Background: In a multicenter study, 28 patients with cancer pain and insufficient pain relief with analgesic treatment according to step II of the guidelines of the World Health Organization (WHO) were switched to oral slow-release morphine.
Methods: Patients received intravenous morphine through a patient-controlled pump (PCA) for the first 24 hours (bolus = 1 mg, lockout interval = 5 minutes, maximum dose = 12 mg/hour). From day 2 patients were treated with oral slow-release morphine. Daily doses were calculated from the requirements of the day before. Breakthrough pain was treated with PCA until stable doses were reached (<2 boluses/day) and then with oral immediate-release morphine solution. Pain intensity was reported in a diary four times a day, in addition to mood, activity, and quality of sleep once daily.
Results: Mean duration until adequate pain relief reported (<30 on a 101-step numerical scale; NRS) was 5 hours (range = 80-620 minutes). Mean pain intensity was reduced from 67 NRS to 22 NRS. Mean doses of oral morphine were 133 mg/day initially and then 154 mg/day on day 14. Serious adverse events such as respiratory depression were not observed. Two patients terminated the study due to progressive symptoms of gastrointestinal obstruction. Seventy-five percent of the patients evaluated the effectiveness of the analgesic regime as good.
Conclusions: Dose finding with intravenous PCA may be appropriate for a small minority of patients with severe pain. Higher treatment costs and the risk of complications are drawbacks of this method compared with conventional oral titration.