Cancer
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Clinical Trial Controlled Clinical Trial
Evaluation of a cancer pain model for the testing of long-acting analgesics. The effect of MS Contin in a double-blind, randomized crossover design.
A double-blind, double-dummy, crossover study compared oral controlled-release morphine sulfate (MS Contin tablets [MSC], Purdue Frederick, Norwalk, CT) every 12 hours, and immediate-release morphine sulfate (IRMS) tablets, every 4 hours, in 14 evaluable patients with chronic cancer pain. The test model described showed assay sensitivity for steady-state analgesia, requiring relatively few subjects to yield statistical significance in pharmacologic potency estimates. Initial doses were the calculated equivalents of about one third the previous opioid requirements or at least 30 mg MSC every 12 hours or 15 mg IRMS every 4 hours. ⋯ MS Contin exhibits a 12-hour duration of action as previously shown in other well-controlled trials. A problem of pain exacerbation at the start of each study phase was found to be associated with the design of this study. It may be resolved with a higher initial study dose and/or use of a patient-controlled analgesia device for parenteral rescue doses.
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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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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.