Opioid switching from morphine to transdermal fentanyl for toxicity reduction in palliative care.

The study objective was to determine whether switching patients from morphine to transdermal fentanyl resulted in a reduction of morphine-associated side effects, and an improvement in cognitive function and patients' well being while maintaining adequate pain and symptom control. Nineteen patients aged 42-86 with terminal cancer, maintained on morphine for pain and distressed as a result of morphine toxicity, were given the dose of fentanyl corresponding to their current morphine dose. Pain control was then maintained (mostly fentanyl 50-100 microg/h) over the 14-day study period. Throughout the study, patients' global assessment of well being (primary efficacy variable) was statistically significantly improved. Sleepiness and drowsiness were significantly less of a problem. There was a trend towards improvement in attention span/concentration, and in the power and quality of concentration. Cognitive function tests also revealed a significant improvement in working (short term) and speed of memory although not in secondary (long term) memory. Patients did not experience hallucinations or delusions and there was no change in levels of anxiety or depression (Hospital Anxiety Depression Scale). The incidence of dizziness was significantly reduced, and there was a nonsignificant decrease in number of patients who suffered myoclonus and in the severity of this condition over the 14 days. The investigator's overall impression of treatment with transdermal fentanyl was 'fair', which was not in agreement with the positive impression expressed by patients (score 74, range: 0 worst, 100 best). Further work is required to determine if the improvement in patients' well being and cognitive function is achieved in larger study populations.