Changes in cortical evoked potentials as correlates of the efficacy of weak analgesics.

The relationship between subjective measurements of pain (pain report and threshold of sensation) and evoked potentials following painful electrical stimulation of tooth pulp was evaluated after intake of different weak analgesics. These time-response curves for the dolorimetric parameters were correlated to the in vivo drug levels obtained in corresponding experiments by analyzing saliva. Based on the comparison between the drug levels of analgesics in saliva on the one hand and the threshold of sensation, the pain rating and changes in the amplitude of the cortical EP on the other hand, the sensitivity of the EP to changes in drug concentration was superior than to subjective pain judgement. The data were correlated to clinical pain relief investigations. The results support the suggestion of earlier research that EP evaluation may well serve as a correlate for laboratory pain.