depression Ketamine is a “promising” new antidepressant that has had rapid effects on people with previously treatment-resistant depression, a small study has claimed.

Researchers from the University of Oxford confirmed that ketamine has a rapid antidepressant effect in some patients with severe and enduing depression who have not responded to other treatments including various antidepressants and talking therapies. Although many patients relapsed within a day or two, 29% had benefit which lasted at least three weeks and 15% took more than two months to relapse. 

In the study, 28 patients with treatment-resistant depression were treated over three weeks. They received either 3 or 6 ketamine infusions lasting 40 minutes. Memory tests were carried out a few days after the final infusion. Patients reported their mood symptoms daily via text or email.

Ketamine is a licensed medical drug and widely used as an anaesthetic and in pain relief. It is also used as a recreational drug, and is to be reclassified as a Class B banned substance by the Home Office. However, the researchers pointed out that the doses used are very different. When used on the street at a level of several grams a day, severe bladder problems occur and cognitive function is impaired. The dose used in this study was no more than 80 mg (80 thousandths of a gram) every week in the controlled and closely monitored setting of an NHS hospital. 

In the study, ketamine did not cause cognitive or bladder side effects when given on up to six occasions, although some people did experience other side effects such as anxiety during the infusion or being sick. The team have now given more than 400 infusions to 45 patients and are exploring ways to maintain the effect. They report their findings in the Journal of Psychopharmacology. The study was funded by National Institute for Health Research Research for Patient Benefit Programme.

“Remarkable changes”

“Ketamine is a promising new antidepressant which works in a different way to existing antidepressants. We wanted to see whether it would be safe if given repeatedly, and whether it would be practical in an NHS setting. We especially wanted to check that repeated infusions didn't cause cognitive problems,” explained principal investigator Dr Rupert McShane, a consultant psychiatrist at Oxford Health and a researcher in Oxford University's Department of Psychiatry.

“We've seen remarkable changes in people who've had severe depression for many years that no other treatment has touched. It's very moving to witness. Patients often comment that that the flow of their thinking seems suddenly freer. For some, even a brief experience of response helps them to realise that they can get better and this gives hope.

“We now need to build up clinical experience with ketamine in a small number of carefully monitored patients. By trying different infusion regimes and adding other licensed drugs, we hope to find simple ways to prolong its dramatic effect.”