Use of Orally Administered Opioids for Cancer-Related Pain

To summarize the important principles of opioid analgesia for cancer-related pain. We reviewed our personal experience and reports in the literature to characterize commonly prescribed high-potency opioids and their relative efficacy. The pharmacologic features of various opioids, selection of appropriate agents, titration of doses, routes of administration, conversions between drugs, and management of side effects are discussed. In general, the oral route is preferred because of ease of administration and good oral bioavailability of most opioids. In addition to the scheduled dosage of an opioid, extra “rescue” doses (5 to 10% of the total daily opioid dosage) should be available to the patient for breakthrough pain. Morphine is the prototype strong opioid against which other drugs are compared. Common adverse effects of opioids are sedation, nausea, constipation, respiratory depression, and myoclonus. Although no “standard” dose of opioid exists, the goals are to achieve adequate control of pain and to avoid major, unmanageable toxic effects. Pain is commonly associated with all stages of malignant disease. Despite its widespread occurrence, cancer pain is often inadequately managed because of poor assessment of pain and physicians' misconceptions about use of opioids. The cause of the pain should be carefully sought because it may yield important information about the underlying malignant disease. In most patients with moderate to severe cancer-related pain, oral administration of the appropriate opioid will achieve effective analgesia.