Effects of Tapentadol on chronic pain and parameters of central sensitization. A prospective, open label, randomized cross-over study with pregabalin as comparator (study protocol)

Background There is growing evidence for an important role of central sensitization (CS) in the development and maintenance of chronic pain. Consequently, alleviation of CS might be helpful, as was demonstrated for pregabalin. For tapentadol this is unknown. Tapentadol is a drug with a dual mechanism: 1) it acts on the mu-opioid receptor (µ-OR) and 2) it inhibits the reuptake of noradrenalin in the central nervous system3. The noradrenergic effect might involve a modulation of descending pain pathways and thereby reduce or alleviate CS. Aim The aim of the present study is to determine the alterations in CS parameters by tapentadol in patients with chronic visceral (endometriosis) pain and deep somatic (low back) pain, using pregabalin as comparator. Hypothesis In both visceral and deep somatic pain when using tapentadol or pregabalin a decrease in pain (NRS) correlates to a decrease in CS. Method/design Prospective, open label 2x2 randomized cross-over study in 30 patients with proven endometriosis and 30 patients with chronic (> 3 months) low back pain radiating to the leg (CLBPr). Each group of patients will start with either pregabalin of tapentadol for 8 weeks, followed by a wash out period of one week, after which the second drug is used for 8 weeks. Discussion The rationale for this study is to provide more insights about the affect tapentadol has on CS parameters in comparison to pregabalin in patients suffering from chronic pain that has a visceral or deep somatic origin