Twice-daily versus once-daily morphine sulphate controlled-release suppositories for the treatment of cancer pain. A randomized controlled trial.

We evaluated the safety and efficacy of controlled-release morphine sulphate suppositories administered 12-hourly and once daily in patients with chronic cancer in a randomized double-blind crossover trial. Pain was assessed using a 100-mm VAS pain scale and a five-point ordinal pain scale. The VAS pain intensity score was 17.5+/-17.2 after suppositories every 12 h, versus 16.2+/-13.4 after suppositories every 24 h (difference not significant). The difference between the mean VAS pain scores with 12-hourly and once-daily dosing was 1.3 mm (not significant). The mean ordinal pain scores were 1.0+/-0.7 versus 1.0+/-0.6 for 12-hourly and once-a-day dosing, respectively (not significant). A retrospective power analysis indicated that a difference of 5.9 mm was detectable, even with only 6 patients. Adverse events noted were constipation, nausea, anorexia, and dry mouth. The use of once-a-day controlled-release morphine suppository is a more convenient and equally effective alternative to twice a day dosing.