Ketamine was first synthesized in 1962 by a team led by Calvin Lee Stevens, a professor of organic chemistry at Wayne State University who was also a chemical consultant for the pharmaceutical company Parke-Davis. What began as a search for a safer alternative to existing anesthetics has since become one of the most versatile drugs in modern medicine, with uses spanning surgery, battlefield trauma, and psychiatric treatment.
The Chemist Behind the Molecule
Stevens created ketamine as a derivative of phencyclidine (PCP), which was already being studied as an anesthetic but caused severe side effects including prolonged delirium and psychosis. Parke-Davis needed something that worked similarly but wore off faster and with fewer problems. Stevens’s new compound, cataloged internally as CI-581, fit the bill. He originally called it “keet-amine,” a nod to the two chemical groups at the heart of its structure: a ketone and an amine. The name was eventually shortened to ketamine.
First Tests in Humans
On August 3, 1964, two University of Michigan professors administered the first anesthetic dose of ketamine to a human patient. Edward Domino, a pharmacologist, and Guenter Corssen, an anesthesiologist, ran the trial on 20 volunteers and found the drug was both safe and effective for clinical anesthesia. But the experience it produced was unlike anything other anesthetics caused. Patients weren’t simply unconscious. They seemed detached from their surroundings and their own bodies, awake in some neurological sense but disconnected from sensory input.
No existing medical term captured this state, so Domino struggled to describe it in his early papers. His wife suggested the phrase “dissociative anesthesia,” and the term stuck. It became the defining label for ketamine’s unique pharmacological profile and later gave its name to an entire class of drugs.
FDA Approval and Wartime Use
The FDA approved ketamine as a general anesthetic in 1970, making it available for use on its own or in combination with other medications. Its timing coincided with the Vietnam War, and the drug quickly proved valuable on the battlefield. Unlike most anesthetics, ketamine doesn’t suppress breathing or drop blood pressure significantly. For wounded soldiers in austere conditions, where monitoring equipment was limited and patients were often already in shock, these properties made ketamine far safer than alternatives. It required minimal equipment, worked fast, and allowed relatively stable recovery even in field hospitals. Military medical teams adopted it widely, earning it the informal title “the drug of war.”
Ketamine also entered veterinary medicine early in its history. It was tested on animals, including horses, during its initial development in the 1960s and became a standard anesthetic across species. This is the origin of the “horse tranquilizer” label that still follows the drug in popular media. The characterization isn’t wrong, exactly, but it’s incomplete to the point of being misleading. Ketamine was developed for human use, approved for human use, and has been used in human operating rooms for over five decades.
How It Works in the Brain
For the first two decades after its synthesis, researchers knew ketamine worked but didn’t fully understand why. That changed in 1983, when a team of British pharmacologists demonstrated that ketamine blocks a specific type of receptor in the brain called the NMDA receptor. These receptors normally respond to glutamate, the brain’s primary excitatory chemical messenger. Ketamine slips into the receptor’s ion channel when it opens and physically blocks it, preventing the normal flow of signals. This mechanism explained not only its anesthetic effects but also the strange dissociative state it produces, since NMDA receptors are heavily involved in how the brain integrates sensory information and forms a coherent sense of self.
The Unexpected Leap Into Psychiatry
Ketamine might have remained a workhorse anesthetic if not for a small study published in 2000. Researchers at Yale gave seven patients with major depression a single low-dose intravenous infusion of ketamine, at roughly one-tenth of an anesthetic dose, and compared the results to a placebo saline drip. The patients who received ketamine showed significant improvement in depressive symptoms within 72 hours. Their scores on a standard depression rating scale dropped by an average of 14 points, while the placebo group showed no change at all.
Seven patients is a tiny sample, but the finding was striking for a different reason: speed. Traditional antidepressants take weeks to produce noticeable effects. Ketamine appeared to work in days or even hours. This challenged a fundamental assumption in psychiatry, that treating depression required slow, gradual changes in brain chemistry, and opened an entirely new line of research into glutamate-based treatments for mood disorders.
That initial study sparked two decades of clinical trials that eventually led to the FDA approving a nasal spray form of a ketamine-related compound for treatment-resistant depression in 2019. Meanwhile, clinics offering intravenous ketamine infusions for depression have proliferated across the United States, operating under the original 1970 approval that allows physicians to prescribe it off-label.
Recreational Use and Legal Status
Ketamine’s dissociative effects made it attractive outside of medical settings. Recreational use grew through the 1980s and 1990s, particularly in club and rave scenes, where users sought the dreamlike detachment the drug produces at sub-anesthetic doses. At higher recreational doses, users describe what’s known as a “K-hole,” a state of profound dissociation that can feel like an out-of-body experience.
In response to rising non-medical use, the Drug Enforcement Administration placed ketamine into Schedule III of the Controlled Substances Act in August 1999. Schedule III means the drug has accepted medical uses but carries moderate potential for abuse. This classification keeps it legally available for medical and veterinary purposes while imposing criminal penalties for unauthorized possession or distribution. It remains in Schedule III today, a lower restriction level than drugs like oxycodone or fentanyl but still subject to prescription requirements and DEA oversight.
From Lab Bench to Operating Room to Psychiatrist’s Office
Ketamine’s journey is unusual in pharmacology. Most drugs are developed for one purpose and stay there. Ketamine started as a safer alternative to PCP, proved itself in wartime trauma surgery, became a staple of veterinary medicine, was adopted by recreational users, and then reemerged as one of the most promising treatments for depression in decades. Each chapter built on the same core property that Stevens’s molecule demonstrated in 1962: a fast-acting, reversible disruption of how the brain processes signals, powerful enough to erase the sensation of surgery but subtle enough, at lower doses, to shift the neurochemistry of mood.