Interactions between fentanyl and drugs that inhibit CYP3A4

摘要

A theoretical patient,Mr X is has been taking morphine up to lOOmg daily for cancer-related pain but,since his pain is sti 11 not properly control led,a transdermal fentanyl patch is prescribed at a dose of 25mu g/h.He has a past medical history of angina,high blood pressure and osteoarthritis,and his long-term medication includes aspirin,simvastatin,ramipril,diltiazem,isosorbide mononitrate and glucosamine/chondroitin.Two months later during a hospital admission he is found to be bradycardic and diltiazem is stopped,During this admission he develops more breakthrough pain than normal so the fentanyl dose is increased to 50mu g/h.One week after this,Mr X develops a chest infection and erythromycin is prescribed.He also develops severe oesophageal candidiasis for which he is prescribed itraconazole.Three days later,Mr X is admitted to hospital with severe breathing difficulties and new onset of confusion.He is diagnosed as having opioid toxicity and the fentanyl patch is removed.Mr X's symptoms improve over the next five days and he is discharged on a lower strength fentanyl patch.