Sublingual buprenorphine used postoperatively: clinical observations and preliminary pharmacokinetic analysis.

1 Buprenorphine is a long-acting opiate analgesic. This study was designed to investigate the pharmacokinetics of this drug when given by the sublingual route to ten postoperative patients. Plasma levels of buprenorphine were measured by a specific radioimmunoassay. 2 Plasma levels of the drug following sublingual administration of 0.4 mg showed an apparent delay in absorption and then rose slowly to reach low but significant levels by 3 h. There was considerable variation in the time at which peak levels were achieved. The average systemic availability of the drug by this route was estimated to be 30% by 3 h. 3 Analgesic efficacy and duration of sublingual buprenorphine were assessed using demand analgesia. The analgesia was of about 9 h duration, similar to that achieved by parenteral administration of 0.3 mg of the drug to an equivalent group of patients. The sublingual dose caused a significant fall in the postoperatively elevated group of patients. The sublingual dose caused a significant fall in the postoperatively elevated plasma glucose, and prevented any further rise in plasma cortisol. 4 Reasons for the efficacy of the sublingual route are discussed and it is suggested that this route may be particularly appropriate for highly lipophilic drugs like buprenorphine.