Influences of Alprazolam on EMG in maximal voluntary efforts

Abstract

A randomized controlled double-blind study was conducted to investigate the influences of different doses of Alprazolam (a benzodiazepine; 0.5, 1.5 and 3.0 mg) on the electromyogrophic activity (EMG) during standardized movement controlled maximal efforts. Nineteen healthy male subjects were tested 90 and 360 minutes after administration of the drug. Electromyography of the M. vastus medialis was measured during different exercise tests on an isokinetic dynamometer. The signals (both EMG and dynamometer output) were registrated by means of active surface electrodes (gain: 10: CMRR: 90 dB), amplified by means of differential amplifiers (gain: 300; CMRR: 85 dB); recorded on an FMtape recorder, low-pass filtered (second-order Butterworth) at 500 Hz. analog-to-digital converted and sampled at 2000 Ht. It was found that moderate to high doses of Alprazolam (1.5 and 3.0 mg) significantly (~4.05) reduced both integrated EMG and maximal EMG amplitude, and that 360 minutes after administration. only the high dose demonstrated significant decrease of the EMG signal. It is suggested that the observed relaxating effects of the drug may be due to the enhancement of gamma-aminobutyric acid (GABA) activity not only in the central nervous system, but also in peripheral receptor sites.