Montelukast, commonly known as Singulair, is a prescription medication used to manage and prevent symptoms of asthma and allergic rhinitis (hay fever). It works by blocking leukotrienes, which are inflammatory chemicals that can cause narrowing of airways and other allergy symptoms. Available as tablets, chewable tablets, and oral granules, it is typically taken once daily. This article examines the scientific understanding of montelukast’s potential connection to weight changes.
The Evidence on Montelukast and Weight Gain
Initial clinical trials for montelukast’s FDA approval did not identify significant weight gain as a frequent side effect. The official drug label for montelukast does not list weight gain as a primary or common adverse event. In these pre-market studies, montelukast’s safety profile was often comparable to a placebo.
Despite initial trial findings, post-marketing surveillance and anecdotal patient reports have prompted discussions about a possible link between montelukast and weight changes. While comprehensive studies establishing a common causal link are limited, one pharmacovigilance study analyzing FDA adverse event reports from 2004 to 2022 identified “obesity” as a previously unreported adverse event. However, another study in obese patients with type 2 diabetes found that montelukast, combined with metformin, led to greater reductions in body weight, BMI, and body fat than metformin alone, suggesting potential for weight loss in this specific population. This indicates individual responses vary, and a widespread causal link for weight gain is not widely supported by major clinical data.
Other Potential Side Effects
Montelukast has a broader safety profile that includes other reported side effects. Common adverse events observed in clinical trials include:
Upper respiratory infections
Fever
Headaches
Sore throat
Cough
Stomach pain
Diarrhea
Earache
Flu-like symptoms
Runny nose
A more serious concern with montelukast involves neuropsychiatric events, which led the FDA to issue a Boxed Warning for the medication in 2020. This warning highlights the risk of serious mood and behavior-related changes, even in patients without a prior history of psychiatric illness. Examples include:
Agitation
Aggression
Anxiety
Depression
Sleep disturbances (e.g., nightmares, insomnia)
Disorientation
Memory problems
Suicidal thoughts or actions (rare instances)
Patients and caregivers are advised to be aware of these potential reactions and to seek medical attention immediately if they occur.
What to Do if You Have Concerns
If you are taking montelukast and have concerns about weight changes or other side effects, consult your healthcare provider promptly. They can assess your situation, consider other causes for weight fluctuations, and determine if the medication contributes to your symptoms. Do not stop taking montelukast abruptly without medical supervision, especially for asthma control, as this could worsen your respiratory condition.
To help your doctor evaluate your concerns, keep a record of your weight and any new or worsening symptoms. Your healthcare provider can then discuss the benefits and risks of continuing montelukast therapy and explore alternative treatment options if necessary. Open communication with your medical team ensures your treatment plan remains appropriate for your health needs.