Strides are being made towards treating severely depressed patients with ketamine, an anaesthetic often referred to colloquially as "horse tranquiliser".
Ketamine is typically administered medically to induce and maintain anaesthesia or provide pain relief, but it's popular with recreational drug users due to its hallucinogenic properties. It's also often used to anaesthetise animals - leading to its nickname - as it doesn't affect the breathing or blood pressure like other anaesthetics.
While ketamine has been used to treat severe depression for some time, the side effects can be significant, Otago University Psychological Medicine Professor Paul Glue told AM on Wednesday. As a result, researchers have been developing a slow-release tablet that provides effective treatment for the mental illness, without the debilitating aftereffects.
Side effects of injected or inhaled ketamine can include disassociation, drowsiness and impaired movement, he said, meaning a patient cannot receive it outside of a clinic as the administration must be medically supervised.
Professor Glue, the lead research author, said human testing is so far proving "promising", but there's still a way to go before the tablet is available for patients.
The slow-release formula works over a 10-hour period, he explained, allowing most of the ketamine to be metabolised in the liver before it enters the bloodstream.
"By getting rid of most of the parent drug and just concentrating on having metabolites... you get rid of the side effects. This would be a formulation that patients can take at home; they wouldn't have to come into a clinic every time they need to be dosed," he told AM.
Drug developers have been working on the formulation for about seven years, he said, and there are hopes it might be made publicly available within the next three years. Large phase three trials still need to be completed, and the tablet would need to be reviewed and approved by medical regulatory bodies such as Medsafe in New Zealand or the FDA in the US.
"There's still quite a way to go," he said. "You can never be confident in drug development - but it's very, very promising."
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