The Patient with Difficult Cancer Pain.

Most patients with cancer pain can be managed with relatively simple methods using oral analgesics at relatively low doses, even for prolonged periods of time. However, in some clinical conditions pain may be more difficult to manage. Various factors can interfere with a desirable and favorable analgesic response. Data from several studies assessing factors of negative pain prognosis have indicated that neuropathic pain, incident pain, psychological distress, opioid addiction, and baseline pain intensity were associated with more difficult pain control. In this narrative review, the main factors that make the therapeutic response to opioids difficult are examined.