Disposition of nalbuphine in patients undergoing general anaesthesia

The pharmacokinetics of nalbuphine 20 mg i.v. were studied in 10 patients undergoing lower abdominal or body surface surgery. Blood sampling was carried out for 600 min after injection and drug concentrations were measured by HPLC using electrochemical detection. Disposition was best described as a triexponential function, with a mean elimination half-life of 135.5 min. Mean residence time, clearance, and volumes of distribution, Vss and V beta, were determined by a model independent method, and gave mean values of 149.7 min (MRT), 1095 ml min-1 (ClP), 159.9 litre (Vss) and 207.1 litre (V beta).