Study procedures
The study included a screening visit, four 13-h test sessions with follow-up measurements 24 h after drug intake, and an end-of-study visit which took place on average 31 days after the last test session. Test days were separated by at least 10 days. The sessions were conducted in a calm hospital room. Only one research subject and one investigator were present during each test session. The test sessions began at 8:00 AM. A urine sample was taken to verify abstinence from drugs of abuse, and a urine pregnancy test was performed in women. The subjects then underwent baseline measurements. A standardized breakfast (two croissants) was served. Substances were administered at 9:00 AM. The outcome measures were repeatedly assessed for 12 h. Standardized lunches and dinners were served at 1:30 PM and 6:00 PM, respectively. The subjects were never alone during the acute effect phase. The subjects were sent home at 9:15 PM and returned the next day for follow-up measurements at 9:00 AM.