Alterations in response to somatic pain associated with anaesthesia. XDC: Studies with drugs used in neuroleptanaesthesia

The effects of some intravenously administered drugs on sensitivity to tibial pressure-induced somatic pain were investigated in a controlled, double-blind trial. The drugs included those commonly employed in neuroleptanaesthesia (fentanyl, phenoperidine and droperidol), standard opiates (morphine, diamorphine), and a standard tranquillizer (diazepam). The analgesics were given in what are commonly regarded as clinically equipotent dosages. Fentanyl and phenoperidine decreased the subjects ' sensitivity to somatic pain, whilst saline, morphine, diamorphine and diazepam did not have any effect. Droperidol caused an increase in sensitivity, and the addition of droperidol to either phenoperidine or fentanyl was associated with a simple summation of effect. It was concluded that there is a difference in the mode of action of fentanyl and phenoperidine in comparison to morphine, the former having a relatively greater effect on the perceptual mechanisms of pain and the latter a relatively greater effect on the affective experience of pain. The usefulness of experimental pain threshold studies in the assessment of analgesic drugs i