Ketamine Therapy: Medical Uses, Depression Treatment & Risks

Most patients who come to me asking about ketamine therapy have already tried two or three antidepressants without real relief. What surprises them most is not the speed, though relief within hours does catch people off guard, it is learning that ketamine works through a completely different brain system than everything they have tried before. That is genuinely useful clinically. What also surprises them is how quickly recreational use can tip into a pattern that is hard to stop.

What Is Ketamine Therapy?

Ketamine hydrochloride was first synthesised in 1962 and FDA-approved as a surgical anaesthetic in 1970. For decades it lived in operating rooms and emergency departments, where its ability to produce sedation without suppressing breathing made it invaluable. Its psychiatric applications came later, largely by accident, when anaesthesiologists noticed patients reporting mood improvements after procedural doses.

Ketamine therapy refers to the controlled medical use of ketamine at sub-anaesthetic doses to treat mental health conditions or chronic pain. The doses used clinically are far lower than those used for surgical anaesthesia. At these doses, you remain conscious but may feel detached from your surroundings, a dissociative effect that is part of the mechanism, not just a side effect.

There are two FDA-approved forms of ketamine in clinical use. Esketamine (brand name Spravato) is a nasal spray approved specifically for treatment-resistant depression and for major depressive disorder with acute suicidal ideation. Racemic ketamine, the original compound, is approved as an anaesthetic but used off-label for depression and pain management as an IV infusion or intramuscular injection. Off-label means the prescribing is legal and common, but it operates with less regulatory oversight around administration protocols.

How Ketamine Works on the Brain

Most antidepressants work on the monoamine system: they adjust serotonin, noradrenaline, or dopamine. Ketamine does not. It primarily blocks NMDA receptors, which are glutamate receptors, glutamate being the brain’s main excitatory neurotransmitter. That is a fundamentally different target, which is why ketamine can help patients who have failed every standard antidepressant.

Here is what happens mechanically. When NMDA receptors are blocked, there is a downstream surge of AMPA receptor activity. This activates a signalling protein called BDNF (brain-derived neurotrophic factor), which in turn triggers a process called synaptogenesis: the rapid formation of new synaptic connections between neurons. In patients with chronic depression, the prefrontal cortex loses synaptic density over time. Ketamine appears to reverse that, quickly.

The speed is the clinically remarkable part. Standard SSRIs take two to six weeks to work, partly because they rely on gradual receptor desensitisation. Ketamine’s downstream synaptogenesis can produce measurable mood improvement within two to four hours of a single infusion. A landmark 2000 study from Yale showed significant depression symptom reduction within four hours of a single IV dose, results that genuinely changed how psychiatrists thought about the disease.

One additional pathway worth naming: ketamine also modulates the mTOR signalling pathway, which is upstream of synaptogenesis. Some researchers believe this is the more important mechanism. The honest answer is that the full picture is still being worked out, but the clinical results are not in dispute.

Ketamine vs Standard Antidepressants: Key Differences

What Ketamine Therapy Is Used For

Treatment-Resistant Depression

Treatment-resistant depression is defined as a major depressive episode that has not responded to at least two adequate antidepressant trials at therapeutic doses. Around 30% of people with major depression fall into this category. For them, ketamine is genuinely useful, and the evidence base is stronger here than for any other indication.

The typical IV protocol for treatment-resistant depression is six infusions over two to three weeks, each lasting 40 minutes. Response rates in clinical studies range from 50% to 70% after a full course, which is substantially higher than switching to a third antidepressant. The problem is durability: without maintenance infusions, most patients relapse within two to twelve weeks.

PTSD and Anxiety

Ketamine’s effect on PTSD is increasingly supported by clinical data. A 2021 randomised controlled trial published in the American Journal of Psychiatry found that repeated ketamine infusions produced significantly greater PTSD symptom reduction than midazolam (an active placebo) after two weeks. The mechanism likely involves reconsolidation interference, ketamine appears to disrupt the re-storing of traumatic memories during a brief window after they are recalled.

For generalised anxiety disorder and social anxiety, the data is thinner. Ketamine is used off-label in some clinics, but I would not present it to a patient as a proven first-line option for anxiety without exhausting other treatments first.

Chronic Pain and Suicidal Ideation

Ketamine has a long history in anaesthesia as an opioid-sparing analgesic. At sub-anaesthetic doses it reduces central sensitisation (the process by which the spinal cord and brain amplify pain signals over time), making it useful for complex regional pain syndrome, fibromyalgia, and neuropathic pain refractory to standard medications.

The anti-suicidal effect is perhaps the most clinically urgent use. Multiple studies have shown that a single sub-anaesthetic dose can reduce suicidal ideation within hours. For a patient in acute crisis, that window matters enormously. Esketamine’s FDA approval specifically covers major depressive disorder with acute suicidal ideation partly on this basis.

Ketamine Infusion Therapy: What Happens During Treatment

A standard IV infusion session runs 40 to 60 minutes. You will be in a reclining chair, not a hospital bed. A nurse or doctor monitors your blood pressure, heart rate, and oxygen saturation throughout because ketamine transiently raises blood pressure and heart rate in most patients.

The dissociative experience begins within a few minutes of the infusion starting. Most patients describe it as a dreamlike state, mild floating, or a sense of being slightly outside themselves. Some find it pleasant; some find it disorienting. You remain conscious and able to communicate. A clinician is in the room or immediately adjacent throughout.

You cannot drive after the session. The dissociative effects clear within 30 to 60 minutes of the infusion ending, but your reaction time is not fully normal for several hours. Plan for someone to take you home.

Most programmes run six infusions over two to three weeks as the induction course. After that, maintenance infusions are typically monthly or as needed based on symptom recurrence.

Esketamine Nasal Spray (Spravato): How It Differs

Esketamine is the S-enantiomer of ketamine, it is the same molecule, isolated to one mirror-image form. It has slightly higher NMDA receptor affinity than racemic ketamine. The nasal spray delivers it directly across the nasal mucosa.

Critically, esketamine must be administered in a certified healthcare setting. You self-administer the spray under supervision, then remain monitored for at least two hours afterwards. You cannot take it home. This is not a bureaucratic inconvenience, it is there because the dissociative and cardiovascular effects require clinical oversight and because the abuse potential of a take-home ketamine prescription is considerable.

The FDA-approved dosing schedule starts at 56mg twice weekly for four weeks, then weekly for four weeks, then once weekly or fortnightly for maintenance. This is not a one-off treatment. It is an ongoing prescription requiring continued supervision.

Side Effects of Ketamine Therapy

The acute side effects during and immediately after infusion are well characterised. Dissociation and perceptual distortion are expected and resolve within 30 to 60 minutes of infusion completion. Nausea occurs in roughly 20% of patients and is usually managed with ondansetron. Transient elevation of blood pressure and heart rate occurs in most patients, which is why uncontrolled hypertension is a contraindication.

Less common acute effects include headache, dizziness, blurred vision, and anxiety during the session. These are generally short-lived.

The long-term risks are more important if you are considering ongoing treatment.

Bladder and Urinary Tract Damage (Ketamine Cystitis)

Ketamine-induced uropathy is a genuine and serious risk. Regular exposure to ketamine causes progressive damage to the bladder wall, leading to a condition called ketamine cystitis: severe pelvic pain, urgency, frequency, and in advanced cases, a shrunken, fibrotic bladder requiring surgical intervention. This was originally described in recreational users taking large daily doses, but cases have been reported in therapeutic settings with repeated infusions over months to years.

If you develop pelvic pain, blood in your urine, or urinary urgency during a course of ketamine therapy, flag it immediately. Continuing treatment through these symptoms is not an option.

Liver Toxicity

Ketamine is metabolised in the liver primarily by CYP3A4 and CYP2B6. Repeated exposure can cause hepatotoxicity. Transaminase elevations are documented in heavy recreational users and in some therapeutic protocols. Baseline liver function tests and periodic monitoring during long-term treatment are standard practice in responsible programmes.

Dissociation and Psychological Distress

Some patients find the dissociative experience distressing rather than pleasant, particularly in the first session. This does not predict treatment outcome, but it warrants clinical support during the session. Patients with a history of psychosis or schizophrenia are generally excluded from ketamine programmes because the dissociative effects can precipitate or worsen psychotic symptoms.

Who Is and Is Not a Good Candidate for Ketamine Therapy

The substance use disorder row deserves a full sentence. A history of substance use disorder is not an automatic disqualification, but it requires careful individual assessment by a clinician experienced in both addiction medicine and psychiatric treatment. The addiction risk of ketamine is real, and a patient with an active or recently active addiction needs a very specific risk-benefit conversation before starting. For a deeper look at how ketamine interacts with addiction specifically, the piece on ketamine-assisted therapy for substance use disorder covers the clinical nuances well.

The Addiction and Dependence Risk of Ketamine Therapy

This is the part that is systematically underplayed in promotional content about ketamine therapy. Ketamine is a Schedule III controlled substance in the US and a Class B drug in the UK for a reason. It has genuine dependence potential.

Ketamine acts on dopamine pathways indirectly, producing reinforcing effects that increase the likelihood of repeated use. Tolerance develops. Users require higher doses to achieve the same dissociative state. Psychological dependence, the compulsive drive to use despite harm, is well documented in recreational populations and is a real clinical risk in therapeutic populations when monitoring is insufficient.

The pattern I see clinically in patients who develop problematic ketamine use follows a predictable arc. It usually starts with legitimate therapeutic use or recreational experimentation. The dissociative relief becomes something a person seeks for its own sake, not for the antidepressant effect. Sessions become more frequent. Between-session use begins. By the time bladder symptoms or occupational consequences appear, daily use is often established.

Telehealth providers prescribing esketamine or referring patients to unsupervised take-home ketamine should be treated with serious scepticism. The FDA requires esketamine to be administered in certified clinical settings specifically because of this risk. If someone offers to mail you ketamine without an in-person clinical assessment, that is not a therapy programme. For a clear breakdown of the full dependency risk profile, see the article on ketamine addiction risks.

Ketamine Therapy vs Psychedelic-Assisted Therapy: Understanding the Difference

Patients frequently ask whether ketamine therapy is the same as psychedelic therapy involving psilocybin or MDMA. It is not, and the distinction matters clinically.

Ketamine is a dissociative anaesthetic, not a classical psychedelic. Classical psychedelics (psilocybin, LSD) work primarily through 5-HT2A serotonin receptors. Ketamine works through NMDA glutamate receptor blockade. The subjective experiences differ considerably. Psilocybin tends to produce a more visually and emotionally expansive experience; ketamine produces a more detached, floating dissociation. The therapeutic models built around them differ too, psilocybin therapy typically involves extensive preparation and integration sessions around a single or double dose experience, while ketamine therapy is primarily biological and does not require the same psychotherapeutic framework, though combining it with therapy is increasingly standard in good programmes.

Research into psychedelic-assisted treatments more broadly is expanding rapidly. For context on where that field is heading, the overview of psychedelic therapy for addiction covers the current evidence landscape.

Cost of Ketamine Therapy and What to Expect Financially

IV ketamine infusions are not cheap, and insurance coverage in most countries is limited because IV administration remains off-label. A single infusion typically costs between $400 and $800 USD in the US, making a standard six-session induction course $2,400 to $4,800. Maintenance infusions add ongoing cost.

Esketamine (Spravato) has better insurance coverage in the US because of its FDA approval, though co-pays and prior authorisation requirements vary significantly by insurer. In Thailand, ketamine therapy is available at specialist psychiatric facilities, and costs are generally lower than US or European equivalents.

Cost should not be the only factor in choosing a programme. A low-cost programme that does not monitor you adequately during infusions, does not screen for contraindications properly, and does not have a clear policy on dependence risk is not a bargain.

The clinical picture of ketamine use disorder is distinct. According to DSM-5 criteria, a substance use disorder is diagnosed when use becomes compulsive, continues despite harm, and impairs functioning across multiple domains. With ketamine, the warning signs include increasing frequency of sessions or doses to achieve the same effect, using ketamine outside of prescribed clinical settings, continued use despite bladder pain or liver test abnormalities, and spending significant time obtaining, using, or recovering from ketamine. These criteria apply whether the original use was recreational or prescribed.

At Phuket Island Rehab, we work with patients who developed ketamine dependency through both routes. The treatment approach combines medically supervised cessation, assessment and management of any uropathy or hepatic damage, and evidence-based addiction therapy to address the psychological dependence that outlasts the physical withdrawal. If you or someone close to you is using ketamine in ways that feel out of control, getting a clinical assessment is the right first step, not something to postpone.

Ketamine therapy is a legitimate and increasingly evidence-supported treatment for conditions that have resisted conventional approaches, particularly treatment-resistant depression and PTSD. Its mechanism, NMDA receptor blockade driving rapid synaptogenesis through BDNF and mTOR pathways, is fundamentally different from standard antidepressants, which is exactly why it works in patients for whom SSRIs and SNRIs have failed. The speed of response, often within hours, is clinically real. The FDA-approved esketamine nasal spray (Spravato) gives that fast-acting mechanism a regulated, supervised delivery route for treatment-resistant and acutely suicidal patients. IV racemic ketamine, though off-label, has the strongest evidence base in terms of volume of clinical data. Both require in-person medical supervision, cardiovascular screening, and ongoing monitoring for bladder, liver, and psychological effects.

The risks are not hypothetical. Ketamine cystitis is a serious, potentially irreversible complication of repeated use. Hepatotoxicity is documented. The dependence potential is real and clinically significant, particularly in patients with any history of substance use. A well-run ketamine programme accounts for all of this before the first infusion. The programmes worth trusting are the ones that turn away patients who are not suitable candidates, not the ones that accept everyone who can pay. As John A. Smith of Phuket Island Rehab puts it: “Ketamine can do things for depression that nothing else I have seen works as fast, but I have also watched patients go from a supervised infusion programme to daily unsupervised use within six months, and unwinding that is a long process. The therapy is only as good as the safeguards around it.”

Is ketamine therapy safe?

Ketamine therapy is safe when administered under proper medical supervision with appropriate patient screening. The acute risks, including elevated blood pressure, dissociation, and nausea, are manageable in a supervised clinical setting. The longer-term risks of bladder damage and liver toxicity are real but largely preventable with dose control, periodic monitoring, and stopping treatment at the first sign of urinary symptoms. Unsupervised or take-home ketamine programmes carry substantially higher risk.

How quickly does ketamine therapy work for depression?

Most patients with treatment-resistant depression notice mood improvement within two to four hours of a single ketamine infusion. This makes it one of the fastest-acting antidepressant interventions known. The problem is durability, effects from a single infusion typically last one to three weeks. A full induction course of six infusions over two to three weeks produces more sustained relief, with some patients maintaining response for two to three months before needing maintenance doses.

What is the difference between ketamine and esketamine?

Esketamine (Spravato) is the S-enantiomer of ketamine, meaning it is one of two mirror-image forms of the same molecule, isolated and delivered as a nasal spray. Racemic ketamine, the original compound, contains both mirror-image forms and is given by IV infusion. Esketamine has FDA approval for treatment-resistant depression and is covered by some insurers; racemic IV ketamine is used off-label but has a larger body of clinical research behind it. Both require supervised administration in a certified clinical setting.

Can ketamine therapy cause addiction?

Yes, ketamine has genuine dependence potential and can cause addiction with repeated use. It acts on dopamine reward pathways indirectly, produces tolerance, and can drive compulsive use patterns, particularly when access is unsupervised. Patients with a personal or family history of substance use disorder carry higher risk and need a careful individual assessment before starting. This is one of the primary reasons responsible programmes do not prescribe take-home ketamine and require in-person monitoring for every session.

Who should not have ketamine therapy?

Ketamine therapy is not suitable for people with uncontrolled hypertension, a history of aortic aneurysm or dissection, active psychosis or schizophrenia, severe liver disease, or a history of ketamine misuse. Pregnancy is also a contraindication. People with a history of other substance use disorders are not automatically excluded but require a careful risk-benefit assessment by an addiction medicine clinician before starting. The contraindications exist because the risks in these groups are disproportionate to the potential benefit.

How much does ketamine therapy cost?

IV ketamine infusions typically cost between $400 and $800 USD per session in the United States, putting a standard six-session induction course at $2,400 to $4,800. Insurance rarely covers off-label IV ketamine. Esketamine nasal spray (Spravato) has better insurance coverage in the US due to its FDA approval. In Thailand, costs at specialist facilities are generally lower. Financial cost should be weighed alongside the quality of clinical monitoring and the rigour of patient screening, not treated as the primary deciding factor.

Is ketamine therapy the same as psychedelic therapy?

No. Ketamine is a dissociative anaesthetic that works through NMDA glutamate receptor blockade. Classical psychedelics like psilocybin work through 5-HT2A serotonin receptors and produce a different subjective experience. The therapeutic models differ too, ketamine therapy is primarily a biological intervention, while psilocybin and MDMA-assisted therapies are typically built around structured psychotherapeutic preparation and integration. Both are areas of active clinical research, but they are distinct treatments with different mechanisms, evidence bases, and regulatory statuses.