Pain
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Electrical high-frequency stimulation (HFS) of skin afferents elicits long-term potentiation (LTP)-like hyperalgesia in humans. Time courses were evaluated in the facilitating (homotopic) or facilitated (heterotopic) pathways to delineate the relative contributions of early or late LTP-like pain plasticity. HFS in healthy subjects (n=55) elicited highly significant pain increases to electrical stimuli via the conditioning electrode (to 145% of control, homotopic pain LTP) and to pinprick stimuli in adjacent skin (to 190% of control, secondary hyperalgesia). ⋯ Dynamic mechanical allodynia (only present in 16 of 55 subjects) lasted for a shorter time than secondary hyperalgesia. Three different readouts of nociceptive central sensitization suggest that brief intense nociceptive input elicits early LTP1 of pain sensation (based on posttranslational modifications), but susceptible subjects may already develop longer-lasting late LTP2 (based on transcriptional modifications). These findings support the hypothesis that LTP may contribute to the development of persistent pain disorders.
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When opioid therapy is initiated for a new pain condition, it may be unknown whether the pain will persist beyond the time of tissue healing. The aim of this study was to determine the prevalence of prescription patterns indicating persistent and/or problematic opioid use in a cohort of opioid-naive patients starting therapy with weak opioids. Data were drawn from the nationwide Norwegian Prescription Database. ⋯ Of these subjects, 686 patients were dispensed more than 365 DDDs of opioids in 2008 and are probably persistent users. There were 191 subjects who met our criteria for probable problematic opioid use. In a cohort of new opioid users who started treatment with weak opioids, only 0.3% and 0.08% developed prescription patterns indicating persistent opioid use and problematic opioid use, respectively.