The effects of ephedrine on the development of fatigue in a prolonged driving-related task were investigated using three independent measures. 15 subjects (aged 18-37 years) received either ephedrine (60 mg) or a placebo before carrying out a 3-way divided attention task for an uninterrupted 4 hour period, during which cardiac inter-beat interval was monitored. A battery of psychomotor tests and two questionnaires were completed before and after the 4 hour session and oral temperature, blood pressure and heart rate were also recorded. A saliva sample was taken at 4 hours for ephedrine assay. The performance of the placebo 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 incr3ase in heart rate variability (HRV) and an increase in the peak log spectral power of the blood pressure frequency component of HRV. Deterioration of performance on the test battery and questionnaires confirmed that fatigue had developed. The mean salivary ephedrine concentration after 4 hour was 0.08 mg ml. The deterioration in performance in the placebo group indicated the development of fatigue which was partially offset by a single therapeutic dose of ephedrine. (A)
Abstract