Models including deep, tonic pain and hyperalgesia are better to predict the effects of analgesics. Experimental models have variable reliability, and validity shall be interpreted with caution. In general, the sensitivity to analgesics is better in patients than in healthy volunteers, but the lower number of studies may bias the results. Fewer studies were performed in patients. For opioids, tonic pain with high intensity is attenuated more than short-lasting pain and nonpainful sensations. Anticonvulsants and antidepressants are sensitive in several models, particularly in models inducing hyperalgesia. In healthy volunteers, the effect of acetaminophen is difficult to detect unless neurophysiological methods are used, whereas the effect of nonsteroidal anti-inflammatory drugs could be detected in most models. Experimental models to evoke pain and hyperalgesia are available for most tissues. The present review outlines the concept and limitations of human experimental pain models and addresses analgesic efficacy in healthy volunteers and patients. Human experimental pain models may therefore help to evaluate mechanisms and effect of analgesics and bridge findings from basic studies to the clinic. Pain models in animals have shown low predictivity for analgesic efficacy in humans, and clinical studies are often very confounded, blurring the evaluation.
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