The Origins: 1956-1962
The story of ketamine begins with phencyclidine (PCP), a compound synthesized in 1956 by the pharmaceutical company Parke-Davis. PCP was initially developed as a surgical anesthetic and showed potent dissociative and analgesic properties. However, clinical trials revealed severe and prolonged psychotomimetic side effects — patients experienced agitation, hallucinations, and delirium upon emergence from anesthesia that could last for hours or even days. By the early 1960s, it was clear that PCP was unsuitable for routine medical use, though it persisted as a recreational drug of abuse.
In response to the problems with PCP, Parke-Davis tasked organic chemist Calvin Lee Stevens with synthesizing and evaluating PCP derivatives that might retain the desirable anesthetic properties while eliminating the disturbing psychological effects. In 1962, Stevens synthesized a compound designated CI-581 — the molecule that would become known as ketamine. It was a shorter-acting analog of PCP with a significantly more manageable side effect profile.
First Human Trials: 1964-1966
The first human trials of ketamine were conducted in 1964 by Drs. Edward Domino and Guenter Corssen at the University of Michigan. They administered the drug to volunteer prisoners at Jackson State Prison in Michigan, a practice that was common in pharmaceutical research at the time but would be considered ethically impermissible today.
The results were striking. Ketamine produced a unique state that Domino's wife, Toni, suggested calling "dissociative anesthesia" — patients were rendered insensible to pain and appeared disconnected from their surroundings, yet maintained protective airway reflexes and spontaneous breathing. The emergence delirium, while present, was far less severe and shorter-lasting than with PCP.
Domino and Corssen published their landmark findings in 1966 in the journal Anesthesia & Analgesia, establishing the fundamental clinical profile of ketamine that would guide its use for decades to come.
FDA Approval and the Vietnam War: 1970-1975
The U.S. Food and Drug Administration approved ketamine for human use in 1970 under the brand name Ketalar, manufactured by Parke-Davis. The timing proved consequential. The United States was deeply engaged in the Vietnam War, and military medicine desperately needed anesthetic agents that were safe in field conditions — environments where sophisticated monitoring equipment and trained anesthesiologists were often unavailable.
Ketamine became the most widely used battlefield anesthetic of the Vietnam War. Its advantages in this setting were profound: it maintained cardiovascular stability (unlike many other anesthetics that lower blood pressure), preserved spontaneous respiration, could be administered intramuscularly without IV access, and had a wide margin of safety. Medics and surgeons could use it in forward operating positions, helicopter evacuations, and field hospitals with confidence.
The Vietnam experience cemented ketamine's reputation as an indispensable tool in emergency and field medicine — a reputation it retains to this day.
Global Adoption and WHO Recognition: 1975-1985
Throughout the 1970s and 1980s, ketamine was adopted worldwide. Its unique safety profile made it especially valuable in low-resource settings where the infrastructure for modern anesthesia — reliable electricity, oxygen supplies, and monitoring equipment — was limited or absent.
In 1985, the World Health Organization added ketamine to its Model List of Essential Medicines, recognizing it as one of the most important medications needed in a basic health system. This designation reflected ketamine's critical role in global surgery, particularly in developing nations across Africa, Asia, and Latin America where it often served as the only available general anesthetic.
The WHO has repeatedly defended ketamine's availability against attempts at international scheduling, arguing that restricting access would have devastating consequences for surgical care in the developing world.
Schedule III Classification and Recreational Concerns: 1981-1999
As ketamine became more widely available, reports of non-medical use began to emerge. By the 1980s and 1990s, ketamine had entered the recreational drug scene, particularly in club and rave culture, where it was known by street names including "Special K," "Vitamin K," and "Kit Kat."
In 1999, the U.S. Drug Enforcement Administration placed ketamine on Schedule III of the Controlled Substances Act, reflecting concerns about its abuse potential while acknowledging its legitimate and important medical uses. This classification imposed regulatory controls on manufacturing, distribution, and prescribing, but did not prevent physicians from using it clinically.
The Psychiatric Discovery: 2000
The year 2000 marks the most transformative moment in ketamine's modern history. A research team led by John Krystal and Dennis Charney at Yale University published a small but groundbreaking study in Biological Psychiatry. Led by first author Robert Berman, the trial demonstrated that a single sub-anesthetic intravenous dose of ketamine (0.5 mg/kg over 40 minutes) produced rapid antidepressant effects in patients with major depression.
The results were remarkable: patients showed significant improvement in depressive symptoms within hours — a timeline that was almost inconceivable given that conventional antidepressants required weeks of daily dosing. However, the study involved only seven subjects and was initially met with skepticism by much of the psychiatric community.
Confirmation and Expansion: 2006-2010
In 2006, Carlos Zarate and colleagues at the National Institute of Mental Health (NIMH) published a larger, more rigorous study in the Archives of General Psychiatry that confirmed and extended the Yale findings. Their randomized, placebo-controlled, crossover trial demonstrated that a single ketamine infusion produced rapid and robust antidepressant effects in patients with treatment-resistant depression, with 71% of patients responding within 24 hours.
This study is widely regarded as the pivotal moment that legitimized ketamine as a psychiatric treatment and launched an entirely new era of antidepressant research. It demonstrated that the glutamate system — rather than the monoamine systems targeted by existing antidepressants — could be a viable therapeutic target.
Between 2006 and 2010, a wave of studies confirmed ketamine's rapid antidepressant effects across multiple populations and explored its mechanisms of action. Researchers discovered that ketamine triggered a cascade involving AMPA receptor activation, BDNF release, and mTOR-mediated synaptogenesis — fundamentally reshaping the neuroscience of depression.
The Clinic Era: 2012-2018
By 2012, the first ketamine infusion clinics began opening across the United States. These were typically established by anesthesiologists and psychiatrists who recognized the clinical potential of the existing research and leveraged the legal framework of off-label prescribing to offer treatment.
The clinic model grew rapidly. By 2018, hundreds of ketamine infusion centers were operating nationwide, though with significant variation in protocols, pricing, and clinical oversight. Professional organizations, including the American Society of Ketamine Physicians, Psychotherapists, and Practitioners (ASKP3), formed to establish standards of care and promote best practices.
Spravato Approval: 2019-2020
In March 2019, the FDA approved esketamine (Spravato), the S-enantiomer of ketamine in nasal spray form, for treatment-resistant depression. This was the first FDA approval of a ketamine-derived medication for a psychiatric indication and represented a watershed moment for the field.
In August 2020, the FDA expanded Spravato's indication to include adults with major depressive disorder who have current suicidal ideation with intent — making it one of the first medications specifically approved for acute suicidality.
The approval came with a Risk Evaluation and Mitigation Strategy (REMS) requiring administration in certified healthcare settings with post-dose monitoring, reflecting ongoing concerns about safety, dissociation, and abuse potential.
Telehealth Expansion and At-Home Protocols: 2020-2023
The COVID-19 pandemic catalyzed a dramatic expansion of telehealth services, including ketamine therapy. The DEA temporarily relaxed requirements for in-person evaluations before prescribing controlled substances, enabling telehealth companies to prescribe oral and sublingual ketamine formulations for at-home use.
Several telehealth companies emerged, offering telemedicine-based ketamine therapy models that dramatically expanded access while sparking debates about safety, appropriate clinical oversight, and the boundaries of responsible prescribing. For a closer look at these developments, see our article on at-home ketamine companies.
Regulatory Tightening and Ongoing Evolution: 2023-Present
Following reports of adverse events associated with unsupervised at-home ketamine use, regulatory scrutiny has intensified. The FDA issued warnings about the risks of compounded ketamine products, and the DEA has signaled its intent to reinstate in-person prescribing requirements for controlled substances prescribed via telehealth. For the latest on these regulatory changes, see DEA telehealth prescribing rules in 2025.
Meanwhile, research continues to advance. R-ketamine (arketamine), the less-studied enantiomer, has shown promising antidepressant effects in clinical trials with potentially fewer dissociative side effects. Novel formulations, combination therapies, and biomarker-guided dosing strategies are under active investigation.
Legacy and Future Directions
Ketamine's journey from surgical anesthetic to psychiatric treatment is one of the most remarkable stories in modern medicine. A molecule synthesized in a chemistry laboratory in 1962 has fundamentally reshaped our understanding of depression, neuroplasticity, and the brain's capacity for rapid healing. For a shorter overview of this timeline, see our companion article on the history of ketamine.
As the field continues to evolve, ketamine's legacy is already secure: it opened the door to an entirely new class of psychiatric treatments and offered hope to millions of patients for whom conventional therapies had failed.
Note: This article is for educational purposes only and should not be used as a substitute for professional medical advice. Ketamine therapy should always be pursued under the guidance of a qualified healthcare provider.
References
- MedlinePlus: Ketamine Injection — National Library of Medicine drug information on ketamine's clinical uses and FDA-approved indications
- FDA: Drug Information — U.S. Food and Drug Administration center for drug evaluation, including ketamine and esketamine approval records
- MedlinePlus: Esketamine Nasal Spray — Drug information on FDA-approved Spravato (esketamine) for treatment-resistant depression
- WHO: Depression Fact Sheet — World Health Organization information on global depression burden and the WHO Essential Medicines list
- StatPearls: Ketamine — Clinical reference covering ketamine's history, pharmacology, and evolution as a medical treatment
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