Ketamine has 'truly remarkable' effect on depression and is effective in elderly patients, scientists say

After six months, 43% of the subjects said they had no significant symptoms of depression

Ketamine is used as a horse tranquiliser (Rex Features)

Ketamine can have a “truly remarkable” effect on people with depression, researchers have said after a new study showed promising results among elderly patients.

Colleen Loo, a professor at the University of New South Wales in Australia, led the world’s first randomised control trial into the drug’s effect on people over 60 with treatment-resistant depression.

“This trial has shown ketamine can be used safely in the elderly and it tends to be effective,” she told The Independent, adding that a similar effect was observed in this age group as in younger patients.

It is important to test how people of different ages respond to a new treatment before it can be offered by doctors, she said: “Sometimes depression in the elderly can be harder to treat, especially with medication.

“Also, they tend to have more medical problems, which can interfere with medication.”

Ketamine was discovered in 1962 and is licenced for medical use in the UK as an anaesthetic, but is also used illegally as a recreational drug.

Of the study’s 16 participants, 11 reported an improvement in their condition while being treated with the drug, according to the research published in the American Journal of Geriatric Psychiatry.

After six months, 43 per cent of the subjects said they had no significant symptoms of depression – a high rate given that the participants had not responded to previous treatment, said Professor Loo.

“It is truly remarkable the way ketamine can work,” she said. “Other people have also found you get a rapid and powerful effect after a single dose of ketamine.”

“Some people mistakenly think we are inducing a temporary, drug-induced euphoria and people are ‘out of it’, which is why they’re not depressed.

“But the effects take place in the first hour, and they’re not euphoric at all. In fact, all of our research participants disliked them. They considered them adverse effects.

“The antidepressant effect kicks in a few hours later and are maximised about 20 hours later, when you’re fully alert and in your usual state of mind.”

While research into the use of ketamine to treat mental health problems is still in its early stages, scientists at Oxford University have said their studies show the drug can provide relief to patients with severe depression “where nothing has helped before”.

Rupert McShane, the consultant psychiatrist who is leading Oxford’s ketamine treatment programme, told The Independent it was “good to see that, contrary to some reports, some older people do respond to ketamine.”

“This study highlights that ketamine can be given in a variety of ways (not just intravenous), that it’s a good idea to adjust the dose, and that the more resistant someone’s depression is, the higher the dose that they are likely to need,” he said.

Professor Loo and her colleagues delivered ketamine to the patients using a small injection under the skin – similar to the insulin jabs given to diabetes patients.

This makes the drug easier and quicker to administer than the intravenous infusions used in other trials, which require a machine pump to regulate the dose and takes up to an hour to complete.

Participants received increasing doses of ketamine over a period of five weeks, with the dose personalised for each patient.

However, she warned that while the research is one step closer to providing a model for how doctors could prescribe ketamine as a treatment for depression in future, it would still be “premature to jump into clinical practice”.

“There are ‘super-responders’, who after a single treatment can be well for several months,” said Professor Loo, giving the example of a subject who, in 2014, remained free of depressive symptoms for five months after just one dose of ketamine.

But “most people are well but then they relapse over around three to seven days,” she said. “That’s where repeated dosing comes in.”

It is estimated around three per cent of the UK population, or nearly two million people, suffer from depression.

A small proportion of this group – around 158,000 people in total – have very severe depression that is resistant to existing treatments, studies have shown.

Professor Loo and her colleagues at the Black Dog Institute in Sydney are also conducting a large-scale trial into the effects of ketamine on treatment-resistant depression.

“These results are a promising early piece of the puzzle, but the risks of ketamine use are still not wholly understood. Future studies with greater sample sizes are needed to formally assess ketamine's side effects, such as its impact on liver function."