Can Singular (montelukast) 10mg daily be added to Allegra (fexofenadine) for rhinitis that is unresponsive to Allegra alone after two weeks?

Adding Montelukast to Fexofenadine for Refractory Rhinitis

Yes, adding Singulair (montelukast) 10 mg daily to Allegra (fexofenadine) is a reasonable and evidence-supported approach for rhinitis that has not responded adequately to antihistamine monotherapy after two weeks. 1, 2

Rationale for Combination Therapy

• Combination therapy with montelukast plus antihistamines is more effective than either agent alone for persistent allergic rhinitis, with the greatest improvement in nasal symptoms occurring after combined treatment 2

• In a randomized controlled trial, patients receiving montelukast combined with either levocetirizine or desloratadine showed significantly greater reduction in total nasal symptom scores compared to monotherapy with any single agent 2

• The combination provides complementary mechanisms of action: antihistamines block histamine receptors while montelukast antagonizes leukotriene receptors, addressing different inflammatory pathways 3, 2

Expected Timeline and Efficacy

• Montelukast begins working within 1-2 hours after administration, with clinical benefits evident by day 2, though maximum effectiveness may take 2-4 weeks to achieve 4

• For seasonal allergic rhinitis, FDA trials demonstrated that montelukast 10 mg once daily significantly reduced daytime nasal symptoms scores (including nasal congestion, rhinorrhea, nasal itching, and sneezing) compared to placebo over 2-4 week treatment periods 1

• The combination of montelukast with antihistamines has been reported to be equivalent to intranasal corticosteroids in some studies, representing a substantial improvement over antihistamine monotherapy 3

Dosing and Administration

• Montelukast 10 mg should be taken once daily in the evening 1

• Continue fexofenadine at its current dose while adding montelukast 2

• Assess response after 4-6 weeks of combination therapy; if clear benefits are not observed by this time, consider alternative therapies or diagnoses 4

Important Considerations About Fexofenadine Limitations

• Fexofenadine (like other antihistamines) is less effective for nasal congestion than for other nasal symptoms such as sneezing, itching, and rhinorrhea 5, 6

• If nasal congestion is the predominant symptom, the combination of fexofenadine plus extended-release pseudoephedrine may provide complementary activity, as these agents work synergistically 6

• Antihistamines are generally less effective than intranasal corticosteroids for overall allergic rhinitis control, particularly in patients with severe symptoms or significant nasal congestion 5

When to Consider Alternative Approaches

• If the combination of montelukast and fexofenadine does not provide adequate relief after 4-6 weeks, intranasal corticosteroids should be considered as they are superior first-line agents for moderate-to-severe rhinitis 5, 3

• Montelukast as monotherapy is equivalent to antihistamines but less effective than intranasal corticosteroids 3

• The combination of montelukast plus antihistamine can approach the efficacy of intranasal corticosteroids in some patients, making it a reasonable trial before escalating to nasal steroids 3

Safety Profile

• Montelukast has a safety profile similar to placebo in adults and children, with approval down to 6 months of age 3

• It is non-sedating, dosed once daily, and can be used long-term without concern for tachyphylaxis 4, 3

• Various neuropsychiatric events have been reported as adverse events of montelukast, though the evidence of association is conflicting 7

• Fexofenadine is well-tolerated with an adverse event profile similar to placebo, does not cause sedation even at high doses, and is not associated with cardiac effects 6

Common Pitfalls to Avoid

• Do not discontinue treatment prematurely if full benefits are not immediately apparent, as some therapeutic effects may take several weeks to fully develop 4

• Do not use montelukast for acute symptom relief; it is a controller medication requiring daily use for optimal effect 4

• If nonallergic rhinitis is suspected (vasomotor rhinitis or NARES), antihistamines including fexofenadine are generally ineffective, and intranasal corticosteroids are more appropriate 5

• If nasal congestion remains the predominant uncontrolled symptom despite combination therapy, strongly consider switching to or adding intranasal corticosteroids rather than continuing ineffective oral therapy 5, 3