University of Otago (Christchurch) researchers launched the trial last year, and have been seeking 60 patient recruits from Christchurch and Dunedin, for whom regular anti-depressant therapy had repeatedly failed.
Study lead investigator and psychological medicine researcher Associate Prof Ben Beaglehole said the trial was seeking a solution for the high rates of relapse experienced by many patients who came off ketamine treatment, by combining oral doses of ketamine with Behavioural Activation Therapy (Bat).
While 28 participants had taken part in the three-year Health Research Council of New Zealand study so far, more were being sought to help the trial reach definitive conclusions, he said.
"Ketamine is probably the most exciting new treatment for depression for a generation.
"We are already seeing benefits from the eight-week course of oral ketamine we have offered our trial participants so far, although it’s still too early to tell whether the addition of Bat is offering protection against the biggest problem many patients taking ketamine experience — the high rates of relapse within days or weeks of treatment ending.
"We need more patients to join the trial to help give us answers."
Bat aimed to activate people with depression, targeting the inactivity that was often part of the disease, as a means of getting them moving — both emotionally and physically — to encourage a lift in mood.
"We chose Bat because it’s an easily accessible and affordable solution for people to embed into their daily lives."
He said the study was seeking more volunteers, aged 18-65, for whom two different types of anti-depressant medication had not worked.
They would receive oral ketamine twice weekly for eight weeks, and half would also receive Bat for eight weeks.
Both groups would be monitored for a further 12 weeks after treatment finished, to see if Bat helped maintain improvements in mood.
He said most studies on ketamine as a treatment for depression had focused on injected ketamine, which could lead to a strong dissociative reaction or "trip".
"However, in our study, participants are being given ketamine to swallow, which works more slowly, is easier to tolerate and lessens the ‘trip’ effect."
However, he warned there was one potential issue that participants needed to be prepared for.
"The study may be a bit of a roller-coaster due to the fact that if they respond, we are not in a position to continue their ketamine treatment once the trial ends."
He said the research team had published a guideline aimed at giving specialist mental health services direction about how to prescribe ketamine to mental health patients, and how to manage them once on it.
The anaesthetic drug has been used legally by doctors in New Zealand since the 1950s for sedation and pain relief, but it has been classified as an illegal drug for recreational use since the 1980s.
Assoc Prof Beaglehole said the trial was being given in a tightly controlled setting to minimise concerns about its abuse potential, alongside concerns it could lead to bladder issues and possible memory side effects.
"If our completed trial is effective and Bat can be proven to help delay relapse, it will give genuine hope to people with treatment-resistant depression and support clinicians more widely in their community use of the drug."
