Notable Drug-Drug Interaction Between Etizolam and Itraconazole in Poor Metabolizers of Cytochrome P450 2C19

Etizolam and Its Major Metabolites: A Short Review

Etizolam is a benzodiazepine (BZD). Etizolam is structurally different from BZDs as a thiophene replaces the benzene ring and a triazole ring is fused to the diazepine ring, but etizolam's pharmacological profile is similar. Etizolam has been used to treat anxiety and panic disorders, to reduce depressive and somatization symptoms and to induce muscle relaxation. Etizolam is used recreationally due to its reinforcing and sedative effects. Etizolam is available in tablet or powder form or administered on blotter paper that can be placed on the tongue for oral absorption. Etizolam metabolizes into two major metabolites: α-hydroxyetizolam and 8-hydroxyetizolam, and all three compounds can be detected in different biological specimens using various common analytical techniques such as immunoassay, chromatography and mass spectrometry. Etizolam is a controlled drug in many countries around the globe but is approved for medical use in some countries, such as Japan, South Korea and Italy. This work is a collation and review of available literature on etizolam to help improve the fundamental understanding of its toxicology, outline best analytical practice, and aid interpretation of toxicology results.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

In vitro study on the effect of peucedanol on the activity of cytochrome P450 enzymes

CONTEXT

Peucedanol is a major extract of Peucedanum japonicum Thunb. (Apiaceae) roots, which is a commonly used herb in paediatrics. Its interaction with cytochrome P450 enzymes (CYP450s) would lead to adverse effects or even failure of therapy.

OBJECTIVE

The interaction between peucedanol and CYP450s was investigated.

MATERIALS AND METHODS

Peucedanol (0, 2.5, 5, 10, 25, 50, and 100 μM) was incubated with eight human liver CYP isoforms (CYP1A2, 2A6, 3A4, 2C8, 2C9, 2C19, 2D6, and 2E1), in pooled human liver microsomes (HLMs) for 30 min with specific inhibitors as positive controls and untreated HLMs as negative controls. The enzyme kinetics and time-dependent study (0, 5, 10, 15, and 30 min) were performed to obtain corresponding parameters in vitro.

RESULTS

Peucedanol significantly inhibited the activity of CYP1A2, 2D6, and 3A4 in a dose-dependent manner with IC50 values of 6.03, 13.57, and 7.58 μM, respectively. Peucedanol served as a non-competitive inhibitor of CYP3A4 with a Ki value of 4.07 μM and a competitive inhibitor of CYP1A2 and 2D6 with a Ki values of 3.39 and 6.77 μM, respectively. Moreover, the inhibition of CYP3A4 was time-dependent with the Ki/Kinact value of 5.44/0.046 min/μM.

DISCUSSION AND CONCLUSIONS

In vitro inhibitory effect of peucedanol on the activity of CYP1A2, 2A6, and 3A4 was reported in this study. As these CYPs are involved in the metabolism of various drugs, these results implied potential drug-drug interactions between peucedanol and drugs metabolized by CYP1A2, 2D6, and 3A4, which needs further in vivo validation.

Pharmacokinetic interaction between peimine and paeoniflorin in rats and its potential mechanism

CONTEXT

Peimine and paeoniflorin can be combined for the treatment of cough in paediatrics. The interaction during the co-administration could dramatically affect the bioavailability of drugs.

OBJECTIVE

The interaction between peimine and paeoniflorin was investigated in this study.

MATERIALS AND METHODS

The pharmacokinetics of paeoniflorin (20 mg/kg) with or without the coadministration of peimine (5 mg/kg for 10 days before paeoniflorin) was orally investigated in Sprague-Dawley rats (n = 6). The group without the peimine was set as the control group. The metabolic stability of paeoniflorin was studied in rat liver with microsomes. The effect of peimine on the absorption of paeoniflorin was investigated with Caco-2 cell monolayers.

RESULTS

The C_max (244.98 ± 10.95 vs. 139.18 ± 15.14 μg/L) and AUC_(0-t) (3295.92 ± 263.02 vs. 139.18 ± 15.14 h·μg/L) of paeoniflorin was increased by peimine. The t_1/2 was prolonged from 5.33 ± 1.65 to 14.21 ± 4.97 h and the clearance was decreased from 15.43 ± 1.75 to 4.12 ± 0.57 L/h/kg. Consistently, peimine increased the metabolic stability of paeoniflorin with rat liver microsomes with the increased t_1/2 (56.78 ± 2.62 vs. 26.33 ± 3.15 min) and the decreased intrinsic clearance (24.42 ± 3.78 vs. 52.64 ± 4.47 μL/min/mg protein). Moreover, the transportation of paeoniflorin was also inhibited by peimine as the efflux ratio decreased from 3.06 to 1.63.

DISCUSSION AND CONCLUSIONS

Peimine increased the systemic exposure of paeoniflorin through inhibiting the activity of CYP3A4 and P-gp. These results provide a reference for further in vivo studies in a broader population.

Classification of drugs for evaluating drug interaction in drug development and clinical management

During new drug development, clinical drug interaction studies are carried out in accordance with the mechanism of potential drug interactions evaluated by in vitro studies. The obtained information should be provided efficiently to medical experts through package inserts and various information materials after the drug's launch. A recently updated Japanese guideline presents general procedures that are considered scientifically valid at the present moment. In this review, we aim to highlight the viewpoints of the Japanese guideline and enumerate drugs that were involved or are anticipated to be involved in evident pharmacokinetic drug interactions and classify them by their clearance pathway and potential intensity based on systematic reviews of the literature. The classification would be informative for designing clinical studies during the development stage, and the appropriate management of drug interactions in clinical practice.

Effect of Drug Combination on Omeprazole Metabolism by Cytochrome P450 2C19 in Helicobacter pylori Eradication Therapy

Helicobacter pylori (H. pylori) infection is common and can result in gastric and duodenal ulcers, and in some cases, gastric lymphoma and cancer. Omeprazole (OMP)-in combination with clarithromycin (CLR), amoxicillin (AMX), tinidazole (TND), or metronidazole (MET)-is used in double or triple combination therapy for eradication of H. pylori. However, the roles of the drugs other than OMP are not clearly understood. Therefore, in the present study, we aimed to investigate any effects of these drugs on OMP metabolism by wild-type CYP2C19 using spectroscopy and enzyme kinetics. The dissociation constants (K_d) for CYP2C19 with OMP, CLR, AMX, TND, and MET were 8.6, 126, 156, 174, and 249 µM, respectively. The intrinsic clearance of OMP was determined to be 355 mL/min/µmol of CYP2C19. Metabolism of OMP was significantly inhibited by 69, 66, 28, and 40% in the presence of CLR, TND, AMX, and MET, respectively. Moreover, the combination of CLR and TND resulted in 76% inhibition of OMP metabolism, while the combination of AMX and MET resulted in 48% inhibition of OMP metabolism. Both combinations of drugs not only have antibacterial effects, but also enhance the effect of OMP by inhibiting its metabolism by CYP2C19. These results indicate that drug-drug interactions of co-administered drugs can cause complex effects, providing a basis for OMP dose adjustment when used in combination therapy for H. pylori eradication.