Emerging analgesics and future directions: Targeting neuroplasticity

Quality of life is defined as an individual's perception of their culture and values, as well as their goals, morals and concerns [1]. Pain induced by progression of disease and adverse events associated with standard therapies significantly diminishes the quality of life in cancer patients [1,2]. Recent findings with a BRAF inhibitor in advanced stages of melanoma have emphasized the need for treatments to reduce pain and increase survival time in terminally ill cancer patients [3]. Reports highlighted the importance in patient quality of life in late stages of cancer and how family and physicians surrounding the patient may be affected [3]. Current therapies for advanced stages of cancer pain include opioids and bisphosphonates. Recent studies have demonstrated that sustained morphine not only intensifies tumor-induced pain but also accelerates tumor-induced bone destruction in a murine bone cancer model [4]. In addition, chronic use of opioids results in several unbearable side effects, including analgesic tolerance, constipation, respiratory depression and somnolence [5]. Bisphosphonates lack analgesic efficacy and entail adverse events, including osteonecrosis of the jaw and disruption of normal serum calcium levels [6]. Although advances in cancer therapeutics have increased survival times of cancer patients, including those with metastases, treatment in advanced stages of cancer and palliative care has not improved. Thus, there is a great need for novel therapeutics that not only have antitumor effects, but attenuate the pain and/or limit the side effects seen with current patient care.