The dosing frequency of sustained-release opioids and the prevalence of end-of-dose failure in cancer pain control: A Korean multicenter study

Background: End-of-dose failure is commonly observed as therapeutic levels of sustained-release opioids fall. However, little is known about using these medications for cancer pain control. To determine the dosing frequency of sustained-release opioids (morphine, oxycodone, and transdermal fentanyl) and the prevalence of end-of-dose failure in clinical practice, a patient-reported survey was performed. Methods: A multicenter survey was conducted in 56 hospitals in Korea between June and November 2008. Results: The study enrolled 1,097 cancer outpatients who were prescribed oral sustained-release opioids (morphine or oxycodone) or transdermal fentanyl. Of the oral sustained-release opioid patients, 67.0% took oral sustained-release oral opioids twice daily, while 26.2% took them more than twice daily. Of the transdermal fentanyl patients, 88.8% wore the patch for 72 h. Of the enrolled patients, 48.3% experienced worsening pain just before the next sustained-release opioid dose, and 36.8% of these patients took medication earlier than the prescribed dosing schedule. Patients felt that oral sustained-release opioids gave adequate pain control lasting an average of 9.6 h, versus an average of 62.9 h for transdermal fentanyl. Conclusion: This survey demonstrated that sustained-release opioids are used by patients in a manner that is inconsistent with standard recommendations. End-of-dose failure is suggested to explain increased dosing frequency, and patients reported that adequate pain relief lasted for less time than was stated in the manufacturers' prescription recommendation.