Antiviral Properties of Azelastine
There is recent evidence that azelastine has broad-spectrum antiviral activity against respiratory viruses including SARS-CoV-2, influenza, RSV, and human coronaviruses. 1
Evidence for Azelastine's Antiviral Properties
Azelastine hydrochloride has demonstrated in vitro antiviral activity against multiple respiratory viruses, including SARS-CoV-2 (including the Omicron variant), seasonal human coronavirus 229E, and Respiratory Syncytial Virus A (RSV A) 1
In a human 3D nasal tissue model, azelastine hydrochloride protected tissue integrity and function from influenza A H1N1 infection and reduced viral load shortly after infection 1
A recent phase 2 clinical trial (2023-2024) found that azelastine nasal spray significantly reduced the incidence of PCR-confirmed SARS-CoV-2 infections compared to placebo (2.2% vs 6.7%) when used as prophylaxis 2
The same trial also demonstrated that azelastine reduced the incidence of rhinovirus infections (1.8% vs 6.3%) compared to placebo, suggesting broader antiviral effects 2
A 2021 study identified azelastine as having direct antiviral activity against SARS-CoV-2 in vitro, along with other antihistamines like diphenhydramine and hydroxyzine 3
Mechanism of Action
While azelastine is primarily known as a second-generation H1-receptor antagonist used for allergic rhinitis 4, its antiviral mechanism appears to be separate from its antihistamine effects
Azelastine may bind to Angiotensin Converting Enzyme-2 (ACE2) and the sigma-1 receptor as off-targets, which could contribute to its antiviral properties 3
Beyond its antihistamine effects, azelastine also inhibits the production or release of many chemical mediators involved in allergic responses, including leukotrienes, free radicals, and cytokines 5
Clinical Implications
Azelastine nasal spray is FDA-approved for allergic rhinitis and vasomotor rhinitis, not specifically for antiviral purposes 4
The standard dosing for allergic rhinitis is 1-2 sprays per nostril twice daily for patients 6 years and older 4
Common side effects include bitter taste (reported in 19.7% of patients), somnolence (11.5%), epistaxis, and headache 4, 6
In the COVID-19 prophylaxis trial, azelastine was administered as 0.1% nasal spray three times daily, with adverse events comparable to placebo 2
Limitations and Considerations
While promising, the antiviral properties of azelastine have primarily been demonstrated in laboratory studies and limited clinical trials 1, 2
Current clinical guidelines for influenza management do not mention azelastine as an antiviral agent, instead recommending neuraminidase inhibitors like oseltamivir and zanamivir for treatment and prophylaxis 4
The 2023-2024 clinical trial showing prophylactic efficacy against SARS-CoV-2 was conducted at a single center and requires confirmation in larger, multicentric trials 2
When considering azelastine for allergic rhinitis, clinicians should be aware of potential sedative properties compared to placebo, though these effects tend to be milder than first-generation antihistamines 4