Inhibition of imrecoxib on mRNA and protein expression of CYP2C11 enzyme in rats.

To evaluate the effect of imrecoxib on CYP2C11 enzyme activity, mRNA, and protein expression, a UPLC method was established. Tolbutamide was selected as the CYP2C11 enzyme-specific probe drug and incubated with imrecoxib in rat liver microsomes. The yield of 4-hydroxytolbutamide was measured using UPLC to investigate the effect of imrecoxib on CYP2C11 enzyme activity. Imrecoxib (10 mg/kg) was administered intragastrically twice daily. After 1, 7, and 14 days of administration, the liver tissues were analyzed. The expression of CYP2C11 enzyme mRNA was determined using reverse transcription-polymerase chain reaction, and its protein expression was determined using Western blot analysis. Imrecoxib concentration was inversely proportional to the production of 4-hydroxytolbutamide in liver microsomes. Imrecoxib demonstrated a dose-dependent inhibitory effect on CYP2C11 activity with IC50 = 74.77 µM. After administration, reverse transcription-polymerase chain reaction showed CYP2C11 enzyme mRNA expressions were 65% (P < 0.05), 35%, and 34% of the control group, respectively (P < 0.01). Western blot analysis showed CYP2C11 enzyme protein expressions were 80, 37, and 34% of the control group, respectively (P < 0.01). Imrecoxib can reduce mRNA and protein expression of CYP2C11 enzyme in rat liver and inhibit the activity of CYP2C11 enzyme in a dose-dependent manner. However, it does not produce clinically significant drug interactions.

Determination of the effect of berberine on epirubicin concentration in MCF-7 cells by LC-MS/MS: The mechanism of synergism explained by intracellular pharmacokinetics.

This study investigated the inhibitory effect of epirubicin combined with berberine on MCF-7 cell proliferation and explored intracellular pharmacokinetics. A CCK-8 assay was used to detect the inhibitory effect of epirubicin alone and in combination with berberine on MCF-7 cell proliferation in vitro. A rapid and sensitive LC-MS/MS method was developed and validated to detect epirubicin in MCF-7 cells. After incubation with epirubicin and berberine at different time points, MCF-7 cells were lysed and precipitated by acetonitrile to extract the analyte. Chromatographic separation was performed on a C18 column. Daunorubicin was selected as the internal standard. The analytical method was applied to determine the epirubicin concentration in MCF-7 cells. Berberine was found to enhance the inhibitory effect of epirubicin (1 µg/mL and 2 µg/mL) on the proliferation of MCF-7 cells (P < 0.05). LC-MS/MS analysis revealed that berberine significantly increased epirubicin concentration in MCF-7 cells at 8, 12, and 24 h (P < 0.05). The results suggest that berberine may enhance the inhibitory effect of epirubicin on cell proliferation by increasing the concentration of epirubicin in MCF-7 cells. The assay provides a basis for research on the intracellular pharmacokinetics of epirubicin and develops analytical methods for other cell-targeted drugs.

Determination of Free Valproic Acid Concentration in 569 Clinical Samples by LC-MS/MS After Hollow Fiber Centrifugal Ultrafiltration Treatment.

OBJECTIVE: To perform therapeutic drug monitoring of total and free plasma valproic acid (VPA) concentrations in clinical samples and to analyze the related factors. METHODS: The total VPA concentration in plasma was determined by ultrahigh-performance liquid chromatography with precolumn derivatization with α-bromoacetophenone, and the free VPA concentration was determined by liquid chromatography-tandem mass spectrometry after the plasma was treated by hollow fiber centrifugal ultrafiltration. Regression analysis was performed to examine the associations between free plasma VPA, total plasma VPA, and the plasma protein binding rate. The impact of individual situations, outpatient or inpatient factors, and drug combinations on VPA concentrations were examined. RESULTS: Of the 569 clinical samples, 268 were inpatients and 301 were outpatients, and the total VPA concentration in 138 cases (24.2%) was lower than the effective treatment concentration range; the total and free VPA concentrations in outpatient samples were 11.0% and 26.1% higher than those of inpatients, respectively. There was no linear relationship between the free and total VPA concentrations. The relationship equation between the plasma protein binding rate and free VPA concentrations was as follows: Y = 0.0255X2 - 1.1357X + 97.429 (r = 0.8011). The total and free VPA concentrations were significantly decreased after the coadministration of phenobarbital (83.7% and 64.3% of the control group, P < 0.05) or carbapenem antibiotics (32.0% and 32.7% of the control group, P < 0.05). CONCLUSIONS: The total VPA concentrations in patients with epilepsy at our hospital was lower than the effective treatment concentration range, which was inadequate for epilepsy control; the total VPA concentrations of outpatients were higher than those of inpatients; as phenobarbital affects VPA metabolism, therapeutic drug monitoring is recommended. Carbapenem antibiotic coadministration with VPA should be avoided because carbapenem antibiotics can lead to the failure of VPA antiepileptic treatment.

Determination of N-nitrosodimethylamine in Ranitidine Dosage Forms by ESI-LC-MS/MS; Applications for Routine Laboratory Testing.

A practical high-performance liquid chromatography-mass spectrometry method was developed for the analysis of N-nitrosodimethylamine (NDMA) characterized as an impurity, in combination with reports of the carcinogen found in ranitidine samples. After simple extraction of ranitidine samples, all compounds were analyzed with a high-performance liquid chromatography-mass spectrometry. Sensitivity was enhanced by employing the ten-way valve switching technology, which was examined to allow NDMA to enter the mass spectrometry and cut out the ranitidine samples extremely. A good linear relationship was observed within 3-100 ng·mL-1 (r = 0.9992). The validated approach was effectively used to evaluate the NDMA contents in ranitidine samples in circulation, which revealed a difference among 21 batches. Quantitative determination of NDMA was within the scope of 3.38-57.05 ng·mL-1. Moreover, the contamination levels of NDMA in seven batches of products from six manufacturers were listed to exceed the acceptable daily intake. The sensitive method was verified to be appropriate to determine NDMA, even with low contents of NDMA in ranitidine products; the analysis of the selected samples reveals that some samples exceeded the national limit requirements. Therefore, it is worthwhile to conduct comprehensive quality control of the other drugs containing NDMA.