By Serena Solomon*
Ketamine is an illegal recreational drug, but it can also be prescribed to treat stubborn depression and anxiety or as a surgical anaesthetic. Photo: Codie McLachlan / Edmonton Sun/QMI Agency / QMI Agency
Explainer - Ketamine is a drug that wears many hats. It's an anaesthetic for horses, badgers, and other animals including humans. It can treat stubborn depression and anxiety. It's a recreational drug that can send users into a euphoric, out-of-body experience called a k-hole. And it's the drug that contributed to the 2023 death of Friends actor Matthew Perry.
Recent news that US law enforcement is investigating the source of Perry's ketamine shows the drug's other hats: legal and illegal. In Perry's case, he was undergoing regular ketamine infusion therapy but high ketamine levels found during an autopsy indicate he was likely also dosing himself at home, which is illegal in the United States.
Like in the US, ketamine is a controlled substance in New Zealand. Medsafe approves it as a surgical anaesthetic. It can be prescribed as an off-label treatment for depression but rarely is. Outside of medical and veterinary settings, ketamine is considered a 'Class C Drug' so buying, selling, importing and using it is illegal, according to the NZ Drug Foundation's website The Level.
University of Otago's Professor Paul Glue has studied ketamine's impact on depression and anxiety. Photo: Supplied
What doses of ketamine are used?
The average amount of ketamine needed to anaesthetise a patient for surgery is 10 mg per kilo of a person's body weight, according to the University of Otago's Professor Paul Glue, who has studied ketamine's impact on depression and anxiety.
The dose required to treat depression and anxiety while avoiding unwanted psychedelic side effects is 0.5 to 1mg per kilo of a patient's body weight. This is typically delivered orally, through a nasal spray or intravenously. Partygoers are likely consuming a similar amount of ketamine used to anaesthetise to achieve a k-hole, according to Glue.
How can I tell if someone is using it?
If taken in lower doses, a person might appear "out of it," said Emily Hughes, principal science advisor from the NZ Drug Foundation. "They might be more socially confident or socially excitable. They might appear relaxed or chilled out or they may be having changes to their perception."
Those who have taken large doses can have trouble speaking, or moving their limbs or "they might appear essentially completely paralysed," Hughes said.
Emily Hughes is a principal science advisor at the NZ Drug Foundation. Photo: Supplied
Is ketamine's recreational use common?
New Zealand's illicit drug of choice is cannabis with 14.2 percent of adults - over half a million people - using it in 2023, according to the NZ Drug Foundation. Around 2.5 percent use psychedelics including LSD and ketamine. Ketamine's popularity grew globally including in New Zealand during and after Covid but growth has since plateaued. "It creates a sense of dissociation within a person and that isn't necessarily something that you can achieve through a lot of other substances," Hughes said.
Ketamine has a perception of safety with very few documented overdose incidents from ketamine alone. However, ketamine can be dangerous when taken with other depressants such as alcohol "slowing down your body's functions to a dangerous level," Hughes said. Heavy users can also damage their bladder.
Growing evidence points to ketamine's effectiveness against treatment-resistant depression. Some New Zealanders are likely illicitly treating their depression or other mood disorders with ketamine, Hughes added.
How can I legally use ketamine to treat my depression?
Medsafe has yet to approve ketamine as a treatment for depression and other mood disorders. It can be prescribed off-label like many other drugs in New Zealand. Still, psychiatrists are hesitant to do so due to a lack of training and experience with ketamine, said Glue, from the University of Otago. (Medsafe has approved Spravato, which contains a version of ketamine called esketamine, to treat depression.)
Pharmac does not subsidise ketamine in any form as a treatment for depression. Glue said there could be around 100,000 New Zealanders who are not responding to conventional treatment for mood disorders and might benefit from ketamine.
- Serena Solomon is a freelance journalist who has written articles for the New York Times and The Guardian.