By Senior Research Fellow Julaine Allan, Charles Sturt University
Ketamine hydrochloride is an anaesthetic that causes people to feel disconnected from their bodies. At low doses, they remain conscious and can talk but do not feel pain. At higher doses, ketamine is used to induce a trance-like state or sedate people with burns or other traumatic injuries.
The drug can be used to perform short operations, particularly on children who are allergic to other drugs. Vets also use ketamine as an anaesthetic.
A small number of people, usually those who also use other party drugs, use ketamine as a recreational drug. Recreational users are seeking the relaxed and disconnected feeling it causes, as well as hallucinogenic effects that change sight, sound and touch. People may take ketamine accidentally because it is sold as ecstasy or is mixed with ecstasy.
Ketamine is produced as liquid in small bottles for medical use. The liquid is evaporated for recreational use to make a white powder that is snorted, swallowed, or dissolved in water and injected.
A brief history of ketamine
Ketamine was discovered in 1962 and approved for use in the United States as a battlefield anaesthetic during the Vietnam war.
Calvin L. Stevens, a professor of chemistry at Wayne State University, made ketamine when he was conducting research on phencyclidine – an anaesthetic also known as angel dust, which worked well but caused hallucinations in people as they woke up. Ketamine was named CI-581 and was one-tenth as strong as phencyclidine.
After research on animals, ketamine was tested on human prisoners in 1964 and 1965. Guenter Corssen, a professor of anaesthetics, conducted experiments on CI-581 using prisoners who had volunteered. He found it was a fast-acting anaesthetic that wore off quickly.
Corssen reported that some of the men it was tested on had hallucinations. These included thinking they had died, their arms and legs had been cut off, or they had been to outer space. Some refused to continue in the research. Corssen was the first to call ketamine a dissociative anaesthetic, meaning it causes you to feel disconnected from your body.
Ketamine is now on the World Health Organisation’s list of essential drugs as an anaesthetic. Ketamine is complicated to make, so is not made illegally. Drug companies manufacture it for medical and veterinary treatment.
Who uses ketamine?
Ketamine started being used as a recreational drug in the 1970s because of its dissociative and hallucinogenic effects. But not many people use ketamine. Use in the past 12 months is reported to be around 0.4% of the Australian population. Only 1.7% ever use ketamine in their lifetime. Lifetime use has doubled since 1999, suggesting greater availability of ketamine for those who want to try it.
Effects and risks
Studies conducted in the 1990s found ketamine caused the same symptoms as schizophrenia – unusual thoughts, hallucinations, trouble explaining things (disorganised speech), emotional withdrawal and difficulty moving.
The effects of ketamine are related to the amount taken. A dose of 1-2mg per kilogram of body weight produces an intense experience lasting about one hour. Effects start in less than five minutes if injected, or 30 minutes if swallowed. The effects last about one hour, with all effects wearing off after two to three hours.
Larger doses of ketamine cause an anaesthetic effect, or what recreational users refer to as a “K-hole”. A K-hole is generally reached when the user is nearly fully sedated and is described as similar to an out-of-body or near-death experience.
High doses of ketamine can cause breathing problems, muscle twitches, dizziness, slurred speech, nausea and vomiting. People may be injured because of problems with balance, numbness, muscle weakness and poor vision. Probably due to its anaesthetic properties, ketamine has been reported as a “date rape” drug.
There are few reports of overdose or death from ketamine. Dosage is controlled in medical settings according to body weight, and recreationally people tend to use less. The greatest risk is when ketamine is combined with alcohol or other central nervous system depressants, such as opioids or benzodiazepines, which can affect breathing and cause death.
Ketamine-related deaths can be because of accidents while affected. An example would be drowning in a bath after taking ketamine and losing consciousness.
Possible future uses
Even though it’s a nervous system depressant, ketamine stimulates circulation. This means it doesn’t cause low blood pressure like most anaesthetics, making it useful for treating people with head injuries.
Ketamine has been used as an antidepressant for people with treatment-resistant depression. A low dose of ketamine is given intravenously, with patients reporting effects in two hours that lasted one or two weeks. Although the quality of the evidence supporting positive effects is generally low, initial studies have resulted in interest because ketamine works quickly and appears to work on different receptors to traditional antidepressants.
Ketamine is not approved for the treatment of depression, so this is an off-label use. From June this year a nasal-spray form of ketamine (esketamine) started clinical trials for treatment of depression.
Australia is conducting the world’s largest study of ketamine as a treatment for depression. A trial of regular ketamine injections helped older people with depression feel less depressed, with about half reporting no depression six months later. But the researchers are cautious about the results because only 16 people participated in the trial.
Another trial is under way with different age groups of people who have tried other treatments that have not reduced their depression.
Evidence is still limited on ketamine’s effect on depression, the side effects, length of time it is safe to use and if tolerance to the drug will become a problem for people who use it.