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ISSUE NO 2 7 NEWS & REVIEWS In order to allow a more targeted approach to the choice of pharma- cological treatment a better under- standing of these mechanisms and pharmacological principles of drugs is vital. Pain processing systems For the modulation of pain the opiodergic and monoaminergic systems are highly relevant. Both play a key role in the ascending and descending pain pathways (Paster- nak, 2010; Benarroch, 2008). In acute nociceptive pain, pain modu- lation is to a large extend regulated Professor Bart Morlion MECHANISM-ORIENTATED PHARMACOLOGICAL MANAGEMENT OF CHRONIC PAIN Current treatment of chronic pain is largely based on the severity of pain. Various guidelines exist to aid clinicians by suggesting recom- mended treatment options for dif- ferent pain conditions. The best known of these is the World Health Organisation (WHO) three-step pain ladder which was originally devel- oped for chronic cancer pain but is now also applied to non-cancer pain (WHO, 1996). It advocates the initial use of non-opioid analgesics, fol- lowed by weak opioids and strong opioids as the severity of pain increases. However, since most chronic pain conditions are multi- factorial in nature (e.g. nociceptive and neuropathic components pres- ent) effective pain management needs to take into account the underlying mechanisms in order to choose the most appropriate treat- ment. Hence, pain management decisions should depend on the underlying mechanisms and not only on the intensity of the pain. Ideally, clinicians would identify the specific causal mechanisms under- lying each patient’s symptoms and correspondingly prescribe the most appropriate therapy. However, identifying these mechanisms in practice is difficult, as one mecha- nism can produce different symp- toms and one symptom can be produced by different mechanisms (Woolf, 1999). by the opioidergic system: µ-opioid receptor agonists influence and directly inhibit the transmission of pain signals via the ascending path- way. In addition, µ-opioid receptor agonists are also involved in the modulation of pain signals on a supraspinal level with modulating impact on the descending path- ways. In chronic pain, which is often associated with neuropathic com- ponents, alterations of the opio- dergic system can lead to a reduction of opioid responsiveness, e.g. analgesic tolerance and/or opioid-induced hyperalgesia (Ballan- Disease / Injury MechanismTreat Syndrome Measure Signs / Symptoms Figure 3: Ideally, pain management measures symptoms and treats pain mechanisms Adapted from Woolf, 2001