Researchers at the National Institute of Mental Health (NIMH), led by Dr. Carlos Zarate, recently found that a single dose of ketamine could rapidly relieve depression in patients with bipolar disorder.
They have now replicated these results in a new study of depressed patients who also have bipolar disorder, this time “blinding” the study by giving some subjects a placebo. Replication is a vital part of the scientific method, as it helps ensure that the first results weren’t accidental.
Bipolar disorder is a serious and debilitating condition in which sufferers experience severe mood swings ranging from mania to depression. The time periods of low or high moods can last for days or months, and the risk of suicide is high.
Antidepressants are often prescribed for bipolar disorder, but they are not universally effective. Many patients continue to suffer through episodes of depression even while on medication, and many individuals must try several different types of antidepressants before finding one that is effective.
In addition, sometimes it takes several weeks before a patient begins to feel relief from the drug’s effects. Because of this, better treatments for depression are desperately needed.
In the new study, patients either received a single dose of ketamine or a single dose of placebo on two different days, two weeks apart. The researchers carefully monitored the patients and asked them to repeatedly rate their depressive symptoms and suicidal thoughts.
In the ketamine group, depression symptoms significantly improved within 40 minutes, and remained improved over 3 days. Overall, 79 percent of the patients improved with ketamine, but none reported improvement when they received placebo.
Significantly, and for the first time in a group of patients with bipolar depression, researchers found that ketamine greatly reduced suicidal thoughts. These anti-suicidal benefits also occurred within one hour. Since bipolar disorder is one of the most deadly of all psychiatric disorders, these results could have a major impact on public health.
“Our finding that a single infusion of ketamine produces rapid antidepressant and anti-suicidal effects within one hour and that is fairly sustained is truly exciting,” said Zarate.
“We think that these findings are of true importance given that we only have a few treatments approved for acute bipolar depression, and none of them have this rapid onset of action; they usually take weeks or longer to have comparable antidepressant effects as ketamine does.”
Ketamine is primarily used as an anesthetic in conjunction with a sedative. It is an N-methyl-D-aspartate (NMDA) receptor antagonist, which means that it works by blocking the actions of NMDA.
“Importantly, confirmation that blocking the NMDA receptor complex is involved in generating rapid antidepressant and antisuicidal effects offers an avenue for developing the next generation of treatments for depression that are radically different than existing ones,” said Zarate.
The study is published in Biological Psychiatry.
Source: Biological Psychiatry