Montelukast sodium, the active ingredient in SINGULAIR, is a selective and
orally active leukotriene receptor antagonist that inhibits the cysteinyl leukotriene
Montelukast sodium is described chemically as [R-(E)]-1-[[[1-[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-[2-(1-hydroxy-1-methylethyl)phenyl]propyl]thio]methyl]cyclopropaneacetic
acid, monosodium salt.
The empirical formula is C35H35CINNaO3S, and
its molecular weight is 608.18. The structural formula is:
Montelukast sodium is a hygroscopic, optically active, white to off-white powder. Montelukast sodium is freely soluble in ethanol, methanol, and water and practically insoluble in acetonitrile.
Each 10-mg film-coated SINGULAIR tablet contains 10.4 mg montelukast sodium, which is equivalent to 10mg of montelukast, and the following inactive ingredients: microcrystalline cellulose, lactose monohydrate, croscarmellose sodium, hydroxypropyl cellulose, and magnesium stearate. The film coating consists of: hydroxypropyl methylcellulose, hydroxypropyl cellulose, titanium dioxide, red ferric oxide, yellow ferric oxide, and carnauba wax.
Each 4-mg and 5-mg chewable SINGULAIR tablet contains 4.2 and 5.2 mg montelukast sodium, respectively, which are equivalent to 4 and 5 mg of montelukast, respectively. Both chewable tablets contain the following inactive ingredients: mannitol, microcrystalline cellulose, hydroxypropyl cellulose, red ferric oxide, croscarmellose sodium, cherry flavor, aspartame, and magnesium stearate.
Each packet of SINGULAIR 4-mg oral granules contains 4.2 mg montelukast sodium, which is equivalent to 4 mg of montelukast. The oral granule formulation contains the following inactive ingredients: mannitol, hydroxypropyl cellulose, and magnesium stearate.
What are the possible side effects of montelukast (Singulair)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have any of these serious side effects:
- skin rash, bruising, severe tingling, numbness, pain, muscle weakness;
- mood or behavior changes, anxiety, depression, or thoughts about suicide or hurting yourself;
- tremors or shaking;
- easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;
Read All Potential Side Effects and See Pictures of Singulair »
What are the precautions when taking montelukast sodium (Singulair)?
Before taking montelukast, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this drug, tell your doctor or pharmacist your medical history, especially of: liver disease.
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).
The chewable tablets may contain aspartame. If you have phenylketonuria (PKU) or any other condition that requires you to limit/avoid aspartame (or phenylalanine) in your diet, ask your doctor or pharmacist about using this medication...
Read All Potential Precautions of Singulair »
Last reviewed on RxList: 8/6/2012
This monograph has been modified to include the generic and brand name in many instances.