Radioimmunoassay of buprenorphine with iodine label: analysis of buprenorphine and metabolites in human plasma.

Quantitative analysis of potent opiate drugs in plasma by radioimmunoassay is potentially inaccurate because of the occurrence of cross-reacting metabolites. This paper describes the chemical synthesis of buprenorphine-3-O-glucuronide, a metabolite of buprenorphine, and an extraction procedure coupled with radioimmunoassay which allows the sensitive and specific measurement of buprenorphine using an iodinated buprenorphine derivative. The measurement of extracted and unextracted samples using two different antisera allowed investigation of the metabolism of buprenorphine. In four patients who had taken sublingual buprenorphine for at least one month, N-dealkyl buprenorphine was present in similar concentrations to those of buprenorphine, while buprenorphine-3-O-glucuronide was present in two to three times those concentrations.