The Effect of Ketamine on Attentiveness

This will be a double-blind (neither physician nor patient knows the name of the assigned drug), placebo-controlled, randomized (study drug assigned by chance), 2 way crossover ketamine challenge study (participants may receive different interventions sequentially during the trial) in 24 healthy male volunteers. For all participants, this study will consist of an eligibility screening examination, two 2-day treatment periods, separated by at least 1 week, and a follow-up examination about 7 days after last dose administration. The maximal study participation for each volunteer will be around 6 weeks. Apart from observing possible neural and vascular ketamine effects, the cerebral ketamine effects will be investigated by simultaneously performing fMRI/EEG during ketamine administration. These investigations will be done while volunteers rest as well as during cognitive testing (visual oddball task). Safety evaluations include continuous monitoring of vital signs and oxygen saturation. Due to the pharmacokinetic properties of ketamine the assessments will start after an intravenous ketamine bolus (drug given directly into the vein over a short period of time) followed by a 1 minute break. During the assessments there is a continuous intravenous (minimal) drug administration. Before the assessments start there will be an intravenous bolus of 0.1 mg/kg ketamine in 5 minutes time followed by a 1 minute break after which a continuous infusion will start of 0.015625 mg/kg/min ketamine. Since the plasma level elevates during the infusion the administered dose will be lowered by 10% every 10 minutes.