What is Montelukast?

  • Montelukast is the generic name of the drug used for the prevention and management of the symptom pertaining to asthma and seasonal allergies.
  • The drug is a member of group of medications called leukotriene receptor antagonists.
  • It acts by its impact on leukotrienes which are chemical substances generated in the body against signals responsible for narrowing and swelling of the passages in the lungs.
  • The term “Mont” in Montelukast denotes the place Montreal, where the drug was developed by Merck.
  • The drug is marketed by Merck & Co. (USA).
  • Montelukast was approved by FDA in 1998 as tablets and chewable tablets and in 2002 in the form of granules.
  • The molecular formula of the drug is C35H36ClNO3S and the molecular weight is 586.18324 g/mol.
  • Monteleukast is chemically known as 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.
  • The drug usually takes at least one day to exhibit its effects.
  • The drug is available in different forms including tablets, chewable tablets and as granules in the dosage strength of 10 mg (for tablets: film coated); 5 mg and 4 mg (for chewable tablets); and 4 mg (for oral granules) respectively.
  • Montelukast is generally administered in the form of montelukast sodium.
  • The usual dosage of the drug is 5 mg (chewable tables) for children under the age of 6-14 years and 10 mg (tablets) for adults as well as teenagers to be taken once during the day orally.


What does Montelukast treat

Montelukast (a leukotriene receptor antagonist) is indicated for a number of medical conditions including the following:

  • Montelukast is used for the prophylaxis of asthma in children and adults with age ranging from 12 months and above.
  • It is used for the management of asthma symptoms including wheezing, tightness in chest and dyspnea (breath shortness) as well as decreases the frequency of asthma attacks in individuals.
  • Montelukast is also indicated for preventing bronchospasm (difficulty in breathing) during exercise occurring as a result of bronchoconstriction i.e., airways constriction in the lungs in individuals with 6 year age and above.
  • The drug is also used to alleviate the symptoms (such as running nose, itching nose or stuffy nose; sneezing) often associated with seasonal allergic rhinitis that occurs at certain time point or perennial rhinitis occurring throughout the year.
  • Montelukast is also prescribed for primary dysmenorrhoea (abdominal pain before or during menstruation) and urticaria (disorder of the skin or a type of skin rash).
  • Montelukast is also implicated as a combination therapy to inhaled corticosteroids in patients when corticosteroids treatment alone is not effective.
  • The drug also prevents the allergic reactions as well as outburst of asthma in case of administration of immunoglobulin by intravenous means.

What is the structure and formula of Montelukast?

  • Chemically Montelukast belongs to the class of organic compounds known as 1,3-diarylpropanoids (linear).
  • 1,3-diarylpropanoids are principally an organic compounds that have a C6-C3-C6 skeleton in which two benzene rings are separated from each other.
  • The molecular formula and molecular weight of Montelukast is C35H36ClNO3S
  • and 586.183 g/mol.
  • The chemical name of Montelukast is2-[1-({[(1R)-1-{3-[(E)-2-(7-chloroquinolin-2-yl)ethenyl]phenyl}-3-[2-(2-hydroxypropan-2-yl)phenyl]propyl]sulfanyl}methyl)cyclopropyl]acetic acid.

Montelukast structure

Generic and brand name of Montelukast

Montelukast is available under generic name “Montelukast” and under diverse type of brand names in different countries such as Singulair, Montelo-10, Tukast L, Montair-10, Monteflo, Montril, Lumenta,  Monkast, Respicare, and Montelair etc.

generic montelukast

Montelukast mechanism of action 

  • Montelukast exhibits its effect via involvement of cysteinyl leukotrienes (leukotriene D4) and their receptors (cysteinyl leukotriene receptor CysLT1).
  • The cysteinyl leukotrienes (including LTC4, LTD4, and LTE4) or eicosanoids comprise a family of inflammatory agents released from a variety of cells such as mast cells as well as eosinophils by metabolism of arachidonic acid.
  • These inflammatory mediators bind to the cysteinyl leukotriene (CysLT) receptors, which comprise CysLT1 and CysLT2 receptors, present in airways.
  • The cysteinyl receptors are known to play an important role in the pathophysiology of asthma (that includes swelling in the airways, contraction of smooth muscles, and cellular activity modification in relation to inflammatory process) and seasonal/perennial allergic rhinitis (release of CysLTs from nasal mucosal membrane after challenge with an allergen or increased secretion of thick and viscous mucus).
  • Montelukast acts as a selective antagonist of the cysteinyl leukotriene CysLT1 receptor, found in smooth muscle cells and macrophages airway, besides being present on some pro-inflammatory cells such as eosinophils and some myeloid stem cells.
  • The drug binds to the cysteinyl leukotriene receptor CysLT1 and negatively affects the action of leukotriene D4, thereby reducing the bronchoconstriction and inflammation.
  • Montelukast has a high affinity and selectivity for the CysLT1in contrast to other pharmacologically relevant airway receptors, including cholinergic, prostanoid, or beta-adrenergic receptor.

What are the side effects associated with the use of Montelukast?

Administration of Montelukast may be associated with some adverse effects along with the beneficial actions. An individual may encounter some of the side effects and should bring it to the notice of the doctor if the side effects become bothersome or persist for a longer time. Some common side effects include the following:

  • stomach pain
  • headache
  • dizziness
  • heartburn
  • tiredness

Some serious side effects can also be associated with the use of Montelukast. These can be divided into various categories, including

  • Cardiac: Strong and irregular heartbeart
  • Neurologic: Seizures, drowsiness, abnormal sensation in skin (tingling, burning, pricking, tickling) or reduced sense of sensation pertaining to skin
  • Hematologic: Decreased blood platelets, enhanced tendency to bleed
  • Immunologic: Anaphylactic reactions
  • Musculoskeletal: Joint pain,  muscle pain and cramps
  • Psychiatric: Depression, tremor, hallucinations, insomnia, anxiousness, irritability, restlessness, disorientation, suicidal behavior
  • Hepatobiliary: Cholestatic hepatitis, hepatocellular and mixed-pattern liver injury
  • Dermatologic: Urticaria, erythema multiforme, angioedema, pruritus, bruising
  • General: Swelling of the body parts (face, feet, tongue, lips, ankles, throat, hands, eyes, or lower legs)

Besides the above mentioned side effects, use of Montelukast may be responsible for other side effects. It is prescribed to contact the doctor in case any unusual effect occurs on taking the drug.

What are the warnings or precautions for the use of Montelukast?

 Special warnings or precautions are associated with the use of Montelukast and are summarized below:

  • Use of Montelukast is contraindicated in case you are allergic to it or any or any of the components of the drug.
  • The drug is not given to alleviate the already started asthma attack.
  • Use of Montelukast should not be stopped abruptly and only under the supervision of a doctor.
  • Contact your doctor immediately in case you experience any behavior change while taking Montelukast.
  • If case you or any other family member taking the medication experience symptoms, modification in sleep habits, weight change etc., contact your doctor immediately.
  • The drug should be used with caution in case of patients with phenylketonuria (characterized by inability of the body to break down phenylalanine) or any medical condition that requires avoiding phenylalanine or aspartame as the chewable tablets of Montelukast contains aspartame. The quantity of phenylalanine in the chewable tablets of 4 mg is 0.674 mg and 5 mg is 0.842 mg.
  • Liver disease may cause a buildup of the drug in the body and hence associated with a number of side effects. It is therefore recommended to consult your doctor in case you experience any symptom of liver problem including skin yellowing, dark color urine, reduced appetite, fatigue, nausea, pale and watery stools etc.
  • The medication should be avoided during pregnancy unless and until the benefits outweigh the risks. In case you become pregnant while using the drug, it is advisable to consult your doctor as soon as possible.
  • Consult with the doctor about the use of Montelukast before breast-feeding as it may affect the baby.
  • It is recommended to not abruptly substitute the medication for inhaled /oral corticosteroids (which need to be reduced only gradually).

What is the difference between Montelukast and Montelukast sodium?

montelukast sodium structure, montelukast vs montelukast sodium
montelukast sodium structure


  • Montelukast refers to the generic name of the medication indicated for the prevention and management of the symptom related to asthma and allergies (seasonal/perennial).
  • The drug is chemically known as 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.
  • The drug has a molecular formula of C35H36ClNO3S and molecular weight of 586.18324 g/mol.

 Montelukast sodium

  • Montelukast sodium is an orally active, and selective monosodium salt of Montelukast.
  • It is the active constituent in Singulair, which is the brand name of the drug Montelukast.
  • It acts as a cysteinyl leukotriene receptor antagonist, anti-inflammatory as well as bronchodilating agent.
  • Montelukast sodium is chemically known 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 molecular formula of Montelukast sodium is C35H35ClNNaO3S, and molecular weight is 608.18 g/mol.
  • Presence of sodium ion in the structure of the drug increases its attachment to the receptor as well as its metabolism.
  • Montelukast sodium is hygroscopic in nature, white to off-white in color and with a powdery texture.
  • It is freely soluble in methanol, ethanol, as well as water and is practically not soluble in acetonitrile.

Montelukast structure, montelukast vs montelukast sodium

Montelukast structure

More Details about Montelukast 10 mg

montelukast 10 mg

Montelukast 10 mg: Facts

  • Montelukast is available in various dosage strengths including 10 mg film coated tablets.
  • Each tablet of 10-mg Montelukast comprises the following
  • Active ingredient: Montelukast (10 mg)
  • Inactive ingredients (in core): Magnesium stearate, hydroxypropyl cellulose, lactose monohydrate, microcrystalline cellulose, and croscarmellose sodium.
  • Film coating ingredients: Titanium dioxide, hydroxypropyl methylcellulose, carnauba wax, yellow ferric oxide, hydroxypropyl cellulose, and red ferric oxide.
  • The 10 mg tablet is squared, beige, biconvex with a film coating and engraved with10 on one side.
  • The drug is prescribed for treating asthma in the form of add-on therapy in cases of mild to moderate asthma, relieving symptoms of seasonal allergic rhinitis (in patients of asthma) and also for preventing asthma induced by exercise.
  • The drug is recommended for use in case of adolescents as well as adults from the age of 15 years onwards.
  • Montelukast 10 mg is taken orally with or without food.
  • The recommended dose for Montelukast 10 mg for its medical benefits (for treating asthma and asthma/seasonal allergic rhinitis together) in patients 15 years and older includes 1 tablet daily usually in the evening.
  • Montelukast gets rapidly absorbed in the blood stream following oral administration. The peak plasma concentration for the 10 mg tablet is achieved within 3 hours after oral administration in adults in the fasting state.
  • The drug has a mean oral bioavailability of 64%.

What is the best time to take Montelukast?

 The best time for the administration of Montelukast depends upon the medical condition being treated. These are as follows:

  • For the treatment of Asthma, the drug should be taken in the evening.
  • When the drug is prescribed for the prevention of breathing problems encountered during exercise, the drug is recommended to be taken atleast 2 hours prior to exercise. However, avoid the use of the drug before exercise when you are taking the drug regularly once a day.
  • Treatment of allergic rhinitis requires the administration of the drug at any time of the day.
  • It is generally recommended to take the drug at almost the same time every day for best results.

Can Montelukast get you high?

  • Montelukast is a prescription drug which is indicated for the treatment of asthma, exercise-induced bronchoconstriction, as well as allergies which may be seasonal or perennial.
  • Montelukast is not a drug of abuse and do not belong to the category of controlled substance.
  • However, in certain circumstances (very rarely), generally overdose, the drug results in adverse effects such as hallucinations, suicidal thinking, aggressive behaviour, and also depression.

Can Montelukast be used for recreational use?

No such studies are available that suggested the use of Montelukast as a recreational drug.

What is the role of Montelukast in the treatment of allergies?

  • Montelukast has been approved by FDA for the treatment of allergic rhinitis which includes seasonal allergic rhinitis as well as perennial allergic rhinitis.
  • Seasonal allergic rhinitis (also known as hay fever) occurs during any time of the year, often in response to airborne pollens grains, weeds as well as grasses and often characterized by sneezing; stuffed and running nose; as well as red, watery, swollen, and itching eyes.
  • Perennial rhinitis (also known as persistent rhinitis) occurs throughout the year in response to mites and pets and characterized by nose congestion and sneezing.
  • The drug is recommended for the treatment of symptoms related to seasonal rhinitis in individuals who are atleast 2 years or older and perennial rhinitis in individuals atleast 6 months and older.
  • The drug acts via its active ingredient Montelukast which acts as a leukotriene receptor antagonist responsible for the prevention of inflammation caused by leukotriene (involved in the pathophysiology of allergic rhinitis).
  • The dosage of the drug varies with the age and type of rhinitis.
  • The drug is taken once a day at any time of the day.

Can I drink alcohol while taking Montelukast?

Alcohol consumption is not likely to cause serious side effects for the patients who take Montelukast. However, one should always consult the doctor before consuming alcohol as it is contraindicated under certain conditions.

The combination of alcohol and the drug can enhance the risk of certain side effects, more common, dizziness and drowsiness. These effects can get worsen if already occurring on consumption of alcohol. It is therefore recommended to avoid operating heavy machinery and driving that require alertness.

Alcohol consumption is associated with certain health risks including the following:

  • Use of alcohol is prohibited while using Montelukast for the treatment of asthma and allergies as it can cause worsening of the asthma symptoms and can induce allergic attacks.
  • Alcohol consumption can result in acid reflux. Entry of acid into the breathing tube causes a cascade of events including swelling, irritation, and also mucus production which may result in asthma attack.
  • Certain constituents in alcohol including sulfites and preservatives can result in triggering and worsening the condition of asthma in people who are sensitive to these components.
  • Histamine like agents in the alcoholic beverages can cause stuffiness in the nose. These symptoms get aggravated in people suffering with asthma or having seasonal allergies.

 Can I take Montelukast while pregnant?

  • Montelukast is generally considered safe for the pregnant women.
  • It is classified in the pregnancy category B by the FDA.
  • Although, no studies are available from the human pregnant population but results from the animal studies (rats) suggest that there are no harmful effects in relation to the high doses of the drug on pregnancy or on the development of the embryo or any malformation in the embryo. However, the medication should be used with caution in the pregnant women and should only be administered if the benefits outweigh the associated risks (due to lack of studies in pregnant women).
  • It is recommended to take only the prescribed amount and in case of overdose, contact the doctor immediately.
  • In case you become pregnant or plan to become pregnant during the use of the drug, consult your doctor.


Can I take Montelukast while breastfeeding?

 It is generally recommended to avoid the use of Montelukast while breastfeeding.

  • Studies indicate the excretion of the drug in the milk in case of animals but no studies are available regarding the excretion of the medication in human milk and its associated harmful effects on the nursing child.
  • Montelukast should be taken during breastfeeding only when considered indispensable.
  • The drug should be used with caution during breastfeeding as it may affect the infant and exhibit harmful effects on the child.
  • It is recommended to monitor the child for the appearance of any side effect during the use of the drug and contact doctor immediately if any symptom appears.


How long does Montelukast take to work?

  • The time duration for the Montelukast to show its effect or to kick in usually varies from 1 day to 30 days.
  • In case of asthma induced by exercise, the drug is taken atleast 2 hours before the exercise to experience the effects of the medication.
  • However, for the treatment of asthma characterized by inflammation in relation to other conditions, the drug usually takes a longer time or may be numerous days to attain the beneficial effects of the drug.

How long does Montelukast stay in your system? 

  • The mean plasma half life of Montelukast varies in the range of 2.7 to 5.5 hours and the plasma clearance of the drug is 45 ml/min for a healthy individual.
  • The drug stays in the blood for a very short time and then rapidly eliminated from the body system via liver as well as bile.
  • After an oral administration, the drug is detected maximally for 5 days in feces (bile is eliminated from the body by feces) and for a day or two in blood and urine.

Does Montelukast show up on a drug test?

  • The drug tests being performed often looks for the presence of drugs belonging to the category of medications such as benzodiazapenes, opiates, THC (tetrahydrocannabinol), amphetamines, and PCP (Phencyclidine).
  • Since, Montelukast does not belong to any of these categories of drugs; hence, it would not show up on a drug test.
  • However, the administration of the drug may cause drug screen false positive in some cases (especially in case of females with age of 30-39 years, having asthma and are on the drug for the last 1 to 6 months, and also taking the drug Albuterol).

Montelukast and Zyrtec Drug Interactions

Can Montelukast be taken with Zyrtec? Yes, Montelukast in combination with Zyrtec is recommended in the treatment of severe allergic reactions. Montelukast is an antileukotriene and widely used to treat asthma, allergic Rhinitis, bronchospasm prophylaxis, asthma maintenance, and COPD.

Despite Montelukast, Zyrtec (a brand name of drug Cetirizine) is  belong to the drug class antihistamines that reduces the effects and production of natural chemical involved in allergic reaction (histamine) in the body. Zyrtec is used to treat cold or allergy symptoms such as itching, sneezing, runny nose or watery eyes, itching/ swelling caused by chronic urticaria (hives) and seasonal allergic rhinitis etc.

The Montelukast is act through selective inhibition of the cysteinyl leukotriene CysLT1 receptor (smooth muscle cells, macrophages airway, eosinophils and myeloid stem cells) involve in bronchoconstriction and inflammation.

Cetirizine is an antihistamine molecule that acts through inhibition of Histamine inside the body. Since, Montelukast and Cetirizine works on same aspect of allergic reaction but acts differently they can be used together for prophylactic treatment of seasonal allergic reactions.

Can Montelukast be taken with Zyrtec

Benadryl and Singulair Drug Interactions

Can Montelukast be taken with Benadryl? Yes, Montelukast and Benadryl can be used in combination together at the same time to treat allergic conditions. The active ingredient of Montelukast is Montelukast sodium, while active ingredient of Benadryl is diphenhydramine hydrochloride. Montelukast is a leukotriene modifier that used to treat asthma, allergic rhinitis and bronchospasm.

In contrast, Benadryl is an anticholinergic antihistamine class of drug that is used to treat symptoms of allergic reactions, cold, cough, arllergic rhinitis, motion sickness, extrapyramidal reaction, nausea, vomiting, urticaria and pruritus. Benadryl is a Histamine-1 Receptor Antagonist antihistamine and ethanolamine (Histamine-1 Receptor antagonist) that have sedative and anti-allergic properties.

Since, mode of action of both Montelukast and Benadryl is different. Both Montelukast and Benadryl act at different part of body therefore no potential inter action between the two has been reported.

Benadryl and Singulair Drug Interactions

Can Montelukast be taken with Claritin?

Yes, Montelukast may be taken together with Claritin to treat allergic conditions such as allergic rhinitis, asthama, bronchospasm etc. Montelukast is well known anti leukotriene that acts trough leukotriene CysLT1 receptor. It is commonly used to treat allergic conditions such as asthma, brochospasm, allergic rhinitis and COPD.

Contrary to this, Claritin (also known as loratadine) is an antihistamine drug that primarily acts through inhibition of natural chemical histamine. Claritin treats runny nose, sneezing, watery eyes, skin rash, hives, itching, and common cold or allergy symptoms. Since, both Montelukast and Claritin act differently they can be taken together. Clinical studies have reported lack of any interaction between the two.

Claritin and Singulair Drug Interactions

Difference between kaopectate and pepto bismol