Results of a pilot study to develop computer-assisted self infusion of ethanol: the Freibier paradigm

Human alcohol self-administration studies with oral drinking are flawed by the high variability of resulting breath alcohol concentrations (BrAC). We seek to develop a paradigm with better control over BrAC. The CASE system employs i.v. infusion of ethanol. Subjects are guided through the experiment by a computer screen and can order “drinks“ at any time by pressing a button. The computer calculates the necessary infusion rates using a pharmacokinetic model to account for individual variation among subjects. It controls the pump, adjusting infusion rates once every 30 seconds. The Freibier paradigm is the first application for CASE. Its principle is that subjects get alcohol without work, pay or other prerequisites, on the sole condition that their BrAC stays below the safety limit of 100mg%. BrAC rises by 7.5mg% upon each button press and declines by 1mg% per minute thereafter until the next drink is requested. Six males and 4 females participated in 3 sessions each. Peak BrAC ranged between 0.24 and 1.13 ‰ (mean 0.78, median 0.8 ‰). Most subjects managed to achieve a fairly stable BrAC plateau for prolonged periods of time. The maximum and plateau BrAC varied considerably between the 1st and 2nd test, but was rather stable between 2nd and 3rd session in most of the subjects. These preliminary data suggest that CASE is a practical method to investigate human alcohol self-administration. Its readout is reliable, supporting the potential for use in scientific studies.