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Singulair Side Effects

Generic name: montelukast

Medically reviewed by Last updated on Aug 13, 2022.

Note: This document contains side effect information about montelukast. Some dosage forms listed on this page may not apply to the brand name Singulair.

Applies to montelukast: oral packet, oral tablet, oral tablet chewable.


Oral route (Tablet; Tablet, Chewable; Granule)

Warning: Serious Neuropsychiatric EventsSerious neuropsychiatric (NP) events have been reported in patients taking montelukast. The types of events reported were highly variable, and included, but were not limited to, agitation, aggression, depression, sleep disturbances, suicidal thoughts and behavior (including suicide). The mechanisms underlying NP events associated with montelukast use are currently not well understood.Because of the risk of NP events, the benefits of montelukast may not outweigh the risks in some patients, particularly when the symptoms of disease may be mild and adequately treated with alternative therapies. Reserve use of montelukast for patients with allergic rhinitis who have an inadequate response or intolerance to alternative therapies. In patients with asthma or exercise-induced bronchoconstriction, consider the benefits and risks before prescribing montelukast.Discuss the benefits and risks of montelukast with patients and caregivers when prescribing montelukast. Advise patients and/or caregivers to be alert for changes in behavior or new NP symptoms when taking montelukast. If changes in behavior are observed, or if new NP symptoms or suicidal thoughts and/or behavior occur, advise patients to discontinue montelukast and contact a healthcare provider immediately.

Serious side effects of Singulair

Along with its needed effects, montelukast (the active ingredient contained in Singulair) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking montelukast:

More common

  • Body aches or pain
  • cough
  • difficulty in breathing
  • dryness or soreness of the throat
  • fever
  • headache
  • loss of voice
  • pain or tenderness around the eyes and cheekbones
  • pain, redness, or swelling in the ear
  • stomach pain
  • stuffy or runny nose
  • tender, swollen glands in neck
  • trouble in swallowing
  • unusual tiredness or weakness
  • voice changes

Less common

  • Bloody nose
  • general feeling of discomfort or illness
  • joint pain
  • sweating


  • Pus in the urine

Incidence not known

  • Agitation
  • anxiety
  • attempts at killing oneself
  • breathing problems
  • confusion about identity, place, and time
  • constipation
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling sad or empty
  • hives or welts
  • indigestion
  • itching, puffiness, or swelling of the eyelids or around the eyes, face, lips, or tongue
  • lack of appetite
  • pains in the stomach, side, or abdomen, possibly moving to the back
  • redness of the skin
  • shaking or trembling of the hands or feet
  • trouble with concentrating
  • unable to sleep
  • unpleasant breath odor
  • vomiting of blood
  • yellow eyes or skin

Other side effects of Singulair

Some side effects of montelukast may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

  • Acid or sour stomach
  • belching
  • blurred vision
  • change in near or distance vision
  • dental pain
  • heartburn
  • lack or loss of strength
  • pain
  • skin rash, encrusted, scaly and oozing
  • stomach discomfort, upset, or pain

Incidence not known

  • Burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
  • dreams that are unusual
  • increased tendency to bleed
  • large, flat, blue or purplish patches on the skin
  • muscle aching or cramping
  • sleepiness
  • swollen joints

For Healthcare Professionals

Applies to montelukast: oral granule, oral tablet, oral tablet chewable.


The most common adverse reactions (incidence more than 5% and greater than placebo) were: Upper respiratory infection, fever, headache, pharyngitis, cough, abdominal pain, diarrhea, otitis media, influenza, rhinorrhea, sinusitis, otitis.[Ref]


Churg-Strauss syndrome is a rare granulomatous eosinophilic condition that involves the upper and lower airways and manifests as rhinitis, sinusitis and asthma. If untreated the syndrome may progress to systemic vasculitis, peripheral neuropathy and potentially fatal cardiac complications. In most cases, the condition emerged during withdrawal of oral corticosteroid therapy. A causative role for leukotriene receptor antagonists has not been ruled out.[Ref]

Very rare (less than 0.01%): Churg-Strauss Syndrome[Ref]

Nervous system

Very common (10% or more): Headache (18.4%)

Common (1% to 10%): Dizziness (1.9%)

Postmarketing reports: Disturbance in attention, irritability, memory impairment, tremor, drowsiness, paraesthesia/hypoesthesia, seizures[Ref]


Common (1% to 10%): Rash (1.6%), atopic dermatitis, skin infection, eczema, urticaria

Postmarketing reports: Angioedema, bruising, erythema multiforme, erythema nodosum, pruritus, Stevens-Johnson syndrome/toxic epidermal necrolysis[Ref]


Common (1% to 10%): Abdominal pain (2.9%), dyspepsia (2.1%), dental pain (1.7%), gastroenteritis (1.5%), nausea, diarrhea, dyspepsia, gastroenteritis, tooth infection[Ref]


Common (1% to 10%): ALT increase (2.1%), AST increased (1.6%)

Postmarketing reports: Hepatic eosinophilic infiltration; cases of cholestatic hepatitis, hepatocellular liver-injury, and mixed-pattern liver injury. Most of these occurred in combination with other confounding factors, such as use of other medications, or when administered to patients who had underlying potential for liver disease such as alcohol use or other forms of hepatitis.[Ref]


Common (1% to 10%): Myopia, conjunctivitis[Ref]


Common (1% to 10%): Asthenia, fatigue (1.8%), fever (1.5%), trauma (1%), influenza, fever, otitis, viral infection, varicella, ear pain, otitis media

Uncommon (0.1% to 1%): Malaise

Postmarketing reports: Edema[Ref]


Common (1% to 10%): Influenza (4.2%), cough (2.7%), nasal congestion (1.6%), pharyngitis, sinusitis, laryngitis, infective rhinitis, acute bronchitis, rhinorrhea, pneumonia, upper respiratory infection, wheezing, tonsillitis

Postmarketing reports: Epistaxis, pulmonary eosinophilia[Ref]


Postmarketing reports: Palpitations[Ref]


Postmarketing reports: Enuresis in children[Ref]


Postmarketing reports: Increased bleeding tendency, thrombocytopenia[Ref]


Postmarketing reports: Anaphylaxis[Ref]


Postmarketing reports: Arthralgia, myalgia including muscle cramps[Ref]


Postmarketing reports: Agitation including aggressive behavior or hostility, anxiousness, depression, disorientation, dream abnormalities, hallucinations, insomnia, restlessness, somnambulism, suicidal thinking and behavior (including suicide), tic, obsessive-compulsive symptoms, dysphemia/stuttering[Ref]

Frequently asked questions


1. "Product Information. Singulair (montelukast)." Merck & Company Inc (2001):

2. McMorran M "Leukotriene receptor antagonists: suspected adverse reactions." Can Med Assn J 161 (1999): 868-70

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

4. Cerner Multum, Inc. "Australian Product Information." O 0

5. "Product Information. Montelukast Sodium (montelukast)." Ajanta Pharma USA (2016):

6. Bronsky EA, Kemp JP, Zhang J, Guerreiro D, Reiss TF "Dose-related protection of exercise bronchoconstriction by montelukast, a cysteinyl leukotriene-receptor antagonist, at the en of a once-daily dosing interval." Clin Pharmacol Ther 62 (1997): 556-61

7. De Lepeleire I, Reiss TF, Rochette F, Botto A, Zhang J, Kundu S, Decramer M "Montelukast causes prolonged, potent leukotriene D4-receptor antagonism in the airways of patients with asthma." Clin Pharmacol Ther 61 (1997): 83-92

8. Reiss TF, Chervinsky P, Dockhorn RJ, Shingo S, Seidenberg B, Edwards TB "Montelukast, a once-daily leukotriene receptor antagonist, in the treatment of chronic asthma: A multicenter, randomized, double-blind trial." Arch Intern Med 158 (1998): 1213-20

9. Noonan MJ, Chervinsky P, Brandon M, Zhang J, Kundu S, McBurney J, Reiss TF "Montelukast, a potent leukotriene receptor antagonist, causes dose-related improvements in chronic asthma." Eur Respir J 11 (1998): 1232-9

10. Leff JA, Busse WW, Pearlman D, et al. "Montelukast, a leukotriene-receptor antagonist, for the treatment of mild asthma and exercise-induced bronchoconstriction." N Engl J Med 339 (1998): 147-52

11. Reiss TF, Altman LC, Chervinsky P, Bewtra A, Stricker WE, Noonan GP, Kundu S, Zhang J "Effects of montelukast (MK-0476), a new potent cysteinyl leukotriene (LTD4) receptor antagonist, in patients with chronic asthma." J Allergy Clin Immunol 98 (1996): 528-34

12. Sabio JM, Jimenez-Alonso J, Gonzalez-Crespo F "More About Churg-Strauss Syndrome and Montelukast Treatment." Chest 120 (2001): 2116

13. Minciullo PL, Saija A, Bonanno D, Ferlazzo E, Gangemi S "Montelukast-induced generalized urticaria." Ann Pharmacother 38 (2004): 999-1001

14. Sass DA, Chopra KB, Wu T "A case of montelukast-induced hepatotoxicity." Am J Gastroenterol 98 (2003): 704-5

15. Goldstein MF, Anoia J, Black M "Montelukast-induced hepatitis." Ann Intern Med 140 (2004): 586-7

16. Wechsler ME, Finn D, Gunawardena D, Westlake R, Barker A, Haranath SP, Pauwels RA, Kips JC, Drazen JM "Churg-Strauss syndrome in patients receiving montelukast as treatment for asthma." Chest 117 (2000): 708-13

17. Price D "Tolerability of montelukast." Drugs 59 (2000): 35-42

18. Jarvis B, Markham A "Montelukast - A review of its therapeutic potential in persistent asthma." Drugs 59 (2000): 891-928

19. Dempsey OJ "Leukotriene receptor antagonist therapy." Postgrad Med J 76 (2000): 767-73

20. Tang MB, Yosipovitch G "Acute churg-strauss syndrome in an asthmatic patient receiving montelukast therapy." Arch Dermatol 139 (2003): 715-8

21. Sabbagh R, Sheikh-Taha M "Possible montelukast-induced angioedema." Am J Health Syst Pharm 66 (2009): 1705-6

22. Kelsay K "Assessing risk: Data from montelukast clinical trials." J Allergy Clin Immunol 124 (2009): 697-8

23. Philip G, Hustad C, Noonan G, et al. "Reports of suicidality in clinical trials of montelukast." J Allergy Clin Immunol 124 (2009): 691-696.e6

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.