A Cochrane review [Abstract] 1 included 62 studies with a total of 4 241 patients. The comparisons were either between modified release morphine and immediate release morphine, between different strengths, dose intervals or administration routes, or between morphine and other opioids. Daily doses in studies ranged from 25 mg to 2000 mg with an average of between 100 mg and 250 mg.
Morphine was shown to be an effective analgesic for cancer pain. Eighteen studies recorded the proportion of participants achieving either no worse than mild pain or some global outcome indicating satisfaction or success. No worse than mild pain was achieved by 96% of participants (362/377). For an outcome equivalent to treatment success, successful pain control, or participant global evaluation of very good or excellent, the overall success rate was 63% (400/638). Pain relief did not differ between modified release and immediate release preparations. Modified release versions of morphine were effective for 12 or 24 hour dosing depending on the formulation. Dose titration were undertaken with both forms. There was no significant difference in pain relief whether 24-hour morphine modified release preparations were administered in the morning or evening, nor whether 12-hourly or 24-hourly modified release preparations were used. Adverse effects (such as constipation and nausea) were common but only 6% of patients discontinued treatment because of intolerable adverse effects.
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