What to Expect When Starting Montelukast
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Introduction
Montelukast (brand name Singulair) is a leukotriene receptor antagonist used to prevent asthma attacks, treat exercise-induced bronchoconstriction, and relieve symptoms of allergic rhinitis (hay fever). It works by blocking leukotrienes — inflammatory chemicals your body releases during an allergic or asthmatic response that cause airway swelling, mucus production, and bronchoconstriction.
Montelukast is taken as a once-daily tablet and is not a rescue inhaler — it is a preventive medication that works over time to reduce inflammation. If you need immediate relief from an asthma attack, continue using your rescue inhaler (such as albuterol).
In 2020, the FDA added a boxed warning to montelukast regarding potential neuropsychiatric side effects including mood changes, sleep disturbances, and behavioral changes. While these effects are uncommon, it is important to be aware of them. Your doctor has weighed these risks against the benefits for your specific situation.
Week-by-week timeline
Starting Montelukast
You begin taking montelukast once daily. The medication starts blocking leukotriene receptors immediately, but noticeable improvement in symptoms takes several days to develop.
- No immediate dramatic change in symptoms
- Continue using all other prescribed medications
- Possible mild headache
- Possible mild stomach discomfort
Early Response
Some people begin to notice improvement in nasal or respiratory symptoms during the first week. For allergic rhinitis, improvement may be noticed sooner than for asthma.
- Possible improvement in nasal congestion and sneezing
- Slight reduction in asthma symptoms for some
- Adjusting to the daily routine
- Few if any side effects for most people
Building Effectiveness
Montelukast's anti-inflammatory effects are building. Asthma control should be improving, with fewer symptoms and less need for rescue inhaler use.
- Reduced frequency of asthma symptoms
- Less rescue inhaler use
- Improved nasal symptoms for allergic rhinitis
- Better exercise tolerance if exercise-induced symptoms were a problem
Full Therapeutic Effect
Montelukast has reached its full effect. Your doctor will assess whether it is providing adequate control as part of your overall treatment plan.
- Established asthma or allergy control
- Possible step-down of other medications if control is good
- Routine well established
- Clear sense of whether montelukast is helping
Ongoing Maintenance
Montelukast can be used long-term for asthma and allergy management. Periodic assessment of continued need and monitoring for any neuropsychiatric effects is recommended.
- Sustained symptom control
- Periodic asthma control assessments
- Annual evaluation of treatment plan
- Ongoing awareness of mental health changes
When to call your doctor
Contact your healthcare provider if you experience:
- New or worsening mood changes, depression, or anxiety
- Suicidal thoughts or self-harm ideation (seek immediate help)
- Agitation, aggression, or unusual behavioral changes
- New or worsening sleep disturbances, nightmares, or sleepwalking
- Tremor or unusual involuntary movements
- Worsening asthma symptoms despite taking montelukast
- Signs of allergic reaction: rash, hives, swelling of face or throat
- Numbness or tingling in arms or legs
- Signs of Churg-Strauss syndrome (rare): flu-like illness, rash, worsening asthma, numbness
Tips for getting started
Take montelukast once daily in the evening for asthma, or at any consistent time for allergic rhinitis. For exercise-induced asthma, take it at least 2 hours before exercise. Montelukast can be taken with or without food.
Montelukast is a preventive medication — it does not replace your rescue inhaler. Always have your rescue inhaler available for acute asthma symptoms. Do not reduce or stop other asthma medications (inhaled corticosteroids, long-acting bronchodilators) without your doctor's guidance.
Be vigilant about monitoring your mental health while on montelukast. The FDA boxed warning highlights that neuropsychiatric events including agitation, depression, sleep disturbances, and suicidal thinking have been reported. While uncommon, inform your doctor immediately if you notice any mood or behavioral changes. Discuss the benefits and risks with your doctor periodically to ensure montelukast remains the right choice for your treatment plan.
Frequently asked questions
More about Montelukast
References
- [Observational] Montelukast Drug Label https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4a158768-1e5f-4ad2-8a5b-4f487bd7b598 Accessed 2026-03-01.
- [Observational] Montelukast Monograph https://medlineplus.gov/druginfo/meds/a600014.html Accessed 2026-03-01.
- [Observational] FDA Boxed Warning for Montelukast https://www.fda.gov/drugs/drug-safety-and-availability/fda-requires-boxed-warning-about-serious-mental-health-side-effects-asthma-and-allergy-drug Accessed 2026-03-01.
- [Observational] Leukotriene Receptor Antagonists https://www.ncbi.nlm.nih.gov/books/NBK554445/ Accessed 2026-03-01.
Written and fact-checked by PrescriptionDrugs.org Editorial Team
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