Treatment of cancer pain with transdermal fentanyl.

Pain is a feature of many cancers, particularly in the advanced stages at which the palliative care approach to symptom control achieves the best outcomes. The holistic approach generally dictates that any treatment of the cancer per se has symptom control as the primary objective at this advanced stage. Pain, which invariably increases with disease progression, is treated with opioids and adjuvant analgesic drugs together with physical therapies. Orally administered opioid drugs are used preferentially because of cost and convenience, but other routes of administration (subcutaneous, rectal, spinal) are also possible. More recently, transdermal fentanyl has been evaluated in the treatment of moderate to severe cancer pain. The rate of fentanyl absorption is constant (after a lag period), and the dose is altered by increasing or decreasing the area of skin covered by the patch (size and/or number of patches). The dosing interval for these systems is generally 3 days. The extent of pain relief provided by transdermal fentanyl and sustained release morphine formulations is similar, with quality-of-life instruments showing no consistent preference for either formulation. Open studies have suggested a lower risk of constipation. Transdermal fentanyl is effective in the treatment of severe cancer pain, particularly when the oral route is unavailable.