Lack of effects of ethanol pretreatment on the abuse liability of nitrous oxide in light and moderate drinkers

Aims. To determine effects of ethanol-use history and ethanol pretreatment on abuse liability of nitrous oxide (N2O). Design. Placebo-controlled, doub le-blind, cross-over design evaluating effects of N2O, 0% (100% O-2, placeb o) and 30% (in O-2), in the presence of three doses of ethanol: 0 g/kg (pla cebo), 0.35 g/kg and 0.7 g/kg. Setting. Subjects sat in a reclining chair i n a hospital laboratory. Participants. Eight healthy light drinkers (one dr ink or less/week) and eight healthy moderate drinkers (seven or more drinks /week) with no history of drug dependence completed the study. Intervention . On three sessions (1, 3, 5) subjects drank a beverage that contained one of the three ethanol doses, then sampled for 10 minute each 0% and 30% N2O. During choice sessions (2, 4, 6), subjects received the same ethanol dose as in the previous session, then chose six times, once every 5 min, between 0% and 30% N2O. Measurements. Subjective (self-reported) drug effects, rei nforcing effects of N2O as assessed by choice, and psychomotor effects were measured. Findings. Choice of N2O did not differ between light (mean = 3.4 choices) and moderate (mean = 3.2 choices) drinkers and was not influenced by ethanol dose (0 g/kg: 3.3 choices, 0.35 g/kg: 3.5 choices, 0.7 g/kg: 3. 1 choices). Subjective effects of N2O also did not depend on ethanol-use hi story or ethanol dose. N2O liking and desire to inhale the drug again were positively correlated with N2O choice. Conclusions. Ethanol pretreatment an d ethanol-use history had no effect on the abuse liability of N2O as assess ed in the present study.