The largest ketamine data set for fibromyalgia yet shows durable relief in a third of patients

Fibromyalgia sits entirely outside ketamine's labeled indications, and formulary and prior-authorization decisions for this off-label use have rested on studies of 34 patients or fewer. A new 92-patient retrospective with two years of follow-up is the largest and longest such dataset yet, and it shows both a durable benefit for some patients and a hard ceiling on how many respond at all.

Ketamine has no FDA-labeled indication for fibromyalgia, and every prior study supporting its off-label use in this condition enrolled somewhere between 11 and 34 patients, too small a base for the kind of formulary and prior-authorization decisions payers and prescribers are already making around it. A new retrospective from Leonardo Kapural and colleagues at the Carolinas Pain Institute, published in the Journal of Pain Research, is considerably larger and longer than anything that came before it: 92 patients, followed for a minimum of two years, tracking repeated single-day IV ketamine infusions rather than a single dose.

What the data shows

Median baseline pain score was 8 out of 10. That fell to 5 at three months and, notably, stayed at 5 through the full 24-month follow-up, a durability signal this population’s prior literature never had the follow-up length to test. At three months, 32 of the 92 patients, about a third, reported more than 50 percent pain relief; at 24 months, 30 of 92 still did, a strikingly stable response rate over two years rather than the fading effect this desk has flagged in other ketamine literature. Patients received between one and 32 infusions over the study period, averaging roughly one every six months, a real-world dosing pattern rather than a fixed protocol.

Nineteen patients, about one in five, reported minimal or no benefit at all.

The opioid signal

Thirty-three of the 92 patients were on opioids at baseline, with a median morphine sulfate equivalent dose of 30 milligrams daily. By 24 months, that number had fallen to 27. This is a retrospective chart review, not a controlled trial designed to test opioid-sparing effects directly, and the study cannot establish that ketamine caused that reduction rather than other concurrent factors in these patients’ care. It is still a specific data point in a population where opioid reduction is a clinical and payer priority, and it is consistent with the broader pattern this desk has tracked across ketamine’s off-label pain applications.

Why the size and duration matter more than the topline number

A third of patients sustaining meaningful pain relief for two years matters, but the more useful contribution of this study is what it lets a reader do with the number. Every prior study in this specific population was too small and too short to say whether an initial response would hold up, fade, or require dose escalation over time. This dataset, precisely because it tracked 92 patients with a substantially long follow-up window and real-world, variable dosing intervals, gives prescribers and payers something the smaller studies could not: a durability curve, not a single snapshot.

The caveats

This is a retrospective, single-site chart review with no control group, meaning it cannot establish that ketamine specifically, rather than concurrent care, patient selection, or regression to the mean, produced the observed pain reduction or the opioid reduction. Fibromyalgia remains entirely off-label for ketamine, and this study does not change that regulatory status; it adds real-world evidence to a formulary conversation that will continue to happen without FDA involvement either way. Nineteen non-responders out of 92 is a substantial fraction, and this study offers no way to predict in advance which patients will fall into that group.

This desk has spent the year reading ketamine’s expanding footprint across pain indications with the same question each time: what does the evidence support, and for whom. This dataset doesn’t resolve that question for fibromyalgia specifically, but it meaningfully raises the evidentiary floor, replacing a literature of small, short studies with the first close look at what happens to a substantial patient population over two full years of real-world use. That is exactly the kind of evidence formulary committees and prior-authorization reviewers have been missing, and exactly the kind of evidence this desk will keep watching for as ketamine’s off-label pain indications continue to accumulate real-world data faster than the label itself expands.