Cancer
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Cancer pain can be divided into three classes: somatic, visceral, and deafferentation. Somatic and visceral pain result from activation of nociceptors by tumor infiltration of tissues and from secondary inflammatory changes with release of algesic chemicals that act to sensitize nociceptors. Pain may be experienced locally (somatic and visceral) or referred to remote cutaneous sites (visceral). ⋯ Somatic, visceral, and deafferentation pain may be complicated by sympathetically maintained pain, in which efferent sympathetic activity promotes persistent pain, hyperpathia, and vasomotor and sudomotor changes after tissue injury from cancer or its therapy. The neurobiology of cancer pain is complex and incompletely understood. This article summarizes current knowledge in this area and briefly discusses approaches to cancer pain management that are based on this knowledge.
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Randomized Controlled Trial Clinical Trial
Oral controlled-release morphine sulfate. Analgesic efficacy and side effects of a 100-mg tablet in cancer pain patients.
Fifty-one cancer pain patients with limited opioid exposure participated in a randomized, double-blind, repeated-dose, parallel-group comparison of two dosage strengths of the controlled-release morphine preparation, MS Contin tablets (The Purdue Frederick Company, Norwalk, CT). The patients were first stabilized on immediate-release oral morphine 30 mg every 4 hours, with 15 mg available every 2 hours as needed for breakthrough pain ("rescue" dose). Each patient then received either one 100 mg MS Contin tablet or three 30-mg MS Contin tablets every 12 hours, with rescue medication as needed, for 3 days. ⋯ In the study population as a whole, pain intensity was lower and total morphine intake higher during the period on controlled-release morphine. These data establish comparable analgesic efficacy and side effect potential of these two dosage strengths and confirm a 12-hour duration of effect for both. The improved analgesia on the controlled-release morphine may be attributable to increased consumption of drug resulting from improved compliance.
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The results of nine US multicenter, sequential crossover, dose titration studies of controlled-release oral morphine (MS Contin 30 mg tablets [MSC], Purdue Frederick, Norwalk, CT) are reviewed in Part I. The studies demonstrated the prolonged analgesic efficacy of the preparation in the treatment of patients with moderate to severe cancer-related pain. Approximately 93% of the patients achieved satisfactory to excellent analgesia on a 12-hour regimen when appropriate dose titration was allowed. ⋯ The results showed that MSC 15-mg, 30-mg, 60-mg, and 100-mg dosage strengths are bioequivalent and dose proportional, and, therefore, therapeutically interchangeable. It was concluded that with routine assessment of the patient and adherence to the principles of analgesic dosing, MSC can be successfully used to control cancer-related pain. Furthermore, the availability of various MSC tablet strengths can be expected to facilitate the analgesic management of a patient population with widely differing opioid requirements.