Switching opioids to transdermal fentanyl in a clinical setting

Introduction:The use of transdermal fentanyl is gaining in importance in th e management of cancer pain. We describe the reasons for switching opioid m edication to transdermal fentanyl in a pain management unit. Methods: Case records of patients treated with transdermal fentanyl in our pain clinic were evaluated retrospectively. Conversion ratios were calculat ed from the opioid dosage before and after conversion. Pain intensities wer e assessed on a numeric raring scale (NRS 0: no pain, 10: worst pain imagin able). Results: From October 1995 to December 1997 101 patients received transderm al fentanyl. Thirty-six patients had been treated with transdermal fentanyl before admission to our pain clinic, and relevant information was missing for one patient, so 64 patients were evaluated. Opioid therapy was switched to transdermal fentanyl during in-patient treatment for 53 patients and du ring outpatient treatment for 11 patients. Before conversion patients were treated with slow-release morphine (48%), immediate-release morphine (17%), buprenorphine (11%), tramadol (11%), levomethadone (5%), tilidine/naloxone (5%) and piritramid (3%). Reasons for opioid rotation were inadequate pain relief (33%), the patients' wish to reduce oral medication (20%), gastroin testinal side effects such as nausea (31%), vomiting (13%) and constipation (19%), dysphagia (27%) or others. Reduction of side effects was reported b y 10 of 19 patients. In 12 of 21 patients, in whom the medication was switc hed because of inadequate pain relief, a reduction in pain intensity was re ported. Discussion: Conversion to transdermal therapy may readjust the balance betw een opioid analgesia and side effects. The opioid switch resulted in more p ain relief or fewer side effects in half of the patients. A proposed equian algesic conversion ratio between 70:1 and 100:1 from oral slow-release morp hine to transdermal fentanyl can be confirmed by our data; Conversion rates from other opioids to transdermal fentanyl are suggested.