PHARMACOKINETICS AND PHARMACODYNAMICS OF KETAMINE ENANTIOMERS IN SURGICAL PATIENTS USING A STEREOSELECTIVE ANALYTICAL METHOD

In a randomized, double-blind study, we have examined the stereoselect ive disposition and pharmacodynamic characteristics of ketamine in sur gical patients after iv. administration of S(+)-ketamine 1 mg/kg body weight (25 patients) or racemic ketamine 2 mg/kg body weight (25 patie nts). S(+)-Ketamine was not inverted to R(-)-ketamine. After racemate administration we observed statistically significant (P < 0. 0 1) smal ler clearance and volume of distribution for R(-)-ketamine compared wi th S(+)-ketamine. In contrast, the pharmacokinetic variables of S(+)-k etamine were not significantly different between treatment groups. Sys tolic and diastolic arterial pressure and heart rate increased signifi cantly (P < 0.005) in both groups. At 1, 3 and 15 min after S(+)-ketam ine administration, significantly greater increase in systolic and dia stolic pressures were observed compared with the racemate group. There was no correlation between the changes in haemodynamic variables and plasma catecholamine concentrations, which remained unaffected after a dministration of the medications.