Repeated intravenous infusions of ketamine provide rapid relief for patients with posttraumatic stress disorder, new research suggests.
In what investigators are calling the first randomized controlled trial of repeated ketamine administration for chronic PTSD, 30 patients received six infusions of ketamine or midazolam (used as a psychoactive placebo) over 2 consecutive weeks.
Between baseline and week 2, those receiving ketamine showed significantly greater improvement than those receiving midazolam. Total scores on the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) for the first group were almost 12 points lower than the latter group at week 2, meeting the study’s primary outcome measure.
In addition, 67% vs. 20% of the patients, respectively, were considered to be treatment responders; time to loss of response for those in the ketamine group was 28 days.
Although the overall findings were as expected, “what was surprising was how robust the results were,” lead author Adriana Feder, MD, associate professor of psychiatry, Icahn School of Medicine, Mount Sinai, New York, told this news organization.
It was also a bit surprising that, in a study of just 30 participants, “we were able to show such a clear difference” between the two treatment groups, said Dr. Feder, who is also a coinventor on issued patents for the use of ketamine as therapy for PTSD, and codirector of the Ehrenkranz Lab for the Study of Human Resilience at Mount Sinai.
The findings were published online Jan. 5 in the American Journal of Psychiatry.
Unmet need
Ketamine is a glutamate N-methyl-D-aspartate (NMDA) receptor antagonist that was first approved by the U.S. Food and Drug Administration for anesthetic use in 1970. It has also been shown to be effective for treatment-resistant depression.
PTSD has a lifetime prevalence of about 6% in the United States. “While trauma-focused psychotherapies have the most empirical support, they are limited by significant rates of nonresponse, partial response, and treatment dropout,” the investigators write. Also, there are “few available pharmacotherapies for PTSD, and their efficacy is insufficient,” they add.
“There’s a real need for new treatment interventions that are effective for PTSD and also work rapidly, because it can take weeks to months for currently available treatments to work for PTSD,” Dr. Feder said.
The researchers previously conducted a “proof-of-concept” randomized controlled trial of single infusions of ketamine for chronic PTSD. Results published in 2014 in JAMA Psychiatry showed significant reduction in PTSD symptoms 24 hours after infusion.
For the current study, the investigative team wanted to assess whether ketamine was viable as a longer-term treatment.
“We were encouraged by our initial promising findings” of the earlier trial, Dr. Feder said. “We wanted to do the second study to see if ketamine really works for PTSD, to see if we could replicate the rapid improvement and also examine whether a course of six infusions over 2 weeks could maintain the improvement.”
Thirty patients (aged 18-70; mean age, 39 years) with chronic PTSD from civilian or military trauma were enrolled (mean PTSD duration, 15 years).
The most cited primary trauma was sexual assault or molestation (n = 13), followed by physical assault or abuse (n = 8), witnessing a violent assault or death (n = 4), witnessing the 9/11 attacks (n = 3), and combat exposure (n = 2).
During the 2-week treatment phase, half of the patients were randomly assigned to receive six infusions of ketamine hydrochloride at a dose of 0.5 mg/kg (86.7% women; mean CAPS-5 score, 42), while the other half received six infusions of midazolam at a dose of 0.045 mg/kg (66.7% women; mean CAPS-5 score, 40).
In addition to the primary outcome measure of 2-week changes on the CAPS-5, secondary outcomes included score changes on the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Impact of Event Scale-Revised (IES-R).
Treatment response was defined as a 30% or more improvement in symptoms on the CAPS-5. A number of measures were also used to assess potential treatment-related adverse events (AEs).