The conversion ratio of intravenous morphine to transdennal fentanyl in patients with cancer pain

Objective To determine the conversion ratio of intravenous PCA with morphine to transdermal fentanyl and evaluate the efficacy of PCIA morphine - transdermal fentanyl combination and the safety of transdermal fentanyl in patients with cancer pain. Methods Sixteen cancer patients with severe pain (VAS 5) who were conscious and had no obvious cardio-respiratory and hepato-renal dysfunction were enrolled in this study. The patients received intravenous PCA with morphine for the first 48 hours. The PCIA morphine solution contained morphine 2-6mg·ml-1 and droperidol 1-2 mg·30 ml-1 . PCIA included a bolus dose of morphine 1-3 mg with a 5 min lockout. No background infusion was given. Morphine PCIA was then combined with transdermal fentanyl. The initial dose of transdermal fentanyl was 25μg · h-1 in the first two to three days. The dose was then gradually increased in 25 μg·h-1 increments according to VAS scores and the amount of Ⅳ morphine needed to reduce the persistent pain until transdermal fentanyl alone could provide sufficient relief of persistent pain and Ⅳ morphine was given only for breakthrough pain. Pain intensity (VAS scores) before and after treatment, daily consumption of morphine (mg·d-1) and transdermal fentanyl (μg·h-1), vital signs and side effects were recorded.Results The 13 patients included 6 males and 7 females. Their mean (±SD) age was 54±15 yrs and body weight 53± 8 kg. There was positive correlation between the titrated dose of transdermal fentanyl (μ·k-1) and the initial need of Ⅳ morphine (mg·day-1). Y= 1.3606 X + 6.5088. Persistent pain intensity and breakthrough pain intensity evaluated by VAS scores were significantly reduced during the treatment ( P 0.01) . The need forⅣ morphine during transdermal fentanyl treatrment decreased gradually. No severe side effects were noted.Conclusion The Ⅳ morphine / transdermal fentanyl conversion ratio is 31 (mg·day-1) : 1(mg·day-1) . The combination of PCIA morphine and transdermal fentanyl provides an effective treatment in patients with severe persistent pain. During the treatment of pain with transdermal fentanyl,Ⅳ morphine provides sufficient relief of breakthrough pain.