From the Journals

Metformin fails as early COVID-19 treatment but shows potential



Neither metformin, ivermectin, or fluvoxamine had any impact on reducing disease severity, hospitalization, or death from COVID-19, according to results from more than 1,000 overweight or obese adult patients in the COVID-OUT randomized trial.

However, metformin showed some potential in a secondary analysis.

Early treatment to prevent severe disease remains a goal in managing the ongoing COVID-19 pandemic, and biophysical modeling suggested that metformin, ivermectin, and fluvoxamine may serve as antivirals to help reduce severe disease in COVID-19 patients, Carolyn T. Bramante, MD, of the University of Minnesota, Minneapolis, and colleagues wrote.

Metformin tablets Thinglass/iStock Editorial/Getty Images

“We started enrolling patients at the end of December 2020,” Dr. Bramante said in an interview. “At that time, even though vaccine data were coming out, we thought it was important to test early outpatient treatment with widely available safe medications with no interactions, because the virus would evolve and vaccine availability may be limited.”

In a study published in the New England Journal of Medicine, the researchers used a two-by-three factorial design to test the ability of metformin, ivermectin, and fluvoxamine to prevent severe COVID-19 infection in nonhospitalized adults aged 30-85 years. A total of 1,431 patients at six U.S. sites were enrolled within 3 days of a confirmed infection and less than 7 days after the start of symptoms, then randomized to one of six groups: metformin plus fluvoxamine; metformin plus ivermectin; metformin plus placebo; placebo plus fluvoxamine; placebo plus ivermectin; and placebo plus placebo.

A total of 1,323 patients were included in the primary analysis. The median age of the patients was 46 years, 56% were female (of whom 6% were pregnant), and all individuals met criteria for overweight or obesity. About half (52%) of the patients had been vaccinated against COVID-19.

The primary endpoint was a composite of hypoxemia, ED visit, hospitalization, or death. The analyses were adjusted for COVID-19 vaccination and other trial medications. Overall, the adjusted odds ratios of any primary event, compared with placebo, was 0.84 for metformin (P = .19), 1.05 for ivermectin (P = .78), and 0.94 for fluvoxamine (P = .75).

The researchers also conducted a prespecified secondary analysis of components of the primary endpoint. In this analysis, the aORs for an ED visit, hospitalization, or death was 0.58 for metformin, 1.39 for ivermectin, and 1.17 for fluvoxamine. The aORs for hospitalization or death were 0.47, 0.73, and 1.11 for metformin, ivermectin, and fluvoxamine, respectively. No medication-related serious adverse events were reported with any of the drugs during the study period.

The possible benefit for prevention of severe COVID-19 with metformin was a prespecified secondary endpoint, and therefore not definitive until more research has been completed, the researchers said. Metformin has demonstrated anti-inflammatory actions in previous studies, and has shown protective effects against COVID-19 lung injury in animal studies.

Previous observational studies also have shown an association between metformin use and less severe COVID-19 in patients already taking metformin. “The proposed mechanisms of action against COVID-19 for metformin include anti-inflammatory and antiviral activity and the prevention of hyperglycemia during acute illness,” they added.

The study findings were limited by several factors including the population age range and focus on overweight and obese patients, which may limit generalizability, the researchers noted. Other limitations include the disproportionately small percentage of Black and Latino patients and the potential lack of accuracy in identifying hypoxemia via home oxygen monitors.

However, the results demonstrate that none of the three repurposed drugs – metformin, ivermectin, and fluvoxamine – prevented primary events or reduced symptom severity in COVID-19, compared with placebos, the researchers concluded.

“Metformin had several streams of evidence supporting its use: in vitro, in silico [computer modeled], observational, and in tissue. We were not surprised to see that it reduced emergency department visits, hospitalization, and death,” Dr. Bramante said in an interview.

The take-home message for clinicians is to continue to look to guideline committees for direction on COVID-19 treatments, but to continue to consider metformin along with other treatments, she said.

“All research should be replicated, whether the primary outcome is positive or negative,” Dr. Bramante emphasized. “In this case, when our positive outcome was negative and secondary outcome was positive, a confirmatory trial for metformin is particularly important.”


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