Can Allegra and Singulair Be Taken on the Same Day?
Yes, Allegra (fexofenadine) and Singulair (montelukast) can safely be taken on the same day, and this combination is explicitly supported for treating allergic rhinitis and asthma. There are no contraindications or significant drug interactions between these medications.
Evidence Supporting Concurrent Use
FDA-Approved Dosing
The Singulair FDA label explicitly addresses concurrent use: "For patients with both asthma and allergic rhinitis, administer only one SINGULAIR dose orally once daily" 1. This guidance confirms that montelukast can be part of a multi-medication regimen for allergic conditions.
Clinical Guidelines Support Combination Therapy
Multiple asthma and rhinitis guidelines recognize both medications as appropriate concurrent therapies:
- For asthma management, leukotriene receptor antagonists (like montelukast) can be used as adjunctive therapy with other medications at various treatment steps 2, 3.
- For allergic rhinitis, both oral antihistamines and leukotriene receptor antagonists are recognized treatment options that can be used together 4, 5.
Research Evidence on Combined Use
Clinical trials have directly studied fexofenadine and montelukast combination therapy:
- A bioequivalence study confirmed that fixed-dose combination tablets containing both fexofenadine 120 mg and montelukast 10 mg are safe and bioequivalent to taking the components separately 6.
- A randomized controlled trial of 275 patients demonstrated that fexofenadine combined with montelukast provided significantly better control of nasal congestion compared to fexofenadine alone, with improvements shown both objectively (rhinomanometry, physical examination) and subjectively (patient diaries, visual analog scales) 7.
- Combination therapy has shown efficacy in treating difficult conditions like prurigo nodularis and pemphigoid nodularis, with 73.3% of patients improving without side effects 8.
Practical Dosing Recommendations
Standard adult dosing when taking both medications:
- Fexofenadine: 60-180 mg once daily (typically 180 mg for allergic rhinitis) 4
- Montelukast: 10 mg once daily, preferably in the evening for asthma; timing can be individualized for allergic rhinitis alone 1
Both medications can be taken with or without food 1.
Important Caveats
Montelukast Neuropsychiatric Warning
The FDA has issued a boxed warning for montelukast regarding serious neuropsychiatric events, including agitation, depression, sleep disturbances, suicidal thoughts, and behavior changes 1. For allergic rhinitis specifically, montelukast should be reserved for patients with inadequate response or intolerance to alternative therapies (like antihistamines alone or intranasal corticosteroids) 1.
Relative Efficacy Considerations
While the combination is safe, evidence shows:
- Fexofenadine is significantly more effective than montelukast for suppressing allergic responses, with faster onset of action (40 minutes vs. no significant effect) 9.
- Intranasal corticosteroids are more effective than either oral antihistamines or leukotriene receptor antagonists for moderate-to-severe allergic rhinitis 5, 10.
- The combination of fexofenadine and montelukast may provide additional benefit primarily for nasal congestion control 7.
No Need to Discontinue for Testing
Importantly, montelukast does not need to be discontinued before allergen skin testing, as it does not significantly suppress skin test responses, unlike antihistamines 11.
Bottom Line
Allegra and Singulair can absolutely be taken together on the same day without safety concerns. However, given montelukast's neuropsychiatric risks and the superior efficacy of intranasal corticosteroids for most patients with allergic rhinitis, this combination should be considered when simpler approaches (antihistamine alone or intranasal corticosteroid) have failed 5, 10, 1.