Metformin Shows Promise in Reducing Long COVID Risk, Studies Suggest
An editorial commentary published in Clinical Infectious Diseases has reviewed evidence from large randomized clinical trials and real-world analyses, highlighting the potential of metformin – a common diabetes drug – to reduce the long-term effects of COVID-19. The commentary supports the safety and efficacy of early metformin administration in mitigating the risk of post-COVID-19 condition, commonly known as long COVID, following SARS-CoV-2 infection.
Understanding Long COVID
Long COVID is characterized by persistent symptoms that can last months or even years after the initial infection. These debilitating symptoms include fatigue, shortness of breath, chest pain, and cognitive impairment. Researchers worldwide have intensified their focus on understanding these symptoms, their underlying mechanisms, and, crucially, effective preventive measures.
Metformin's Unexpected Antiviral Potential
While primarily known as a diabetes medication, metformin has demonstrated antiviral properties in laboratory studies. These effects are attributed to its influence on immune function and cellular metabolism. Historically, biguanides, the drug class to which metformin belongs, were explored for treating various viruses and malaria. Its inherent advantages—low cost, widespread availability, a strong safety profile, and no requirement for extensive monitoring during short-term use—made it an attractive candidate for COVID-19 clinical trials.
Key Clinical Trial Results
The COVID-OUT Trial
The COVID-OUT Trial, initiated in July 2021, rigorously assessed early treatments for long COVID. Findings from this trial indicated that metformin reduced the risk of long COVID by 41% over a 10-month period. Notably, participants who began metformin within three days of symptom onset experienced an even greater reduction of 63%. The trial also provided evidence that metformin effectively reduced viral load.
Confirming Findings with ACTIV-6
A separate, large randomized trial, ACTIV-6, was conducted to confirm these findings in a more diverse patient population. This included individuals with normal BMI and those with prior COVID-19 infection. Utilizing the same metformin dose and administration schedule as COVID-OUT, ACTIV-6 estimated a 50% lower risk of clinician-diagnosed long COVID. While the uncertainty interval was wide, this result strongly supported the earlier COVID-OUT findings.
An Excellent Safety Profile
Both trials consistently reported that metformin did not lead to significant gastrointestinal issues or notable safety concerns. Instances of low blood sugar were rare and occurred less frequently in the metformin groups compared to placebo groups.
Conclusion and Recommendations
Two large randomized controlled trials, supported by electronic health record analyses, suggest that metformin taken during acute COVID-19 infection can reduce the risk of clinician-diagnosed long COVID by approximately 40% to 50%.
While long COVID was a secondary outcome in both studies, and some statistical uncertainty naturally exists, the consistency of these results across diverse populations and analytical approaches is compelling.
Given its established safety, demonstrated efficacy, low cost, wide availability, good tolerability, and lack of interactions with other COVID-19 treatments, the authors of the commentary advocate for offering metformin to outpatients with acute COVID-19 as a preventive option. This proactive approach holds the potential to significantly reduce the burden of long COVID on both individuals and global healthcare systems.