Teicoplanin is a recently introduced long-acting glycopeptide antibiotic effective against Gram-positive aerobic and anaerobic bacteria. The effects of hypothermic extracorporeal circulation on teicoplanin serum pharmacokinetics have been studied in 18 patients undergoing open-heart surgery for coronary artery bypass graft or prosthetic cardiac valve insertion. The patients received a single 600 mg dose of teicoplanin by intravenous (i.v.) bolus (five cases) or by i.v. infusion over 20 min (13 cases) approximately 1 h before the anticipated skin incision and 2 h before the anticipated extracorporeal circulation. Serum drug concentrations were measured by a microbiological method using Bacillus subtilis ATCC 6633 as the test organism. Following i.v. bolus injection and i.v. infusion, teicoplanin levels in serum (mean +/- s.d.) were respectively 13.9 +/- 6.8 and 11.4 +/- 2.4 mg/l at the beginning of extracorporeal circulation, 8.8 +/- 3.5 and 10.2 +/- 2.3 mg/l at the end of this procedure and 2.8 +/- 0.6 and 2.9 +/- 1.0 mg/l at 24 h after surgery. Mean AUCs were 378.1 +/- 52.5 and 328.9 +/- 88.0/l.h and mean elimination half-life values were 27.9 +/- 12.7 and 30.3 +/- 11.0 h, respectively under the same conditions. These differences in plasma pharmacokinetic parameters were not significant. Teicoplanin pharmacokinetics in patients undergoing cardiopulmonary bypass surgery were similar to those observed in non-surgical patients with normal renal and hepatic function, confirming experimental evidence for lack of effects of extracorporeal circulation.