Repeated intravenous infusions of ketamine, given over two weeks, significantly reduced symptom severity in chronic PTSD compared to a psychoactive placebo (midazolam). At two weeks, the ketamine group scored nearly 12 points lower on the Clinician-Administered PTSD Scale, and 67% of participants responded to treatment versus 20% in the placebo group. Among responders, the median time to loss of response was 27.5 days after the infusion course. Ketamine was well tolerated with no serious adverse events. This is the first randomized controlled trial to show efficacy of repeated ketamine infusions for chronic PTSD.
Harmine, a component of the hallucinogenic brew ayahuasca, was tested in a phase 1 clinical trial to determine its safety, tolerability, and psychoactive effects when taken alone. Twenty-five healthy adults received single oral doses of 100 to 500 mg of pharmaceutical-grade harmine hydrochloride. The maximum tolerated dose was between 100 and 200 mg, and doses above 2.7 mg/kg caused vomiting, drowsiness, and limited psychoactive effects in 90% of participants. No serious adverse events occurred. Harmine alone can be safely administered at low doses, but higher doses produce dose-limiting side effects and only mild psychoactivity.