Unlike LSD or MDMA, the hallucinogen ketamine – aka the party drug Special K – is already a recognised pharmaceutical; it has been used as an anaesthetic as well as an animal tranquilliser since the 1960s.
It works primarily by blocking the receptor for the neurotransmitter glutamate in nerve cells, but its interaction with numerous other brain cell receptors makes it hard to know which activities are responsible for its effects.
Because it is a controlled but not illegal drug, doctors are able to prescribe ketamine ‘off label’ – to treat conditions for which it hasn’t officially been approved – such as chronic pain, depression, alcohol addiction and OCD. The drug is usually given intravenously, and not necessarily paired with psychotherapy, according to Colleen Loo, a clinical psychiatrist responsible for the first randomised controlled trials of ketamine in Australia.
Loo, who works at the University of New South Wales, was initially sceptical about ketamine’s effectiveness against depression. She changed her mind, however, when she saw it work. “The first person I treated, I was just astounded,” she says. “The speed of the powerful effects was unlike any other treatment I’ve seen for depression.” Pooled data from three separate studies support Loo’s experience. Two thirds of people with treatment–resistant diagnoses improved with ketamine infusions.
One drawback of ketamine is that, while its hallucinations are reminiscent of classical psychedelics, its effects don’t last and people can become desensitised over time. “Just because one dose works for a few days doesn’t mean that giving five or 10 doses is going to lead to a long-term benefit,” Loo says. She and her team are conducting a trial of 200 people with depression – the largest of its kind so far – to see if repeat dosing of ketamine is safe and leads to lasting remission.