Ketamine and Esketamine

What Ketamine and Esketamine Are

Ketamine is a medication that has been used safely as an anesthetic in hospitals and emergency departments for many years, including in children and on battlefields, because it provides pain relief and sedation without strongly suppressing breathing. At lower doses than those used for anesthesia, it produces a dissociative, dreamlike state and, importantly, a rapid antidepressant effect.

The molecule exists in two mirror-image forms, called enantiomers: an "R" form and an "S" form. Standard ketamine is a racemic mixture, meaning it contains roughly equal amounts of both. Esketamine is the isolated S-enantiomer, purified into a single form. It is formulated as a nasal spray and is marketed under the brand name Spravato. Esketamine has been formally approved by regulatory agencies, including the U.S. Food and Drug Administration, for treatment-resistant depression and for depressive symptoms in adults with major depressive disorder who have suicidal thoughts or behavior.

Generic ketamine, by contrast, is approved as an anesthetic but is used off-label for depression. Off-label means a clinician prescribes an approved drug for a condition it was not specifically licensed to treat, which is a common and legal practice when supported by evidence. Ketamine for depression is most often given as an intravenous (IV) infusion, though intramuscular injections, sublingual lozenges, and other routes are also used in some clinics.

Why the Distinction Matters

The practical differences between the two shape access, cost, and oversight. Esketamine comes with a strict, regulator-mandated risk program: it can only be administered in certified healthcare settings where patients are monitored for at least two hours afterward, and it cannot be taken home. Because it is an approved branded product, it is more likely to be covered by insurance, but it can be expensive and logistically demanding. Generic IV ketamine is often less expensive per dose and more flexible in dosing, but because it is off-label, insurance coverage is inconsistent and quality varies between clinics.

Origins and Discovery

Ketamine was synthesized in the 1960s as a safer alternative to an earlier anesthetic that caused severe agitation and hallucinations on emergence. It quickly became valued in surgery and emergency medicine for its favorable safety profile. For decades its psychiatric potential went largely unrecognized outside of research curiosity about its dissociative effects.

The turning point came around the start of the 2000s, when controlled studies reported that a single low-dose infusion could produce a rapid and substantial reduction in depressive symptoms, sometimes within hours, in people whose depression had resisted other treatments. This was striking because the prevailing model of depression centered on the slow adjustment of serotonin and other monoamine systems through drugs like SSRIs and SNRIs, and through older agents such as MAOIs and tricyclic antidepressants. Ketamine seemed to work through an entirely different chemical pathway and on a completely different timescale.

That discovery reshaped depression research, spotlighting the glutamate system as a target and eventually leading to the development and approval of esketamine. It also contributed to broader interest in rapid-acting and non-traditional interventions, a category that now includes the emerging field of psychedelic-assisted therapy.

How They Work in the Brain

Most traditional antidepressants act primarily on serotonin, norepinephrine, or dopamine. Ketamine and esketamine work mainly on glutamate, the brain's most abundant excitatory neurotransmitter. Their best-understood action is blocking a particular receptor called the NMDA receptor. However, blocking that receptor is only the trigger; the antidepressant effect appears to come from a cascade of downstream events.

The Glutamate Surge and Synaptic Repair

By temporarily blocking NMDA receptors on certain inhibitory neurons, ketamine is thought to release a brief "surge" of glutamate. This surge activates other glutamate receptors and switches on signaling pathways that promote the growth of new synaptic connections between neurons. Chronic stress and depression are associated with the loss or weakening of synapses in regions involved in mood and motivation, such as the prefrontal cortex. Ketamine appears to rapidly stimulate the regrowth and strengthening of these connections, a form of neuroplasticity.

This synaptic model helps explain two clinical observations: why the antidepressant effect can appear so quickly (the molecular machinery acts within hours), and why it can outlast the drug itself for days or weeks (the structural changes persist after the chemical has cleared). Research also points to the role of certain metabolites of ketamine and to other signaling molecules, so the full picture is still being worked out.

The Dissociative Experience

During administration, many people experience dissociation, a sense of detachment from the body, surroundings, or the normal flow of time. Perceptions may feel dreamy, distorted, or floating. While early thinking sometimes assumed this altered state was necessary for the antidepressant benefit, current evidence suggests the mood effect and the dissociative effect are at least partly separable. The dissociation is generally short-lived, fading within an hour or two of dosing, and is one reason monitoring during treatment is essential.

What a Session Looks Like

The experience varies by setting and by whether you are receiving IV ketamine or esketamine nasal spray, but the structure is broadly similar: careful preparation, supervised dosing, monitoring, and integration.

Before Treatment

• Medical and psychiatric screening: A clinician reviews your diagnosis, medication history, blood pressure, heart health, and any history of psychosis or substance use that might make treatment unsafe.
• Setting expectations: You learn what the dissociative state may feel like, how long it lasts, and what the goals are.
• Practical preparation: You are usually asked not to eat for a few hours beforehand and to arrange transportation home, since you cannot drive afterward.

During the Session

An IV ketamine infusion typically runs over roughly 40 minutes in a calm, comfortable room. Esketamine is self-administered as a nasal spray under direct supervision, in a series of sprays over a short period. In both cases, staff monitor blood pressure, heart rate, oxygen, and mental state, because ketamine can transiently raise blood pressure. Many people simply rest with eyes closed, sometimes with music. The dissociative effects build and then ease over the session.

After the Session

Following esketamine, patients are observed for at least two hours before being released to a companion. After IV ketamine, a recovery period is also standard. People are advised not to drive or make important decisions for the rest of the day. Some clinics, especially those offering ketamine-assisted psychotherapy, schedule a talk-therapy "integration" session afterward to help process the experience and connect any insights to lasting behavior change.

The Overall Course

Single doses rarely produce durable remission on their own. A typical induction phase involves a series of treatments over several weeks, followed by a tapering maintenance schedule tailored to the individual. The right frequency is decided collaboratively with the prescriber based on response and side effects, and the plan usually continues alongside other care such as an oral antidepressant or ongoing psychotherapy.

What They Treat and the Evidence

Treatment-Resistant Depression

The strongest and most established use is treatment-resistant depression, broadly defined as major depressive disorder that has not responded adequately to at least two different antidepressants taken at sufficient dose and duration. For this population, esketamine added to an oral antidepressant has been shown in clinical trials to improve depressive symptoms, and it is approved for this purpose. IV ketamine has a substantial body of trial evidence showing rapid antidepressant effects as well, though much of it comes from smaller or shorter studies, and questions about the best long-term protocols remain active areas of research.

Suicidal Thoughts

One of the most clinically meaningful findings is ketamine's rapid effect on suicidal ideation. Because it can reduce acute suicidal thinking within hours, it offers a potential bridge during a crisis while slower treatments take effect. Esketamine carries a specific approval for major depressive disorder with suicidal thoughts or behavior. This does not make it a standalone emergency cure, but it adds an important tool for acutely ill patients in supervised care. Anyone in immediate danger should contact local emergency services or a crisis line.

Other Conditions Under Study

Researchers are investigating ketamine for several other conditions, with varying levels of evidence:

• Bipolar depression: Some evidence of rapid benefit, but used cautiously given the need to avoid triggering mania; see bipolar disorder.
• Post-traumatic stress disorder: Early and mixed findings for PTSD, often explored in combination with therapy.
• Obsessive-compulsive disorder: Small studies suggest possible short-term reductions in symptoms of OCD.
• Chronic pain: Ketamine has long-standing uses in pain management, which overlaps with the psychology of chronic pain.

For most of these, ketamine is not an approved or first-line option, and the evidence is still developing. Decisions should always involve a knowledgeable prescriber weighing benefits against risks.

Where It Fits Among Treatments

Ketamine and esketamine sit alongside other interventions for severe or resistant depression, including electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS). They are generally not first-line; the usual sequence still begins with established medications and evidence-based psychotherapy such as cognitive behavioral therapy. The broader question of how biological and psychological treatments compare is explored in our overview of therapy versus medication.

Benefits and Limitations

Key Benefits

• Speed: Relief can begin within hours, a major advantage in severe or crisis situations where waiting weeks is dangerous.
• New mechanism: Because it works on glutamate rather than serotonin, it can help people who have not responded to conventional antidepressants.
• Rapid reduction in suicidal thinking: Potentially life-saving as a short-term bridge.
• Compatibility: Often added to existing treatment rather than requiring patients to stop what they are doing.

Important Limitations

• Effects can fade: Without maintenance, benefits frequently wane over days to weeks, so it is rarely a one-time fix.
• Not a cure: It treats symptoms; lasting recovery usually still depends on therapy, lifestyle, and ongoing support.
• Access and cost: Treatment requires specialized, monitored settings, and out-of-pocket costs can be high, especially for off-label IV ketamine.
• Variable quality: The rapid growth of private ketamine clinics means standards differ, and some operate with limited psychiatric oversight.
• Open research questions: Optimal dosing, long-term safety with repeated use, and the best maintenance strategies are still being studied.

Risks and Safety

When used appropriately under medical supervision, ketamine and esketamine have a manageable safety profile, but they are not risk-free, and understanding the cautions is essential.

Common Short-Term Effects

• Dissociation, dizziness, and a sense of unreality during and shortly after dosing
• Nausea, sometimes with vomiting, especially with the nasal spray
• Temporary increases in blood pressure and heart rate, which is why monitoring is required
• Sedation, blurred vision, and headache
• Anxiety or unease during the experience for some people

Longer-Term and Serious Concerns

• Potential for misuse and dependence: Ketamine has recognized abuse potential, so doses are controlled and take-home medication is restricted. People with histories of addiction need careful screening.
• Bladder and urinary problems: Heavy, frequent, long-term use, particularly recreational, is linked to serious bladder damage.
• Psychiatric cautions: It is generally avoided in people with active psychosis because it can worsen such symptoms.
• Cardiovascular cautions: Uncontrolled high blood pressure or certain heart conditions may make treatment unsafe.

Why Supervision Matters

The gap between therapeutic and recreational use is wide. Clinical treatment uses measured doses, trained staff, vital-sign monitoring, and clear protocols for who should and should not receive it. This is also why esketamine's risk-management program forbids taking it home and mandates observation after each dose. The molecule is the same as the one sometimes misused, but the controlled context is what makes supervised treatment reasonably safe.

Finding a Provider

If you and your clinician think ketamine or esketamine might be appropriate, choosing a careful, well-run program matters as much as the treatment itself.

What to Look For

• Psychiatric oversight: A program led by or closely involving a psychiatrist or other qualified prescriber, not just an infusion technician.
• Thorough screening: A real assessment of your diagnosis, medical history, and risk factors before any dose is given.
• Proper monitoring: Blood pressure, heart rate, and recovery monitoring, with a plan for adverse reactions.
• Integration and continuity: Coordination with your existing mental health team, and ideally access to therapy to consolidate gains.
• Honest expectations: A provider who explains the limits, the need for maintenance, and the lack of guarantees, rather than promising a miracle.

Questions Worth Asking

• Who supervises the treatment and what are their qualifications?
• Are you offering esketamine (Spravato) or off-label ketamine, and why?
• How do you screen for safety, and what conditions would rule me out?
• What does a full course cost, and what does insurance cover?
• How will this coordinate with my current prescriber and therapist?

A good starting point is a conversation with your current mental health professional, who can advise whether these treatments fit your situation and refer you to a reputable program. Our guides to finding a therapist and the broader field of psychopharmacology can help you frame that discussion.

Frequently Asked Questions

Is ketamine therapy the same as recreational ketamine use?

No. Therapeutic ketamine is delivered in carefully controlled, low-to-moderate doses under medical supervision, with monitoring of blood pressure, breathing, and mental state. Recreational use involves uncontrolled doses without supervision and carries a much higher risk of harm, dependence, and bladder damage. The same molecule is involved, but the setting, dose, and safeguards are completely different.

How quickly does ketamine work for depression?

Many people notice a reduction in depressive symptoms within hours to a day or two after a single dose, which is dramatically faster than standard antidepressants that typically take several weeks. However, these early effects are often short-lived, which is why treatment usually involves a series of sessions and a maintenance plan to sustain the benefit.

What is the difference between ketamine and esketamine?

Esketamine is the S-enantiomer, one of the two mirror-image forms found in standard racemic ketamine. Esketamine is delivered as a nasal spray (brand name Spravato) and is approved specifically for treatment-resistant depression and depression with suicidal thoughts. Generic ketamine is usually given by intravenous infusion and used off-label for depression. Both act on the glutamate system, but they differ in approval status, delivery, and cost.

Is ketamine therapy addictive?

Ketamine has recognized potential for misuse and dependence, which is why medically supervised treatment uses controlled doses, monitored administration, and limits on take-home medication. In a structured clinical program the risk is managed carefully, but ketamine is not appropriate for everyone, particularly people with a history of substance use disorders, who need extra caution and screening.

Does ketamine therapy replace antidepressants or therapy?

Usually not. Ketamine and esketamine are most often added to an existing treatment plan rather than replacing it. Esketamine, in fact, is approved for use alongside an oral antidepressant. Many clinicians pair ketamine with psychotherapy to help patients consolidate insights and sustain gains, and ongoing care from a mental health professional remains important.