For millions of people living with the aftermath of a COVID-19 infection, the most grueling symptom isn’t a lingering cough or a loss of taste—it is a profound, systemic exhaustion that refuses to lift. This debilitating fatigue, a hallmark of Long COVID, often renders basic daily activities impossible, leaving patients trapped in a cycle of exertion and collapse.
New evidence suggests a potential path forward. A randomized, adaptive trial has found that fluvoxamine shows promise for Long COVID fatigue, significantly reducing the severity of exhaustion and improving the overall quality of life for affected adults compared to a placebo.
As a physician, I have seen how “supportive care”—the current standard of treatment—often feels like a dismissal to patients. Telling a patient to “pace themselves” is necessary, but it is not a cure. The results of this study, published in the Annals of Internal Medicine, represent a shift toward targeted pharmacological intervention for post-acute sequelae of SARS-CoV-2 (PASC).
The study focused on 399 adults across 22 outpatient sites in Brazil who had suffered from persistent fatigue for at least 90 days following a confirmed infection. Researchers tested two different medications: fluvoxamine, an antidepressant with unique anti-inflammatory properties, and metformin, a common type of medication used to treat type 2 diabetes.
The biological battle against exhaustion
To understand why fluvoxamine might work where other treatments fail, it is necessary to look at the complex biology of Long COVID. The condition is not caused by a single factor but is likely a combination of persistent viral fragments remaining in the body, immune system dysregulation, damage to the lining of blood vessels (endothelial dysfunction), and mitochondrial impairment—the failure of the cell’s “power plants” to produce energy.
Fluvoxamine is known as a selective serotonin reuptake inhibitor (SSRI), but its role here extends beyond mood. It acts as an agonist for the sigma-1 ($sigma$-1) receptor, which helps regulate the body’s inflammatory response and protects cells from oxidative stress. By modulating this receptor, fluvoxamine may dampen the chronic inflammation that contributes to the “brain fog” and physical lethargy associated with the condition.
Metformin was included in the trial because of its known anti-inflammatory and mitochondrial-modulating effects. While some earlier research suggested metformin might reduce the risk of developing Long COVID if taken during the acute phase of infection, this trial sought to determine if it could treat the fatigue once it had already become chronic.
Trial outcomes and the “superiority” finding
The trial utilized an adaptive design, meaning the researchers could adjust the study based on interim results to ensure efficiency and patient safety. The primary measure of success was the change in the Fatigue Severity Scale (FSS), a validated tool used to quantify how much fatigue interferes with daily life.
The results were stark. Participants receiving fluvoxamine (100 mg twice daily) showed a statistically significant reduction in fatigue by day 60, an improvement that remained sustained through day 90. These patients reported consistent improvements in their general quality of life.
Metformin, however, provided no meaningful benefit. In fact, the metformin arm of the study was stopped early for futility, as the data indicated it was unlikely to meet the primary goal of reducing fatigue. Conversely, the fluvoxamine arm was stopped early for superiority, meaning the drug performed so much better than the placebo that it was deemed unethical to continue denying the placebo group the treatment.
| Treatment Group | Dosage | Primary Outcome (Fatigue) | Adverse Event Rate |
|---|---|---|---|
| Fluvoxamine | 100 mg (2x daily) | Significant Reduction | 20.0% |
| Metformin | 750 mg (2x daily) | No Meaningful Benefit | 28.8% |
| Placebo | N/A | No Significant Change | 29.7% |
Safety data also favored the fluvoxamine group, which reported fewer adverse events than both the metformin and placebo groups. Serious adverse events remained rare across all three cohorts.
Necessary cautions for clinical application
While these findings are encouraging, they must be viewed through a lens of clinical caution. The study had several limitations that prevent it from being a definitive “cure.” First, the follow-up period was only 90 days, leaving the long-term durability of the improvement unknown.
There is also the question of subjectivity. Because fatigue was measured via a self-reported scale, the results can be influenced by the participants’ perceptions. More importantly, while patients with major depressive disorder were excluded, those with general depressive symptoms were included. This creates a clinical ambiguity: it is unclear if the fluvoxamine reduced fatigue directly through its anti-inflammatory action or indirectly by improving the patients’ mood.
Finally, the study population was recruited exclusively in Brazil. While the biological drivers of Long COVID are likely universal, geographic and genetic homogeneity can sometimes limit how well results generalize to global populations.
What this means for patients
For those currently struggling with Long COVID, these results suggest that fluvoxamine is a viable candidate for discussion with a healthcare provider. However, it is not a “one size fits all” solution. The absence of benefit from metformin indicates that not all anti-inflammatory or mitochondrial-targeting drugs are effective for this specific symptom.
Patients should avoid self-medicating with SSRIs, as these medications require careful titration and monitoring for side effects, particularly in those with pre-existing mood disorders or those taking other medications.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
The next phase of research will likely move toward identifying biological markers—such as specific cytokines or mitochondrial proteins—to predict which patients are most likely to respond to fluvoxamine. By moving toward a personalized medicine approach, clinicians hope to match the right drug to the right biological driver of fatigue.
We invite you to share your experiences with Long COVID recovery in the comments below and share this update with others seeking evidence-based treatment options.
