Ketamine is an anesthetic drug increasingly used at lower, sub-anesthetic doses to treat chronic pain conditions that haven’t responded to standard treatments. It’s FDA-approved only as a general anesthetic, so its use for pain management is considered off-label. Despite that, pain clinics across the country offer ketamine infusions for conditions like complex regional pain syndrome (CRPS), neuropathic pain, and post-surgical pain, with studies showing it can reduce pain scores by roughly 1 point on a 10-point scale on average.
How Ketamine Works on Pain
Ketamine targets pain through a different pathway than opioids or anti-inflammatory drugs. Its primary action is blocking NMDA receptors, which are proteins on nerve cells that play a central role in how the brain and spinal cord amplify pain signals over time. In chronic pain, these receptors can become overactive, a process called central sensitization. Essentially, your nervous system gets stuck in a state where it keeps turning up the volume on pain, even after the original injury has healed. Ketamine interrupts that cycle by physically blocking the receptor’s ion channel, reducing calcium flow into nerve cells and dampening the exaggerated pain signaling.
Beyond NMDA receptors, ketamine also interacts with opioid receptors, the brain’s mood-related chemical systems, and other receptor types. This broad activity helps explain why it can relieve pain that doesn’t respond to more targeted medications. The dissociative, dreamlike state ketamine produces at higher doses may itself contribute to pain relief by altering how the brain processes painful sensations.
Which Pain Conditions Respond Best
The strongest evidence for ketamine in pain management comes from complex regional pain syndrome, a notoriously difficult condition involving severe, burning pain usually in an arm or leg. In studies of CRPS patients, roughly half achieve meaningful pain relief lasting one to three months after a ketamine infusion series. One particularly striking open-label study found that 50% of participants experienced complete pain relief lasting 5 to 11 years after high-dose infusions delivered under intensive care monitoring. More typical results from moderate-dose protocols show 48% to 65% of patients achieving clinically meaningful pain reduction at the one-month mark.
Ketamine also shows benefit for broader neuropathic pain, the kind caused by nerve damage from conditions like diabetes, shingles, or spinal cord injury. A meta-analysis found ketamine effective at reducing neuropathic pain with a moderate effect size, though long-term data remains limited. For acute post-surgical pain, a meta-analysis of 14 trials with 649 patients found that sub-anesthetic ketamine lowered pain scores and reduced the amount of morphine patients needed for up to 24 hours after spine surgery, with no increase in side effects.
What an Infusion Looks Like
Ketamine for pain is most commonly given as an intravenous infusion in a clinic or hospital setting. The doses used are well below what would put you under general anesthesia. A typical session starts with a small initial dose, followed by a slow drip usually running between 0.1 and 0.5 mg/kg per hour. Patients who have been on high-dose opioids may receive somewhat higher infusion rates, up to 1 mg/kg per hour, because their nervous systems have adapted to stronger pain-blocking signals.
Treatment protocols vary widely. Some clinics run outpatient sessions lasting a few hours per day over a series of 5 to 10 days. Others admit patients for continuous infusions lasting 4 to 7 days. The approach depends on the severity of the condition, the patient’s pain history, and the clinic’s protocol. During the infusion, you’re awake but monitored. Many people feel a floating or dreamlike sensation, and some experience mild visual distortions or a sense of detachment from their surroundings. These effects typically fade within an hour or two after the infusion ends.
How Long Pain Relief Lasts
This is the key question for most patients, and the answer depends heavily on how long the infusion protocol runs. Short, single-session infusions tend to provide relief only during the infusion itself or for a few days afterward. Longer protocols, spanning 4 to 14 days, produce more durable results. A meta-analysis of prolonged infusion studies found a large pain-reducing effect in the first week after treatment, which declined but remained statistically significant at four weeks. Three-month follow-ups in CRPS studies consistently show that a meaningful percentage of patients still report reduced pain.
The catch is that the effect fades. Most patients who respond to ketamine will need repeat infusions, typically within 4 to 6 weeks of their initial treatment course. Some clinics set up maintenance schedules with periodic single-day “booster” infusions to sustain the relief achieved during the initial series. The timeline is highly individual: some people maintain lower pain levels for months, while others notice pain creeping back within weeks.
Reducing Opioid Use
One reason ketamine has drawn interest in pain medicine is its potential to reduce reliance on opioids. In acute pain settings, patients receiving ketamine infusions alongside standard pain management consistently use less morphine in the first 24 hours after surgery. For chronic pain, the picture is more complicated. In one study of patients with high opioid requirements, only 5 out of the group maintained a reduction of more than 50% in their opioid use at six months. The rest returned to their baseline opioid levels or higher. Ketamine can provide a window of reduced opioid need, but for most chronic pain patients, that window closes without ongoing ketamine treatment.
Side Effects During and After Treatment
The most common side effects are directly tied to how ketamine affects the brain. During infusions, you may experience a dreamlike or dissociative state, double vision, dizziness, nausea, and flushed or warm skin. These are expected at sub-anesthetic doses and typically resolve shortly after the infusion stops. Some people find the dissociative feeling pleasant, others find it unsettling. Unusual thoughts, vivid imagery, or a sense of seeing or hearing things that aren’t there can occur and generally pass within 24 hours.
More concerning side effects are less common but worth knowing about. Ketamine can cause changes in heart rate and blood pressure, which is why infusions are given under medical monitoring. Repeated or prolonged use carries a risk of bladder problems, including painful urination, urgency, and in severe cases, bladder damage. This risk is better documented in people who use ketamine recreationally at high doses over long periods, but it’s a consideration for anyone on repeated infusion cycles. Liver function abnormalities have also been reported, and most clinics will monitor liver markers during extended treatment courses.
Who Is and Isn’t a Good Candidate
Ketamine for pain is generally reserved for people who haven’t found adequate relief from first-line treatments. The most common candidates are those with CRPS, other neuropathic pain syndromes, or chronic pain with features of central sensitization, meaning the nervous system itself has become part of the problem rather than just the original injury site. People on high-dose opioids who want to reduce their dependence sometimes pursue ketamine as a bridge strategy.
People with poorly controlled high blood pressure, significant heart disease, or active psychotic disorders are typically not considered good candidates, since ketamine raises blood pressure and can trigger hallucinations or paranoid thinking. A history of substance abuse also requires careful evaluation, as ketamine is a Schedule III controlled substance with abuse potential. Because it’s used off-label for pain, insurance coverage varies widely, and out-of-pocket costs for an infusion series can be substantial.
The Current State of Evidence
Ketamine occupies an unusual place in pain medicine. It has decades of clinical use as an anesthetic, a growing body of evidence for chronic pain, and wide adoption in specialized pain clinics, yet it remains without FDA approval for any pain indication. The evidence is strongest for CRPS, where randomized placebo-controlled trials have demonstrated clear superiority over placebo lasting up to 11 to 12 weeks. For other chronic pain conditions, the data is more mixed, with a 2022 systematic review and meta-analysis concluding that IV ketamine significantly reduces chronic pain scores but acknowledging the evidence base is still somewhat limited. Consensus guidelines from major anesthesiology and pain medicine societies support its use in acute pain settings and acknowledge its potential in chronic pain, while noting that most recommendations carry moderate rather than high certainty.