Ketamine injections are low-dose infusions of an anesthetic drug, delivered through an IV or intramuscular shot, used to treat severe depression and certain chronic pain conditions. Originally developed as a surgical anesthetic in the 1960s, ketamine gained attention over the past two decades for its ability to relieve depression symptoms within hours, far faster than traditional antidepressants that take weeks to work. Most ketamine injections for mental health are administered in specialized clinics under medical supervision, typically at a fraction of the anesthetic dose.
How Ketamine Works in the Brain
Traditional antidepressants target serotonin or norepinephrine. Ketamine takes a completely different route. It blocks a specific type of receptor involved in how brain cells communicate, which triggers a cascade of effects that ultimately increases levels of glutamate, the brain’s primary excitatory chemical messenger. This surge of glutamate activates alternate pathways that strengthen connections between neurons and promote the growth of new synaptic links, a process called synaptic plasticity.
These changes appear to happen in brain areas responsible for mood regulation, including the frontal cortex and hippocampus. Ketamine also boosts production of a protein that supports the survival and growth of nerve cells. This combination of rapid chemical signaling changes and structural brain remodeling is what researchers believe produces ketamine’s unusually fast antidepressant effects, sometimes noticeable within hours of a single session.
Conditions Treated With Ketamine Injections
The two main categories are treatment-resistant depression and chronic pain syndromes, particularly those involving nerve damage.
For depression, ketamine is typically offered to people who haven’t responded to two or more standard antidepressants. It’s used for both unipolar and bipolar depression. The rapid onset makes it especially valuable for people in acute crisis, since conventional medications can take four to six weeks to show results.
For pain, clinicians use ketamine to treat a wide range of nerve-related conditions: complex regional pain syndrome (CRPS), fibromyalgia, phantom limb pain, post-shingles nerve pain, spinal cord injury pain, chemotherapy-induced neuropathy, trigeminal nerve pain, and chronic migraines, among others. Short infusions tend to provide relief only during and shortly after administration. Longer infusion protocols lasting several days have shown pain relief lasting up to three months. In one study of CRPS patients, a multi-day ketamine infusion produced significant pain reduction that persisted for 12 weeks after treatment ended.
IV vs. Intramuscular Injections
Intravenous infusions are the most common method. A small IV line is placed in your arm or hand, and the medication drips in slowly over 40 to 60 minutes. This allows the clinical team to adjust the rate in real time if side effects become uncomfortable.
Intramuscular injections are a simpler alternative: a single shot, usually in the upper arm or thigh, with no IV line needed. Research comparing the two routes for depression found no significant difference in effectiveness. In one study, depression scores dropped by roughly 58 to 60 percent within two hours regardless of whether the dose was given by IV or intramuscular injection. The choice between routes often comes down to clinic setup and patient preference.
Typical Dosing for Depression
The standard dose for depression is 0.5 mg/kg of body weight, meaning a 150-pound person would receive about 34 mg. Some patients respond to doses as low as 0.1 mg/kg, while others need up to 0.75 mg/kg. This is a fraction of what’s used in surgery.
Most clinics recommend an induction series of six infusions, typically spaced two to three times per week over two to three weeks. After the initial series, some patients transition to maintenance sessions. The ideal frequency varies from person to person, with clinicians generally timing the next session just before the effects of the previous one are expected to fade. Some people need a session every few weeks; others may go longer between treatments.
How Long the Effects Last
After a single ketamine session for depression, symptom relief peaks around 24 hours and lasts roughly one week on average. The antidepressant effect is strongest in the first day, with depression scores showing a large improvement at 24 hours, a moderate improvement at three to four days, and a smaller but still measurable benefit at seven days compared to placebo.
A full induction series extends those benefits considerably. Pooled data from clinical trials show that repeated ketamine sessions produce significant symptom reduction lasting two to three weeks. After stopping treatment, the antidepressant effects generally persist for about one additional week. This is why ongoing maintenance sessions are common for people who respond well to the initial course.
What a Session Feels Like
Preparation starts the day before. You’ll be asked to avoid alcohol and recreational substances for at least 24 hours. If you take certain anti-anxiety medications or opioid painkillers, the clinic will likely ask you to hold those for eight hours beforehand, since they can interfere with ketamine’s effects. Blood pressure medications should still be taken as usual. You’ll need to arrange a ride home, as you won’t be able to drive afterward.
On treatment day, you fast from solid food that morning (clear liquids are fine) and arrive about 15 minutes early. The clinical team checks your vital signs to establish a baseline, confirms you’ve followed preparation instructions, and gets you settled in a private treatment room. Many people bring an eye mask or headphones with calming music.
Once the infusion begins, most people first notice a sense of relaxation. As the medication takes full effect, you may experience a dreamlike, dissociative state where your sense of time and space feels altered. Some people describe floating sensations or vivid mental imagery. This is a normal part of how ketamine works and typically feels more surreal than unpleasant. Staff monitor your blood pressure, heart rate, and oxygen levels throughout the 40 to 60 minute infusion.
When the infusion ends, the dissociative effects start clearing within 10 to 15 minutes. You’ll likely feel groggy or mentally foggy for another 30 to 60 minutes afterward. Most clinics keep you for observation during this window before releasing you to your designated driver.
Side Effects and Risks
The most common side effects during and shortly after infusion include dizziness, nausea, sedation, and the dissociative feelings described above. These are temporary and resolve within an hour or two of treatment ending.
Blood pressure elevation is a consistent cardiovascular effect. In a study tracking over 2,300 infusion sessions across 138 patients, systolic blood pressure rose by an average of 16 mmHg and diastolic by 11 mmHg, peaking about 40 minutes into the infusion. Severe blood pressure spikes occurred in about 1 percent of sessions, and were more common during the first three treatments and in patients who were older or had a history of high blood pressure.
Because of this blood pressure effect, ketamine is not appropriate for everyone. People with uncontrolled hypertension, a history of aneurysm, recent heart attack, or aortic dissection should not receive ketamine. It’s also avoided in people with schizophrenia, as it can worsen psychotic symptoms. Anyone with a known allergy to ketamine is excluded as well.
FDA Status and Insurance Coverage
An important distinction exists between two forms of this drug. Racemic ketamine, the version given by IV or intramuscular injection, is not FDA-approved for depression. It’s used off-label, meaning doctors prescribe it based on clinical evidence even though it hasn’t gone through the formal approval process for psychiatric use. In 2019, the FDA approved esketamine (brand name Spravato), a nasal spray derived from one half of the ketamine molecule, specifically for treatment-resistant depression. Esketamine must be administered in a certified healthcare setting under a special safety monitoring program.
This regulatory gap has real financial consequences. Because IV ketamine is off-label, insurance companies generally don’t cover it. A typical session costs around $500 out of pocket, and a six-infusion induction series runs roughly $3,000. Some clinics offer payment plans or can provide documentation for partial reimbursement. Esketamine nasal spray, by contrast, is covered by most commercial insurance plans and Medicare, with many patients paying $0 to $50 per visit after coverage kicks in.