The effects of ephedrine on the development of fatigue in a prolonged driving-related task

The effects of ephedrine on the development of fatigue in a prolonged drivi ng-related task were investigated using three independent measures. Subject s (n = 15) received either ephedrine (60 mg) or a placebo before carrying o ut a 3-way divided attention task for an uninterrupted 4 h period, during w hich cardiac inter-beat interval was monitored. A battery of psychomotor te sts and two questionnaires were completed before and after the 4 h session and oral temperature, blood pressure and heart rate were also recorded. A s aliva sample was taken at 4 h for ephedrine assay. The performance of the p lacebo group on the prolonged task deteriorated over time, whereas that of the ephedrine group improved. In placebo subjects, there was a progressive decrease in heart rate, an increase in heart rate variability (HRV) and an increase in the peak log spectral power of the blood pressure frequency com ponent of HRV. Deterioration of performance on the test battery and questio nnaires confirmed that fatigue had developed. The mean salivary ephedrine c oncentration after 4 h was 0.08 mg/ml (0.03 SEM). The deterioration in perf ormance in the placebo group indicated the development of fatigue which was partially offset by a single therapeutic dose of ephedrine. Copyright (C) 1999 John Wiley & Sons, Ltd.