Researchers have identified a low-cost antidepressant drug called fluvoxamine that can help save the lives of COVID-19 patients and cut hospital admissions by up to 30 per cent.

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The team led by McMaster University, described fluvoxamine as "a game-changer" for poorer countries with low access of COVID vaccines, in the study published in The Lancet Global Health. Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI), currently used to treat mental health conditions such as depression and obsessive-compulsive disorders. It was chosen for study as a potential treatment for COVID-19 due to its anti-inflammatory properties, said researchers.

"Fluvoxamine is, so far, the only treatment that, if administered early, can prevent COVID-19 from becoming a life-threatening illness. It could be one of our most powerful weapons against the virus and its effectiveness is one of the most important discoveries we have made since the pandemic began," said Edward Mills, Professor at McMaster University's Department of Health Research

"Fluvoxamine may reduce the production of inflammatory molecules called cytokines that can be triggered by SARS-CoV-2 infection," added Dr Angela Reiersen, Associate Professor of Psychiatry at Washington University in St. Louis. The study is part of an ongoing trial to investigate the efficacy of eight repurposed treatments for COVID-19 among high-risk adult outpatients.

About 739 Brazilian COVID-19 patients were randomly selected for treatment with fluvoxamine, while another 733 received a placebo, between January 15 to August 6 of this year. The patients who received fluvoxamine during the trial were tracked for 28 days.

Researchers found about a 30 per cent reduction in hospitalisations among those receiving fluvoxamine compared to those receiving the placebo. This effect went up to 65 per cent among patients taking all of their drugs.

Fluvoxamine is cheap, costing about $4 per 10-day course, and is an easily-accessible which could turn out to be a game-changer for poorer countries with low vaccination rates and lacking access to more advanced COVID-19 therapies, Mills said.

However, while fluvoxamine is widely available, it is not on the World Health Organisation's Essential Medicines List. A closely related SSRI, fluoxetine, is on this list, and it is now crucial to establish if these drugs can be used interchangeably for COVID-19, as well as determining whether combining fluvoxamine with other drugs will provide a larger treatment effect, the researchers said.

Fluvoxamine has been used since the 1990s for various conditions and its safety profile is well-known. It was identified early in the pandemic for its potential to reduce the cytokine storm in COVID-19 patients. Cytokine storms are severe immune responses to COVID-19 that can cause potentially lethal organ damage.

Although mortality was not a primary outcome of the study, in a secondary "per protocol" analysis of patients who took at least 80 per cent of medication doses, there was one death in the fluvoxamine group, compared to 12 in the placebo group, the study showed.