| AIM: To develop a rapid and sensitive method for the determination of pitavastatin in human plasma by liquid chromatography-mass spectrometry (LC/MS/MS).The essay has been successfully applied to a pharmacokinetic study of pitavastatin in healthy volunteers after oral administrations of single dose pitavastatin calcium tablets containing 1,2,4 mg pitavastatin calcium, respectively, and multiple dose of 2 mg pitavastatin calcium.Method: Pitavastatin and internal standard telemisartan, were extracted from plasma after adding formic acid in it, using diethyl ether-dichloromethane(3: 2, v: v), and separated on a zorbax Extend C18 column using acetonitrile-10 mM ammonium acetate(45: 55, v: v). Detection wan carried out by multiple reaction monitoring(MRM) mode on a API 4000 LC/MS/MS system with an ESI interface in the positive ion mode. MRM was performed at unit resolution using the mass transition ion-pairs m/z 421.9→m/z 290.1 for pitavastatin and m/z 515.2→m/z 276.1 for telemisartan, respectively. The linearity, specificity, precision, accuracy, recovery, matrix effect, LLOQ and stability were estimated for the validation of pitavastatin.Concentrations of pitavastatin in health volunteers'plasma samples after single oral dose of 1,2,4 mg and multiple oral dose of 2 mg pitavastatin calcium were measured, respectively. After the plasma concentration-time profile was shown, the main pharmacokinetics parameters were calculated by Topfit 2.0, and statistical analysis of these parameters were carried out by SPSS 14.0.RESULT: Highly selective, sensitive, rapid and reproducibility methods for determination of pitavastatin in human plasma using LC/MS/MS have been developed and validated in this paper. The standard curve of pitavastatin was linear over a working range of 0.287~287 ng/ml with LLOQ of 0.287 ng/ml. In the range of standard curve, there are no co-eluting endogenous substances and metabolites, such as pitavastatin lactone, significantly influenced the determination of pitavastatin. The accuracy and precision were both less than 15%. It was shown high and stable recovery for the extraction procedure which proved the stability of pitavastatin. Plasma samples were stable in three freeze-thaw cycles test, in the autosampler at room temperature for 8 h, and in storage at ?20℃for 80 days. The method, which kept the conformance to the relevant standards of Pharmacopoeia of People's Republic of China, was ideally suited for the study of pharmacokinetics of pitavastatin.After administrated a single dose of 1,2,4 mg of pitavastatin calcium, the results of pharmacokinetic parameters were as follows: 11.0±2.71, 9.99±2.36 and 9.74±3.15 h for t1/2, 201±49.9, 327±71.7 and 987±515 ng?h/l for AUC0-t; 80.99±20.29, 102.7±25.3 and 77.2±29.7 ml/min for CL/F;75.8±24.3,86.7±21.1 and 65.3±25.8 l for Vd/F; 71.2±20.5, 109.2±30.5 and 239±62.5 ng/ml for Cmax, Tmax 0.61±0.16,0.63±0.16 and 1.59±1.99 h。After administrated a nultiple dose of 2 mg of pitavastatin calcium, the results of pharmacokinetic parameters were as follows: 9.25±3.11 and 13.5±5.6 h h for t1/2, 309±64.2 and 276±109 ng?h/l for AUC0-τ; 102±25.3 and 137±46.4 ml/min for CL/F;78.5±22.1 and 165±93.7 l for Vd/F; 110±30.1 and 92.5±33 ng/ml for Cmax, 0.63±0.16和0.692±0.174 h for Tmax, 8.36±1.54 and 7.97±1.55 for DF.The results of statistical analysis of main pharmacokinetic parameters between gender shows that, no gender differences exist in pharmacokinetics of pitavastatin (P>0.05).The results of statistical analysis of main pharmacokinetic parameters after different single doses of pitavastatin (1~4 mg) indicates that, pitavastatin showed linear pharmacokinetic characteristics (P<0.05), and there were no significant differences of t1/2 between any two single dose groups (P>0.05). After oral administration of pitavastatin calcium tablet, pitavastatin was absorbed rapidly, and Tmax was relatively short. The value of Vd/F is greater than 36 l (36 l is the average volume of body fluid of a 60 kg adult) indicates that the concentration of pitavastatin is greater in tissue than in plasma, which could lead that the elimination of the drug in plasma is slow, and t1/2 is long. On one hand, this could point out the elimination of pitavastatin is slow and therefore the accumulation in tissue is likely to occur. On the other hand, this is consistent that pitavastatin has high selectivity of liver cells, which could demonstrate pitavastatin is good at liver targeting. The results of statistical analysis of main pharmacokinetic parameters after single and multiple dose of pitavastatin shows: after multiple dose of pitavastatin, the absorption rate of the drug turned a little slow; the drug accumulated in tissues and the elimination of the drug turned slow; the exposure of the drug remained unchanged between delivery intervals; the accumulation of pitavastatin is slight. Pitavastatin is of good security. |
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