The Adverse Effects of Morphine: A Prospective Survey of Common Symptoms During Repeated Dosing for Chronic Cancer Pain

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Abstract
Little information is available about the incidence, prevalence, or severity of morphine side effects during repeated individualized dosing for chronic cancer pain, although it has been widely used in this way for more than 30 years. The authors’ aim was to describe the prevalence of symptoms possibly attributable to morphine side effects in a convenience sample of patients with pain due to advanced cancer. They used a prospective survey of inpatients and outpatients on regularly dosed morphine, with a questionnaire administered weekly for 4 weeks. Forty-two of 56 eligible patients completed at least the first questionnaire, with 30 completing all 4. Dry mouth was the most common symptom reported (point prevalence, 95%); this was often moderate to severe in intensity (57%) and was the most persistent symptom (period prevalence, 20%). Sedation and constipation were frequent (point prevalence, 88%) and was often moderate or severe at some point (55% and 62%, respectively) but had low period prevalence. Nausea was reported by less than half the patients. Myoclonus was common (point prevalence, 83%) but was usually mild and not persistent. Total daily morphine dose had little impact on side-effect patterns. Constipation, dysphoria, myoclonus, nausea, and sedation were more likely to be severe following dose increases. In conclusion, although constipation, nausea, and sedation are well described as side effects of morphine administration, others such as dry mouth and myoclonus appear to be underestimated. Validated patient-based measures of opioid side effects are needed.