Singulair Side Effects: The Mood and Behaviour Warning Explained

Singulair (montelukast) is a popular prescription medication used to prevent asthma attacks and relieve seasonal allergies. While many people tolerate it well, it carries a rare but important warning about mood and behaviour changes. This article breaks down what you need to know, based on credible sources like the U.S. Food and Drug Administration (FDA) and peer-reviewed studies.

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What Is Singulair and How Does It Work?

Singulair belongs to a class of drugs called leukotriene receptor antagonists. It works by blocking leukotrienes, inflammatory chemicals your body produces when exposed to allergens or asthma triggers. By reducing inflammation in your airways, Singulair can:

• Prevent asthma attacks
• Decrease wheezing and shortness of breath
• Relieve nasal congestion, sneezing, and itching in allergic rhinitis

Most patients take a single 10 mg tablet daily. For children under 15, lower doses are available in chewable or granule form.

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Common Side Effects of Singulair

Like all medications, Singulair can cause side effects. Most are mild and resolve on their own. Common side effects include:

• Headache
• Abdominal pain or indigestion
• Cough or nasal congestion
• Fever (in children)
• Dizziness

If these symptoms persist or worsen, talk to your doctor. They may adjust your dose or recommend an alternative treatment.

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The Mood and Behaviour Warning

What the FDA Says

In March 2020, the FDA required a “boxed warning” on montelukast (Singulair) to highlight the risk of serious neuropsychiatric events. Though rare, these events can be severe. They include:

• Agitation or restlessness
• Irritability, aggression, or anger
• Depressed mood or suicidal thoughts
• Sleep disturbances (insomnia or vivid dreams)
• Hallucinations

These symptoms have been reported in both adults and children, sometimes within days of starting treatment. In a small number of cases, they persisted or even began after the drug was discontinued.

How Common Are These Events?

While most people on Singulair do not experience severe mood changes, studies suggest:

• Between 1 in 100 and 1 in 1,000 patients report mild mood changes (e.g., vivid dreams).
• Between 1 in 1,000 and 1 in 10,000 patients report more serious events (e.g., depression, suicidal ideation).

Because these reactions are unpredictable, both patients and caregivers should remain vigilant.

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Why Might Singulair Affect Mood?

The exact mechanism is not fully understood, but hypotheses include:

• Central nervous system penetration: Montelukast may cross the blood-brain barrier and influence brain chemicals related to mood regulation.
• Leukotriene pathways in the brain: Leukotrienes aren’t limited to the lungs—they may play a role in brain inflammation or neurotransmitter balance.

More research is needed, but the existing data were sufficient for regulatory bodies to issue warnings.

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Who Is at Higher Risk?

While anyone taking Singulair could develop neuropsychiatric side effects, certain factors may increase risk:

• A personal or family history of mental health disorders
• Concurrent use of other medications known to affect mood (e.g., antidepressants, corticosteroids)
• Younger age, especially children and teenagers still undergoing brain development

If you fall into any of these categories, discuss the risks and benefits carefully with your healthcare provider before starting Singulair.

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Monitoring for Warning Signs

Early detection is key. Patients, parents, and caregivers should watch for:

• Sudden changes in behaviour or school/work performance
• New or worsening mood swings, irritability, or depression
• Unexplained anxiety or panic attacks
• Trouble sleeping, nightmares, or unusual dreams
• Statements of self-harm, hopelessness, or suicidal thoughts

If any of these occur, stop Singulair immediately and contact a healthcare professional.

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What to Do If You Notice Mood Changes

1. Stop the medication: Discontinue Singulair at the first sign of serious mood changes.
2. Seek medical help: Call your doctor or go to the nearest emergency department if symptoms are severe or life-threatening.
3. Report side effects: You can report adverse events to the FDA’s MedWatch program.
4. Consider alternatives: Other asthma and allergy treatments exist, such as inhaled corticosteroids, antihistamines, or allergy immunotherapy.

For non-urgent concerns or a quick check of your symptoms, consider a free, online symptom check, using the doctor approved Ubie Symptom Checker (https://ubiehealth.com/).

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Balancing Benefits and Risks

Singulair remains a valuable option for many with asthma or allergic rhinitis. When used responsibly, its benefits in preventing asthma attacks and controlling allergy symptoms can outweigh the rare risk of neuropsychiatric events. To make an informed choice:

• Discuss your full medical history with your healthcare provider.
• Review other medications and supplements you take.
• Agree on a monitoring plan, including regular check-ins.
• Know how and when to stop the medication if troubling symptoms appear.

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Frequently Asked Questions

Q: Can I restart Singulair if I had mild mood changes?
A: Only under close medical supervision. If symptoms resolved quickly after stopping, your doctor may try a lower dose or switch treatments.

Q: Are there warning signs in children different from adults?
A: Children might show increased irritability, clinginess, or changes in school performance. Always involve a parent or caregiver in monitoring.

Q: How long after stopping Singulair do mood effects last?
A: Most resolve within days to weeks, but some have reported symptoms lasting longer. Keep in touch with your doctor until you feel back to baseline.

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When to Speak to Your Doctor

Always take any potential side effect seriously. Contact your healthcare provider immediately if you experience:

• Thoughts of self-harm or suicide
• Severe depression or anxiety
• Psychotic symptoms (hallucinations, paranoia)
• Any new or worsening breathing difficulties

Never ignore warning signs, especially if they’re life-threatening or severely impact daily life.

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Conclusion

Understanding singulair side effects—especially the mood and behaviour warning—helps you use this medication safely. While most people tolerate Singulair well, remain alert for any neuropsychiatric symptoms. Balance its clear benefits in asthma and allergy control against potential risks, and maintain open communication with your healthcare team. If in doubt, use resources like the free, online symptom check, using the doctor approved Ubie Symptom Checker (https://ubiehealth.com/), and always speak to your doctor about any serious or life-threatening concerns.