[Pharmacokinetics of ketamine and pentazocine during total intravenous anesthesia with droperidol, pentazocine and ketamine].

Pharmacokinetics was studied in ten surgical patients who underwent various operative procedures of about 4 hours under total intravenous anesthesia with droperidol, pentazocine and ketamine (DPK). Plasma levels of ketamine, its metabolites and pentazocine were determined thirteen times during and after DPK. During anesthesia, ketamine (KO) and norketamine (KMI) levels ranged from 0.7 to 1.0 micrograms.ml-1 and from 0.09 to 0.74 micrograms.ml-1, respectively. A small amount of dehydronorketamine (KM II) was detected only 90 min after the start of DPK anesthesia. Plasma half-lives of ketamine were calculated to be 33 min for distribution phase (alpha phase) and 60 min for elimination phase (beta phase), respectively. Pentazocine levels decreased 300 min after the induction of DPK to 10% of the control level measured 5 min after its injection. Plasma half-lives of pentazocine were 60 min for alpha phase and 140 min for beta phase, respectively. The data obtained in this clinical study show that pharmacokinetics of ketamine during DPK is almost similar to that of DFK.