Ethanol Pharmacodynamics at Low Blood Concentrations.

Abstract

Ranitidine has been shown to produce increases in blood alcohol concentration (BAC) after low doses of alcohol. The objective of this study was to reproduce, in a controlled setting, the BACs seen after low oral doses of ethanol in the presence and absence of ranitidine and to assess the effect of these concentrations on cognitive performance. An active control group (0.45 g per kg alcohol) was included as a validation of the methodology used. A randomized, double-blind, placebo-controlled, four-way crossover study was performed in eight healthy males. Subjects received a 20-min intravenous infusion of 0.10, 0.15, or 0.45 g per kg alcohol or placebo. Blood samples were obtained to measure BAC and psychometric effects were assessed over 8 h. A pharmacokinetic model was used to fit simultaneously the BAC--time profiles of all three doses for each subject. Cognitive improvement was assessed using digit symbol substitution, continuous tracking, and divided attention tests. Analysis of variance was conducted in order to compare peak blood alcohol impairment (E(max)) and area under the alcohol impairment--time curve (AUEC) across treatments. Observed median peak BAC (C(max)) for 0.10- and 0.15-g/kg dose groups (median BACs 15.2 and 27 mg/dl, respectively) were very similar to the target C(max) (13 and 26 mg/dl). Analysis of variance of AUEC and E(max) showed difference in impairment measures after the 0.10- and 0.15-g/kg doses. A significant difference in impairment measures between placebo and the active control, 0.45 g/kg (median BAC of 110 mg/dl) was observed, indicating that the methodology was capable of detecting significant psychomotor effects at the legal limit of BAC. Results indicated that the BAC increments from 15 to 27 mg/dl are not associated with significantly impaired performance and, hence, it is unlikely that increases in BAC of this magnitude, such as those caused by ranitidine therapy, are of any clinical relevance.