers, such as phenobarbital or rifampin, are co-administered with montelukast.

Montelukast has been administered with other therapies routinely used in the prophylaxis and chronic treatment of asthma with no apparent increase in adverse reactions. In drug-interaction studies, the recommended clinical dose of montelukast did not have clinically important effects on the pharmacokinetics of the following drugs: theophylline, prednisone, prednisolone, oral contraceptives (norethindrone 1 mg/ethinyl estradiol 35 mcg), terfenadine, digoxin, and warfarin.

Although additional specific interaction studies were not performed, montelukast was used concomitantly with a wide range of commonly prescribed drugs in clinical studies without evidence of clinical adverse interactions. These medications included thyroid hormones, sedative hypnotics, non-steroidal anti-inflammatory agents, benzodiazepines, and decongestants.

Phenobarbital, which induces hepatic metabolism, decreased the AUC of montelukast approximately 40% following a single 10-mg dose of montelukast. No dosage adjustment for montelukast is recommended. It is reasonable to employ appropriate clinical monitoring when potent cytochrome P450 enzyme inducers, such as phenobarbital or rifampin, are co-administered with montelukast.

Singular Contraindications

Hypersensitivity to any component of this product.

Additional information about Singular

Singular Indication: For the treatment of asthma
Mechanism Of Action: Singular selectively antagonizes leukotriene D4 (LTD4) at the cysteinyl leukotriene receptor, CysLT1, in the human airway. Singular inhibits the actions of LTD4 at the CysLT1 receptor, preventing airway edema, smooth muscle contraction, and enhanced secretion of thick, viscous mucus.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Montelukast
Synonyms: Not Available
Drug Category: Antiarrhythmic Agents; Leukotriene Antagonists
Drug Type: Small Molecule; Approved
Other Brand Names containing Montelukast: Singulair; Singular;
Absorption: Rapidly absorbed following oral administration (bioavailability is 64%)
Toxicity (Overdose): Side effects include headache, abdominal or stomach pain, cough, dental pain, dizziness, fever, heartburn, skin rash, stuffy nose, weakness or unusual tiredness.
Protein Binding: 99% (to plasma proteins)
Biotransformation: Hepatic
Half Life: 2.7-5.5 hours
Dosage Forms of Singular: Tablet Oral
Granule Oral
Chemical IUPAC Name: 2-[1-[[(1R)-1-[3-[(E)-2-(7-chloroquinolin-2-yl)ethenyl]phenyl]-3-[2-(2-hydroxypropan-2-yl)phenyl]propyl]sulfanylmethyl]cyclopropyl]acetic acid
Chemical Formula: C35H36ClNO3S
Montelukast on Wikipedia:
Organisms Affected: Humans and other mammals

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