Clinical pharmacology of buprenorphine: ceiling effects at high doses

OBJECTIVE: The purpose of this study was to characterize the acute effects of buprenorphine, an opioid partial mu-agonist, across a wide range of doses in comparison to methadone. METHOD: Healthy adult male volunteers, who had experience with but were not physically dependent on opioids, participated while residing on a closed research unit. Four subjects received buprenorphine (0, 1, 2, 4, 8, 16, and 32 mg sublingually and five subjects received methadone (0, 15, 30, 45, and 60 mg orally) in ascending order at 1-week intervals. Physiologic, subjective, and behavioral measures were monitored for 96 hours after drug administration. RESULTS: Both drugs produced typical opioid agonist effects (positive mood, sedation, respiratory depression, and miosis), some of which persisted for 24 to 48 hours. A plateau was observed for the dose effects of buprenorphine on subjective measures and respiratory depression. Pharmacokinetic data revealed that plasma concentrations of buprenorphine were linearly related to dose, indicating no limits on sublingual absorption in this dose range. CONCLUSIONS: This study shows a plateau on buprenorphine effects, consistent with its partial agonist classification, and that single doses of buprenorphine up to 70 times the recommended analgesic dose are well tolerated by nondependent humans.