Insanity: Horse tranquilizer/club drug being developed for use in depression

© resus.me

Ketamine: Action on multiple receptors earns it the nickname: ‘the nightmare of the pharmacologist’

A drug being newly tested as a fast-acting antidepressant has shown it can help lift heavy depression within 40 minutes.

Researchers at the National Institute of Mental Health have been testing the effects of a single dose of ketamine on people with bipolar disorder.

When depressed, bipolar patients find it difficult to seek out and experience rewards - they feel there is nothing to look forward to.

The drug works by changing how people think about rewards.

Dr. Carlos Zarate, who led the study, said:

"Our findings help to deconstruct what has traditionally been lumped together as depression.

We break out a component that responds uniquely to a treatment that works through different brain systems than conventional antidepressants - and link that response to different circuitry than other depression symptoms."

In the study, 36 patients with bipolar disorder who were currently depressed were given either ketamine or a placebo (Lally et al., 2014).

They were then asked about their depression and symptoms of anhedonia, the inability to experience pleasure.

The first effect of the drug was to reduce patients' anhedonia within 40 minutes: they could once again anticipate and experience pleasure.

After two hours, the drugs anti-depressant effects were also felt.

This reduction in anhedonia was still detectable two weeks after the single dose.

Brain scans revealed that the drug likely works by changing the way the motivational parts of the brain respond to imagining and taking part in pleasurable experiences.

Ketamine - sometimes known as a 'horse tranquiliser' - is not a new drug, although its use for those with depression is relatively new.

Along with its use in veterinary medicine, it is also a club drug, known as 'Special K'.

Researchers are now looking at ways of providing it in a more useable form, such as a nasal spray.

That said, the drug is not currently licensed to treat depression and abusing it can lead to delirium, hallucinations and even amnesia.

Similar drugs to ketamine, though, without the side-effects, which act on the same chemical pathways, are also being developed.

These could provide hope for those who suffer some of the most debilitating types of depression.