Lopirazepam is a short-acting benzodiazepine analog of the pyridodiazepine type. In a double-blind study the clinical symptomatology and quantitatively analyzed EEG of hospitalized chronic alcoholics undergoing alcohol withdrawal were investigated before, during and after 3 weeks' treatment with 2 pharmacokinetically different benzodiazepines: the short-acting lopirazepam and the long-acting prazepam. Blood level investigations demonstrated that even after a 3-week treatment period, blood levels dropped down to a morning minimum 12 h after the last evening medication of the short-acting lopirazepam, while plasma levels of the long-acting prazepam remained high. This was also reflected in the spectral analyzed EEG, which showed, after one single dosage of both drugs, a typical anxiolytic profile which was more pronounced after lopirazepam than prazepam, while after the chronic administration (12 h after the evening medication) only prazepam showed an anxiolytic profile. The lopirazepam-treated patients exhibited on the one hand a lack of benzodiazepine-specific alterations, but showed on the other hand EEG changes possibly reflecting clinical improvement.