Hair analysis for buprenorphine and its dealkylated metabolite by RIA and confirmation by LC/ECD

Hair samples were obtained from 14 subjects admitted 2 or 3 months previously to a detoxification center. All reported an history of intravenous heroin abuse. After decontamination by two dichloromethane washes, about 50 mg hair were pulverized in a ball mill and incubated at 56 degrees C overnight in 1 mL 0.1 HCl. After neutralization, buprenorphine analyzed by RIA was in the range of 0.01 to 0.47 ng/mg. To confirm buprenorphine, liquid chromatography was used. After neutralization, drugs were extracted with toluene at pH 8.5 during a 3-step extraction procedure. A portion of the reconstituted residue was injected into a Lichrosorb CN column, with a mobile phase of phosphate buffer (pH 4.0)-acetonitrile-1-heptane sulfonic acid-butylamine (85:17:2:0.01, v/v). Detection was achieved by coulometry, and the potential of the electrodes was 0.15 and 0.50 V, respectively. Linear calibration curves were obtained from 0.02 to 2.0 ng/mg with a correlation coefficient r > 0.99 for both drugs. The detection limit for the major metabolite was about 0.01 ng/mg and 0.02 ng/mg for buprenorphine, using a 50 mg hair sample. Recovery (at 0.2 ng/mg) was 54 and 62% for norbuprenorphine and buprenorphine, respectively. Drugs concentrations in hair were in the range 0.02-0.59 and not detected--0.15 ng/mg for buprenorphine and norbuprenorphine, respectively. Results suggest that a dose-response relationship exists between the concentration of buprenorphine in hair and the administered dose.