Ketamine is FDA-approved as an anesthetic, but its medical uses now extend well beyond the operating room. Originally developed in the 1960s as a surgical sedative, ketamine has become an important tool for treating severe depression and chronic pain. It’s classified as a Schedule III controlled substance, meaning it has accepted medical uses but carries some potential for misuse.
Anesthesia and Sedation
Ketamine’s only FDA-approved indication is for induction and maintenance of general anesthesia. It works differently from most anesthetics: instead of slowing brain activity across the board, it blocks a specific receptor involved in pain signaling and consciousness. This makes it especially useful in emergency medicine and field settings because it doesn’t suppress breathing or heart function the way many other anesthetics do. Patients maintain their airway reflexes, which is a significant safety advantage when ventilators or advanced monitoring aren’t available.
At lower doses, ketamine provides strong pain relief and sedation without full unconsciousness. Emergency departments frequently use it for painful procedures like setting broken bones or stitching deep wounds, particularly in children.
Treatment-Resistant Depression
The most significant expansion of ketamine’s role has been in psychiatry. In 2019, the FDA approved a nasal spray form called esketamine (brand name Spravato) specifically for treatment-resistant depression. To qualify, a patient generally needs to have tried multiple antidepressants without adequate improvement, including at least one augmentation strategy such as combining medications or adding evidence-based psychotherapy.
What makes ketamine remarkable for depression is speed. Traditional antidepressants take weeks to start working. Ketamine can produce noticeable mood improvement within hours. It works by boosting the brain’s ability to form new neural connections, essentially helping the brain rewire pathways that depression has disrupted.
Treatment follows a structured schedule. During the first four weeks, patients receive the nasal spray twice per week. This tapers to once weekly for the next month, then every one to two weeks for ongoing maintenance. Each session happens at a certified clinic, not at home. You’ll need to stay for monitoring afterward until your vital signs return to baseline and any dissociative effects wear off, and you’ll need a driver to take you home. You also can’t drive, operate heavy machinery, or make major legal or financial decisions for the rest of that day.
Esketamine is also approved for adults with major depression who are experiencing acute suicidal thoughts or behavior. In that context, the dose is typically higher and given twice weekly for four weeks while the patient is hospitalized or closely monitored.
Chronic Pain
Ketamine is widely prescribed off-label as a later-line treatment for chronic pain that hasn’t responded to standard therapies. Cleveland Clinic’s pain protocol, for example, uses low-dose intravenous infusions over 40 minutes daily for five consecutive days. This approach targets a different pain pathway than opioids do, which makes it useful for conditions where opioids have failed or aren’t appropriate.
The types of chronic pain most commonly treated with ketamine infusions include complex regional pain syndrome (CRPS), neuropathic pain from nerve damage, fibromyalgia, and certain centralized pain conditions where the nervous system has become hypersensitive. Relief from a single course of infusions can last weeks to months for some patients, though results vary considerably.
PTSD and Anxiety Disorders
Ketamine is being used off-label for PTSD, with growing clinical evidence behind it. A review of five randomized clinical trials found that ketamine infusion produced rapid, clear benefits for PTSD symptoms that hadn’t responded to conventional medications. The response rate was approximately 80%, with improvements across three of four major symptom categories: intrusive memories, avoidance behavior, and negative changes in thinking and mood.
The effects appear to be stronger and longer-lasting when ketamine infusions are combined with psychotherapy. Researchers believe ketamine promotes a type of brain plasticity that helps with fear extinction, essentially making it easier for the brain to unlearn the threat responses that drive PTSD. Ketamine infusion was well-tolerated in these studies, with temporary dissociation being the most common side effect. It also showed benefits for conditions that frequently accompany PTSD, including chronic pain, alcohol use disorder, and major depression.
Early research also suggests benefit for anxiety disorders and obsessive-compulsive symptoms, though these uses are less established than the depression and PTSD applications.
Common Side Effects During Treatment
At the doses used for depression and pain, ketamine’s side effects are generally short-lived. The most distinctive is dissociation: a feeling of detachment from your body or surroundings that can range from mild dreaminess to a more intense altered state. This typically fades within an hour or two after the infusion or nasal spray dose ends. Other common effects include dizziness, nausea, increased blood pressure, and a sense of sedation. Clinics monitor your blood pressure and mental state before clearing you to leave.
Some people experience a temporary increase in anxiety during the dissociative phase, while others find it neutral or even pleasant. These effects become more predictable after the first session, and doses can be adjusted if they’re poorly tolerated.
Risks of Long-Term or Heavy Use
The safety picture changes significantly with frequent, high-dose, or prolonged use. The most serious known risk is damage to the urinary tract. Among people who use ketamine heavily, roughly 30% develop lower urinary tract symptoms. This condition, sometimes called ketamine cystitis, causes painful urination, urgent and frequent need to urinate, and bladder pain. Urine cultures come back negative because the problem isn’t an infection. It’s caused by ketamine metabolites irritating and inflaming the bladder lining, leading to swelling, scarring, and loss of bladder capacity over time.
In severe cases, particularly with continued heavy use, the damage can extend beyond the bladder to the kidneys. Some patients develop hydronephrosis (swelling of the kidneys from backed-up urine) and permanent kidney injury. Quality of life in these cases is significantly impaired, and the damage may not respond to standard treatments if ketamine use continues.
Ketamine also carries a risk of psychological dependence. The DEA notes it has potential for high psychological dependence, though physical dependence tends to be moderate or low. This is one reason clinical ketamine treatment is administered in supervised settings rather than prescribed for home use. The exception is certain at-home ketamine programs offered through telehealth companies, which have drawn scrutiny from regulators concerned about oversight and safety.
How Ketamine Works in the Brain
Most psychiatric medications work on serotonin, norepinephrine, or dopamine. Ketamine targets a completely different system: glutamate, the brain’s primary excitatory chemical messenger. By temporarily blocking a receptor called NMDA, ketamine triggers a cascade of effects that increase the brain’s ability to form and strengthen connections between neurons. This process, called neuroplasticity, is thought to explain both the rapid antidepressant effects and the benefits seen in PTSD.
This mechanism is why ketamine works for some people who haven’t responded to anything else. It’s acting on a different biological pathway than virtually every other available psychiatric medication. The effect is not just symptom suppression but appears to involve actual structural changes in how brain cells communicate, particularly in regions involved in mood regulation and fear processing.