Adjuvant agents in cancer pain.

Cancer-related neuropathic pain derives from peripheral or central lesions of the nervous system and is often associated with the hallmark symptoms of allodynia (pain from a stimulus that does not normally evoke pain) and hyperalgesia (an exaggerated pain response to a normally painful stimulus). Pain is prevalent in patients with cancer and considerably undermines their quality of life, thereby making the development of a comprehensive pain management approach essential. Coanalgesics have been well integrated into cancer pain management strategies and are often used as first-line options for treatment of certain disease processes such as neuropathic pain. These medicines, including antidepressant and anticonvulsant agents, are recommended by evidence-based guidelines, whereas others, such as lidocaine patch 5%, are supported by randomized, controlled, clinical trial data. In addition to understanding which agents are recommended for neuropathic pain, it is useful to know which agents are of limited utility or are to be avoided when prescribing treatment for neuropathic pain. Notwithstanding the need for head-to-head studies before firm statements on comparative efficacy can be made, it is worth considering the numbers needed to treat statistic for the treatment of neuropathic pain with coanalgesics. Potentially harmful treatments are considered, as well as the numbers needed to treat, mechanisms of action, and clinical trial data for agents that can be beneficial for the management of cancer-associated neuropathic pain.