Effects of tapentadol on chronic pain and parameters of central sensitization.

Chronic pain is a serious debilitating factor for health and welfare with a mean prevalence of 27% in the general European adult population. In most of these conditions a cause for the pain is seldom to be found. It is speculated that central sensitization (CS) is directly involved in the process of chronification and maintenance of chronic pain in many conditions.

For that reason, alleviation of central sensitization should be part of the treatment of patients with chronic pain. This has been demonstrated for pregabalin, but in case of tapentadol it is unknown if and how it interferes with CS. Most relevant to this study is the association of CS with chronic low back pain, chronic pelvic pain, endometriosis, vulvodynia, and dysmenorrhea as well as interstitial cystitis/bladder pain syndrome.

Tapentadol is a new class of opioids with a dual mechanism of function. Tapentadol agonises the mu-opioid receptor (ì-OR) and inhibits the reuptake of noradrenaline in the central nervous system. Its particular efficacy in managing chronic neuropathic pain that is attributed to the latter mechanism. The noradrenergic effect might result in modulating descending pain pathways in the central neural system and thereby reduce or alleviate CS.
Due to the low binding affinity of tapentadol to the ì-OR (with adequate analgesic effects), adverse effects associated with opioid usage such as opioid-induced-hyperalgesia, gastrointestinal complications, dependency and tolerability issues are less likely to occur.
The core of this study is to explore the effects of tapentadol on parameters of CS in patients suffering from chronic pain. This has not been previously performed.

The main objective is to determine the change in CS parameters upon administration of tapentadol in comparison to pregabalin in patients suffering from chronic pain that has a visceral or deep somatic origin.

T1: Before start of first treatment

T2: At the end of the first treatment

T3: Before the start of the second treatment

T4: At the end of the second treatment

- Tapentadol:

Dose: start dose of 50mg 2x/day, increase by 50mg 2x/day every 3 days until sufficient analgesia is reached with tolerable adverse effects. Max 500 mg/day.

Route: Oral administration

Duration: 8 weeks

- Pregabalin:

Dose: start dose of 75mg 2x/day, increase by 75mg 2x/day every 3 days until sufficient analgesia is reached with tolerable adverse effects. Max 600 mg/day.

Route: Oral administration

Duration: 8 weeks