[Comparative study of the effects of diazepam and fentanyl on the blink reflex threshold in the normal, conscious...

The search in man for experimental techniques suitable for study of the neurospecificity of anaesthetic drugs led us to use the blink reflex. Thirteen female volunteers undergoing gynaecological surgery received as a double-blind basis either 0.2 mg/kg of diazepam (7 cases) or 3 X 10(-1) mg/kg of fentanyl (6 cases) intravenously. The thresholds of the two components of the reflex R1 + R2, of respectively tactile and painful natures, were sought before and for three minutes after the injection of the drugs. The threshold of R2 rose to four times its initial value (P less than 0.001) after diazepam, whilst R1 remained unchanged. Fentanyl was not associated with any change in the thresholds. Study of the blink reflex may be used to dissociate and analyse the effects of two drugs on precise nervous functions. The nature of these functions and of their controls are discussed.