Article
Quantitative chiral and achiral determination of ketamine and its metabolite in human serum, urine and feces
Search Medline for
Authors
-
Mahmoud Hasan
- Klinische Pharmakologie, Universitätsmedizin Greifswald, Greifswald, Germany
-
Werner Siegmund
- Klinische Pharmakologie, Universitätsmedizin Greifswald, Greifswald, Germany
-
Stefan Oswald
- Klinische Pharmakologie, Universitätsmedizin Greifswald, Greifswald, Germany
| Published: | September 24, 2015 |
|---|
Outline
Text
Ketamine is an anesthetic drug that has also been shown to induce potent analgesia by non-opioid mechanisms. The active enantiomer S(+)-ketamine is about two times as potent as the racemic form and four times as the R(-)-enantiomer. The major metabolite nor-ketamine exerts own analgesic effects (~20-30 % of ketamine). Moreover, R(-)-ketamine can be transformed to S(+)-norketamine.
In order to analyze biological samples from a clinical study investigating the pharmacokinetics of ketamine after oral administration, it was the aim of this study to develop and validate quantification methods for racemic ketamine and its major metabolite nor-ketamine as well as S-ketamine in human serum, urine and feces.
Sample preparation was done by liquid-liquid extraction using methyl t-butyl ether to separate the analytes from the biological matrices. D4-Ketamnie and D4-nor-ketamine were used as internal standards. Achiral chromatographic separation was achieved on a reversed-phase column (Waters XTerra®MS, C18) within 4 min using an isocratic elution while chiral separation of S(+)- / R(-)-ketamine in serum was performed on the (CHIRAL-AGP) column within 25 min using a gradient elution at a flow rate of 250 µL/min with ammonium acetate 10 mM (pH=7,5) and isopropanol as mobile phase.
Detection was done on the triple quadrupole mass spectrometer (API 4000 QTRAP) using the following mass transitions: 238.1 / 125.1, 238.1 / 179.0, 238.1 / 163.0 for ketamine and 224.1 / 125.1, 224.1 / 207.1 and 224.1 / 179.1 for nor-ketamine. The analytical ranges were 0.1–500 ng/ml for ketamine (0.1-100 ng/ml for S(+)- / R(-)-ketamine) and its metabolite in serum and 1-1000 ng/ml for both compounds in urine and feces.
The methods were validated according to current bioanalytical guidelines and fulfilled the required bioanalytical criteria in terms of specificity, accuracy, precision, recovery, matrix effects and stability. Finally, the developed methods were successfully applied to analyze samples from a pharmacokinetic study in healthy volunteers.
