Buprenorphine pharmacokinetic parameters during coronary artery bypass graft surgery

The pharmacokinetic parameters of buprenorphine (BN) after a single bolus dose of 10 microg/kg i.v. was investigated in 6 male patients whose age averaged 59+/-9.8 years and body weight of 65.8+/-5.7 kg undergoing coronary artery bypass graft surgery (CABG). The unbound BN plasma concentrations were detected using ultrafiltration and high performance liquid chromatography/electro-chemical detection (HPLC/ECD) method. During cardiopulmonary bypass (CPB) there was a fall in BN plasma concentrations, observations similar to reports on fentanyl, sufentanil and alfentanil. This is probably due to haemodilution, hypothermia and hydrophobic sequestration of drug on to the CPB tubing. After CPB the concentrations rose to values higher than during CPB, though it did not attain pre CPB concentrations. These variations were not statistically significant indicating that plasma levels were adequately stable during CPB. The plasma concentration time curves were biexponential and the pharmacokinetic parameters obtained were : distribution half-life 37.24+/-6.57 min, elimination half-life 482.69+/-79 min, clearance 1221.97+/-209.42 ml/min, and volume of distribution 736.46+/-71.25 L. BN in the dose used follows the pharmacokinetic pattern of other commonly used narcotics during CABG. The mean +/- SEM plasma BN concentration during CPB was 0.51+/-0.03 ng/ml which was adequate for the maintenance of analgesia and anaesthesia, as none of our patients expressed the signs and symptoms of awareness during surgery. Further, unlike the other narcotics muscle rigidity was absent. Thus BN is a safe and good alternative to other narcotics for patients undergoing CABG.