S. Bardin et al., Determination of free levels of phenytoin in human plasma by liquid chromatography/tandem mass spectrometry, J PHARM B, 23(2-3), 2000, pp. 573-579
A liquid chromatography combined with tandem mass spectrometry assay for th
e determination of free levels of the highly protein bound drug phenytoin (
5,5-diphenylhydantoin) in human plasma is described. The assay was demonstr
ated to be reliable, accurate and precise, and specific for phenytoin. The
procedure involves isolation of the unbound drug from the drug/protein comp
lex by ultrafiltration. Liquid-liquid extraction was employed to extract th
e resultant ultrafiltrate. PHT was separated on a 50 x 3 mm reversed-phase
column using isocratic mobile phase conditions that yielded a run time of 1
.5 min, enabling high throughput sample analysis. Linearity was obtained ov
er the range 5.00 to 500 ng/ml, Both between-run and within-run coefficient
s of variation were less than 15% and accuracy's across the assay range wer
e all within 100+/-10%. The assay was successfully implemented to support a
clinical interaction study with phenytoin. (C) 2000 Elsevier Science B.V.
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