Ketamine Beat Placebo for Nerve Pain. Twelve of the Fifteen Trials Stopped Measuring During the Infusion
A new meta-analysis says intravenous ketamine beats placebo for chronic nerve pain. Clinical Pain Advisor covered the finding this week. The number that should interest clinic owners is not the headline result. It is how long the trials bothered to keep measuring.
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| Key Takeaway | Detail |
|---|---|
| The study | 15 randomized trials, 251 patients, published in Pain Management on August 11 |
| The headline result | Ketamine nearly tripled the rate of a 50 percent pain cut, RR 2.79 |
| The actual sample | The primary meta-analysis pooled 6 trials and 135 patients |
| The number rarely printed | The 95 percent prediction interval runs 0.80 to 9.71, crossing 1 |
| Side effects | More frequent on ketamine, RR 3.27, though mild and transient |
| The measurement gap | 12 of the 15 trials stopped measuring during or just after the infusion |
What the Researchers Did
A team at the Federal University of Bahia in Brazil searched PubMed, Cochrane CENTRAL and EMBASE through March 2026. They wanted randomized trials of intravenous ketamine against placebo in adults with chronic neuropathic pain.
Fifteen trials met the bar, covering 251 randomized patients. Doses ranged from 60 micrograms per kilogram up to 1 milligram per kilogram. The review was registered in advance on PROSPERO.
The paper is published in Pain Management. Response was defined as a 50 percent or greater drop in pain on a 0 to 100 visual analogue scale.
The Headline Number Rests on 135 Patients
Fifteen trials sounds like a solid evidence base. The primary outcome analysis used six of them.
Those six trials contributed 135 patients in total. Sixty three received ketamine and 72 received saline. That is the entire foundation of the pooled efficacy result.
Within that pool, ketamine performed well. Patients on ketamine were nearly three times as likely to report their pain cut in half, a relative risk of 2.79.
A subgroup using an identical 400 microgram per kilogram dose did better still, at 5.68. That subgroup was three trials and 73 patients.
The Prediction Interval Is the Number to Read
The confidence interval on that main result runs from 1.47 to 5.30. It does not cross 1, so the finding is statistically significant.
The prediction interval runs from 0.80 to 9.71. It does cross 1.
Those two numbers answer different questions. The confidence interval describes the average effect across the trials already run. The prediction interval estimates what the next trial, in a new setting with a new population, would likely find.
A prediction interval that crosses 1 means a new clinic population could see no benefit at all. The review authors flagged this themselves, noting the effect may vary by clinical setting.
There is a real counterpoint, and it deserves equal weight. The reviewers reran the analysis with one high risk of bias study removed. The effect got stronger, at 4.64, and the prediction interval moved to 1.53 through 14.11.
That version no longer crosses 1, and the heterogeneity between studies fell to zero. Read generously, the weak trial was dragging the estimate down. Read cautiously, a result that swings on one study is a result built on very few patients.
Side Effects Were the Steadier Signal
Adverse events came in at a relative risk of 3.27, with a prediction interval of 1.67 to 6.40. That interval does not cross 1.
In plain terms, the side effects are the more statistically reliable finding here than the pain relief. That is an unusual thing to be able to say about a treatment.
It is not an alarming finding on its own. The events reported were dizziness, drowsiness and nausea, and the authors describe them as generally mild and transient. Nothing here suggests the infusions are dangerous.
It does mean the consent conversation has firmer ground under it than the efficacy pitch does.
Twelve of Fifteen Trials Stopped Measuring Early
This is the finding that matters most for anyone running a pain program.
In 12 of the 15 trials, pain was assessed only at baseline and during the infusion, or a few minutes after it finished. The reviewers say this prevented any evaluation of a delayed effect.
So the strongest available evidence for ketamine in neuropathic pain largely describes how patients feel while the drip is running.
That is a real result. It is not the result most pain clinics are selling. A series of six infusions over three weeks rests on a durability claim this literature does not yet test.
How This Sits Against the Other Pain Data
We have covered several individual pain studies that reach past the infusion window.
A Toronto trial ran three infusions across twelve weeks and tracked patients well beyond the chair. A retrospective review followed 92 fibromyalgia patients across 24 months on roughly two infusions a year.
Separate work has suggested ketamine may relieve pain without relying on dissociation, and cluster headache has its own emerging trial record.
None of that is overturned by this review. The review simply shows how thin the randomized, placebo-controlled core is once you pool only what qualifies.
What a Pain Program Should Take From It
Three practical things follow.
The 400 microgram dose has the cleanest signal. Three trials used it identically and showed no heterogeneity between them. That is worth knowing when protocols get compared.
Durability claims need your own data. If a program sells a multi-infusion course for chronic pain, the published literature will not support the durability argument. Outcome tracking inside the clinic will.
Lead with the consent conversation. The adverse event profile is well characterized and mild. Saying so plainly costs nothing and builds more trust than overselling the relief.
The Bottom Line
This is a real finding and a genuinely positive one for ketamine. Patients got meaningful relief more often than patients on saline did.
It is also 135 patients, measured mostly during the infusion, with a prediction interval that leaves room for no effect at all. The authors were direct about it, calling for larger and longer studies.
Referrers who read the primary literature will know all of this. Clinics that know it too are in a stronger position than clinics quoting the headline.
Patients looking for supervised care can start with our directory of verified ketamine clinics.
This article is for informational purposes and is not medical advice. Ketamine is not FDA approved for the treatment of chronic pain.
