Wen-Xing Peng

Combination of isoniazid (INH) and rifampicin (RFP) causes liver injury frequently among tuberculosis patients. However, mechanisms of the hepatotoxicity are not entirely understood. Protoporphyrin...

Co-treatment of isoniazid (INH) and rifampicin (RFP) is well known for clinically apparent liver injury. However, the mechanism of INH/RFP-induced liver injury is controversial. Emerging evidence shows links between inhibition of bile acids transporters and drug-induced liver injury (DILI). The present study investigates whether sodium taurocholate cotransporting polypeptide (NTCP/Ntcp; SLC10A1) and bile salt export pump (BSEP/Bsep; ABCB11) are involved in the anti-tuberculosis medicines induced liver injury. ICR female mice were intragastrically treated with INH (50 or 100 mg/kg), RFP (100 or 200 mg/kg), or the combination of INH/RFP (50 + 100 mg/kg or 100 + 200 mg/kg) for 14 consecutive days. Liver histopathological examination, serum biochemical and liver malondialdehyde tests were evaluated. Apparent histopathological alterations and hepatic oxidative stress showed in INH (100 mg/kg), RFP (200 mg/kg) and their combination group. The hepatoxic effect was also indicated by increased serum biomarkers, such as aspartate transaminase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), direct bilirubin (DBil), total bilirubin (TBil) and total bile acids (TBA). Both doses of INH/RFP administration significantly down-regulated the expression of Ntcp and Bsep in liver. Furthermore, the combination of INH and RFP displayed stronger effect on the expression of Ntcp compared with the corresponding dose of INH or RFP alone. In conclusion, down-regulated expression of hepatic Ntcp and Bsep might play an important role in the development of INH and RFP induced liver injury.

Mildronate has been used as antianginal drug in parts of Europe for many years, but its pharmacokinetic (PK) properties in humans remain unclear. This study was designed to assess and compare the PK properties of mildronate capsules after single escalating oral dose and multiple doses in healthy Chinese volunteers. Volunteers were randomly assigned to receive a single dose of 250, 500, 1000, 1250 or 1500 mg of mildronate capsules. Those who received the 500‐mg dose continued on the multiple‐dose phase and received 500 mg three times a day for 13 days. Plasma drug concentrations were analysed by ultraperformance liquid chromatography coupled with tandem mass spectrometry (UPLC‐MS/MS). Tolerability was assessed throughout the study. A total of 40 Chinese volunteers were enrolled in the study. No period or sequence effect was observed. Area under the concentration andC_maxwere increased proportionally with the dose levels, whereast_1/2andV_d/fwere dependent on the dose. Nonlinear PK properties were found at doses of 250–1500 mg. There was an accumulation after multiple‐dose administration. No serious adverse events (AEs) were reported in the PK study. The formulation was well tolerated.

A solid‐phase extraction–liquid chromatographic–tandem mass spectrometry method for the determination of nalbuphine concentrations in human plasma has been developed. Samples (1 mL) were extracted using a Strata™‐X solid phase extraction cartridges. Chromatographic separation of nalbuphine and naloxone (internal standard) was achieved on a Phenomenex Kinetex PFP (2.6 μm, 100 A, 100 × 2.1 mm) column using a mobile phase consisting of 0.1% formic acid, 15 mM ammonium acetate in deionized water and acetonitrile (60:40, v/v). The flow rate was 0.3 mL/min and the total run time was 2 min. Detection of the analytes was achieved using positive ion electrospray ionization via multiple reactions monitoring mode. The mass transitions were m/z 358 → 340 for nalbuphine and m/z 328 → 310 for naloxone. The assay was linear over the concentration range 0.50–500.00 ng/mL, with correlation coefficients ≥0.995. The lower limit of quantitation was set at 0.5 ng/mL plasma based on an average signal‐to‐noise ratio of 44.79. The intra‐ and inter‐day precision was less than 8.07% in terms of relative standard deviation and accuracy ranged from 94.97 to 106.29% at all quality control levels. The method was applied successfully to determine nalbuphine concentrations in human plasma samples obtained from subjects receiving intravenous administration of nalbuphine. The method is rapid, sensitive, selective and directly applicable to human pharmacokinetic studies involving nalbuphine. Copyright © 2011 John Wiley & Sons, Ltd.

Objective To evaluate the effect of duloxetine (DLX) on the P-glycoprotein (P-gp) function in vitro and in vivo. Method In vitro experiment was conducted using the Caco-2 cell, a human colon cancer cell line that naturally expresses the P-gp and P-gp function was evaluated by monitoring whether DLX affect the accumulation of Rhd123. In vivo study was conducted by quantitating the effect of orally administered DLX on the bioavailability of talinolol. Results In the in vitro study, incubation of Caco-2 cell with DLX caused a concentration-dependent increase in the accumulation of Rhd123. In the in vivo study, co-administration of DLX increased the bioavailability of talinolol. The ratio (90% confidence intervals) of AUC_0–60, AUC_0–∞, and C_max (talinolol alone versus talinolol plus DLX) were 0.87(0.77–1.06), 0.85(0.74–1.01), 0.87 (0.68–1.12). Conclusion Our results suggest that DLX could inhibit the function of P-gp in vitro and in vivo, and caution should be exercised when DLX is to be co-administered with drugs that are P-gp substrate. Copyright © 2011 John Wiley & Sons, Ltd.

To identify the cytochrome P450 (CYP) isoform (s) involved in daidzein mono-hydroxylated metabolites using human liver microsomes. Kinetic analysis of the rates of formation of mono-hydroxylated metabolites of daidzein, including 7,8,4'-trihydroxyisoflavone (7,8,4'-THI), 7,3',4'-trihydroxyisoflavone (7,3',4'-THI) and 6,7,4'-trihydroxyisoflavone (6,7,4'-THI), was performed using human liver microsomes (HLM) and recombinant enzymes at substrate concentrations ranging from 0.5 to 400 micromol x L(-1). Nine selective inhibitors or substrate probes specific for different CYP isoforms were applied for screening the isoform(s) responsible for mono-hydroxylated metabolism of daidzein. Michaelis-Menten kinetic parameters were best fitted to one-component enzyme kinetic model. The mean Km (micromol x L(-1) ) and V(max) (micromol x g(-1) x min(-1)) values were 27 +/- 10 and 4. 8 +/- 2.1, 54 +/- 22 and 2.3 +/- 1.0, 51 +/- 29 and 2.2 +/- 0.8, for the formation rates of 7,8,4'-THI, 7,3',4'-THI, and 6,7,4'-THI, respectively. Furafylline, the CYP1A2 specific inhibitor, estrogen, and monoclonal antibody raised against human CYP1A2 (MAB-1A2) apparently inhibited the formation of mono-hydroxylated metabolites, The IC50 of Fur for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI was 1.0, 0.9 and 0. 8 mol x L(-1), respectively. The IC50 of estrogen for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI were 51, 60 and 64 mol x L(-1) respectively. The IC50 of MAB-1A2 for the formation of the mono-hydroxylated products was 1 mol x L(-1), but neither other selective inhibitor nor substrate probes, including coumarin (CYP2D6), sulphaphenzole ( CYP2C9/10), omeprazole ( CYP2C19), quinidine (CYP2D6), diethyldithiocarbamate (CYP2E1), troleandomycin (CYP3A4) and keteconazole (CYP3A4), did so with human liver microsomes. The in vitro studies indicated that daidzein mono-hydroxylated products were principally metabolized by CYP1A2 in human.