Human protein tyrosine kinases play an essential role in carcinogenesis and have been recognized as promising drug targets. By the end of 2012, eight small molecule tyrosine kinase inhibitors (TKIs) have been approved by State Food and Drug Administration of China for cancer treatment. In this paper, the pharmacokinetic characteristics (absorption, distribution, metabolism and excretion) and drug-drug interactions of the approved TKIs are reviewed. Overall, these TKIs reach their peak plasma concentrations relatively fast; are extensively distributed and highly protein bound (> 90%); are primarily metabolized by CYP3A4; most are heavily influenced by CYP3A4 inhibitors or inducers except for sorafenib; are mainly excreted with feces and only a minor fraction is eliminated with the urine; and are substrate of the efflux transporters ABCB1 (P-gp) and ABCG2 (BCRP). Additionally, many of the TKIs can inhibit some CYP450 enzymes, UGT enzymes, and transporters. Gefitinib, erlotinib, dasatinib, and sunitinib are metabolized to form reactive metabolites capable of covalently binding to biomolecules.

The study aims to develop a rapid, sensitive and specified method of liquid chromatography with heated electrospray ionization tandem mass spectrometry (LC-HESI/MS/MS) for simultaneous determination of amlodipine, benazepril and benazeprilat in human plasma using amlodipine-d4 and ubenimex as internal standards (ISs). Selected reaction monitoring (SRM) with heated electrospray ionization (HESI) was used in the positive mode for mass spectrometric detection. Analytes and ISs were extracted from plasma by simple protein precipitation. The reconstituted samples were chromatographed on a C18 (100 mm x 4.6 mm, 5 microm) column with mixture of methanol-acetonitrile-5 mmol.L- ammonium acetate-formic acid (30 : 30 : 40 : 0.1) as mobile phase at a flow rate of 0.6 mL.min-1. The standard curves were demonstrated to be linear in the range of 0.02 to 6.00 ng.mL-1 for amlodipine, 0.2 to 1,500 ng.mL-1 for benazepril and benazeprilat with r2>0.99 for each analyte. The lower limit of quantitation was identifiable and reproducible at 0.02, 0.2 and 0.2 ng mL-1 for amlodipine, benazepril and benazeprilat, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limit across all concentrations. The plasma samples were stable after four freeze-thaw cycles and being stored for 93 days at -20 degrees C. The method was applied to a pharmacokinetic study of a fixed-dose combination of amlodipine and benazepril on Chinese healthy volunteers.

A simple, sensitive, selective, and reproducible liquid chromatography-tandem mass spectrometric method was developed for the simultaneous determination of repaglinide and metformin in human plasma using d5-repaglinide and d6-metformin as internal standards (ISs). After a simple protein precipitation using acetonitrile as the precipitation solvent, both analytes and ISs were separated on a Venusil ASB C 18 (150 mm x 4.6 mm, 5 microm) via gradient elution using acetonitrile--10 mmol x L(-1) ammonium acetate as the mobile phase. A chromatographic total run time of 7.5 min was achieved. Mass spectrometric detection was conducted with atmospheric pressure chemical ionization under positive-ion and multiple-reaction monitoring modes. The method was linear over the 0.2 to 60.0 ng x mL(-1) concentration range for repaglinide and over the 4 to 1 000 ng x mL(-1) range for metformin. For both analytes, the intra- and inter-accuracies and precisions were within the +/- 15% acceptable limit across all concentrations. The validated method was successfully applied to a clinical bioequivalence study.

Objective To evaluate the bioequivalence of two formulations of minocycline hydrochloride capsules administered orally after fasting administration and fed administration.Methods An open-label,randomized,two-period,self-crossover design was employed to assess the bioequivalence study.Twenty-eight healthy subjects were enrolled in both fasting and fed groups,with each period involving a single administration of either the reference formulation or the test formulation of 50 mg,separated by a washout period of 7 days.The concentration of minocycline in human plasma was determined by HPLC-MS/MS and was used for calculating pharmacokinetic parameters and evaluating the bioequivalence of the test formulation and reference formulation.Results After oral administration of test and reference formulations of minocycline under fasting condition,the Cmax Values of minocycline were(541±137)ng·mL-1 for the test formulation and(558±140)ng·mL-1for the reference formulation.The AUC0-t values were(8 347±1 986)h·ng·mL-1 for the test and(8 205±1 790)h·ng·mL-1 for the reference.The t1/2 values were(18.2±2.84)h for the test and(18.0±3.05)h for the reference.After oral administration of the test and reference formulations of minocycline under fed condition,the Cmax values of minocycline were(349±72.1)ng·mL-1 for the test and(352±73.2)ng·mL-1for the reference.The AUC0-twere(6 428±1 077)h·ng·mL-1 for the test and(6 588±1 118)h·ng·mL-1 for the reference.The t1/2values were(18.5±3.10)h for the test and(18.4±3.21)h for the reference.Under fasting condition,the 90% confidence intervals for the geometric mean ratios of Cmax,AUC0-t,and AUC0-∞ between the test and reference formulations were(90.84%,101.46% ),(95.2%,102.8% ),and(95.31%,102.71% ),respectively.Under fed conditions,the 90% confidence intervals for the geometric mean ratios of Cmax,AUC0-t,and AUC0-∞ between the test formulation and the reference formulation were(94.71%,103.42% ),(95.40%,99.83% ),and(95.79%,100.02% ),respectively.Conclusions Bioequivalence of the two minocycline formulations was demonstrated after fasting administration and fed administration in a healthy Chinese population.