Optimal Conversion Ratio of Oral Morphine to Transdermal Fentanyl Patches to the Cancer Pain

Abstract

In Japan, the initial dose of 2.5 mg/3 d is recommended in the package insert of the fentanyl patch preparation to substitute for oral morphine in the dose range of 45 135 mg/d (90 mg/d at the midpoint), while a higher dose is recommended in other countries. To validate the recommended dose of this drug in Japan, we investigated how long the initial recommended dose of the fentanyl patch could control the pain of cancer patients after the switch from other opioids. The dose of the fentanyl patch was increased on the 20th day after the switch from prior opioids at a lower dose than the midpoint of the indicated range, while it was increased on the 3rd day after the switch from the higher dose of prior opioids. Regression analysis showed that the e‹cacy ratio of the fentanyl patch : oral morphine＝80 : 1, suggesting that oral morphine of 25 75 mg/d should be substituted for by the fentanyl patch preparation at a dose of 2.5 mg/3 d.

Indication of Adequate Transdermal Fentanyl Dose in Opioid Switching From Oral Oxycodone in Patients With Cancer

“…In most cases, the conversion ratio in the group that was unable to swallow was either 50:1 (35 patients) or 100:1 (20 patients), which was in close agreement with previously reported ratios of 70 to 80:1. 7,18,19 Prior to the onset of dysphagia, opioid-related adverse effects and cancer pain had apparently been adequately controlled by oral oxycodone, suggesting the need for careful consideration prior to opioid switching from oral agents to transdermal fentanyl.…”

“…The clinicians assessed the clinical pain levels using a Numerical Rating Scale (NRS) every day and determined the daily fentanyl dose according to the measured NRS. We considered the analgesic effect to be stable when fentanyl doses were unchanged for more than or equal to 7 days after opioid switching following the method by Ogawa et al, 19 and the daily fentanyl dose at this stable condition was judged to be adequate for pain control and used for the data analysis. The oxycodone dose before opioid switching was calculated as the corresponding morphine dose using an oxycodone to morphine conversion ratio of 2:3.…”