Ketamine for Chronic Pain: What the Evidence Shows

Most people who've heard of ketamine therapy associate it with depression. And the evidence for depression is strong — I've written about it extensively. But ketamine's role in pain management actually predates its psychiatric applications, and the evidence for chronic pain is substantial and growing.

For patients living with chronic pain who haven't found adequate relief from conventional treatments — or who want to reduce their reliance on opioids — ketamine deserves a serious look.

Why Ketamine Works for Pain

Ketamine's analgesic properties come from several mechanisms:

NMDA receptor antagonism. This is the big one. NMDA receptors play a central role in a process called central sensitization — essentially, the nervous system becoming amplified so that normal signals are perceived as painful, and painful signals are perceived as more intense. This is the mechanism behind many chronic pain conditions, particularly neuropathic pain. Ketamine blocks these receptors, effectively turning down the volume on an overamplified pain system.

Anti-inflammatory effects. Emerging research suggests ketamine has direct anti-inflammatory properties, reducing neuroinflammation that contributes to chronic pain states.

Opioid receptor interaction. Ketamine has some activity at opioid receptors, providing additional analgesic effects through a separate pathway.

Descending pain modulation. Ketamine appears to enhance the brain's own pain-suppression pathways, helping restore the balance between pain signals going up to the brain and inhibitory signals coming down.

Neuroplasticity. The same synaptogenesis that helps with depression — the formation of new neural connections — may help the pain processing system "reset" away from chronic pain patterns.

This multi-mechanism approach is part of what makes ketamine valuable for pain. Unlike opioids, which simply mask pain perception without addressing the underlying neural dysfunction, ketamine actually modulates the pain processing system itself.

Which Pain Conditions Respond Best

The evidence is strongest for certain types of chronic pain:

Neuropathic Pain

This is where ketamine shines. Neuropathic pain — caused by nerve damage or dysfunction — is notoriously difficult to treat with conventional medications. Conditions include diabetic neuropathy, post-herpetic neuralgia, chemotherapy-induced neuropathy, and nerve injury pain.

The central sensitization that drives neuropathic pain is heavily dependent on NMDA receptors, making it a natural target for ketamine. Multiple studies have shown significant pain reduction in neuropathic pain patients treated with ketamine, with effects lasting well beyond the drug's direct action.

Complex Regional Pain Syndrome (CRPS)

CRPS is one of the most severe chronic pain conditions, and conventional treatments often fall short. Ketamine has some of the strongest evidence in this population, with studies showing meaningful pain reduction and functional improvement. Some CRPS researchers consider ketamine a cornerstone of treatment.

Fibromyalgia

The widespread pain and central sensitization that characterize fibromyalgia make it a reasonable target for ketamine. Evidence is growing, with several studies showing improvement in pain scores and function. Results are variable between patients, but for those who respond, the improvement can be substantial.

Chronic Migraine

There's emerging evidence for ketamine in refractory chronic migraine, particularly as a bridge treatment during severe episodes. This application is earlier in its evidence development but promising.

Cancer Pain

Ketamine has a long history as an adjunct for cancer pain, particularly when pain is poorly controlled by opioids or when opioid side effects are limiting. Guidelines from several oncology organizations include ketamine as an option for refractory cancer pain.

Post-Surgical Chronic Pain

When acute surgical pain transitions to chronic pain, central sensitization is often involved. Ketamine can help interrupt this process, and there's evidence that perioperative ketamine reduces the incidence of chronic post-surgical pain.

Ketamine as an Opioid-Sparing Tool

This is one of the most practically important applications of ketamine for pain, and it deserves its own section.

Millions of Americans manage chronic pain with long-term opioid therapy. While opioids can be effective, they come with well-documented risks: tolerance (needing increasing doses for the same effect), physical dependence, constipation, hormonal disruption, cognitive effects, and the risk of overdose.

Ketamine offers a potential path to reducing opioid doses without losing pain control. Here's why:

Different mechanism. Ketamine doesn't work through opioid pathways (primarily), so it provides additive analgesia without simply stacking more opioid effect.

Anti-tolerance effect. There's evidence that NMDA receptor antagonism can actually reverse or prevent opioid tolerance, making existing opioid doses more effective.

Central sensitization reset. By addressing the neural amplification that drives chronic pain, ketamine may reduce the total pain burden, allowing opioid doses to be lowered.

I want to be clear: I'm not suggesting patients stop their opioids and switch to ketamine. Opioid tapering should always be gradual, medically supervised, and patient-directed. But for patients who want to reduce their opioid burden, ketamine can be a valuable tool in that process.

What Treatment Looks Like for Pain

Ketamine for chronic pain can be administered via several routes:

IV infusion. Higher doses than those used for depression, typically over longer infusion periods. This is the most studied route for pain indications. Usually done as a series of infusions.

Sublingual. At-home sublingual ketamine can be used for ongoing pain management at lower doses. This is more accessible and affordable than repeated infusions.

Topical. Compounded ketamine creams are sometimes used for localized pain, particularly neuropathic pain. Evidence is mixed but some patients find them helpful.

Nasal spray. Compounded ketamine nasal spray can provide relatively rapid pain relief. Different from the esketamine (Spravato) product approved for depression.

The dosing for pain and depression overlaps but isn't identical. Pain applications sometimes use higher doses, and the treatment schedule may differ. This is why working with a physician experienced in both applications matters.

Limitations and Honest Expectations

Ketamine is not a pain cure. Let me set realistic expectations:

It doesn't work for everyone. Response rates for chronic pain are encouraging but far from universal. Some patients experience dramatic relief; others notice modest improvement; some don't respond at all. There's no reliable way to predict who will respond before trying.

Effects can be temporary. Some patients need ongoing treatment to maintain pain relief. Like many chronic pain treatments, ketamine may require regular dosing.

It's part of a plan, not the plan. Ketamine works best as part of a comprehensive pain management strategy that includes physical therapy, psychological approaches, lifestyle modifications, and sometimes other medications.

Cost and access. Same challenges as the depression indication — ketamine for pain is largely an out-of-pocket expense. Insurance coverage for off-label use is limited.

Who Should Consider It

If you're living with chronic pain — particularly neuropathic pain, CRPS, or fibromyalgia — and you haven't found adequate relief from conventional treatments, ketamine therapy is worth discussing with your physician.

If you're on long-term opioid therapy and want to explore reducing your opioid dose, ketamine may help make that possible.

At Coral Health, I evaluate chronic pain patients for ketamine therapy as part of a comprehensive approach to pain management. The goal isn't just to add another medication — it's to find the combination that gives you the best quality of life with the fewest side effects.

Chronic pain is complex, and there's no single treatment that works for everyone. But ketamine has earned its place in the toolkit, and more patients should know it's an option.