Long-term patterns of morphine dosage and pain intensity among cancer patients.

Abstract

Cancer pain remains a worldwide problem and some patients continue to be undermedicated because of concerns about tolerance and drug dependence. The aim of this study was to document the morphine intake of patients with chronic cancer pain in an inpatient palliative care unit and to describe the long-term pattern of morphine use and pain intensity in this patient population. With IRB approval and written informed consent, patients admitted over a 64-week period to the palliative care unit at the Royal Victoria Hospital, Montreal, were candidates for this study. Cancer patients receiving morphine for 30 days or longer who were able to complete the pain scale were included. Excluded were patients with a confused or clouded sensorium. Daily pain intensity was recorded by the PPI (0-5 scale) of the McGill pain questionnaire. The daily morphine consumption was recorded and the occurrence and intensity of breakthrough pain were also recorded. Of the 35 potential candidates for study, 17 patients with a mean age of 59 (14) years completed the study. Patients were followed up for a mean of 82 (52) days. The mean (S.D.) daily morphine dosage at study entry was 135 (127) mg, and the daily morphine dose at study completion was 244 (240) mg. There was no evidence that any patient rapidly developed tolerance to morphine. Pain was well controlled for most patients. For 10 of 17 patients, 93% reported PPI scores of either 0 or 1. Occasional breakthrough pain was experienced by 4 of these 10 patients. Four other patients reported 79% of their PPI scores as either 0 or 1, and 18% of the PPI scores as either 2 (discomforting) or 3 (disturbing), Thus 82% of patients had good to excellent pain control. Three of 17 patients spent more than four months in the unit and had less than good pain control. All of these patients had neuropathic cancer pain. These results support the conclusion that pain was well controlled for most cancer patients, and that increases in daily morphine dose, when it occurred, generally developed over a period of weeks to months, and a pattern of rapid escalation in morphine dose did not occur.