The intracutaneous pain model in the assessment of analgesic efficacy

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Abstract
This review summarizes the results of studies using the intracutaneous pain model in the assessment of nociceptive information transfer from cutaneous afferents to pain-relevant cortical structures, as measured by spontaneous and stimulus-evoked electroencephalographic activity. The application of multivariate statistical analyses, such as principal component analysis, on the late brain potentials, results in the identification of two pain-related principal components with loading maxima around 150 and 250 ms after stimulation, which vary with the reported painfulness of the stimulus. The application of pain-related evoked cerebral potentials in studies of pain-relieving drugs makes possible a quantitative comparison of their analgesic potency. The drugs tested were acetaminophen, phenazone, acetylsalicylcic acid, ibuprofen, anpirtolin, diclofenac, denaverine, flupirtine, imipramine, meperidine, naloxone, pentazocine, tilidine and tramadol, several of them in different dosages and formulations. The interstudy comparison revealed that there was a high correlation (r = 0.91) between pain relief at the subjective measurement level and a decrease in pain-related brain potentials.