Objective To develop a method on evaluating the uncertainty during the determination of cefixime in human plasma by high performance liquid chromatography-tandem mass spectrometry ( HPLC-MS/ MS). Methods We analyzed various factors that can cause the uncertainty in the whole process of determination, which includ repeatability, weighting,preparation of standard solutions, sample preparation, equipment error and calibration curve fitting. The expanded uncertainty was evaluated by calculating uncertainty of each component and combined. Results The expanded uncertainty for low ( 80 ng ? mL-1 ), medium ( 560 ng ? mL-1 ) and high ( 9 600 ng ? mL-1 ) level of cefixime was 14. 93, 23. 65, 137.95 ng?mL-1 ,respectively (P= 95%). Conclusion The uncertainty of determining cefixime in human plasma by HPLC-MS/ MS is mainly caused by the calibration curve fitting,repeatability and HPLC-MS/ MS error.

Objective: To establish an HPLC-MS/MS method for the determination of hypericin in rat plasma. Methods: The sample was analyzed by HPLC-MS/MS after the addition of internal standard and then protein precipitation using acetonitrile. The sepa-ration was carried out on an Ultimate C18 column (150 mm × 2. 1 mm,5. 0 μm). The mobile phase was composed of acetonitrile∶ 5 mmol·L-1 ammoniumacetate (containing 0. 1% formic acid) (90∶10) at a flow rate of 0. 5 ml·min-1 under 35℃. The detection was performed with multiple teactions monitoring ( MRM) using an electrospray ionization ( ESI) . The precursor/product ion transitions were monitored at m/z 503. 2→m/z 405. 1 for hypericin and m/z 355. 0→m/z 41. 9 for the internal standard pioglitazone ( anion mode). Results:The good linearity of hypericin was obtained within the range of 0. 1-13. 2 ng·ml-1. The correlation coefficient was more than 0. 99 and the lower limit of quantification was 0. 1 ng·ml-1. The extraction recovery was within the range of 84. 19%-98. 71%. The precision of intra-and inter-day was below 18. 47%. Conclusion: The method is fast, sensitive and accurate, which provides research basis for the clinical further study of hypericin.

Objective:To investigate the in vitro effect of capsaicin on four major rat cytochrome P450 ( CYP) enzymes using a cocktail probe drug method. Methods:The in vitro incubation was divided into capsaicin group and the control group. Rat liver micro-somes, probe drugs, capsaicin at various concentration ( buffer solution in the control group) and cofactors were cultured altogether for 20 min. After the culture, the concentration of metabolites was determined by HPLC to assess the activities of enzymes. IC50 value of capsaicin on every isoform was calculated using Graphpad prism 5. 0. Capsaicin and hepatic microsomess were pre-incubated respec-tively for 0, 5, 10, 15, 20 and 30 min, and then the relative activity of the four isoforms at different time was calculated. Results:The activity of the rat liver microsomes enzyme CYP450 isoforms (CYP1A2, CYP2C11, CYP2E1 and CYP3A2) was all inhibited by capsaicin in vitro with IC50 value of 36. 21, 17. 19, 51. 64 and 18. 86 μmol·L-1 , respectively. Pre-incubation could not increase cap-saicin inhibitory activity against the four CYP enzymes. Conclusion:Capsaicin shows inhibition on CYP1A2, CYP2C11, CYP2E1 and CYP3A2 in rat liver microsomes in vitro without pre-incubation time-dependent property.

Objective:To establish an HPLC-MS/MS method for the determination of vinblastine in rat plasma. Methods:Aceto-nitrile was used to precipitate protein in the samples after the addition of internal standard, and then the concentration was analyzed by HPLC/MS/MS. All the separations were carried out on an Ultimate C18 column (150 mm × 2. 1 mm, 5. 0 μm). The mobile phase was composed of acetonitrile and 10 mmol·L-1 ammoniumacetate (containing 0. 1% formic acid) (49 ∶51) and was pumped at a flow rate of 0. 3 ml·min-1 under 40 °C. The detection was performed with multiple reactions monitoring (MRM) using electrospray ioniza-tion (ESI). The precursor/product ion transitions were monitored at m/z 811. 4→m/z 224. 2 (positive ion mode) for vinblastine and m/z 825. 4→m/z 807. 4(positive ion mode) for internal standard vincristine. Results:Good linearity of vinblastine was obtained with-in the range of 0. 457-950 ng·ml-1(r=0. 997 1). The lower limit of quantification was 0. 457 ng·ml-1. The extraction recoveries were within the range of 89. 15%-95. 28%. The precision of intra-and inter-day was not more than 7. 95%. T1/2 of vinblastine in rats was (5. 86 ± 2. 37) h, and AUC(0-t) and AUC(0-∞) was (68. 45 ± 14. 51) and (95. 03 ± 33. 09)μg·L-1 ·h, respectively. Conclu-sion:The method is fast, sensitive and accurate, which provides research basis for the development of vinblastine and transporters re-search in medicine. The concentration of vinblastine in rats is low, and the half-life is long.

OBJECTIVE:To establish physiological pharmacokinetic (PBPK) model of cefdinir in healthy volunteers,and to predict pharmacokinetic process of cefdinir in volunteers after oral administration. METHODS:Using“toubao dini”“cefdinir”“logP”“pKa”as keywords,related literatures about physico-chemical constants of cefdinir were retrieved from CNKI,ScienceDi-rect,PubMed and other databases;according to related guidelines and preliminary clinical trial plan of FDA,GastroPlusTM 8.6 soft-ware was used to establish PBPK model of oral administration of cefdinir;the effectiveness of the model was evaluated by multiple error. The model was used to simulate the absorption of cefdinir in the gastrointestinal tracts. The bioequivalence of test preparation and reference preparation were evaluated through single and population(n=500)simulation tests using cmax and AUC0-∞ of cefdinir reference preparation (capsule and granular formulation) as factors when release rate t85%=15 min (i.e. accumulatively released 85% within 15 min). RESULTS:The blood concentration-time curves of cefdinir predicted by PBPK model fitted well with mea-sured value(R2≥0.95);the pharmacokinetic parameters(cmax,tmax,AUC0-∞)were close to measured results,and the multiple er-rors were less than 2. After oral administration,cefdinir was mainly absorbed by the intestinal tract (45.6%),especially by seg-ment 1 of jejunum(14.8%);the absorption amount was significantly lower than the release amount of absorption site,and reached the maximal value(about 40%)within 4 h. The results of single simulation test showed that there was no statistical significance in cmax and AUC0-∞ between cefdinir test and reference preparations (P>0.05). The results of population simulation test showed that the relative bioavailability of cefdinir test particle and test capsule respectively were 99.01%-102.99% and 97.60%-105.90%;90%CI of cmax and AUC0-∞ values were within 80%-125% of reference preparation. CONCLUSIONS:The PBPK model is accurate and reliable in this study,can provide reference for pharmacokinetic study and bioequivalence evaluation of cefdinir preparations. Test preparation and reference preparation are equivalent.

Objective:To establish an LC–MS/MS method for the determination of the active metabolite(SN-38) and secondary metabolite(SN-38G) of irinotecan in rat liver microsomes incubation system, and optimize the incubation conditions. Methods:Meth-anol was selected to precipitate protein in the samples, and then the concentrations were analyzed by LC–MS/MS. All the separation was carried out on a ZORBAX Eclipse XDB-C18 column(2. 1 mm × 50 mm, 3. 5 μm) with the mobile phase of acetonitrile – water (containing 0. 1% formic acid) (23 :77) at a flow rate of 0. 3 ml·min-1. The mass spectrometer was operated with multiple reac-tions monitoring ( MRM) using electrospray ionization ( ESI) . The incubation conditions were optimized by single factor design. Re-sults:SN-38 and SN-38G showed a good linearity ( r≥0. 9972) respectively within the range of 2. 3-920 ng·ml-1 and 2. 5-1000 ng ·ml-1. The intra-and inter-day RSD was below 14. 6%(n=6). The average recovery was within the range of 74. 1%-123. 4% with RSD below 13. 5% (n=6). The optimal incubation conditions were as follows:the concentration of liver microsomal protein was 0. 3 mg·ml-1 and the incubation time was 30 min. Conclusion:The method is rapid, sensitive and accurate in the quantification of SN-38 and SN-38G in the incubation system,which provides methodological basis for the activity determination of UGT1A1 enzyme in vitro.

Objective To evaluate postprandial pharmacokinetics and bioequivalence of two preparations of cefdinir capsules in Chinese healthy volunteers. Methods In a two-way cross-over study, 24 healthy male volunteers were divided into two groups randomly and a single dose of cefdinir capsules of test and reference preparation were administered orally, respectively.The concentration in plasma was determined by LC-MS/MS. Pharmacokinetic parameters and bioequivalence were calculated and evaluated by DAS. Results The main pharmacokinetic parameters of test and reference were as follows: AUCt (4.35±1.09) μg??h??mL-1 and (4.12±1.22) μg??h??mL-1, AUC0-∞(4.53±1.12) and (4.53±1.73) μg??h??mL-1, t1/2 (1.74±0.29) h and (2.13±1.65) h, tmax(4.44±0.86) h and (4.54 ±1.16) h, Cmax(900±250) ng??mL-1 and (876±269) ng??mL-1 . Conclusion The test and reference preparation of cefdinir capsules are bioequivalent.

Objective:To develop a quantitative HPLC-MS/MS method for the determination of astragulin and kaempferol in Bairui granule. Methods:A column of Ultimate XB-C C18(100 mm×2.1 mm,5 μm)was used. The mobile phase was composed of 0.1% formic acid-water(A) and 0.1% formic acid-acetonitrile(B) with gradient elution. The flow rate was 0.3 ml·min-1. The detection was performed with multiple teactions monitoring (MRM) using electrospray ionization (ESI). The precursor/product ion transitions were monitored at m/z 447.2→m/z 284.0 (anion mode) for astragulin and m/z 285.1→m/z 187.1 (anion mode) for kaempferol. The temperature of column was set at 40℃. Results:A good linearity was obtained with the concentration ranging from 9.86 to 1 970 ng·ml-1(r=0.999 5) for astragulin and 8.73 to 437 ng·ml-1(r=0.999 6) for kaempferol. The average recovery of the two inves-tigated compounds at low, medium and high concentrations was 99.23%, 99.65% and 99.23%, and 98.24%, 99.13% and 99.69% with the RSD of 1.84%,1.37% and 1.21%,and 1.38%,0.96% and 1.47%, respectively (n=6). Conclusion: The method is rapid,accurate and reliable,which can be used to control the quality of Bairui granule.