Buprenorphine (Butrans): A mu opioid partial agonist analgesic and a Schedule III controlled substance for the management of chronic pain in patients requiring a continuous, around-the-clock opioid analgesic for an extended period of time

Buprenorphine transdermal system for transdermal administration 5 µg/h, 10 µg/h, and 20 µg/h patches were approved by FDA in June 2010 for the management of moderate-to-severe chronic pain in patients requiring a continuous, around-the-clock opioid analgesic for an extended period of time. The patches, which are designed to be worn for 7 consecutive days, contain buprenorphine, a Schedule III controlled substance. Buprenorphine acts as a partial agonist at mu opioid receptors, an antagonist at kappa opioid receptors, an agonist at delta opioid receptors, and a partial agonist at ORL-1 (or nociceptin) receptors. Buprenorphine's clinical effects result from binding to these opioid receptors.

Efficacy. The efficacy of the buprenorphine transdermal patch has been evaluated in a total of four 12-week double-blind, controlled clinical trials in opioid-naïve and opioid-experienced patients with moderate-to-severe chronic lower back pain or osteoarthritis. In each of these trials, pain scores were the primary efficacy end points. The prescribing information highlights the results of 2 trials, both of which enrolled more than 1,000 patients. One compared maximally tolerated transdermal buprenorphine (up to 20 µg per hour) to placebo and the other compared maximally tolerated transdermal buprenorphine (up to 20 µg/h) to low-dose buprenorphine (5 µg/h) or active control. In both trials, patients receiving maximally tolerated transdermal buprenorphine had statistically significantly lower average pain scores over the last 24 hours at the end of the study (week 12/early termination) compared with patients treated with control.

Safety. In clinical trials the most common adverse reactions (reported in ≥5% of patients) included nausea, headache, application site pruritus, dizziness, constipation, somnolence, vomiting, application site erythema, dry mouth, and application site rash. As buprenorphine is an opioid analgesic, it may be associated with respiratory depression (particularly in elderly or debilitated patients as well as those suffering from conditions accompanied by hypoxia or hypercapnia or when given with other opioids). At doses of >20 µg per hour, QTc prolongation (>9 milliseconds) has been observed.