Transdermal buprenorphine in cancer pain and palliative care
Transdermal buprenorphine has been assessed as a therapy for chronic cancer and non-cancer pain in both clinical and postmarketing surveillance studies. Data from 239 patients who had participated in a follow-up study of up to six years have shown efficacy and safety, and good tolerability over prolonged treatment periods with a marked stability of doses. From the cancer pain population (134 patients), 20% stayed on transdermal buprenorphine until the end of their lives. Postmarketing surveillance study data from 13 179 patients, including 3690 cancer patients assessed during a 10-week observation period, showed that 81% of patients achieved good/very good pain relief with transdermal buprenorphine. Furthermore, 49.6% of patients did not require any analgesic comedication or rescue therapy, a point that is particularly important in the elderly population. Results from the Spanish Pain Society on transdermal buprenorphine in chronic non-cancer, neuropathic and cancer-related pain, and on switching from morphine, also confirmed its beneficial efficacy and safety, and showed that buprenorphine does not antagonize pain relief, or cause withdrawal when combined with full μ-agonists. The effectiveness of buprenorphine is further supported by evidence of its pronounced anti-hyperalgesic effect in a human pain model, which may be a factor in explaining the efficacy of buprenorphine in neuropathic pain. When switching of opioids is indicated to improve pain relief or reduce adverse events, equipotency dosage ratios are important. The equipotency ratio for morphine to buprenorphine, previously established as 75:1, is now being questioned as new data from a retrospective cohort study were published indicating a ratio of 100:1. Moreover, transdermal buprenorphine has superior safety in respect to respiratory depression, immunological and renal effects compared with standard World Health Organization step III opioids, which makes it highly suitable for treating moderate-to-severe pain also in cancer patients, a per se vulnerable patient population requiring a sensible selection of potent analgesics.