Ketamine works for depression for a few days up to about two weeks after a single dose, while a full course of treatment extends relief to several weeks or months, and maintenance sessions help sustain those gains over the long term. Ketamine also starts working faster than any traditional antidepressant, often within hours to days.

Ketamine's speed and staying power both come from the same source: a brain pathway that traditional antidepressants never touch. Below, we break down how long each stage of ketamine treatment lasts, how fast it works, why it works the way it does, how long people stay on it, and how esketamine (Spravato®), the FDA-approved nasal spray form, fits into a depression treatment plan.

How Long Does Ketamine Work for Depression?

How long ketamine works for depression depends on the stage of treatment: days to two weeks after one dose, weeks to months after a full series, and longer still with ongoing maintenance. Each stage builds on the one before it, which is why ketamine is given as a planned course rather than a one-time treatment.

Treatment Stage	When Relief Starts	How Long Relief Lasts	Typical Schedule
Single dose	Within hours to a day	A few days to about two weeks	One session
IV ketamine series	Often after the first few sessions	Several weeks to months	6 to 8 infusions over 2 to 4 weeks
Esketamine (Spravato) induction	Within 24 hours of the first dose in clinical trials	Builds steadily across the first 4 weeks	Twice weekly for 4 weeks
Maintenance	Already established	Sustains relief long term and lowers relapse risk	Weekly or every other week, based on response

Esketamine follows its own schedule, separate from IV ketamine. Spravato treatment starts with twice-weekly sessions during a four-week induction phase, then moves to weekly or every-other-week maintenance based on how well you respond.

How Long Does One Dose of Ketamine Last?

One dose of ketamine lasts a few days to about two weeks for most people who respond. Research cited by Keta Medical Center shows that most patients experience some return of symptoms within seven days of a single infusion.

A single dose proves that ketamine can lift depression quickly, but a single dose rarely holds that lift in place. The short window after one dose is exactly why treatment moves on to a series of sessions.

How Long Does a Full Course of Ketamine Last?

A full course of ketamine lasts several weeks to several months, because repeated sessions build on each other and produce more durable relief than a single dose. Yale New Haven Health reports that IV ketamine is typically given as eight treatments over four weeks, and most patients feel relief within those eight treatments.

Repeated dosing strengthens the response. In an open-label study cited by Keta Medical Center, 70.8% of people with treatment-resistant depression met response criteria by the end of a 12-day series of up to six infusions. Once a series ends, maintenance sessions take over the job of keeping depression from returning.

How Fast Does Ketamine Work for Depression?

Ketamine works for depression within hours to days, far faster than traditional antidepressants, which take 4 to 8 weeks to show their full benefit. Many people feel a meaningful lift in mood within 24 hours of their first ketamine treatment.

The speed holds up in research. Yale School of Medicine researchers found in several studies that more than half of participants showed a significant decrease in depression symptoms just 24 hours after a single low dose of ketamine. Esketamine shows the same rapid pattern: in the TRANSFORM-2 clinical trial, people taking esketamine showed significant improvement compared with placebo within 24 hours of the first dose, an effect that largely held through the four-week study.

Rapid relief matters most for people whose depression has not responded to other options. People comparing faster treatments to daily pills often weigh TMS vs. medication as well, because both TMS and ketamine work through brain pathways that standard antidepressants do not reach. That different brain pathway is the key to why ketamine works so quickly.

How Does Ketamine Work for Depression?

Ketamine works for depression by blocking NMDA receptors in the brain, which triggers a surge of the chemical messenger glutamate and prompts brain cells to grow new connections. Ketamine physically repairs and rebuilds connections between brain cells, rather than slowly shifting chemical levels like traditional antidepressants.

Long-term stress and depression wear down the connections between brain cells, especially in areas that control mood and thinking. Yale New Haven Health describes ketamine as helping the brain form new connections by rebuilding pathways damaged by long-term stress or depression, a process called neuroplasticity.

The Glutamate and NMDA Pathway, Step by Step

The glutamate and NMDA pathway explains how one ketamine treatment sets off a chain of changes inside the brain:

Ketamine blocks NMDA receptors, a type of glutamate receptor on brain cells.
Blocking NMDA receptors quiets the inhibitory (calming) signals that normally hold glutamate in check.
Glutamate, the brain's main excitatory chemical messenger, surges between brain cells.
The glutamate surge activates AMPA receptors, a second type of glutamate receptor.
AMPA activation releases brain-derived neurotrophic factor (BDNF) and switches on the mTOR signaling pathway.
BDNF and mTOR drive synaptogenesis, the growth of new synapses, or connections, between brain cells.
New synapses restore communication in mood circuits weakened by depression.

Why Ketamine Works Faster Than SSRIs

Ketamine works faster than SSRIs because ketamine acts directly on the glutamate system, while selective serotonin reuptake inhibitors (SSRIs) work on serotonin and need weeks for the brain to adapt. SSRIs gradually raise serotonin levels, and the brain changes that follow build slowly over 4 to 8 weeks.

Columbia University Irving Medical Center notes that ketamine targets different neurotransmitters than conventional SSRIs, so people who have not responded to traditional antidepressants may respond to ketamine. Ketamine skips the slow adjustment period and starts rebuilding connections within hours.

Why the Effect Outlasts the Drug

Ketamine's effect outlasts the drug because the new brain connections it creates remain long after ketamine leaves the body. Ketamine has a half-life of about 2 to 3 hours and is cleared from the bloodstream within 10 to 15 hours, according to NIH StatPearls.

The relief that follows lasts days or weeks, well beyond that 15-hour window. The drug starts the rebuilding process, and the rebuilt connections keep working once the drug is gone. Those connections slowly fade without reinforcement, which is why repeated sessions and maintenance matter so much.

Does Ketamine Work for Depression?

Yes, ketamine works for depression, especially treatment-resistant depression, which is depression that has not improved after trying at least two antidepressants. Esketamine nasal spray, sold as Spravato, became the first new type of treatment approved for treatment-resistant depression in three decades when the FDA approved it in March 2019.

Depression has become more common, raising the need for options that work when standard treatments fall short. A study in the American Journal of Preventive Medicine, reported by Columbia University Irving Medical Center, found that nearly one in 10 adults reported having depression in 2020, up from 6.6% in 2005.

Ketamine is not the only option for depression that resists treatment. Comprehensive depression treatment starts by reviewing which medications and therapies you have already tried.

Some people do better with a non-medication approach, such as TMS therapy, which uses magnetic pulses to activate mood regions of the brain.

Severe depression with thoughts of suicide needs immediate support. Call or text 988, the Suicide & Crisis Lifeline, which offers free and confidential support 24 hours a day, or call 911 in an emergency.

How Long Do You Have to Take Ketamine for Depression?

You have to take ketamine for depression for at least the full induction phase, usually about four weeks, and many people continue with maintenance sessions for months or longer to keep depression from returning. The total length depends on how well you respond and how severe your depression has been.

Maintenance makes a measurable difference. In the SUSTAIN-1 trial, published in JAMA Psychiatry in 2019, 297 adults with treatment-resistant depression who had improved on esketamine either continued esketamine or switched to a placebo spray, while keeping their oral antidepressant. Among people in stable remission, 26.7% of those who continued esketamine relapsed, compared with 45.3% of those who stopped. Continuing esketamine cut the risk of relapse by 51% for people in remission and by 70% for people with a stable response.

Long-term data shows benefits growing with time. A long-term esketamine study following patients for nearly five years, cited by Keta Medical Center, found that remission rates rose from 35.6% at the end of induction to 46.1% during ongoing maintenance.

Planning esketamine treatment length is an ongoing conversation. Some people continue maintenance long term, while others taper off gradually under medical guidance once they have been stable for a sustained period. We often see patients in Miami Lakes surprised to learn that the induction month is just the beginning of their plan, not the whole of it.

What Makes Ketamine's Effects Last Longer?

Ketamine's effects last longer when treatment combines the right supports around each session. The factors that help extend ketamine's effects include:

Completing the full induction phase rather than stopping after early relief
Staying on schedule with maintenance sessions
Continuing the oral antidepressant prescribed alongside esketamine
Pairing treatment with therapy that builds lasting coping skills
Protecting sleep, regular routines, and daily movement
Avoiding alcohol and other substances that worsen depression

Therapy carries special weight. Yale New Haven Health notes that ketamine is most effective when combined with cognitive behavioral therapy (CBT), because new brain connections are easiest to shape while they are forming. Ongoing psychotherapy turns the window ketamine opens into longer-lasting change.

The oral antidepressant matters too. Esketamine is always used with an oral antidepressant, and careful medication management keeps that daily medication working alongside each session.

IV Ketamine vs. Esketamine Nasal Spray

IV ketamine and esketamine nasal spray both work on the same glutamate pathway, but esketamine is the only form FDA-approved for depression. IV ketamine is delivered through a vein, with an infusion that typically takes 40 minutes to an hour, according to Columbia University Irving Medical Center, and its use for depression is off-label.

Esketamine is a form of ketamine delivered as a nasal spray and absorbed through the lining of the nose. Spravato is FDA-approved for adults with treatment-resistant depression, used together with an oral antidepressant, and given only in certified healthcare settings under a Risk Evaluation and Mitigation Strategy (REMS) program.

Each esketamine session follows a set routine. Patients give themselves the nasal spray under direct supervision, then stay for at least two hours of monitoring. At our Miami Lakes office, each session takes about two to three hours from arrival to departure. Specialized psychiatric care surrounds each session, with ongoing review of how your symptoms are changing.

How Long Has Ketamine Been Used for Depression?

Ketamine has been used for depression for about 25 years, since researchers at Yale School of Medicine first tested it in people with depression. Ketamine itself has a much longer history: the FDA first approved ketamine in 1970 as an anesthetic for surgery.

The Yale studies in the early 2000s showed that a single low dose could rapidly reduce depression symptoms, even in people who had not responded to traditional antidepressants. Dr. Robert Ostroff of Yale New Haven Psychiatric Hospital describes those first results as dramatic. Two decades of research followed, leading to the FDA approval of esketamine nasal spray in March 2019.

Ketamine's long medical history is one reason providers understand its safety profile well. Knowing when to see a psychiatrist about depression that has not improved is the first step toward finding out whether ketamine-based treatment fits your situation.

Frequently Asked Questions

What Happens When You Stop Ketamine Treatment?

When you stop ketamine treatment, depression symptoms can gradually return, because the brain connections ketamine builds fade without reinforcement. The SUSTAIN-1 trial found relapse rates of 45.3% among people in remission who stopped esketamine, compared with 26.7% among those who continued. Providers plan any taper gradually to watch for early signs of returning symptoms.

How Long Does Dissociation From Ketamine Last?

Dissociation from ketamine lasts about 1.5 to 2 hours after an esketamine dose. Dissociation feels like a temporary sense of detachment from your surroundings or your body. The required two-hour monitoring period covers the time dissociation, dizziness, and sedation take to wear off.

Can You Drive After Ketamine Treatment?

No, you cannot drive after ketamine treatment. People receiving esketamine should not drive or operate machinery for the rest of the treatment day and need to arrange a ride home after each session.

Do You Still Need Your Antidepressant With Ketamine?

Yes, you still need your antidepressant with esketamine treatment. Spravato is FDA-approved for use together with an oral antidepressant, and esketamine adds to that medication rather than replacing it.

Is Ketamine Addictive?

Ketamine carries a potential for misuse, which is why esketamine is only available through the REMS program and given in certified clinics under direct supervision. Esketamine is never sent home with patients. Supervised dosing at the prescribed schedule keeps the risk of misuse low.

Who Is a Candidate for Ketamine Treatment for Depression?

A candidate for ketamine treatment for depression is typically an adult with major depressive disorder who has tried at least two antidepressants without enough relief. People with a history of aneurysmal vascular disease, arteriovenous malformation, bleeding in the brain, or a sensitivity to ketamine or esketamine are not candidates. A full mental health evaluation confirms whether esketamine fits your history.

What It All Comes Down To

Ketamine works for depression within hours to days, and its effects last a few days to two weeks after one dose, weeks to months after a full course, and longer with maintenance. The reason lies in the glutamate pathway: ketamine blocks NMDA receptors, sets off a glutamate surge, and helps the brain grow new connections that outlast the drug itself.

Esketamine nasal spray brings that same pathway into a supervised, FDA-approved treatment for depression that has not responded to standard medications. At South Florida Med Group, we help adults with treatment-resistant depression find out whether esketamine belongs in their plan.

Depression that has outlasted medication after medication is worth a fresh conversation, and we are glad to talk it through whenever you reach out.

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