Relative bioavailability of different buprenorphine formulations under chronic dosing conditions

Background: Buprenorphine is an approved medication for the treatment of opioid dependence. Three sublingual formulations have been used at various times during its development—a solution containing alcohol, tablets containing buprenorphine alone, and tablets containing buprenorphine plus naloxone. This study compared the relative buprenorphine bioavailability of these different formulations. Methods: Outpatient volunteers ( N=10) were maintained for 14 days of daily administration on each formulation; the dose of buprenorphine (8 mg) was constant across formulations. Blood samples were collected and tested for buprenorphine and norbuprenorphine concentrations after 7 and 14 days maintenance on each formulation. Serial samples were collected before and for 6 h after a daily dose of each formulation. Results: Peak buprenorphine concentrations ( C max) and area under the curve (AUC) for the 6 h interval (AUC 0–6) were highest for the solution and lowest for buprenorphine alone tablets; values for combination tablets were more similar to those for solution. Differences between formulations were less pronounced at day 14 than day 7. There was considerable between-subject variability in concentrations produced. Conclusions: These results suggest there may be greater bioavailability of buprenorphine/naloxone versus buprenorphine alone tablets, and that the bioavailability of buprenorphine from the former is very similar to that seen with solution after 2 weeks of stabilization on each formulation.