Determination of 20(S)-protopanaxadiol in human plasma by HPLC–MS/MS:application to a pharmacokinetic study

A rapid,specific and sensitive HPLC-MS/MS method was developed and validated for the determination of 20(S)-protopanaxadiol(PPD)in human plasma.PPD and the internal standard PD were extracted from plasma by liquid-liquid extraction with cyclohexane-methylene dichloride(2:1,v/v).The separation was performed on a HyPURIYTY C18 column using methanol-5 mM ammonium formate(90:10,v/v)as mobile phase at a flow rate of 0.35 mL/min.Mass spectrometric detection was carried out by electrospray ionization(ESI)in the positive ion mode using multiple reaction monitoring(MRM).The monitored transitions were m/z 425.4-217.2 for PPD and at m/z 461.4-425.5 for PD.The method was linear over the range 0.512-100 ng/mL with a lower limit of quantification(LLOQ)of 0.512 ng/mL.The mean extraction recovery of PPD was greater than 78.2%and no significant matrix effect was detected.The intra-and inter-day precisions were less than 10%and the biases below 4%for PPD.The validated method was applied to a three-level single-dose clinical pharmacokinetics study of 12 healthy Chinese volunteers and the main pharmacokinetic parameters of PPD were obtained.

New techniques of on-line biological sample processing and their application in the field of biopharmaceutical analysis

Biological sample pretreatment is an important step in biological sample analysis. Due to the diversity of biological matrices, the analysis of target substances in these samples presents significant challenges to sample processing. To meet these emerging demands on biopharmaceutical analysis, this paper summarizes several new techniques of on-line biological sample processing: solid phase extraction, solid phase micro-extraction, column switching, limited intake filler, molecularly imprinted solid phase extraction,tubular column, and micro-dialysis. We describe new developments, principles, and characteristics of these techniques, and the application of liquid chromatography–mass spectrometry(LC–MS) in biopharmaceutical analysis with these new techniques in on-line biological sample processing.

Intracellular pharmacokinetic study of zidovudine and its phosphorylated metabolites

Zidovudine(AZT), the first drug approved by the US Food and Drug Administration for the treatment of human immunodeficiency virus(HIV) infection, is metabolized in the host cells to 5′-AZT triphosphate(AZT-TP) which inhibits HIV reverse transcriptase. As the pharmacokinetics of AZT and its phosphorylated metabolites in human peripheral blood mononuclear cells(h PBMCs) is limited, the aim of this study was to determine the pharmacokinetic parameters of AZT and its phosphorylated metabolites in h PBMCs from 12 healthy Chinese male subjects after a single oral dose of 600 mg of AZT. Blood samples were collected prior to drug administration, then at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 8 and 10 h after drug administration. Mononuclear cells collected by Ficoll-Hypaque density gradient centrifugation were used for determination of AZT and metabolites [AZT monophosphate(AZT-MP), AZT diphosphate(AZT-DP) and AZT-TP] and the plasma was used to evaluate the pharmacokinetics of AZT. Plasma concentration of AZT peaked within 0.583 h and intracellular concentrations of AZT, AZT-MP, AZT-DP and AZT-TP peaked within 1.083, 1.500, 1.417 and 1.583 h, respectively. AZT in plasma was eliminated rapidly with t1/2of 2.022 h, and AZT-MP, AZT-DP and AZT-TP were eliminated with t1/2of 13.428,8.285 and 4.240 h, respectively. The plasma concentration of the phosphorylated metabolites was not quantifiable.

Implementation of a reference-scaled average bioequivalence approach for highly variable generic drug products of agomelatine in Chinese subjects

The aim of this study was to apply the reference-scaled average bioequivalence(RSABE)approach to evaluate the bioequivalence of 2 formulations of agomelatine,and to investigate the pharmacokinetic properties of agomelatine in Chinese healthy male subjects.This was performed in a single-dose,randomized-sequence,open-label,four-way crossover study with a one-day washout period between doses.Healthy Chinese males were randomly assigned to receive 25 mg of either the test or reference formulation.The formulations were considered bioequivalent if 90% confidence intervals(CIs)for the log-transformed ratios and ratio of geometric means(GMR)of AUC and C_(max) of agomelatine were within the predetermined bioequivalence range based on RSABE method.Results showed that both of the90% CIs for the log-transformed ratios of AUC and C_(max) of 7-desmethyl-agomelatine and 3-hydroxyagomelatine were within the predetermined bioequivalence range.The 90% CIs for natural logtransformed ratios of C_(max) ,AUC_(0–t)and AUC_(0–∞) of agomelatine(104.42–139.86,101.33–123.83 and97.90–117.94)were within the RSABE acceptance limits,and 3-hydroxy-agomelatine(105.55–123.03,101.95–109.10 and 101.72–108.70)and 7-desmethyl-agomelatine(104.50–125.23,102.36–111.50 and101.62–110.64)were within the FDA bioequivalence definition intervals(0.80–1.25 for AUC and0.75–1.33 for C_(max)).The RSABE approach was successful in evaluating the bioequivalence of these two formulations.