The dilemma of conversion from systemic to epidural morphine: a proposed conversion tool for treatment of cancer pain.

There is lack of concensus over what constitutes an appropriate method to affect an equianalgesic conversion from systemic to epidural morphine. A systematic approach to calculate the appropriate starting dose for epidural morphine is needed. A model is proposed here and data from a pilot study are described supporting the concept as well as its utility in the clinical setting. Several key factors may have an impact upon the selection of a starting dose in the opioid-tolerant cancer population such as pain severity, age, previous systemic opioid use, and presence of neuropathic pain. A conversion tool was developed taking these 4 factors into account and was tested in a small number of patients with cancer pain. The rationale for this approach is explored. Four case examples are presented to demonstrate the utilization of the tool and the effectiveness of this formula for clinical practice. Further study is needed to firmly establish the validity and reliability of this tool.