New Zealand researchers have found that ketamine — a drug commonly used as general anesthetic — can reduce symptoms of treatment–resistant anxiety disorders.

Previous research had found that ketamine produced an antidepressant effect in patients with treatment-resistant major depressive disorder. The new study provides the first evidence that ketamine improves symptoms of anxiety in patients with treatment-resistant anxiety who are not currently depressed.

Paul Glue of the University of Otago, the study’s corresponding author, has been interested in clinical psychopharmacology since the mid 1980s.

“I am a psychiatrist working in clinical practice and seeing research patients,” he explained, “and for reasons outlined in the study anticipated that treatment refractory anxiety would be likely to respond to ketamine in the same way reported for patients with treatment-resistant depression. Most of my patients are adults with refractory negative mood states.”

In the study, which was published in the Journal of Psychopharmacology, 12 adults with general anxiety disorder or social anxiety disorder received three ascending ketamine doses (0.25, 0.5 and 1 mg/kg) once per week. The doses of ketamine produced rapid anti-anxiety effects, which lasted for 3 to 7 days at higher doses.

Ketamine works by blocking the NMDA (N-methyl-d-aspartate) glutamate receptor in the brain. The drug also has euphoric and dissociative effects, making it a potential drug of abuse.

Overall, the drug was well tolerated. But some patients did experience side effects. Two patients reported the highest dose produced an experience that was very intense and felt out of control. Two participants also reported transient nausea.

“At some point in the future there will be ketamine formulations for treatment-resistant depression (maybe Janssen Pharmaceutica’s ketamine nasal spray),” Glue told PsyPost. “Potentially, this will also work for patients with treatment-resistant anxiety.”

Ketamine is not yet approved for use in the treatment of anxiety or depression. More research needs to be done to determine the most effective and safest dose regimen for patients. It is also unclear how long patients need to receive treatment.

“There are more questions than answers at present but lots of interesting possibilities, especially in an area that Big Pharma has no new candidate drugs that might compete with ketamine,” Glue explained. “The research in this area may well come from small centers rather than Big Pharma-sponsored studies in the near future.”

The study, “Ketamine’s dose-related effects on anxiety symptoms in patients with treatment refractory anxiety disorders“, was also co-authored by Natalie J Medlicott, Sarah Harland, Shona Neehoff, Bridie Anderson-Fahey, Martin Le Nedelec, Andrew Gray and Neil McNaughton.

