The Nuclear Receptor PXR in Chronic Liver Disease

Pregnane X receptor (PXR), a nuclear receptor known for modulating the transcription of drug metabolizing enzymes and transporters (DMETs), such as cytochrome P450 3A4 and P-glycoprotein, is functionally involved in chronic liver diseases of different etiologies. Furthermore, PXR activity relates to that of other NRs, such as constitutive androstane receptor (CAR), through a crosstalk that in turn orchestrates a complex network of responses. Thus, besides regulating DMETs, PXR signaling is involved in both liver damage progression and repair and in the neoplastic transition to hepatocellular carcinoma. We here summarize the present knowledge about PXR expression and function in chronic liver diseases characterized by different etiologies and clinical outcome, focusing on the molecular pathways involved in PXR activity. Although many molecular details of these finely tuned networks still need to be fully understood, we conclude that PXR and its modulation could represent a promising pharmacological target for the identification of novel therapeutical approaches to chronic liver diseases.

Predicting drug–drug interactions by electrochemically driven cytochrome P450 3A4 reactions

Objectives Human cytochrome P450 3A4 is the most abundant hepatic and intestinal Phase I enzyme that metabolizes approximately 60% marketed drugs. Simultaneous administration of several drugs may result in appearance of drug–drug interaction. Due to the great interest in the combination therapy, the exploration of the role of drug as “perpetrator” or “victim” is important task in pharmacology. In this work the model systems based on electrochemically driven cytochrome P450 3A4 for the analysis of drug combinations was used. We have shown that the analysis of electrochemical parameters of cytochrome P450 3A4 and especially, potential of the start of catalysis, Eonset, possess predictive properties in the determination of the leading (“perpetrator”) properties of drug. Based on these experimental data, we concluded, that the more positive potential of the start of catalysis, Eonset, the more pronounced the role of drug as leading medication. Methods Electrochemically driven cytochrome P450 3A4 was used as probe and measuring tool for the estimation of the role of interacting drugs. Results It is shown that the electrochemical non-invasive model systems for monitoring the catalytic activity of cytochrome P450 3A4 can be used as prognostic devise in assessment of drug/drug interacting medications. Conclusions Cytochrome P450 3A4 activity was studied in electrochemically driven system. Method was implemented to monitor drug/drug interactions. Based on the obtained experimental data, we can conclude that electrochemical parameter such as potential of onset of catalysis, Eonset, has predictive efficiency in assessment of drug/drug interacting medications in the case of the co-administration.

Co-Administration of Vonoprazan, Not Tegoprazan, Affects the Pharmacokinetics of Atorvastatin in Healthy Male Subjects

Potassium-competitive acid blocker is a new class of drugs inhibiting gastric acid. It is controversial that vonoprazan showed the inhibitory activities of cytochrome P450 3A4. This study aimed to evaluate the pharmacokinetics (PK) of atorvastatin and safety when atorvastatin was administered alone and co-administered with vonoprazan or tegoprazan. An open-label, multiple-dose, 3-intervention, 4-sequence, 4-period, partial replicate crossover study was conducted, and three interventions were; one is orally administered atorvastatin 40 mg alone once daily for 7 days, another is atorvastatin co-administered with vonoprazan 20 mg, and the other is atorvastatin co-administered with tegoprazan 50 mg. PK blood samples were collected up to 24 h after the last dose, and PK parameters for atorvastatin, 2-hydroxyatorvastatin and atorvastatin lactone were estimated by a non-compartmental method. Safety was evaluated, including adverse events and clinical laboratory tests. A total of 28 subjects completed the study. When atorvastatin was co-administered with vonoprazan, the systemic exposures of atorvastatin and atorvastatin lactone significantly increased, and the metabolic ratio of 2-hydroxyatorvastatin significantly decreased. Hypergastrinemia only occurred when atorvastatin was co-administered with vonoprazan. However, the plasma concentration profiles of atorvastatin, 2-hydroxyatorvastatin and atorvastatin lactone were similar when atorvastatin was administered alone or co-administered with tegoprazan. In conclusion, after multiple doses of atorvastatin co-administered with vonoprazan in healthy subjects, the systemic exposure of atorvastatin and the incidence of hypergastrinemia increased. With tegoprazan, however, those interactions were not observed.

Buprenorphine not detected on urine drug screening in supervised treatment

Introduction: Urine drug screens (UDS) assist in clinical planning and assessment of adherence in opioid agonist treatment (OAT). Urine drug screens may also be used in criminal justice and child protection settings. Buprenorphine (BPN) UDS testing is complex. Immunoassay often does not detect BPN and gas chromatography-mass spectrometry (GC-MS) is needed. A limited understanding of testing can negatively influence UDS interpretation and clinical decision making.Objectives: The primary aim was to determine detection rates of BPN in UDS in participants on BPN or buprenorphine/naloxone (BNX) treatment. The secondary aim was to identify if comorbidities, sex, co-prescribed medications, or dosing site and observation were associated with BPN detection.Setting: Public outpatient clinic in a specialist addiction treatment service.Design/participants: In this retrospective observational study, records of clients on supervised BPN/BNX treatment between September 2017 and 2018 were reviewed.Measures: Data extracted included UDS results, age, sex, indication for BPN, frequency of observed doses, dose of BPN, dosing site, co-morbid medical conditions, and medications.Results: One hundred and sixty-one medical records were reviewed. Ninety-seven (60 percent) underwent screening urine immunoassay. Of these 97, 51 (53 percent) had further GC-MS testing for BPN of which 22 (43 percent) did not detect BPN despite directly observed OAT. Co-prescription of medications known to interact with cytochrome P450 3A4 was associated with nondetection of BPN (p 0.05). No significant association between median dose, dosing site, and observed dosing and BPN detection was identified.Conclusion: Urine drug testing for BPN is complex. Failure to detect BPN does not betoken nonadherence to treatment and is associated with co-prescription of drugs interacting with cytochrome P450 3A4.