Determination Of Valproic Acid By Reversed-phase High-performance Liquid Chromatography And Study Of TDM In Clinical

Valproic acid (VPA) is a compound of fatty acid and a commonly used anti-epileptic drug .The blood of concentration of VPA in epileptic patients is one of the important basis for adjusting dosage, evaluating curative effect, avoiding side-effects and performing individual therapeutic. Monitoring VPA levels in serum of epileptic patients is desirable mainly for study its pharmacokinetics and drug-drug interaction. Generally, it's difficult to determin VPA in serum with HPLC because VPA lacks nitrogen and a ring moiety and therefore has no chromophoric characteristics. According to the determination of fatty acids, we established an HPLC method for the analysis of VPA in serum by RP-HPLC after transfered VPA into an ester which has chromophoric characteristics. The method is sensitive, accurate, selective, simple and fast and widely suitable for the clinical research and application.Objective : To establish a commonly used method for determination of valproic acid in serum by RP-HPLC and apply to clinical therapeutic monitoring. Method: A RP-HPLC method applied with 4-bromomethyl-7-ethoxycoumain (BrMMC) as derivative reagent which transform valproic acid into an ester detectable with photodiode-array detector. The condition of valproic acid derivation and the stability of derivatives were investigated. 156 epileptic outpatients received valproic acid as monopharmacy or in combination with either the antiepileptic drug were monitored during their clinical routine care. The effect of age, total body weight and combination with either the antiepileptic drug on serum concentration of valproicacid were evaluated.Result: The ratio of peak heights correlated linearly with concentration of valproic acid ranging from 15 to 200μg.ml-1.The calibration curve was Y=1.03×10X+2.33 ( r = 0.999l).The lowest detection limit was 3μg.ml-1.The mean recovery is 101.8%. RSD between days or within days was lower then 5%.The reaction of derivation is quick. The derivatives can story in -20 for one week or in room temperature at least for 72 hours. Some other common anti-epileptic drugs did not interfere with the analysis. The method has been applied to the clinical therapeutic drug monitoring. The result has showed that the rate of valproic acid clearance in patient decreased with increasing age, total body weight. The rate of valproic acid clearance in patients increased when combination with carbamazepine and phenobarbitone.Conclusion: The method is sensitive, accurate, selective, simple and fast, and widely suitable for the clinical research and application. Those effects of age, total body weight and combination with either the antiepileptic drug on the serum level of valproic acid were obviously.Postgraduate: Chen zhan fang Directed by: Yue Wang Wang lei...