Cortical-evoked potentials and saliva levels as basis for the comparison of pure analgesics to analgesic combinations.

Cortical-evoked potentials, pain ratings and thresholds of sensation were monitored after tooth pulp stimulation under the influence of marketed mixtures of analgesics. Simultaneously the saliva levels of the individual pharmacological active components of these mixtures were measured by high-performance thin-layer chromatography. The action of the mild analgesics in the mixtures was calculated from the linear correlations of changes in cortical-evoked potential with saliva levels of the analgesics. The ineffectiveness of low doses of salicylamide in the combinations was demonstrated by this method. None of the investigated combination products was superior to the same doses of either acetylsalicylic acid, paracetamol or phenazone.