Ketamine, an anaesthetic drug, is to be used in clinical trials in the South Island to study how effective it can be in treating depression.
Otago University is seeking 60 patients from both Christchurch and Dunedin who have been regular users of anti-depressant therapy, but for whom the treatment has not worked.
Ketamine has been legally prescribed by New Zealand doctors since the 1950s, but classified as an illegal recreational drug since the 80s.
One of the study's researchers, Dr Ben Beaglehole, told Morning Report there was a lot of evidence to show ketamine was an effective short-term treatment for depression.
"But obviously depression is a longer-term problem, so our study is looking to adverse some of those issues to see how we can extend and enhance the benefits of ketamine over the longer term."
Beaglehole said traditional anti-depressants took weeks to work. Ketamine worked far quicker and the benefits only lasted a short time.
"We know some of the short term effects cause disassociation, psychedelic effects, but it's probably some of the metabolites, some of the downstream products of ketamine, that are heaving its therapeutic benefits on depression."
During the trial, rather than give participants an injection of ketamine, it would be given them in liquid form for them to sip slowly over an hour.
"So that should minimise and pretty much do away with the trip-like effects."
Beaglehole said half the participants will be treated solely with ketamine, and the other half will receive ketamine alongside another mood disorder treatment known as behavioural activation therapy.
"We're going to compare how people do between those two groups overtime, so we will ask people to stay in the study for a further three months and will compare their mood scores over time."