As the world continues to seek effective strategies to prevent COVID-19 infection, an intriguing candidate has emerged from the ranks of common allergy medications: azelastine nasal spray. Known primarily as an antihistamine used for allergic rhinitis, recent research suggests it may also play a role in reducing the risk of SARS-CoV-2 infection.

The Science Behind Azelastine and COVID-19

In early 2021, researchers began exploring how various antihistamines might interact with the SARS-CoV-2 virus. Molecular docking studies predicted that azelastine could bind to the sigma-1 receptor, a site implicated in the virus’s entry into human cells. Laboratory experiments supported this idea, showing that azelastine exhibited antiviral activity against the virus in vitro.

While lab results are promising, clinical effectiveness requires evidence from well-designed human trials. That’s where a recent phase 2 randomized, double-blind, placebo-controlled trial in Germany steps in.

The Contain Trial: Evaluating Azelastine for COVID-19 Prevention

This study enrolled 450 healthy adults, aged 18 to 65, all confirmed negative for SARS-CoV-2 at baseline. Participants were randomized to receive either:

• Azelastine nasal spray (0.1%), or
• Placebo nasal spray

The spray was administered three times daily for 56 days. Additionally, if participants developed symptoms or had confirmed exposure to COVID-19, dosing was increased temporarily.

Twice weekly, participants were tested for SARS-CoV-2 using rapid antigen tests, with PCR confirmation for any positives.

Key Findings:

• Infection Rates: Only 2.2% of the azelastine group contracted COVID-19, compared to 6.7% in the placebo group.
• This translates to a 69% reduction in odds of infection with azelastine use.
• Time to infection was longer in the treatment group, and duration of positivity shorter.
• Symptomatic infection rates were also lower in the azelastine group.
• Relative Risk Reduction: 67.3% — the chance of getting COVID-19 was reduced by two-thirds.
• Absolute Risk Reduction: 4.53% — meaning about 5 fewer cases per 100 people treated.
• Number Needed to Treat (NNT): 23 — you’d need to treat 23 people with azelastine for 56 days to prevent one infection.

Safety and Side Effects

Azelastine was generally well tolerated. Interestingly, the placebo group experienced more overall adverse events, likely due to more infections. However, nasal-related side effects like nosebleeds and bitter taste were higher in the azelastine group.

It’s worth noting that azelastine is less anticholinergic than some other antihistamines (like diphenhydramine) and does not cross the blood-brain barrier, potentially reducing long-term risks.

What’s Inside the Spray?

The active ingredient is azelastine hydrochloride, an antihistamine. The spray also contains benzalkonium chloride, a preservative with antimicrobial properties. While some wondered if this preservative might contribute to the antiviral effect, similar nasal sprays with this additive have not consistently shown benefit in COVID-19 prevention.

Availability and Usage

The 0.1% azelastine nasal spray used in the trial is prescription-only and typically dosed twice daily for allergies. However, an over-the-counter version (Astelin or Astepro) exists at a higher concentration (0.15%) and is used once daily, making it more convenient.

What Does This Mean for You?

While vaccination remains the cornerstone of COVID-19 prevention, adjunctive therapies like azelastine nasal spray may offer additional protection, especially in high-risk settings or for those with allergies.

The trial’s results are encouraging, showing significant reduction in infection rates with a well-known, accessible medication. However, further research is needed to confirm long-term safety and efficacy.

Final Thoughts

The azelastine nasal spray story highlights the potential of repurposing existing drugs to tackle new health challenges. If you’re considering azelastine for COVID-19 prevention, consult your healthcare provider to weigh benefits and risks.

LINKS / REFERENCES: Azelastine Nasal Spray for Prevention of SARS-CoV-2 Infections (JAMA) | https://jamanetwork.com/journals/jama…

Identification of antiviral antihistamines for COVID-19 repurposing (Biochemical and Biophysical Research Communications) | https://www.sciencedirect.com/science…

Early intervention with azelastine nasal spray may reduce viral load in SARS-CoV-2 infected patients (Nature) | https://www.nature.com/articles/s4159…

Absolute Risk Reduction versus Relative Risk Reduction: Is One Better for COVID vaccines? (MedCram) |    • Absolute Risk Reduction versus Relative Ri…