A common antidepressant appears to help reduce fatigue in people living with long COVID, a new study says.

Fluvoxamine – a low-cost and widely available antidepressant – significantly improved fatigue among long COVID patients within two to three months, researchers reported March 31 in the Annals of Internal Medicine.

“This is an important step forward for patients who have been desperate for evidence‑based options,” senior researcher Edward Mills, a professor at McMaster University in Ontario, Canada, said in a news release.

“Fluvoxamine showed consistent and meaningful benefits, and because it's already widely used and well understood, it has clear potential for clinical use,” he said.

Fatigue is the most common and debilitating symptom of long COVID, researchers said in background notes.

For the new study, they recruited nearly 400 adults in Brazil who continued to experience fatigue for at least three months after they’d become infected with COVID.

Participants were randomly asked to take fluvoxamine (Luvox); the diabetes medication metformin; or a placebo for 60 days.

“We wanted to test whether two existing, widely available and affordable medications could help,” Mills said. “Both had biological reasons to think they might work against long COVID fatigue, but neither had been rigorously tested for this purpose in a proper clinical trial.”

Fluvoxamine reduced fatigue more than a placebo, with researchers finding a 99% probability that it outperformed the placebo.

However, metformin did not offer any meaningful benefit against long COVID-related fatigue, even though it’s been shown to reduce the risk of long COVID when taken during infection, researchers said.

“This trial gives clinicians their first strong evidence for a medication that helps reduce long COVID fatigue. Patients want something they can try today – and this finding brings us closer to that reality,” investigator Jamie Forrest, a postdoctoral research fellow at the University of British Columbia, said in a news release.

Despite these findings, researchers said more study is needed to understand who would benefit most from fluvoxamine and how the drug works to ease fatigue among long COVID patients.