Impact of carbapenem antibiotics on mycophenolate mofetil in hematopoietic stem cell transplant patients with interruption of the enterohepatic recycling: a retrospective study.

Background: Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is widely used in the prophylaxis for graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation (HSCT). MPA undergoes enterohepatic recycling (EHR). Oral antibiotics can affect MPA concentration by reducing intestinal flora-mediated EHR. However, the effect of intravenous antibiotics on MPA concentration is not clear, especially in patients whose EHR is already interrupted. This study was conducted to determine whether intravenous carbapenem antibiotics (CBP) influence the pre-dose plasma concentration (C0) of MPA in HSCT patients when the EHR of MPA is interrupted by cyclosporine and gut decontamination. Methods: The HSCT patients who received immunosuppressive therapy with MMF and cyclosporine, as well as treatment with CBP were screened as potential candidates. Patients who lacked MPA C0 measurements before or during CBP use, had combination therapy of rifampin with MMF, or switched from IV to oral MMF were excluded. The liver/renal function, demographic information, albumin/cyclosporine concentration, MPA C0 and medication information were collected. The changes in the MPA C0 before and during CBP use were evaluated, and the influence of related clinical factors was also estimated. Results: CBP resulted in a significant reduction in the MPA C0 from 0.65±0.33 to 0.43±0.30 µg/mL. Linear regression analysis indicated a weak correlation between the dose-normalized C0 of MPA and the dosage of CBP during CBP use (r2=0.129, P=0.009). Univariate and multivariate analysis confirmed that the MPA C0 had no relevance to rifaximin administration (P=0.249-0.700), demographics (P=0.118-0.599), fluctuation of plasma albumin (ALB, P=0.943 and 0.609) and cyclosporine concentrations (P=0.647 and 0.112), or liver and renal functions (P=0.078-0.887) no matter whether the CBP were used. However, compared with the non-gut decontamination group, larger interindividual variabilities and smaller decreases in MPA C0 (6.60% vs. 41.73%) during CBP therapy were seen in the gut decontamination group, although it was a nonsignificant trend. Conclusions: CBP decreased the MPA C0 in Chinese HSCT patients even when MMF is used in combination with cyclosporine and rifaximin. If antibiotics must be used, and CBP in particular, therapeutic drug monitoring should be performed to ensure adequate exposure.

Multicenter-Based Population Pharmacokinetic Analysis of Ciclosporin in Hematopoietic Stem Cell Transplantation Patients.

PURPOSE: To explore the contribution of physiological characteristics to variability in ciclosporin pharmacokinetics in hematopoietic stem cell transplantation patients. METHODS: Clinical data from 563 patients were collected from centers in three regions. Ciclosporin concentrations were measured using immunoassays. The patients' demographics, hematological and biological indicators, coadministered drugs, region, and disease diagnosis were recorded from medical records. Data analysis was performed using NONMEM based on a one-compartment model to describe the pharmacokinetics of ciclosporin. The reliability and stability of the final model were evaluated using bootstrap resampling, goodness-of-fit plots, and prediction-corrected visual predictive checks. RESULTS: The population estimate of the clearance (CL) was 30.4 L/h, the volume of distribution (V) was 874.0 L and the bioavailability (F) was 81.1%. The between-subject variability in these parameters was 26.3, 68.0, and 110.8%, respectively. Coadministration of fluconazole, itraconazole, or voriconazole decreased CL by 17.6%, 28.4%, and 29.2%, respectively. Females' CL increased by approximately 12.0%. In addition, CL and V decreased with hematocrit, total protein, and uric acid increase, and CL also decreased with age and aspartate aminotransferase increase. However, CL increased with creatinine clearance increase. CONCLUSIONS: A multicenter-based population pharmacokinetic model of ciclosporin was established. The pharmacokinetics of ciclosporin exhibited discrepancies among different regions.

Analysis of dihydroindole-type alkaloids in Strychnos nux-vomica unprocessed and processed seeds by high-performance liquid chromatography coupled with diode array detection and mass spectrometry.

The ripened seeds of Strychnos nux-vomica L. have been extensively used as herbal medicines in Asian countries. Dihydroindole-type alkaloids are not only the active constituents but also the toxicants in Strychnos. However, the simultaneous determination of these alkaloids in both crude and processed Semen Strychni is still lacking. The present study represents the first quantitation and relative quantitation assay of 12 dihydroindole-type alkaloids in Strychnos nux-vomica unprocessed and sand-processed seeds using high-performance liquid chromatography coupled with diode array detection and mass spectrometry. The relative concentration of ten alkaloids was calculated by semi-quantification using the internal standard and their amounts in unprocessed and detoxified Semen Strychni were compared. We report here for the first time the significant increase of the two alkaloids, 19-N-methyl-strychnine, and 2,3-dimethoxy-19-N-methyl-strychnine, during the processing of Semen Strychni. Our study provides new insight into the true complexity of seed processing procedure and valuable information for assessing the efficacy and safety for clinical applications of Semen Strychni-containing drugs.

Tacrolimus Levels in the Prophylaxis of Acute Graft-Versus-Host Disease in the Chinese Early After Hematopoietic Stem Cell Transplantation.

BACKGROUND: Tacrolimus has been widely accepted as the backbone of acute graft-versus-host disease (aGVHD) prophylaxis in allogeneic hematopoietic stem cell transplantation (alloHSCT). The present work evaluated whether tacrolimus concentrations early after transplant correlate with the incidence of aGVHD in Chinese alloHSCT recipients. METHODS: One hundred four Chinese alloHSCT recipients were included in this retrospective study. All patients received standard prophylaxis with tacrolimus and short-term methotrexate. Blood samples were taken at steady-state for those on i.v. tacrolimus (Cv) or predose (C0) and 2 hours after the last oral dose (C2). RESULTS: In the first 8 weeks after alloHSCT, significant variability in Cv, C0, and C2 of Chinese patients was observed. It was found that higher tacrolimus C0 and C2 values tended to be associated with a reduced risk of aGVHD, although this was a nonsignificant trend due to the small sample size involved. Receiver operating characteristic curve analysis indicated that Cv levels of ≥16.52 ng/mL, C0 levels of ≥5.56 ng/mL, and C2 levels of ≥7.83 ng/mL minimized the incidence of treatment failure during weeks 3-4 with intravenous administration and weeks 5-6 with oral administration. There was no statistically significant association of the patient liver and kidney function with the blood concentration of tacrolimus in the desired range of 5-20 ng/mL. CONCLUSIONS: Tacrolimus therapeutic drug monitoring improved treatment outcomes of Chinese alloHSCT recipients. Cv measurements during weeks 3-4 and C0 or C2 measurements during weeks 5-6 better predicted aGVHD (I-IV) than the concentrations measured at other time points during the first 6 weeks after alloHSCT.

Metabolism of brucine: the important metabolic pathways of dihydroindole-type alkaloid for excretion in rats.

BACKGROUND: Brucine is a widely prescribed glycine antagonist, but a complete understanding of its metabolic pathway is still lacking. The present work represents the first investigation of in vivo metabolism of brucine in rats using LC-ESI-ion trap-TOF-MS. RESULTS: A total of 12 Phase I and five Phase II metabolites were tentatively identified. Brucine can be metabolized by hydrolysis, demethylation and methoxylation, in addition to diverse oxidations in a Phase I manner followed by glucuronidation in Phase II metabolism. Both the renal and biliary routes were observed for the excretion of brucine and its metabolites. CONCLUSION: Our results update the metabolism and disposition data on brucine, which provides basic information for better understanding of the pharmacological and toxicological activities of brucine-containing medicines.

Characterisation and identification of dihydroindole-type alkaloids from processed semen strychni by high-performance liquid chromatography coupled with electrospray ionisation ion trap time-of-flight mass spectrometry.

INTRODUCTION: For centuries, Semen Strychni (the ripened seeds of Strychnos nux-vomica) has been used extensively as a herbal medicine in Asian countries. However, the chemical composition of the dihydroindole-type alkaloids contained in processed Semen Strychni is not fully understood. OBJECTIVE: To develop an improved strategy using mass defect filtering (MDF) in combination with MS(n) analysis and theoretical calculations for identification and structural characterisation of dihydroindole-type alkaloids in processed Semen Strychni extracts. METHODS: The experimental work was conducted using a high-performance liquid chromatography coupled with electrospray ionisation ion trap time-of-flight mass spectrometry (HPLC-ESI/IT-TOF/MS) system. Upon acquisition of full-scan MS data, the potential dihydroindole-type alkaloids were screened using a well-defined mass defect range of 50 mDa. With the assistance of MS(n) analysis, the diagnostic fragment ions (DFIs) were used as primary screening references for targeting the characteristic analogues. For better discrimination of the isomers, quantum chemical calculations were utilised to provide additional structural information. RESULTS: Twenty-four dihydroindole-type alkaloids, including four that were previously not described, were tentatively identified. CONCLUSION: A new, rapid and sensitive method was developed for the discovery and characterisation of dihydroindole-type alkaloids in extracts of processed Semen Strychni. The successful application of this method indicates a potential for adaptation to other classes of natural product from other sources.

In vitro metabolism study of Strychnos alkaloids using high-performance liquid chromatography combined with hybrid ion trap/time-of-flight mass spectrometry.

In this report, the in vitro metabolism of Strychnos alkaloids was investigated using liquid chromatography/high-resolution mass spectrometry for the first time. Strychnine and brucine were selected as model compounds to determine the universal biotransformations of the Strychnos alkaloids in rat liver microsomes. The incubation mixtures were separated by a bidentate-C18 column, and then analyzed by on-line ion trap/time-of-flight mass spectrometry. With the assistance of mass defect filtering technique, full-scan accurate mass datasets were processed for the discovery of the related metabolites. The structural elucidations of these metabolites were achieved by comparing the changes in accurate molecular masses, calculating chemical component using Formula Predictor software and defining sites of biotransformation based upon accurate MS(n) spectral information. As a result, 31 metabolites were identified, of which 26 metabolites were reported for the first time. These biotransformations included hydroxylation, N-oxidation, epoxidation, methylation, dehydrogenation, de-methoxylation, O-demethylation, as well as hydrolysis reactions.

Analysis of saikosaponins in rat plasma by anionic adducts-based liquid chromatography tandem mass spectrometry method.

Saikosaponins (SSs) are a class of triterpene saponins with a wide spectrum of bioactivities. A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of saikosaponin a, saikosaponin c, saikosaponin d and saikosaponin b2 in rat plasma. Plasma samples were prepared by liquid-liquid extraction. The analytes and the internal standard (IS) digoxin were well separated on an octadecyl column using gradient elution and analyzed by monitoring the fragmentation transition pair of anionic adducts to deprotonated molecules in negative-mode electrospray. By neutral loss of HCOOH, the transition pairs of m/z 825 → 779 for SSa, SSd, SSb2 and the IS, and m/z 971 → 925 for SSc were sensitive for MS/MS detection with the lower limits of quantification in the range of 0.20-0.40 ng/mL. Method validation experiments were performed, including selectivity, precision, accuracy, linearity, matrix effect, recovery and stability. The validated method was further applied to determine the pharmacokinetics parameters of SSa, c and d in rats following a single oral administration of the extract of chaihu (the dried roots of Bupleurum chinense DC).

Pharmacokinetics and bioequivalence study of valacyclovir hydrochloride capsules after single dose administration in healthy Chinese male volunteers.

The aim of the present study was to compare the bioavailability of valacyclovir (CAS 124832-26-4; INN: valaciclovir) from two valacyclovir hydrochloride (CAS 214832-27-5) capsules (150 mg/capsule as test preparation and 150 mg/capsule commercially available original capsule of the drug as reference preparation) in 20 Chinese healthy male volunteers, aged between 20 and 27. The study was conducted according to an open, randomized, single blind, 2-way crossover study design with a wash-out phase of 7 days. Blood samples for pharmacokinetic profiling were taken up to 24 h post-dose. Valacyclovir hydrochloride is rapidly converted to acyclovir (CAS 59277-89-3) after oral administration, so the pharmacokinetics and bioequivalence of valacyclovir hydrochloride can be studied by determining the plasma concentration of acyclovir. Plasma concentrations of acyclovir were determined with a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The pharmacokinetic parameters of test and reference formulations were estimated as follows: the maximum plasma concentrations (C(max)) were 2.04 +/- 0.43 microg/mL and 2.01 +/- 0.50 microg/mL; the median T(max) were 1.1 +/- 0.3 h and 1.0 +/- 0.3 h; plasma elimination half-lives (t1/2) were 2.94 +/- 0.42 h and 2.85 +/- 0.28 h. Values of AUC(0-t) demonstrate nearly identical bioavailability of valacyclovir hydrochloride from the examined formulations. AUC(0-15) were 6.70 +/- 1.26 microg x h/ mL and 6.96 +/- 1.25 microg x h/mL. Areas under the plasma concentration-time curve (AUC(0-infinity)) were 6.90 +/- 1.30 microg x h/mL and 7.15 +/- 1.31 microg x h/mL. Both primary target parameters, AUC(0-infinity) and AUC(0-t) were tested parametrically by analysis of variance (ANOVA) and relative bioavailabilities were 96.69 +/- 7.89% for AUC(0-infinity), 96.40 +/- 8.0% for AUC(0-15). Bioequivalence between test and reference preparation was demonstrated for both parameters, AUC(0-infinity) and AUC(0-t). The 90% confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80-125%. It meant that the test formulation was bioequivalent to the reference formulation for valacyclovir hydrochloride.