Sl. Huang et al., DETERMINATION OF S R RATIO OF MEPHENYTOIN IN HUMAN URINE BY CHIRAL HPLC AND ULTRAVIOLET DETECTION AND ITS COMPARISON WITH GAS-CHROMATOGRAPHY/, Zhongguo yaoli xuebao, 19(6), 1998, pp. 548-550
AIM: To improve HPLC method for rapid determination of urinary S/R-rat
io of mephenytoin, a widely used metabolic index for cytochrome P-450
2C19 (CYP2C19) activity. METHODS: Aliquots of 0 - 8-h urine sample aft
er dosing racemic mephenytoin 100 mg underwent one-step extraction wit
h dichloromethane. Analysis was performed on a chiral column (250 mm x
4 mm, 5 mu m) at lambda = 207 nm. The eluent was a mixture of acetron
itrile and water containing both 0.1% glacial acetic acid and 0.2% tri
ethylamine (14:86, vol/vol) at a now-rate of 0.9 mL . min(-1). RESULTS
: The enatiomers of mephenytoin in urine were well separated within 9
min.; A linear correlation was observed between 50 - 5000 mu g . L-1 w
ith the detection limit of 12.5 mu g . L-1 for both enantiomers of mep
henytoin. This HPLC analysis was comparable to gas chromatography in a
ccuracy and sensitivity, but with much shorter retention time and bett
er resolution. CONCLUSION: The present HPLC method is good for rapid d
etermination of the ability of subjects to hydroxylate S-mephenytoin a
fter oral administration of the racemic drug.