Equipotent doses to switch from high doses of opioids to transdermal buprenorphine

The aim of this study was to evaluate the equianalgesic ratio of transdermal buprenorphine (TD BUP) with oral morphine and TD fentanyl in a sample of consecutive cancer patients receiving stable doses of 120-240 mg of oral morphine or 50-100 microg of TD fentanyl, reporting adequate pain and symptom control.

Patients receiving daily stable doses of opioids for more than 6 days, with no more than two doses of oral morphine (20 and 40 mg, respectively) as needed, were switched to TD BUP using a fentanyl-BUP ratio of 0.6:0.8 and an oral morphine-BUP ratio of 70:1. Opioid doses, pain and symptom intensity, global satisfaction, and number of breakthrough medication were recorded before switching (T0), 3 days after (T3), and 6 days after (T6). Eleven patients were recruited in a period of 1 year, and data were complete for ten patients. The mean age was 61.6 (SD 9.5), and five patients were males. No significant changes in pain and symptom intensity were found, except improvement in reported constipation (p = 0.014), as well as in global satisfaction with the analgesic treatment. No significant changes in breakthrough pain medication were observed.

The results of this study suggest that stable patients receiving relatively high doses of oral morphine or TD fentanyl could be safely switched to TD BUP, by using a ratio of 70:1 and 0.6:0.8, respectively, maintaining the same level of analgesia.