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

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. “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.”
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."