How does ketamine work for CRPS?

The NMDA receptor sits in the spinal cord and brain. It is central to how pain signals get louder over time. In complex regional pain syndrome, a first injury — often minor, sometimes barely remembered — sets off an outsized response that keeps feeding itself. The limb turns extremely sensitive, discolored and swollen. It hurts far more than the tissue would explain. NMDA receptor activation is a major driver of that amplification. That is why blocking it with ketamine matters. It is one of the few treatments aimed straight at the central mechanism, not only at the limb.

How is ketamine given for CRPS?

Which route, at what dose and how often, is a clinical call. It is built around severity, response and what you can tolerate. It is not a package deal, and not offered as a pre-set series.

The terrain of a sensitized nervous system

Central sensitization does not stay inside the injured limb, and it does not run on NMDA activity alone. Chronic pain itself drives whole-body inflammation that keeps the amplification loop running. Sleep in CRPS is often wrecked by a limb that burns at rest. Those are two biological drivers feeding each other in a loop ketamine alone cannot fully break. The third driver is social. Living with a limb that looks wrong is lonely, and some patients report disbelief from people who cannot see an obvious injury. That keeps the nervous system on high alert. Ketamine turns down the amplifier. This practice pairs it with the same attention to sleep and nervous system arousal used across every chronic pain plan here, because a quieted receptor sitting in an untreated terrain tends not to stay quiet.

Does ketamine work for CRPS, and how long does relief last?

A 2019 systematic review and meta-analysis of ketamine infusions for chronic pain in general found modest, time-limited benefit across the pooled trials. CRPS was among the better-represented conditions. Two systematic reviews specific to CRPS — one from 2015, one from 2018 — both found real short-term pain reduction from ketamine infusion. Both flagged the same limit. The trials are small, use mixed dosing plans, and rarely follow patients past a few months. So how long relief lasts beyond that window is truly not well established. The people studied also lean toward patients who had already failed several other treatments. That is close to who ends up on this page. But it means the numbers describe a hard-to-treat group, not CRPS in general.

Intranasal ketamine sits between sublingual and IV dosing. It is absorbed quickly through the lining of the nose and reaches the central nervous system without an IV line. Its evidence base is the one built for the esketamine nasal spray, plus a smaller ketamine literature in nerve pain. We read that as supportive, but still smaller than the infusion trials. We tell patients directly: the trial evidence supports trying this, especially after other approaches have not held. It does not yet support promising a set length of relief. That gap gets filled by watching how your own nervous system responds, not by a number from a paper.

Monitoring

IV infusions are done with nonstop blood pressure, heart rate and oxygen monitoring the whole time, because ketamine can raise blood pressure and heart rate and, even at sub-anesthetic doses, can cause dissociative effects — a floaty, detached feeling some patients find unpleasant. You will not drive yourself home after an infusion. Sublingual and intranasal use is checked at follow-up visits, not by nonstop monitoring, since the peak level and the dose are smaller. We still track blood pressure and ask directly about mood and dissociative symptoms at each check-in.

What happens on the day of an infusion

Who should not take ketamine for CRPS?

Poorly controlled high blood pressure or significant heart disease is a concern for IV dosing in particular. That is because ketamine can raise blood pressure and heart rate. A history of psychosis or an active, unstable psychiatric condition is a serious caution, since the detached effects can be truly distressing there. A history of substance use disorder involving ketamine or a similar drug needs an honest talk first. That is not an automatic no, but a reason to go slower and watch closer. Pregnancy rules out systemic (whole-body) dosing.

What are the side effects of ketamine for CRPS?

During an IV infusion: higher blood pressure and heart rate, nausea, and dissociative effects that fade as the infusion ends and the drug clears. Bladder irritation has been reported with frequent, high-dose, long-term ketamine use. Most of those cases come from recreational use, not the supervised, dose-limited plans used here, but you should know about it. Sublingual and intranasal use can cause drowsiness, mild dissociation and, with the nasal route, brief nasal irritation. Both carry clearly less whole-body risk than an infusion.

Common questions

Related reading

• Complex regional pain syndrome
• Sympathetic nerve blocks
• Spinal cord stimulation
• Opioid stewardship
• Sleep, movement and behavior