The Effects of Doxepin, Alone and Together With Alcohol, in Relation to Driving Safety

Psychotropic drug effects depend not only on the pharmacology of the drug, but upon the characteristics of the patient, and upon the environment in which the drug is taken. Since the life-style of most patients includes alcohol use and the control of motor vehicles, doxepin (an antidepressant-antianxiety compound) was tested in a laboratory setting for its effects on skills related to driving safety. Subjects were tested when sober and also when intoxicated by alcohol. Twelve subjects received doses of 25 mg/m2 of body surface area, 10 received half the above dose, and 12 received a placebo. Subjects took 2 doses at an interval of 12 hours. The amount of alcohol used gave a mean blood alcohol level of 73–6 mg/100 ml (Breathalyzer reading mean, 0–069%). Physiological measures, questionnaires and a battery of psychomotor skill tests, including two driving simulators, were used to assess the results. These techniques have previously been shown to reveal deleterious effects on performance by subjects consuming some drugs and alcohol. In this experiment the only significant drug effect was an improvement in performance on one driving simulator by the subjects on the higher dose of doxepin. It seemed that the antianxiety effects of doxepin were to some extent antagonistic to the well-documented detrimental effect which alcohol has on the performance of these tasks. An evaluation of laboratory studies is detailed, and the need for caution by prescribers is stressed.