A ketamine therapy session typically lasts about two hours total: a 40-minute medication phase followed by roughly 30 minutes of recovery and monitoring before you’re cleared to leave. During that window, you’ll experience a range of sensory and emotional shifts, from feeling detached from your surroundings to altered time perception, while a medical team tracks your vital signs. Here’s what the full process looks like, from the first appointment through maintenance.
How Ketamine Works in the Brain
Ketamine’s antidepressant effect isn’t a single action but a chain reaction. It starts by blocking certain receptors on inhibitory brain cells, which temporarily releases the brakes on nearby neurons. This triggers a burst of the brain’s main excitatory chemical, glutamate. That glutamate surge then activates a separate set of receptors that kick off the growth of new connections between neurons, a process called synaptogenesis.
This cascade also switches on internal signaling pathways that promote a protein essential for neuron health and growth. The net result is that ketamine rapidly rebuilds synaptic connections that depression and chronic stress have eroded. This is why relief can begin within hours rather than the weeks typical of standard antidepressants: the drug is physically restructuring neural circuits, not just adjusting chemical levels.
What a Session Looks Like Step by Step
Before anything begins, a clinician takes baseline vital signs: blood pressure, heart rate, and blood oxygen level. You’ll be seated or reclined in a comfortable chair, often in a dimly lit room. Some clinics offer eyeshades and music to help guide the experience.
For intravenous (IV) ketamine, the standard protocol is 0.5 mg/kg of body weight infused over 40 minutes. The dose is sub-anesthetic, meaning it’s far below what would be used for surgery. For the nasal spray form (esketamine, brand name Spravato), the dose is 56 or 84 mg, self-administered under supervision. Either way, a staff member remains nearby throughout.
Vital signs are rechecked at 15 and 30 minutes during the infusion. Continuous pulse oximetry, which clips onto your finger to measure blood oxygen, runs for at least 30 minutes. Heart rhythm is monitored on a cardiac monitor for the same period. After the medication phase ends, you stay in the clinic for an observation period of at least 30 minutes (two hours for the nasal spray form) before being discharged with a driver. You cannot drive yourself home.
What It Feels Like During Treatment
The subjective experience varies from person to person, but certain themes are consistent. The most commonly reported side effect across clinical trials is simply feeling “strange, weird, or loopy.” Many people describe a sense of floating or being disconnected from their body and surroundings. When ketamine was first tested on patients in the 1960s, they described feeling “spaced out” or as though they were dreaming, which is how it earned the label “dissociative.”
Beyond that core dissociation, patients frequently report altered time perception (minutes can feel like hours or seconds), unusual bodily sensations like heaviness or tingling, and changes in how sounds and light register. Some people experience a deep sense of peacefulness or even describe something resembling a spiritual experience, including feelings of unity or bliss. Others find the dissociation uncomfortable or disorienting. The intensity of these effects tends to peak within the first hour and then fade relatively quickly.
Nausea, dizziness, and a temporary rise in blood pressure are the most common physical side effects. Importantly, a comprehensive analysis of side effects across multiple trials found that most peaked within one hour and resolved completely by two hours after the infusion. No serious drug-related adverse events were observed, and no increase in ketamine craving or misuse was reported over a roughly three-month follow-up period.
The Neuroplasticity Window After a Session
What happens after the drug wears off may be just as important as the session itself. Research shows that ketamine opens a time-limited window of heightened brain plasticity. By about two hours after administration, the brain’s capacity to form new synaptic connections roughly doubles. This elevated plasticity lasts through the four-hour mark but fades by 12 hours. The actual growth of new dendritic spines, the physical structures that form connections between neurons, follows shortly after.
This timeline is why many ketamine-assisted therapy programs schedule a psychotherapy “integration” session within the hours or day following treatment. The idea is to use that window of increased neural flexibility to reinforce new thought patterns and emotional processing. The brain is temporarily more receptive to forming new pathways, and combining that biological openness with guided therapeutic work may strengthen and extend the antidepressant benefits.
How Many Sessions to Expect
The standard starting protocol is six sessions spread over two to three weeks. This induction phase is designed to build on the cumulative effects of repeated treatments. Some people notice mood improvement after the first or second session, while others don’t feel a significant shift until later in the series.
After the initial phase, the schedule shifts to maintenance. What this looks like varies considerably. A typical trajectory might be one session every two to four weeks for the first few months, stretching to every four to eight weeks after six months. Some people eventually space sessions out to every three to six months, while others find they need more frequent boosters. For the FDA-approved nasal spray specifically, the protocol calls for twice-weekly sessions for four weeks, then weekly for another four weeks, then every one to two weeks going forward.
Two Forms of Ketamine Therapy
The IV infusion uses racemic ketamine, which contains both mirror-image forms of the molecule. It has 100% bioavailability, meaning the full dose reaches the bloodstream. Clinics that offer IV ketamine are using the drug off-label, which is legal but means it isn’t FDA-approved specifically for depression through this route.
The nasal spray, esketamine (Spravato), contains only one of those two mirror forms and is the only version with full FDA approval for treatment-resistant depression. Because of this, it comes with a strict monitoring program: it can only be dispensed and administered in certified healthcare settings, and patients must be observed for a minimum of two hours afterward. The nasal spray’s bioavailability is lower than IV, which is why the dosing schedules and milligram amounts differ between the two.
Risks and Who May Not Be Eligible
The known safety concerns include sedation, dissociation, temporary blood pressure increases, slower or shallower breathing, and the possibility of worsening certain psychiatric conditions. Urinary tract and bladder symptoms have also been documented, particularly with repeated or high-dose use.
People with uncontrolled high blood pressure are generally not good candidates because ketamine reliably raises blood pressure during the session. Those with a history of psychosis or certain other psychiatric conditions may also be excluded, since the dissociative effects can potentially trigger or worsen symptoms. Active substance use disorders require careful evaluation given ketamine’s potential for misuse, though clinical data has not shown increased craving in supervised treatment settings.
The FDA has specifically warned about compounded ketamine products used at home, noting that without onsite medical supervision, serious adverse outcomes from sedation and dissociation are harder to manage. If you’re considering ketamine therapy, the safest route is in-person treatment at a clinic equipped to monitor your vitals and respond to any complications in real time.