Methimazole (MMI) has been used for the treatment of Graves' Disease (GD) for more than half a century. The MMI treatment has been reported to be associated with hepatotoxicity. Previous studies have demonstrated that human leukocyte antigen (HLA) genetic polymorphisms were associated with many drugs-induced liver injuries. To investigate HLA genetic susceptibility to MMI-induced liver injury (MMI-DILI), we characterized both HLA class I and class Ⅱ in a well-characterized phenotypic cohort with 40 MMI-DILI cases and 118 MMI-tolerant controls. Among the 40 MMI-DILI cases, 57.5% were women and 50% were cholestatic liver damage with occurring time from days to months after MMI dosing. The frequency of HLA-C*03:02 was 6.7% (5/75) in the MMI-DILI case patients and 6.4% (4/62) in MMI-induced cholestatic/mixed liver damage, which were significantly different from the percentage of 0.4% (1/231) in the MMI-tolerant patients (odds ratio (OR) = 15.4, 95% confidence interval (CI) = 1.77-133.9, adjusted P = 0.0292; OR=14.9, 95% CI=2.38-182.9, adjusted P = 0.0323; respectively). HLA-A*02:01 was also found to be associated with MMI-induced cholestatic/mixed liver injury (OR = 3.13, 95%CI=1.45-6.91, adjusted P = 0.0464). The present study demonstrated that individuals carrying HLA-C*03:02 allele are at increased risk of developing MMI-induced DILI. These results may assist doctors to prevent the occurrence of hepatotoxicity in GD patients receiving MMI.

Methimazole (MMI) has been used in the therapy of Grave's disease (GD) since 1954, and drug‐induced liver injury (DILI) is one of the most deleterious side effects. Genetic polymorphisms of drug‐metabolizing enzymes and drug transporters have been associated with drug‐induced hepatotoxicity in many cases. The aim of this study was to investigate genetic susceptibility of the drug‐metabolizing enzymes and drug transporters to the MMI‐DILI. A total of 44 GD patients with MMI‐DILI and 118 GD patients without MMI‐DILI development were included in the study. Thirty‐three single nucleotide polymorphisms (SNPs) in twenty candidate genes were genotyped. We found that rs12422149 of SLCO2B1, rs2032582_AT of ABCB1, rs2306283 of SLCO1B1 and rs4148323 of UGT1A1 exhibited a significant association with MMI‐DILI; however, no significant difference existed after Bonferroni correction. Haplotype analysis showed that the frequency of SLCO1B1*1a (388A521T) was significantly higher in MMI‐DILI cases than that in the control group (OR = 2.21, 95% CI = 1.11‐4.39, P = 0.023), while the frequency of SLCO1B1*1b (388G521T) was significantly higher in the control group (OR = 0.52, 95% CI = 0.29‐0.93, P = 0.028). These results suggested that genetic polymorphisms of SLCO1B1 were associated with susceptibility to MMI‐DILI. The genetic polymorphism of SLCO1B1 may be important predisposing factors for MMI‐induced hepatotoxicity.

Warfarin is extensively used for venous thromboembolism and other coagulopathies. In clinical settings, warfarin is administered as a mixture of S- and R-warfarin, and both enantiomers are metabolized by multiple cytochrome P450 enzymes into many hydroxylation metabolites. Due to the high degree of structural similarity of hydroxylation metabolites, their profile possesses significant challenges. The previous methods generally suffer from lacking baseline resolution and/or involving complex analysis processes. To overcome this limitation, a sensitive and specific chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to simultaneously identify warfarin and hydroxywarfarins enantiomers. Chromatographic separation was achieved on a HYPERSIL CHIRAL-OT column. The mass spectrometric detection was carried out in negative ion MRM mode with electrospray ionization source. The optimized method exhibited satisfactory within-run and between-run accuracy and precision with lower limit of quantification (LLOQ) of 10.0 ng/mL and 1.0 ng/mL for warfarin and 7-, 10(R)-OH-warfarin enantiomers, respectively. Linear responses of warfarin enantiomers and 7-, and 10(R)-OH-warfarin enantiomers in rat plasma were observed over the range of 10.0–8000 ng/mL, and 1.00–800 ng/mL, respectively. The analytes were shown to be stable in various experimental conditions in rat plasma. Protein precipitation was used in sample preparation without a matrix effect. This method was successfully applied to pharmacokinetic study for quantitating the concentrations of S/R-warfarin, S/R-7-OH-warfarin, and S/R-10(R)-OH-warfarin and relatively quantitating 3′-, 4-, 6-, and 8-OH warfarin enantiomers in rat plasma.

Objective: To develop a reliable and sensitive high-performance liquid chromatographytandem mass spectrometry (HPLC-MS/MS) method for the quantification of selegiline in Beagle dog plasma and apply the validated method to study the pharmacokinetics and bioavailability of oral selegiline lyophilizate in Beagle dogs.Methods: Following alkalization with 1 M sodium hydroxide solution, selegiline and the Internal Standard (IS) zolmitriptan were extracted using tert-butyl methyl ether and separated on a CAPCELL PAK C18 column under isocratic conditions. They were detected by MS/MS using electrospray ionization (ESI) in the positive mode. Quantification was performed using multiple reaction monitoring (MRM) with transitions of m/z 188.05→90.9 for selegiline and m/z 288.05→57.95 for IS.Results: Calibration curves were constructed in the concentration range of 0.2–200 ng/mL with a lower limit of quantification (LLOQ) of 0.21 ng/mL. The matrix effect of dog plasma on the selegiline signal ranged from 98.8 to 105.6%, and the mean extraction recovery ranged from 79.0% to 81.4% at concentrations of 1.04, 20.8, and 166 ng/mL. The intra-day precision was lower than 6.86% and the inter-day precisions were lower than 4.63%.Conclusion : The validation results demonstrated the reliability of this bioanalytical method, which was successfully applied to study the pharmacokinetics and bioavailability of 1.25 mg of orally administered selegiline lyophilizate in Beagle dogs. The pharmacokinetic results were also compared with those obtained following intragastric (i.g.) and intravenous (i.v.) administration. Buccal delivery of selegiline was found to significantly increase its bioavailability.

Background and Objective: Hypertension is a common comorbidity of patients with COVID-19, SARS or HIV infection. Those patients are often treated with commonly used antiviral and antihypertensive agents concomitantly, such as ritonavir-containing regimens and nifedipine. Since ritonavir is a strong inhibitor of CYP3A, when nifedipine is combined with ritonavir-containing antiviral drugs, there is a potential risk of drug-drug interaction. This study aimed to provide guidance on nifedipine treatment during and after co-administration with ritonavir-containing regimens using a physiologically-based pharmacokinetic/pharmacodynamic (PBPK/PD) analysis. Methods: A PBPK/PD model was developed for nifedipine by the software of Simcyp®, and the model was verified using published data. The effects of ritonavir on nifedipine exposures and systolic blood pressure were assessed for instant-release, sustained-release and controlled-release formulations. Moreover, various nifedipine regimens were investigated when co-administrated with and withdrawing ritonavir. Results: PBPK/PD models for three formulations of nifedipine were successfully established. The model predicted pharmacokinetic profiles of nifedipine were comparable to the published data. Ratios of predicted versus observed AU _CDDI /AUC _Nifedipine of nifedipine were within 0.70- to 1.83-fold. Model simulations showed that the inhibitory effect of ritonavir on CYP3A4 increased the C _max of nifedipine by 9.82-34.35 times and the AUC _24h by 44.94-50.77 times at steady state. Moreover, nifedipine dose reduced to 1/16 of the regular dose during ritonavir co-administration could lead to severe hypotension. Conclusions: Ritonavir had a pronounced influence on the pharmacokinetics and antihypertensive effect of nifedipine. It is not recommended for patients to take nifedipine and ritonavir-containing regimens simultaneously.