COVID-19 treatment: respiratory tract administration

Over 9,000 compounds predicted to reduce COVID-19 risk. SARS-CoV-2 is easily disabled. SARS-CoV-2 infection and replication involves a complex interplay of over 200 host and viral proteins and other factors1-8, providing many therapeutic targets. Scientists have identified 9,702+ compounds9 potentially beneficial for COVID-19. Hundreds of compounds inhibit SARS-CoV-2 in vitro, including many with known pharmacokinetics and proven safety.

Naso/oropharyngeal treatment is effective. Many compounds with existing safety records are expected to be beneficial within the upper respiratory tract. 81 clinical studies show lower risk for early treatment or prophylaxis with povidone-iodine, alkalinization, nitric oxide, iota-carrageenan, phthalocyanine, hydrogen peroxide, chlorhexidine, NaCl, cetylpyridinium chloride, and chlorpheniramine11-96, confirmed in multiple additional meta analyses97-100. Studies show a degree of efficacy even with delayed treatment. Targeted administration to the respiratory tract has several advantages:

Studies use various administration methods including nasal and oral sprays, nasal irrigation, oral rinses, and inhalation. Combined nasal and oral application shows the highest efficacy. Efficacy depends on administration details, e.g., viscosity, mucoadhesion, sprayability, and the angle of administration for sprays101. Some treatments may disrupt beneficial microbial populations, requiring care to avoid side effects and suggesting a preference for more selective treatments, especially with longer-term use(b).

Only 4% of studies we cover used direct naso/oropharyngeal treatment, despite the strong potential and advantages. With focused research, safe, inexpensive, and effective naso/oropharyngeal treatments may be rapidly identified after discovery of new respiratory pathogens.

Many other treatments may be effective including azelastine102,103, astodrimer sodium104-107, benzalkonium chloride108, CDCM109,110, dequalinium chloride108, hypochlorous acid109, hexadecyl pyridinium chloride111, ethyl lauroyl arginate112, Sinomarin45, PCANS113, SA58114-117, ColdZyme118, Panthexyl119, HH-120120,121, TriSb92122, IBIO123123, homoharringtonine124, A8G6125,126, STI-9167127, FSY-ACE2-NVs nanoSpray128, and Sentinox129.

Naso/oropharyngeal treatments experience regulatory challenges. For example the US FDA shut down a povidone-iodine treatment130 at a time when 7 RCTs indicated efficacy. The FTC sent warning letters to companies that referenced studies showing benefits of nasal/oral hygiene for COVID-19131-133. Similarly, the FDA has failed to approve SaNOtize134, although it is available in many other countries135.

Naso/oropharyngeal treatment reduces transmission. Immediate or prophylactic naso/oropharyngeal treatment also logically reduces transmission. A 621 patient RCT showed 92% reduction in transmission with nasal and oropharyngeal sprays containing povidone-iodine and glycyrrhizic acid18.

Protocols typically combine multiple treatments. No single treatment is guaranteed to be effective and safe for a specific individual. Leading evidence-based protocols combine multiple treatments.

Complementary and synergistic actions. There are many complementary mechanisms of action across treatments, and studies show complementary and synergistic effects with polytherapy137-153. For example, Jitobaom et al.138 shows >10x reduction in IC₅₀ with ivermectin and niclosamide, an RCT by Said et al.145 showed the combination of nigella sativa and vitamin D was more effective than either alone, and an RCT by Wannigama et al.154 showed improved results with fluvoxamine combined with additional treatments, compared to fluvoxamine alone. Treatment efficacy may vary significantly across SARS-CoV-2 variants. For example new variants may gain resistance to targeted treatments155-161, and the role of TMPRSS2 for cell entry differs across variants162. The efficacy of specific treatments varies depending on cell type163 due to differences in viral receptor expression, drug distribution and metabolism, cell-specific mechanisms, and the relevance of drug targets to specific cells. Efficacy may also vary based on genetic variants164-169. Variable efficacy across SARS-CoV-2 variants, cell types, different tissues, and host genetics, along with the complementary and synergistic actions of different treatments, all point to greater efficacy with polytherapy. In many studies, the standard of care given to all patients includes other treatments—efficacy seen in these trials may rely in part on synergistic effects. Meta analysis of all early treatment trials shows 68% [57‑77%] lower risk for studies using combined treatments, compared to 33% [30‑36%] for single treatments.

SARS-CoV-2 evolution and the risk of escape mutants suggests treatments with broader mechanisms of action and polytherapy. SARS-CoV-2 can rapidly acquire mutations altering infectivity, disease severity, and drug resistance even without selective pressure170. Antigenic drift can undermine more variant-specific treatments like monoclonal antibodies and more specific antivirals. Treatment with targeted antivirals may select for escape mutations171. Less variant specific treatments and polytherapy targeting multiple viral and host proteins may be more effective.