Ketamine is administered in several different ways depending on the setting and purpose. In medical and psychiatric clinics, it is given through an IV, as a nasal spray, or as an intramuscular injection under direct supervision. For at-home psychiatric treatment, some patients receive oral lozenges or liquid prescribed by a provider. Outside of medical settings, people use ketamine recreationally by snorting powder, swallowing it, or injecting it, though it is a Schedule III controlled substance and unauthorized possession is illegal.
IV Infusion in a Clinical Setting
Intravenous infusion is the most common clinical method, particularly for treating depression and managing acute pain. For depression, the standard dose is 0.5 mg/kg of body weight delivered over about 40 minutes. That means a 150-pound person would receive roughly 34 milligrams. This is far below the anesthetic dose, which ranges from 1 to 4.5 mg/kg, so patients stay conscious throughout.
During an IV session, you sit in a recliner or lie on a bed in a clinic while the drug drips into a vein. Effects begin within one to five minutes. You may feel floaty, detached from your surroundings, or mildly euphoric. The dissociative sensations typically fade within 15 to 20 minutes after the infusion stops, though some grogginess can linger. Clinics monitor blood pressure, heart rate, and oxygen levels throughout and for at least 15 minutes afterward. A breathing mask device is kept at the bedside as a precaution.
Nasal Spray (Esketamine)
The FDA-approved nasal spray, sold under the brand name Spravato, uses esketamine, a slightly different molecular form of ketamine. It is approved for two specific situations: treatment-resistant depression in adults, and depressive symptoms in adults with major depressive disorder who have acute suicidal thoughts or behavior. It is always used alongside an oral antidepressant, not on its own for the suicidal ideation indication.
You cannot take this spray at home. Because of risks including sedation, dissociation, and respiratory depression, it is only available through a restricted program. You self-administer the spray under supervision in a certified healthcare setting, then must be monitored for at least two hours. Staff check your blood pressure around 40 minutes after dosing and continue monitoring until it returns to a stable level. You cannot drive for the rest of the day.
Intramuscular Injection
Some clinics use intramuscular (IM) injection, where ketamine is injected into the muscle of the upper arm or thigh. This route is sometimes chosen when IV access is difficult or impractical. Onset takes slightly longer than IV, typically a few minutes, and the effects last somewhat longer as well. In acute pain settings, the dose ranges from 0.35 to 0.7 mg/kg, with the same monitoring requirements as IV administration.
Oral Lozenges and Liquid
For at-home use between clinic visits, some providers prescribe ketamine as a sublingual lozenge (also called a troche) or as an oral liquid. These are compounded by specialty pharmacies, not FDA-approved products, which is an important distinction.
Lozenges are placed under the tongue and allowed to dissolve slowly. The drug absorbs through the tissue under the tongue, delivering about 25 to 40 percent of the ketamine into the bloodstream. That bioavailability can vary significantly from session to session, even for the same person. Oral liquid has even lower bioavailability, around 15 to 25 percent, which is why the doses are much higher than IV doses. To match the effect of a 35 mg IV dose, you would need roughly 100 mg in a lozenge or 200 mg in liquid form. Effects from oral forms take about 30 minutes to begin and can last 4 to 12 hours depending on the dose.
The FDA has issued warnings about compounded ketamine products, noting that they carry risks of sedation, dissociation, psychiatric events, blood pressure spikes, respiratory depression, and bladder symptoms, and that these products have not gone through the FDA approval process for safety and effectiveness.
Recreational Use
Outside medical settings, ketamine is most commonly encountered as a white crystalline powder that is snorted in small lines, similar to how people use cocaine. It is also sometimes swallowed as a pill or capsule, dissolved in a drink, or injected intramuscularly. At lower recreational doses, users describe a floaty, mildly euphoric state with altered perception. At higher doses, the experience intensifies into what users call a “k-hole,” a state of profound dissociation where people feel completely detached from their body and surroundings, sometimes described as a near-death or out-of-body experience.
Snorting produces effects within about 5 to 15 minutes. Swallowing takes longer, around 20 to 30 minutes, and delivers less of the drug into the bloodstream due to lower bioavailability. Because the effects wear off relatively quickly, people often redose multiple times in a session, which increases the risk of adverse effects.
How Ketamine Works in the Brain
Ketamine blocks a specific type of receptor in the brain called the NMDA receptor, which normally responds to glutamate, the brain’s primary excitatory chemical messenger. It does this through a clever mechanism: the drug can only enter and block the receptor’s channel after it opens, essentially plugging it from the inside and sometimes getting trapped when the channel closes again.
This blocking action has a counterintuitive result. Ketamine preferentially affects inhibitory brain cells (the ones that normally quiet down other neurons). When those inhibitory cells are suppressed, the excitatory neurons become more active and release more glutamate overall. This surge in activity triggers the brain to strengthen and rebuild synaptic connections, which is believed to be the basis of ketamine’s rapid antidepressant effects. Traditional antidepressants take weeks to produce changes; ketamine can produce noticeable mood improvements within hours.
Side Effects and Risks
The most common immediate side effects are a temporary rise in blood pressure and heart rate, which occur in 1 to 10 percent of clinical uses. Nausea, dizziness, and a feeling of unreality are also common. Some people experience anxiety or agitation during or shortly after a session, and vivid or strange perceptual experiences are part of the drug’s normal pharmacology rather than a complication.
The more serious concern with repeated use is bladder damage. Ketamine can cause cystitis, an inflammation of the bladder lining, that leads to painful urination, blood in the urine, frequent urges to urinate, and in severe cases, a shrunken, scarred bladder that requires surgical intervention. This is rare with supervised medical dosing but well-documented in heavy recreational users, particularly those using daily or near-daily for months or years.
Ketamine also carries a real potential for psychological dependence. As a Schedule III controlled substance, the DEA classifies it as having moderate to low potential for physical and psychological dependence, but regular recreational users can develop tolerance quickly, needing higher doses to achieve the same effects. Respiratory depression, where breathing becomes dangerously slow and shallow, is another risk, particularly at higher doses or when combined with alcohol or other sedatives.
Who Should Not Use Ketamine
People with uncontrolled high blood pressure are generally not candidates for ketamine treatment because the drug reliably raises blood pressure in the short term. Those with a history of psychosis or active psychotic symptoms are also typically excluded, as ketamine can worsen psychiatric conditions. The FDA specifically notes that worsening of psychiatric disorders is among the known safety concerns. Pregnancy, active substance use disorders involving ketamine, and certain cardiovascular conditions like aneurysms also typically disqualify someone from treatment.