Ketamine infusion is primarily used to treat severe depression that hasn’t responded to standard medications, with growing use for acute suicidal crises and certain chronic pain conditions. The treatment involves receiving a low dose of ketamine through an IV in a clinical setting, typically over 40 minutes, and it works far faster than traditional antidepressants, often producing noticeable changes within hours rather than weeks.
Treatment-Resistant Depression
The most common reason people receive ketamine infusions today is depression that hasn’t improved after trying multiple antidepressants. In clinical practice, roughly 55% of patients with treatment-resistant depression respond to IV ketamine, and the effects are described as fast-acting compared to conventional medications, which can take four to six weeks to kick in. For someone who has cycled through several drugs without relief, that speed matters enormously.
It’s worth noting that ketamine itself is not FDA-approved for depression. The FDA approved ketamine decades ago as an anesthetic, and its use for psychiatric conditions is considered off-label. A closely related drug called esketamine (brand name Spravato), delivered as a nasal spray, was approved by the FDA in 2019 specifically for treatment-resistant depression in adults and for depressive symptoms in people with major depression who have acute suicidal thoughts. The IV ketamine infusions offered at clinics operate in a regulatory gray zone: legal for doctors to prescribe off-label, but without the same formal review of safety and effectiveness that Spravato underwent.
Acute Suicidal Ideation
One of the most striking applications of ketamine infusion is its ability to rapidly reduce suicidal thinking. In a double-blind, placebo-controlled trial published in The BMJ, 63% of participants receiving ketamine reached full remission of suicidal ideas within three days, compared to about 32% on placebo. The effect started remarkably fast: nearly 44% of patients in the ketamine group had remission of suicidal thoughts just two hours after the first infusion, versus 7% in the placebo group.
This rapid onset fills a critical gap. Most psychiatric medications take weeks to work, which is a dangerous window for someone in acute crisis. The change in suicidal thinking appeared within 40 minutes of the infusion and persisted over the three-day study period. By six weeks, though, the difference between ketamine and placebo had narrowed and was no longer statistically significant, suggesting the effect on suicidal ideation may require repeated treatments to maintain.
Chronic Pain Conditions
Ketamine infusions are also used for chronic pain that hasn’t responded to other treatments. Complex regional pain syndrome (CRPS) and fibromyalgia are among the conditions most commonly treated this way, along with neuropathic pain and certain centralized pain syndromes. Pain protocols tend to be more intensive than those used for depression. One standardized approach involves five consecutive days of 40-minute infusions, though protocols vary between clinics.
The theory behind using ketamine for pain involves its ability to interrupt pain signaling in the nervous system. In chronic pain conditions, the brain and spinal cord can become “wound up,” amplifying pain signals even when the original injury has healed. Ketamine appears to help reset that signaling, providing relief that can last weeks to months in some patients. Evidence for chronic pain is less robust than for depression, and results vary significantly from person to person.
Other Psychiatric Conditions
Researchers have explored ketamine for PTSD, social anxiety disorder, obsessive-compulsive disorder, and other conditions, but the evidence is still early. A randomized crossover trial tested a single ketamine infusion for social anxiety disorder in 18 participants, measuring anxiety symptoms before and after treatment. These small studies suggest potential, but the data is nowhere near as strong as what exists for depression and suicidal ideation. Most clinics offering ketamine for anxiety disorders are doing so based on limited evidence and clinical judgment.
What a Session Looks Like
A typical ketamine infusion lasts about 40 minutes. You sit in a reclining chair in a clinical setting, often with dimmed lights or the option to listen to music. The dose used for psychiatric treatment is far lower than what’s used in anesthesia, so you remain conscious throughout. Most people describe feeling a sense of detachment or floating during the infusion, and some experience mild visual distortions. These dissociative effects are temporary and typically fade within an hour or two after the IV is removed.
For depression, a common induction schedule involves six infusions spread over two to three weeks. After that initial series, some patients return for maintenance infusions every few weeks or months, depending on how long the effects last. For chronic pain, the five-consecutive-day protocol is one approach, though there is no single universally accepted schedule. You’ll need someone to drive you home afterward, as the cognitive effects make it unsafe to drive for several hours.
Side Effects and Monitoring
The most common side effects during an infusion are dissociation (feeling disconnected from your body or surroundings), nausea, headache, and anxiety. These are generally short-lived and resolve after the session ends.
The more clinically significant concern is blood pressure. Ketamine stimulates the cardiovascular system, raising heart rate and blood pressure during the infusion. Studies show that 10 to 50% of patients experience a transient blood pressure increase, with systolic pressure rising an average of 16 points and diastolic pressure rising about 11 points, peaking around the 40-minute mark. In roughly 12.5% of patients in one study, blood pressure spiked high enough to be classified as severe hypertension, and some required medication to bring it down. These spikes are more common during the first few infusions. For this reason, your blood pressure is typically checked every 10 minutes throughout the session.
Who Should Not Receive Ketamine Infusions
Several conditions disqualify someone from receiving ketamine infusions. The Department of Veterans Affairs, which maintains one of the more detailed screening protocols, lists the following exclusion criteria:
- Psychotic disorders such as schizophrenia or schizoaffective disorder, either current or past
- Bipolar disorder, due to the risk of triggering manic episodes
- Uncontrolled high blood pressure (above 140/90)
- Severe heart failure or unstable angina
- Active substance use disorder (excluding tobacco), including any history of ketamine misuse
- Pregnancy or breastfeeding
- Dementia or recent delirium
- Severe liver impairment
- Uncontrolled seizures
If you’ve previously tried ketamine or esketamine without benefit, most protocols also consider that a reason not to continue. These criteria exist because ketamine can worsen psychotic symptoms, further elevate blood pressure in people who already have cardiovascular risk, and poses addiction potential for people with substance use histories. Screening is typically thorough, involving a psychiatric evaluation, medical history review, and baseline vital signs before your first infusion.