Likar opioid, fentanyl, buprenorphine is the only opioid available in a transdermal formulation. The transdermal buprenorphine patch (Transtec®) The transdermal buprenorphine patch, Transtec®, was first launched in Switzerland and Germany in 2001 and is now marketed all over Europe. Using matrix technology, buprenorphine is homogeneously incorporated in a solid polymer matrix patch which is applied to the skin. The adhesive buprenorphine patch is noninvasive and slowly and continuously releases the drug into the systemic circulation. This matrix patch structure avoids the risk of ‘dose- dumping’, a feature of older reservoir patch systems, which use a regulating membrane to restrict drug diffusion (Budd 2003). Transdermal buprenorphine is available in three different dosage strengths with total loading doses of 20 mg, 30 mg, and 40 mg designed to release buprenorphine at a steady controlled rate of 35 µg/h, 52.5 µg/h, and 70 µg/h, respectively. This corresponds to an administered daily buprenorphine dose of 0.8 mg/day, 1.2 mg/day, and 1.6 mg/ day. The minimum effective concentration (MEC) for cases of moderate to severe pain is in the region of 100 pg/ml (Budd 2002). Pharmacokinetic studies have shown that after single application of the patch plasma levels of buprenorphine continuously increase and reach the MEC after 24 hours using the 35 µg/h patch and 12 hours using the larger 70 µg/h patch. (Sittl et al 2003). The initial recommendation on dose maintenance was that each patch remained effective for 72 hours. However, a recent open, randomised cross-over-study in chronic pain patients found that clinically effective plasma concentrations are reached after 24 hours and that these levels are maintained for the entire 96 hour application period (Likar 2005). The 96 hour buprenorphine TDS application was found to be bio- equivalent to the 72 hour application with regard to area under the curve (AUC) and concentration maximum (Cmax) This allows twice weekly changing of the patch on fixed days (eg, always on Mondays and Thursdays), facilitating therapy for patients, increasing patient compliance, and rendering pain therapy more cost-effective. Indications and dosing Transdermal buprenorphine is indicated for the treatment of moderate to severe cancer-related pain and severe pain unresponsive to nonopioid analgesics, including neuropathic pain. It is not indicated for use in cases of acute pain. 118 Studies of the use of transdermal buprenorphine in patients with chronic tumor and non-tumor pain have shown that the patches achieved a good analgesic effect and reduced the need for additional oral analgesics. In addition, the quality of life of the patient was improved in comparison with conventional therapies, benefits including an increased duration of sleep (Likar et al 2003; Sittl et al 2003). A survey of 13 179 chronic pain patients of varying aetiologies including musculoskeletal, neurogenic, and cancer pain confirmed effective analgesia was provided by treatment with transdermal buprenorphine. Most of the patients had been pretreated with WHO step II or step III opioids, although 30% had not previously been prescribed any opioids. Pain relief was rated as good or very good by 81% of the respondents at the end of the observation period (Griessinger et al 2005). In advanced cancer pain and the final stages of the disease nearly 50% of patients will require parenteral medicine (Zech et al 1995). In these cases, transdermal preparations such as transdermal buprenorphine or transdermal fentanyl offer noninvasive alternatives. A study of three patients with severe pain due to renal and metastasing prostate and breast cancer has shown buprenorphine TDS to be a valuable option, providing effective long-term treatment without dose escalation or compromise in tolerability (Schriek 2004). The efficacy and safety of buprenorphine 70 µg/h has been demonstrated in a trial in patients with chronic tumor-related pain requiring morphine 90–150 mg/day (Poulain et al 2005), demonstrating that transdermal buprenorphine works effectively in the high-dose range of morphine (ie, on step III of the WHO ladder) and is therefore a viable alternative to morphine. Likar and Sittl (2005) reported that transdermal buprenorphine is very effective in patients with neuropathic pain or with pain having a strong neuropathic component when other opioids failed. The effectiveness of transdermal buprenorphine in neuropathic pain has also been investigated by Rodriguez et al (2004) in a study population of 237 patients (37% male, 63% female) who suffered from various typical neuropathic symptoms or pain syndromes where neuropathic pain constituted a major component. After 4 weeks treatment with transdermal buprenorphine, a clear decrease in the percentage of patients reporting moderate to severe pain and a corresponding increase in the percentage reporting none or only slight pain was documented. Although more studies are clearly needed in this area, it seems clear from already available data that buprenorphine Therapeutics and Clinical Risk Management 2006:2(1)