Does azelastine (antihistamine) help prevent influenza (flu) and Coronavirus disease (Covid)?

Azelastine's Role in Preventing Flu and COVID-19

Azelastine nasal spray shows promising efficacy in preventing SARS-CoV-2 infections but is not currently recommended in clinical guidelines for flu or COVID-19 prophylaxis.

Evidence for Azelastine Against COVID-19

Recent research demonstrates azelastine's potential antiviral properties:

• A 2023 phase 2 randomized clinical trial found that azelastine nasal spray (0.1%) used three times daily significantly reduced PCR-confirmed SARS-CoV-2 infections compared to placebo (2.2% vs 6.7%) 1
• Laboratory studies show azelastine inhibits SARS-CoV-2 infection in cell cultures with an EC50 of 2.2-6.5 μM, including against alpha, beta, and delta variants 2
• Azelastine appears to work by binding to the ACE2 receptor (SARS-CoV-2's entry point) with a KD of 2.58 × 10-7 M, effectively blocking viral entry 3
• The medication shows antiviral activity against multiple respiratory viruses including SARS-CoV-2, seasonal coronavirus 229E, RSV, and influenza A H1N1 4

Evidence for Azelastine Against Influenza

• While azelastine shows activity against influenza A H1N1 in laboratory studies 4, there is no clinical evidence supporting its use for influenza prevention
• Current guidelines for influenza prophylaxis recommend neuraminidase inhibitors (oseltamivir, zanamivir) and vaccination, but do not mention antihistamines like azelastine 5

Current Guideline Recommendations

• No major clinical guidelines currently recommend azelastine for COVID-19 or influenza prophylaxis
• The American College of Physicians explicitly recommends against using certain medications (chloroquine, hydroxychloroquine) for COVID-19 prophylaxis but does not address azelastine 6
• For influenza prophylaxis, guidelines recommend vaccination as primary prevention, with neuraminidase inhibitors as chemoprophylaxis for high-risk individuals 5

Safety Considerations

• Azelastine is FDA-approved as an intranasal antihistamine for allergic rhinitis
• Common side effects include bitter taste, epistaxis, somnolence, and headache 5
• The safety profile is generally favorable compared to systemic medications

Clinical Application

For patients interested in COVID-19 prevention:

1. Emphasize that vaccination remains the primary recommended preventive measure
2. Consider that while promising, azelastine is not yet included in clinical guidelines for COVID-19 prophylaxis
3. If using azelastine off-label, the studied regimen was 0.1% nasal spray three times daily 1

For patients interested in influenza prevention:

1. Recommend annual influenza vaccination as the primary preventive strategy
2. For high-risk individuals requiring chemoprophylaxis, use FDA-approved antivirals like oseltamivir
3. Do not recommend azelastine specifically for influenza prevention due to insufficient clinical evidence

Conclusion

While emerging research suggests azelastine may have antiviral properties against SARS-CoV-2 and potentially other respiratory viruses, it is not currently recommended in clinical guidelines for either COVID-19 or influenza prophylaxis. The most recent evidence from a phase 2 trial shows promise for COVID-19 prevention, but larger confirmatory studies are needed before this becomes standard practice.