PAIN TREATMENT · EVIDENCE REVIEW
Ketamine
& CRPS
Intravenous ketamine can reduce pain in some people with CRPS, and randomized trials have shown benefit that can continue after the infusion ends. But the effect is usually temporary, response varies between patients, and repeated treatment adds important safety and monitoring questions.
In the United States, ketamine injection is FDA-approved as a general anesthetic—not as a treatment for CRPS. Its use for CRPS pain is therefore off-label.
THE KEY POINT
TEMPORARY ANALGESIA
Ketamine can reduce CRPS pain without being a proven cure for CRPS.
The best evidence supports a period of pain relief in some patients after monitored IV infusions. Evidence is much less certain about repeated long-term cycles, durable functional recovery and who will respond.
01
Benefit can last beyond the infusion
Consensus guidance describes moderate evidence for improvement in CRPS pain for up to about 12 weeks.
02
Not every patient responds
Responders and nonresponders are seen, and the duration of relief is not predictable for an individual patient.
03
Repeated exposure changes the risk discussion
Liver, urinary, cognitive, tolerance, misuse and dependence concerns become more relevant with recurrent or prolonged use.
WHAT IS KETAMINE?
A dissociative anesthetic with analgesic effects at lower doses.
Ketamine is a non-competitive antagonist of the NMDA receptor, a glutamate receptor involved in pain signaling and central sensitization. Its clinical effects are broader than NMDA blockade alone, but NMDA antagonism is central to why ketamine has been studied in neuropathic and centrally sensitized pain.
01
Analgesia
Ketamine can reduce pain perception at doses below those used to produce general anesthesia.
02
NMDA antagonism
Blocking NMDA signaling may reduce processes involved in central sensitization and amplification of persistent pain.
03
Dissociation
Ketamine can alter perception, awareness and sensory experience. These effects vary with dose and can be distressing for some patients.
04
Symptom modulation, not proof of disease reversal
A decrease in pain after ketamine does not by itself demonstrate that the underlying CRPS process has been eliminated.
U.S. REGULATORY STATUS
Ketamine is FDA-approved as an anesthetic. CRPS treatment is an off-label use.
The current U.S. KETALAR prescribing information lists ketamine injection for general anesthesia: as a sole anesthetic for appropriate procedures, for induction of anesthesia, and as a supplement to other anesthetic agents. CRPS is not an FDA-approved indication.
Off-label does not mean “illegal” or automatically “wrong”.
It means the use is outside the FDA-approved indication. The evidence, clinical rationale, monitoring plan, alternatives and informed consent therefore matter especially.
WHAT THE EVIDENCE SHOWS
Two placebo-controlled trials support short-to-medium-term pain relief after multi-day IV ketamine.
The most frequently cited CRPS trials used intravenous ketamine over several days. They are important because they were randomized and placebo controlled, but both were relatively small and were designed mainly around pain outcomes rather than proof of long-term disease modification.
PAIN · 2009
60 PATIENTS
Sigtermans et al.: multi-day S-ketamine infusion
Sixty patients with CRPS-I and severe pain were randomized to ketamine or placebo. Ketamine was titrated during a prolonged infusion lasting a little over four days.
RESULT
Pain improved significantly, but functional improvement was not demonstrated.
The analgesic effect persisted beyond treatment and gradually diminished during follow-up. Psychomimetic effects occurred more often with ketamine.
PAIN · 2009
19 PATIENTS
Schwartzman et al.: 10 outpatient infusion days
Patients with CRPS were randomized to ketamine or placebo and received four-hour outpatient infusions on ten treatment days, with follow-up extending to three months.
RESULT
Multiple pain measures improved compared with placebo during follow-up.
The study supports the possibility of relief lasting beyond the infusion period, but the sample was very small and the authors called for larger randomized studies.
ASRA · AAPM · ASA CONSENSUS GUIDELINES
Moderate evidence for CRPS pain improvement for up to about 12 weeks.
The 2018 multidisciplinary consensus guidelines reviewed the randomized CRPS evidence and concluded that IV ketamine has moderate evidence for improving CRPS pain for up to 12 weeks using the multi-day regimens studied.
WHAT THIS DOES NOT MEAN
It does not mean that every patient receives 12 weeks of relief, that repeated courses keep working indefinitely, or that ketamine has been shown to permanently reverse CRPS.
HOW LONG CAN BENEFIT LAST?
Think in weeks to a few months—not in guaranteed permanent remission.
Published CRPS studies show that analgesia can outlast the infusion itself. The magnitude of relief generally declines with time, and not all patients obtain sustained benefit.
01
During treatment
Pain reduction can emerge while the infusion course is still underway.
02
After treatment
Some responders continue to experience lower pain after ketamine has been discontinued.
03
Weeks later
The controlled evidence supports benefit extending into the following weeks in some patients.
04
By approximately three months
The evidence becomes much less certain, and many patients experience partial or complete loss of benefit.
PAIN
Ketamine can produce meaningful analgesia.
That is the outcome most consistently supported by the randomized CRPS literature.
≠
FUNCTION
Pain relief does not automatically mean restored function.
The major CRPS trial by Sigtermans et al. found pain reduction without a parallel functional improvement. Rehabilitation goals should therefore remain explicit.
REPEATED INFUSIONS
If relief fades, repeating ketamine is a new risk–benefit decision each time.
Repeated treatment is common in clinical practice, but the long-term evidence base is much thinner than the evidence for a single multi-day course. Frequency, cumulative exposure, diminishing benefit and organ monitoring all deserve attention.
01
Measure the actual duration of benefit
Record when meaningful improvement begins, when it peaks and when pain returns toward baseline. This helps determine whether another course has enough value to justify it.
02
Watch for diminishing returns
If each course provides less relief or shorter relief, repeating the same protocol automatically may not be the best strategy.
03
Consider cumulative toxicity
The FDA label specifically warns about hepatobiliary injury with recurrent use and serious urinary complications with long-term use or abuse.
04
Ask what monitoring changes with repetition
Baseline and periodic liver testing, urinary symptoms, medication interactions, cardiovascular risk and mental-health history may become more important with serial treatment.
RISKS & MONITORING
The safety discussion should match the dose, duration and frequency of treatment.
Ketamine has decades of anesthetic use, but repeated off-label pain treatment creates a different exposure pattern. The current FDA label includes warnings relevant to recurrent dosing as well as acute cardiovascular, respiratory and psychological effects.
01
Blood pressure & heart rate
Ketamine commonly increases blood pressure and pulse. Patients with cardiovascular risk may require additional assessment and monitoring.
02
Dissociation & psychological effects
Vivid imagery, hallucinations, confusion, agitation and unpleasant dissociative experiences can occur.
03
Sedation & respiratory risk
Respiratory depression can occur with high or rapidly administered doses, and risk can increase when ketamine is combined with opioids, benzodiazepines, alcohol or other CNS depressants.
04
Liver & biliary injury
Recurrent ketamine exposure has been associated with hepatobiliary dysfunction and, in some cases, sclerosing cholangitis.
05
Bladder & urinary tract injury
Long-term use or abuse has been associated with cystitis, reduced bladder capacity, ureteral obstruction and hydronephrosis.
06
Drug interactions
Opioids, benzodiazepines and other CNS depressants can deepen sedation and respiratory depression. Medication review is part of safe treatment.
07
Misuse, tolerance & dependence
Ketamine is a Schedule III controlled substance in the United States. Tolerance and physical dependence have been reported with prolonged use.
08
Need for an appropriate monitored setting
Infusion protocols should have trained clinicians, monitoring and the ability to manage cardiovascular, respiratory or neuropsychiatric complications.
DEPENDENCE & MISUSE
“Ketamine can be addictive” needs a precise explanation—not fear and not denial.
01
Controlled substance
Ketamine is classified as Schedule III under U.S. federal law, reflecting recognized medical use alongside abuse and dependence potential.
02
Physical dependence
The current FDA label states that physical dependence has been reported with prolonged use and describes withdrawal after frequent large-dose use over long periods.
03
Tolerance
Tolerance has also been reported with prolonged use, meaning a previously effective exposure may produce less effect over time.
04
Medical treatment is not the same as uncontrolled use
Supervised clinical treatment and recreational misuse are different exposure patterns. A responsible program should still screen risk, track repeated use and avoid minimizing the drug’s abuse potential.
HIGH-DOSE & “KETAMINE COMA” PROTOCOLS
More intense treatment does not automatically mean stronger evidence.
Very high-dose anesthetic ketamine protocols have been reported for severe refractory CRPS. These approaches require intensive monitoring and have attracted attention because some uncontrolled series reported major improvements.
WHAT GUIDELINES SAY
The CRPS Practical Diagnostic and Treatment Guidelines state that high-dose “ketamine coma” is associated with very serious side effects and cannot be recommended.
01
There is no randomized clinical-trial evidence base demonstrating that anesthetic-dose coma protocols are superior for CRPS.
02
Deep anesthesia adds airway, cardiovascular, intensive-care and recovery risks beyond those of subanesthetic infusion protocols.
03
Patients should distinguish uncontrolled case series from randomized placebo-controlled evidence when comparing claims.
WHAT EXACTLY IS BEING OFFERED?
“Ketamine treatment” can mean very different things.
Route, dose, infusion length, number of days, monitoring and whether treatment is repeated all influence both evidence and risk. The strongest CRPS evidence is for monitored IV multi-day treatment, not for every ketamine product or delivery route.
MOST STUDIED IN CRPS
Intravenous infusion
The placebo-controlled CRPS trials and consensus recommendations are based primarily on IV ketamine protocols delivered over multiple days.
LESS DIRECT CRPS EVIDENCE
Oral / compounded ketamine
Oral ketamine has different pharmacokinetics and a much smaller CRPS evidence base. Convenience should not be mistaken for equivalent evidence.
DISTINCT PRODUCT / INDICATION
Intranasal esketamine
FDA-approved intranasal esketamine products are psychiatric treatments with their own indications and safety program; that approval should not be interpreted as approval for CRPS.
QUESTIONS BEFORE PAYING FOR OR STARTING KETAMINE
Ask questions that make the protocol, evidence and follow-up visible.
Clinics can use very different regimens. A patient should be able to understand exactly what is being proposed and why.
01
Is the proposed treatment IV ketamine, oral ketamine, intranasal medication or another formulation?
02
Which published CRPS studies support this exact dose, duration and schedule?
03
What outcome will count as success: pain reduction, function, sleep, medication use or another goal?
04
How long does benefit typically last in your own patients, and how do you measure it?
05
If the effect lasts only a few weeks, how often would you propose repeating treatment?
06
What liver, urinary, cardiovascular and mental-health screening or monitoring do you use for repeated treatment?
07
How do you screen for misuse risk, tolerance or dependence when treatment becomes recurrent?
08
What happens if ketamine stops working, causes side effects or I decide I do not want repeated infusions?
CLAIMS WORTH QUESTIONING
Be cautious when temporary analgesia is marketed as certainty.
Ketamine is a legitimate medical drug with evidence in CRPS pain. That makes accurate communication more important—not less. Strong claims should match the strength and duration of the evidence.
01
“Ketamine cures CRPS.”
Randomized evidence supports pain reduction for a limited period in some patients, not a guaranteed permanent cure.
02
“If it works once, just keep repeating it.”
Recurrent exposure introduces cumulative safety, tolerance, dependence and diminishing-return questions.
03
“High dose means a better chance of success.”
High-dose coma protocols lack randomized evidence and are specifically discouraged in major CRPS guidelines because of serious risk.
04
“All ketamine treatments have the same evidence.”
IV multi-day infusion data should not be used automatically to validate oral, intranasal, at-home or substantially different dosing protocols.
PATIENT SUPPORT
If you are comparing ketamine with other CRPS treatments, organize the questions before the costs begin.
Carla Crowe, Patient Care Coordinator – California, can help you navigate CRPS Support resources and organize practical questions about treatment options. Decisions about ketamine dosing, suitability and monitoring belong with qualified clinicians who know your medical history.
CARLA CROWE
Patient Care Coordinator – California
COMMON QUESTIONS
Questions patients ask about ketamine and CRPS
No. Ketamine injection is FDA-approved as a general anesthetic. Use for CRPS pain in the United States is off-label.
Controlled studies and consensus guidelines support the possibility of relief lasting for weeks and, in some patients, up to about 12 weeks after a multi-day IV course. Individual response and duration vary.
Not necessarily. In the major randomized Sigtermans trial, pain improved without a corresponding functional improvement. Functional goals and rehabilitation therefore remain important even when pain falls.
Ketamine is a Schedule III controlled substance. The FDA label states that physical dependence and tolerance have been reported with prolonged use. Risk depends on the pattern of exposure and individual factors, so repeated treatment should include a deliberate monitoring plan.
No randomized clinical-trial evidence base supports high-dose ketamine coma for CRPS. The CRPS Practical Diagnostic and Treatment Guidelines state that this approach carries very serious side effects and cannot be recommended.
SOURCES & FURTHER READING
Separate randomized evidence, consensus guidance and regulatory safety information.
Ketamine discussions often combine very different types of evidence. These sources allow patients to see the controlled CRPS trials, professional guidance and current U.S. safety labeling separately.
PAIN · 2009
Sigtermans et al.
Randomized placebo-controlled multi-day S-ketamine trial in 60 patients with CRPS-I.
PAIN · 2009
Schwartzman et al.
Randomized placebo-controlled outpatient IV ketamine trial with three-month follow-up.
ASRA · AAPM · ASA
IV ketamine consensus guidelines
Professional guidance on evidence, patient selection, monitoring and CRPS treatment duration.
FDA · 2026 LABEL
KETALAR prescribing information
Current U.S. indications and warnings on recurrent use, liver injury, urinary injury, abuse and dependence.
PAIN MEDICINE · 2022
CRPS Practical Diagnostic and Treatment Guidelines
Multidisciplinary CRPS guideline including ketamine evidence and the high-dose coma warning.
DEA
Controlled-substance scheduling
Ketamine is listed as a Schedule III controlled substance in the United States.
Scientific and regulatory content reviewed for this page: August 2026.
A TEMPORARY TREATMENT DESERVES A LONG-TERM PLAN.