Visits
emesis, Easypump® ST/LT
In our randomized, cross-over design, participants underwent a total of five visits, including the screening visit, baseline visit, and three infusion visits during which the participants, research coordinator (study assessments), research nurses (peripheral IV catheter placement), and licensed study clinicians (ketamine infusions, monitoring, and safety assessments) were blinded to the intervention. At any of the three infusion visits, participants received placebo saline, 0.05 mg/kg ketamine, or 0.5 mg/kg ketamine with the order randomized for each participant. We used IV ketamine administration as it provides the most predictable dosing with 100% bioavailability. Given the within-participants design of the study, each participant received all three of the specified doses across the duration of the trial. Each infusion visit was separated from any other infusion visit by 10–14 days to avoid drug carry-over effects. Participants arrived fasted for infusion visits in the morning to reduce the risk of emesis, and they completed a urine drug screen and pregnancy test (if applicable), had their baseline vitals recorded, and had a peripheral IV catheter placed at the Clinical Trial Research Unit at Stanford University. Participants were then escorted to the Stanford Center for Cognitive and Neurobiological Imaging, where they were met by the study clinician and subsequently began the infusion.Racemic IV ketamine (0.05 mg/kg or 0.5 mg/kg) or 0.9% normal saline (Mariner Advanced Pharmacy Corp, San Mateo, CA) was delivered via an elastomeric pump (Braun Easypump® ST/LT) over a period of 40 min. For safety reasons, pulse, blood pressure, and pulse-oximetry were monitored and recorded every 10–15 min for all conditions during the infusions and scanning sessions. The total visit time for infusion visits was 6–8 h.