Now researchers can predict which individuals will respond favorably with a simple blood test.
The antidepressant effects of ketamine take effect within two hours, compared to the several weeks required by typical antidepressants.
“Doctors know that very small doses of ketamine help relieve depression and pain,” said Michael Goldberg, M.D., professor and chairman of anesthesiology, and associate dean for education at Cooper Medical School of Rowan University.
“But one in three patients do not respond to this treatment. This research will help as we seek ways to provide these patients relief.”
Bipolar disorder causes unusual shifts in mood, energy and activity levels and hinders the ability to carry out basic tasks. The condition is characterized by mood swings that range from severe depression to very elevated or irritable moods.
It can be difficult to diagnose and is often mislabeled as clinical (unipolar) depression.
Researchers identified the compound that ketamine breaks down into, which they called HNK. They also discovered the pattern or “fingerprint” in the fatty acids of the blood that will identify whether a patient with bipolar will respond to HNK.
For the study, 22 participants with bipolar disorder were given intravenous doses of ketamine. Each patient also gave a blood sample.
Responders to ketamine and non-responders were identified using a standardized depression rating scale. A response was considered positive if the patient felt a 50 percent or greater improvement. Additionally, researchers examined metabolic patterns in blood samples.
The difference between responders and non-responders was determined by how the individuals metabolized fatty acids, based on the variability in levels of 18 metabolites.
“These are significant discoveries which should eventually help in the treatment of patients suffering from depression and chronic pain,” said Irving Wainer, Ph.D., senior investigator with the Intramural Research Program at the National Institute on Aging, Baltimore.
“The next step is to look for the genetic or environmental factors that determine whether a person develops the metabolic pattern that responds to the treatment. We hope this leads to the development of customized or individualized treatment for each patient.”
The findings were presented at the Anesthesiology 2013 annual meeting.