[Clinical and economical evaluation of new analgesics for the management of chronic pain].

The management of chronic pain still represent a challenge for physicians. Opioids are the main stem in the treatment of chronic severe pain, not only for their potency, but as they act as central drugs. The main limit to their utilization in clinical practice is the prevalence of side effects, in particular in the gastrointestinal tract, whose constipation represents the most common. Two new formulations are nowadays available on the market: tapentadol PR (TAP PR) and oxycodone/naloxone (OXN). A recent meta-analysis showed that both drugs have a better tolerability profile than a tradizional opioid, such as oxycodone CR (OXY CR), but TAP PR reduces by 47% (RR=0.53) the percentage of patients discontinuing treatment because of side effects, compared to 24% (RR=0.76) of OXN. A similar advantage has been reported in the reduction of the risk of developing nausea and/or vomiting: TAP PR reduces the risk by 47% (RR=0.53), while OXN reduces the risk by only by 10% (RR=0.90). Both drugs reduced by about 40% the risk of constipation (RR=0.61 for TAP PR and for OXN). These results have been recently confirmed by a direct comparison of the two formulations (TAP PR vs OXN) in patients with chronic low back pain with neuropathic component. Both drugs were reported to be effective in reducing pain intensity and neuropathic symptoms, however TAP PR resulted superior to OXN in terms of analgesic efficacy, quality of life, and tolerability, in particular regarding constipation and adherence to treatment. A pharmacoeconomic analysis can be useful to understand the costs of these clinical advantages, and can be done by using a probabilistic analisys and by populating a Markov model that simulates the transition in time of 100 patients through 4 different possible health states: 1) still on treatment; 2) presence of adverse events; 3) discontinuation; 4) death. Both treatments (TAP PR and OXN) have been shown to have an excellent cost-effectiveness profile. In the case of OXN, in one year, 0.29 QALYs were gained compared to the use of OXY CR at an additional cost of € 138 resulting in a cost per QALY gained of € 475 (€ 138/0.29). In the case of TAP PR, instead, 0.31 QALYs were gained with additional savings due to the reduction of drug side effects, hospitalizations and emergency department access. Therefore, the use of TAP PR implies an average saving of € 31.6 per patient. These data are the results of a pharmacoeconomic model and require a further validation in clinical practice.