Comparison of particle size methodology and assessment of nanoparticle tracking analysis (NTA) as a tool for live monitoring of crystallisation pathways.

Sample complexity and polydispersity presents challenges surrounding particle size measurements for nanoparticles (NPs). To ensure the delivery of high quality products to the marketplace it is imperative that this task is performed with the greatest accuracy and certainty. For this reason, particle sizing via more than one technique is critical to the success of the formulation process. Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) are techniques that size particles based on their Brownian motion in liquid medium. However, each technique has advantages and disadvantages associated with its application. This study was designed with the intent of comparing these techniques in a critical manner. NPs were formed using three Biopharmaceutics Classification System class II compounds: itraconazole, ketoconazole and posaconazole, using an anti-solvent addition, bottom up method. The impact of polyethylene glycol, polyethylene glycol methyl ether and polyethylene glycol dimethyl ether with a molecular weight 2000 Da, as stabilizers, was assessed using these two particle sizing techniques. Mie light scattering theory was successfully used to explain the relationship between material composition and particle scattering power. A change in material refractive index, associated with an amorphous to crystalline solid state transformation, was predominantly responsible for the observed change in the light scattering power of posaconazole nano-dispersions. The innovative application of NTA for the live tracking of these physical processes was explored for the first time. This novel finding can serve to deepen our understanding of the dynamic crystallisation pathway undertaken by a nanoparticle.

Drug interaction at hERG channel: In vitro assessment of the electrophysiological consequences of drug combinations and comparison against theoretical models.

Drugs carry a proarrhythmic risk, which gets even greater when they are used in combination. In vitro assessment of the proarrhythmic potential of drugs is limited to one compound and thus neglects the potential of drug-drug interactions, including those involving active metabolites. Here we present the results of an in vitro study of potential drug-drug interactions at the level of the hERG channel for the combination of up to three compounds: loratadine, desloratadine and ketoconazole. Experiments were performed at room temperature on an automated patch-clamp device CytoPatch 2, with the use of heterogeneously, stably transfected HEK cells. Single drugs, pairs and triplets were used. The results provided as the inhibition of the IKr current for pairs were compared against the calculated theoretical interaction. Models applied to calculate the combined effect of inhibitory actions of simultaneously given drugs include: (1) simple additive model with a maximal inhibition limit of 1 (all channels blocked in 100%); (2) Bliss independence; and (3) Loewe additivity. The observed IC50 values for loratadine, desloratadine and ketoconazole were 5.15, 1.95 and 0.74 µm respectively. For the combination of drugs tested in pairs, the effect was concentration dependent. In lower concentrations, the synergistic effect was observed, while for the highest tested concentrations it was subadditive. To triple the effect, it was subadditive regardless of concentrations. The square root of sum of squares of differences between the observed and predicted total inhibition was calculated to assess the theoretical interaction models. For most of the drugs, the allotopic model offered the best fit.

Mechanism-based risk assessment strategy for drug-induced cholestasis using the transcriptional benchmark dose derived by toxicogenomics.

Cholestasis is one of the major causes of drug-induced liver injury (DILI), which can result in withdrawal of approved drugs from the market. Early identification of cholestatic drugs is difficult due to the complex mechanisms involved. In order to develop a strategy for mechanism-based risk assessment of cholestatic drugs, we analyzed gene expression data obtained from the livers of rats that had been orally administered with 12 known cholestatic compounds repeatedly for 28 days at three dose levels. Qualitative analyses were performed using two statistical approaches (hierarchical clustering and principle component analysis), in addition to pathway analysis. The transcriptional benchmark dose (tBMD) and tBMD 95% lower limit (tBMDL) were used for quantitative analyses, which revealed three compound sub-groups that produced different types of differential gene expression; these groups of genes were mainly involved in inflammation, cholesterol biosynthesis, and oxidative stress. Furthermore, the tBMDL values for each test compound were in good agreement with the relevant no observed adverse effect level. These results indicate that our novel strategy for drug safety evaluation using mechanism-based classification and tBMDL would facilitate the application of toxicogenomics for risk assessment of cholestatic DILI.

Assessment of Bioequivalence of Weak Base Formulations Under Various Dosing Conditions Using Physiologically Based Pharmacokinetic Simulations in Virtual Populations. Case Examples: Ketoconazole and Posaconazole.

Postabsorptive factors which can affect systemic drug exposure are assumed to be dependent on the active pharmaceutical ingredient (API), and thus independent of formulation. In contrast, preabsorptive factors, for example, hypochlorhydria, might affect systemic exposure in both an API and a formulation-dependent way. The aim of this study was to evaluate whether the oral absorption of 2 poorly soluble, weakly basic APIs, ketoconazole (KETO) and posaconazole (POSA), would be equally sensitive to changes in dissolution rate under the following dosing conditions-coadministration with water, with food, with carbonated drinks, and in drug-induced hypochlorhydria. The systems-components of validated absorption and PBPK models for KETO and POSA were modified to simulate the above-mentioned clinical scenarios. Virtual bioequivalence studies were then carried out to investigate whether formulation effects on the plasma profile vary with the dosing conditions. The slow precipitation of KETO upon reaching the upper part of the small intestine renders its absorption more sensitive to the completeness of gastric dissolution and thus to the gastric environment than POSA, which is subject to extensive precipitation in response to a pH shift. The virtual bioequivalence studies showed that hypothetical test and reference formulations containing KETO would be bioequivalent only if the microenvironment in the stomach enables complete gastric dissolution. We conclude that physiologically based pharmacokinetic modeling and simulation has excellent potential to address issues close to bedside such as optimizing dosing conditions. By studying virtual populations adapted to various clinical situations, clinical strategies to reduce therapeutic failures can be identified.

Preclinical assessment of the interactions between the antiretroviral drugs, ritonavir and efavirenz, and the tyrosine kinase inhibitor erlotinib.

PURPOSE: Prevalence of non-AIDS-defining cancers (NADCs) has increased in the era of potent antiretroviral treatments. Incidence rates of NADCs now exceed AIDS-defining cancers in HIV-positive patients. Treatment of NADCs may be complicated by interactions between antiretrovirals and chemotherapy mostly via inhibition or induction of CYP3A4. Erlotinib is used to treat non-small cell lung and pancreatic cancer and is primarily metabolized by CYP3A4 into multiple products including the active metabolite (OSI-420). Preclinical in vivo assessment was performed to gain a better understanding of CYP3A4-mediated interactions between antiretrovirals and erlotinib. METHODS: Erlotinib (50 mg/kg p.o.) was administered to male FVB mice in the presence and absence of dexamethasone (10 mg/kg p.o. QDx4), efavirenz (25 mg/kg p.o. QDx4), ketoconazole (50 mg/kg p.o.), or ritonavir (12.5 mg/kg p.o.). Blood samples were collected to characterize exposure (AUC). RESULTS: Administration of erlotinib with CYP3A4 inducers (dexamethasone) and inhibitors (ketoconazole and ritonavir) resulted in significant alterations in erlotinib exposure. Ketoconazole and ritonavir resulted in a 1.7- and 3.0-fold increase in erlotinib AUC, respectively, while dexamethasone results in a 0.6-fold decrease in erlotinib AUC. The CYP3A4 inducer efavirenz did not have a significant effect on erlotinib exposure. CONCLUSION: CYP3A4 inducers and inhibitors altered the exposure of erlotinib. Until a definitive clinical trial is performed, erlotinib should be used with caution in patients on a ritonavir-containing antiretroviral regimen, while standard doses may be appropriate for patients on an efavirenz-containing antiretroviral regimen.

Application of a Bayesian approach to physiological modelling of mavoglurant population pharmacokinetics.

Mavoglurant (MVG) is an antagonist at the metabotropic glutamate receptor-5 currently under clinical development at Novartis Pharma AG for the treatment of central nervous system diseases. The aim of this study was to develop and optimise a population whole-body physiologically-based pharmacokinetic (WBPBPK) model for MVG, to predict the impact of drug-drug interaction (DDI) and age on its pharmacokinetics. In a first step, the model was fitted to intravenous (IV) data from a clinical study in adults using a Bayesian approach. In a second step, the optimised model was used together with a mechanistic absorption model for exploratory Monte Carlo simulations. The ability of the model to predict MVG pharmacokinetics when orally co-administered with ketoconazole in adults or administered alone in 3-11 year-old children was evaluated using data from three other clinical studies. The population model provided a good description of both the median trend and variability in MVG plasma pharmacokinetics following IV administration in adults. The Bayesian approach offered a continuous flow of information from pre-clinical to clinical studies. Prediction of the DDI with ketoconazole was consistent with the results of a non-compartmental analysis of the clinical data (threefold increase in systemic exposure). Scaling of the WBPBPK model allowed reasonable extrapolation of MVG pharmacokinetics from adults to children. The model can be used to predict plasma and brain (target site) concentration-time profiles following oral administration of various immediate-release formulations of MVG alone or when co-administered with other drugs, in adults as well as in children.

Prediction of pH dependent absorption using in vitro, in silico, and in vivo rat models: Early liability assessment during lead optimization.

Weakly basic compounds which have pH dependent solubility are liable to exhibit pH dependent absorption. In some cases, a subtle change in gastric pH can significantly modulate the plasma concentration of the drug and can lead to sub-therapeutic exposure of the drug. Evaluating the risk of pH dependent absorption and potential drug-drug interaction with pH modulators are important aspects of drug discovery and development. In order to assess the risk around the extent of decrease in the systemic exposure of drugs co-administered with pH modulators in the clinic, a pH effect study is carried out, typically in higher species, mostly dog. The major limitation of a higher species pH effect study is the resource and material requirement to assess this risk. Hence, these studies are mostly restricted to promising or advanced leads. In our current work, we have used in vitro aqueous solubility, in silico simulations using GastroPlus™ and an in vivo rat pH effect model to provide a qualitative assessment of the pH dependent absorption liability. Here, we evaluate ketoconazole and atazanavir with different pH dependent solubility profiles and based on in vitro, in silico and in vivo results, a different extent of gastric pH effect on absorption is predicted. The prediction is in alignment with higher species and human pH effect study results. This in vitro, in silico and in vivo (IVISIV) correlation is then extended to assess pH absorption mitigation strategy. The IVISIV predicts pH dependent absorption for BMS-582949 whereas its solubility enhancing prodrug, BMS-751324 is predicted to mitigate this liability. Overall, the material requirement for this assessment is substantially low which makes this approach more practical to screen multiple compounds during lead optimization.

Clinical assessment of drug-drug interactions of tasimelteon, a novel dual melatonin receptor agonist.

Tasimelteon ([1R-trans]-N-[(2-[2,3-dihydro-4-benzofuranyl] cyclopropyl) methyl] propanamide), a novel dual melatonin receptor agonist that demonstrates specificity and high affinity for melatonin receptor types 1 and 2 (MT1 and MT2 receptors), is the first treatment approved by the US Food and Drug Administration for Non-24-Hour Sleep-Wake Disorder. Tasimelteon is rapidly absorbed, with a mean absolute bioavailability of approximately 38%, and is extensively metabolized primarily by oxidation at multiple sites, mainly by cytochrome P450 (CYP) 1A2 and CYP3A4/5, as initially demonstrated by in vitro studies and confirmed by the results of clinical drug-drug interactions presented here. The effects of strong inhibitors and moderate or strong inducers of CYP1A2 and CYP3A4/5 on the pharmacokinetics of tasimelteon were evaluated in humans. Coadministration with fluvoxamine resulted in an approximately 6.5-fold increase in tasimelteon's area under the curve (AUC), whereas cigarette smoking decreased tasimelteon's exposure by approximately 40%. Coadministration with ketoconazole resulted in an approximately 54% increase in tasimelteon's AUC, whereas rifampin pretreatment resulted in a decrease in tasimelteon's exposure of approximately 89%.

Management of oropharyngeal mycosis in head and neck cancer occurring during (chemo) radiotherapy: an Italian radio-oncologist survey.

AIMS AND BACKGROUND: Oropharyngeal candidiasis is a common disorder in head and neck cancer patients (HNCPs) who underwent (chemo)-radiotherapy. An Italian survey was conducted in order to investigate radiation oncologists' behavior in regard to diagnosis, prevention, and treatment of oral candidiasis. METHODS AND STUDY DESIGN: Between April and May 2013, a national online 18-question survey was sent to major Italian radiotherapy centers. RESULTS: All Italian regions were represented and 86 radiation oncologists were involved. Eighty-three percent of responders estimated that oropharyngeal candidiasis occurred in 30%-40% of their HNCPs. The majority of responders were able to recognize oral mycosis when it occurred in a localized pseudomembranous form and all responders agreed with the fact that oral candidiasis was always associated with mucositis. A prophylactic therapy was prescribed occasionally by 35% and routinely by 20% of responders. Forty percent prescribed an antifungal drug in the case of suspected mycotic infection and 20% waited for symptomatic clinical evidence before prescribing a therapy. In the presence of candidiasis, mainly topical fluconazole (59%) and itraconazole (36%) were prescribed. Concomitant chemo-radiotherapy was first identified as a risk factor for mycosis occurrence and development. Ninety-nine percent of responders believed that oral mycosis was associated with increased toxicity and 44% of them interrupted treatment due to candidiasis. CONCLUSIONS: A variety of approaches to oropharyngeal candidiasis emerges from this survey; further clinical trials are necessary to identify the best approach for oral mycosis prevention and treatment and to establish specific international guidelines for HNCPs.

Drug safety assessment of oral formulations of ketoconazole.

INTRODUCTION: Ketoconazole was the first broad-spectrum oral antifungal approved by the FDA in 1981. Post-marketing reports of drug-related hepatotoxicity, endocrine dysregulation and drug interactions resulted in market withdrawal of the drug in some countries and strict product relabeling in others. AREAS COVERED: This drug safety review summarizes reports of oral ketoconazole-related adverse events retrieved from a search of the PubMed database using the search strategy 'ketoconazole OR Nizoral AND hepat*', references from relevant publications, and data from the FDA Adverse Event Reporting System. EXPERT OPINION: Although oral ketoconazole is effective in treating fungal infections, the potential for drug interactions, endocrine dysregulation, and hepatotoxicity may outweigh its benefits. Newer oral antifungals have similar or greater efficacy in treating dermatologic conditions and are associated with less risk. Likewise, newer agents with specific targets and fewer drug interactions have been developed to treat systemic fungal infections. Therefore, by the time ketoconazole prescribing guidelines were amended, its use had already largely been replaced with newer antifungals. Being that ketoconazole was the first broad-spectrum oral antifungal, experience with the drug made patient safety, and especially hepatic safety, an important consideration in future antifungal development.

Co-administration of ketoconazole and tacrolimus to kidney transplant recipients: cost minimization and potential metabolic benefits.

To evaluate the effects of the co-administration of tacrolimus and ketoconazole to a group of kidney transplant recipients, we studied 30 kidney transplant recipients with stable kidney function who were maintained on tacrolimus-based immunosuppression. They were prescribed ketoconazole (100 mg/day) with a concomitant reduction in daily tacrolimus dose to maintain its level within the therapeutic range. The study included 19 males and 11 females with a mean age of 36 ± 12 years. All patients were at least three months post-transplant and had tacrolimus trough levels within the therapeutic range of 5-7 ng/mL. Desired tacrolimus trough levels could be achieved in 29/30 patients after the addition of ketoconazole. This resulted in a significant reduction of the median tacrolimus dose from 5 mg/day (range 3-20 mg/day) at baseline to 2 mg/day (range 1-4 mg/day) (P = 0.00). The median reduction in the tacrolimus dose was 63% (range 50-83%). The median monthly tacrolimus cost dropped from 375 US$ per patient (range 225-1440 US$) to 150 US$ per patient (range 120-300 US$). There were no reported adverse drug effects during the study period. After one year of follow-up, there was a small but significant improvement in the estimated glomerular filtration rate (72 ± 18 versus 78 ± 20 mL/min, P = 0.01) and a significant reduction in serum uric acid levels (7.7 ± 1.7 versus 5.9 ± 0.8 mg/dL, P = 0.003). The co-administration of ketoconazole and tacrolimus to kidney trans-plant recipients is safe and significantly reduces the cost of immunosuppression. In addition, this combination appears to have a beneficial effect on kidney function.

Pityriasis versicolor: avoiding pitfalls in disease diagnosis and therapy.

Pityriasis versicolor is common among young active duty members with overactive sweat glands working in humid environments and results in pigmentary changes that can be profound in those with darker skin. This article addresses several issues related to making the correct diagnosis and providing appropriate treatment, as well as the specific challenges military providers may face in these cases.

Assessment of CYP3A-mediated drug-drug interaction potential for victim drugs using an in vivo rat model.

The present study aims to determine if an in vivo rat model of drug-drug interaction (DDI) could be useful to discriminate a sensitive (buspirone) from a 'non-sensitive' (verapamil) CYP3A substrate, using ketoconazole and ritonavir as perpetrator drugs. Prior to in vivo studies, ketoconazole and ritonavir were shown to inhibit midazolam hydroxylation with IC50 values of 350 ± 60 nm and 11 ± 3 nm, respectively, in rat liver microsomes (RLM). Buspirone and verapamil were also shown to be substrates of recombinant rat CYP3A1/3A2. In the rat model, the mean plasma AUC0-inf of buspirone (10 mg/kg, p.o.) was increased by 7.4-fold and 12.8-fold after co-administration with ketoconazole and ritonavir (20 mg/kg, p.o.), respectively. The mean plasma AUC0-inf of verapamil (10 mg/kg, p.o.) was increased by 3.0-fold and 4.8-fold after co-administration with ketoconazole and ritonavir (20 mg/kg, p.o.), respectively. Thus, the rat DDI model correctly identified buspirone as a sensitive CYP3A substrate (>5-fold AUC change) in contrast to verapamil. In addition, for both victim drugs, the extent of DDI when co-administered was greater with ritonavir compared with ketoconazole, in line with their in vitro CYP3A inhibition potency in RLM. In conclusion, our study extended the rat DDI model applicability to two additional victim/perpetrator pairs. In addition, we suggest that use of this model would increase our confidence in estimation of the DDI potential for victim drugs in early discovery.

A new probabilistic rule for drug-dug interaction prediction.

An innovative probabilistic rule is proposed to predict the clinical significance or clinical insignificance of DDI. This rule is coupled with a hierarchical Bayesian model approach to summarize substrate/inhibitor's PK models from multiple published resources. This approach incorporates between-subject and between-study variances into DDI prediction. Hence, it can predict both population-average and subject-specific AUCR. The clinically significant DDI, weak DDI, and clinically insignificant inhibitions are decided by the probabilities of predicted AUCR falling into three intervals, (-infinity, 1.25), (1.25, 2), and (2, infinity). The main advantage of this probabilistic rule to predict clinical significance of DDI over the deterministic rule is that the probabilistic rule considers the sample variability, and the decision is independent of sampling variation; while deterministic rule based decision will vary from sample to sample. The probabilistic rule proposed in this paper is best suited for the situation when in vivo PK studies and models are available for both the inhibitor and substrate. An early decision on clinically significant or clinically insignificant inhibition can avoid additional DDI studies. Ketoconazole and midazolam are used as an interaction pair to illustrate our idea. AUCR predictions incorporating between-subject variability always have greater variances than population-average AUCR predictions. A clinically insignificant AUCR at population-average level is not necessarily true when considering between-subject variability. Additional simulation studies suggest that predicted AUCRs highly depend on the interaction constant K(i) and dose combinations.

A Bayesian meta-analysis on published sample mean and variance pharmacokinetic data with application to drug-drug interaction prediction.

In drug-drug interaction (DDI) research, a two-drug interaction is usually predicted by individual drug pharmacokinetics (PK). Although subject-specific drug concentration data from clinical PK studies on inhibitor or inducer and substrate PK are not usually published, sample mean plasma drug concentrations and their standard deviations have been routinely reported. Hence there is a great need for meta-analysis and DDI prediction using such summarized PK data. In this study, an innovative DDI prediction method based on a three-level hierarchical Bayesian meta-analysis model is developed. The three levels model sample means and variances, between-study variances, and prior distributions. Through a ketoconazle-midazolam example and simulations, we demonstrate that our meta-analysis model can not only estimate PK parameters with small bias but also recover their between-study and between-subject variances well. More importantly, the posterior distributions of PK parameters and their variance components allow us to predict DDI at both population-average and study-specific levels. We are also able to predict the DDI between-subject/study variance. These statistical predictions have never been investigated in DDI research. Our simulation studies show that our meta-analysis approach has small bias in PK parameter estimates and DDI predictions. Sensitivity analysis was conducted to investigate the influences of interaction PK parameters, such as the inhibition constant Ki, on the DDI prediction.

Microsome biocolloids for rapid drug metabolism and inhibition assessment by LC-MS.

Rat liver microsomes attached to nanoparticles were used for LC-MS studies of CYP3A and 2E1 enzymes in metabolism of N-nitroso compounds. Using these biocolloids, turnover rates were measured within 2 min. Inhibitor IC(50) values for ketoconazole (KET) and 4-methylpyrazole (4-MEP) were estimated.

Transporter-mediated drug interactions: clinical implications and in vitro assessment.

Although they are less frequently compared with the reported cases of CYP-mediated drug interactions, clinically significant transporter-mediated drug interactions, which are mainly based on efflux transporter or P-glycoprotein data, have been reported. Unlike the CYP-mediated drug interactions that can be readily defined by inhibition or induction of CYP enzymes, the evidence for the so-called transporter-mediated drug interactions is often less conclusive. The difficulty in defining transporter-mediated drug interactions is due mainly to the interplay between transporters and drug-metabolizing enzymes in drug disposition, and the lack of specific and potent inhibitors for each transporter and enzyme. An important lesson learned from animal studies is that transporter inhibition has a much greater impact on the tissue distribution of drugs than on the systemic exposure of drugs measured in plasma. The potential risk of transporter-mediated drug interactions might be underestimated if only plasma concentrations are monitored.

Impact of the cyclosporine-ketoconazole interaction in children with steroid-dependent idiopathic nephrotic syndrome.

BACKGROUND: Children with steroid-dependent nephrotic syndrome experience serious side effects from steroid therapy. Cyclosporine A (CsA), which is an effective agent in the treatment of steroid-dependent nephrotic syndrome, is expensive and, consequently, often unaffordable in developing countries. Many studies have documented the benefit of ketoconazole administration in transplant adults treated with CsA. We have conducted a retrospective study with the objective of addressing cost-savings, safety, and the efficacy of the co-administration of ketoconazole and CsA to children with steroid-dependent nephrotic syndrome. METHODS: This study included 102 nephrotic patients who were steroid-dependent and who received cyclosporine therapy. The commonest pathologic lesions were focal segmental glomerulosclerosis (64 patients) and minimal change disease (36 patients). Among the patients participating in the study, 78 received daily ketoconazole therapy (ketoconazole group) in the form of a 50-mg dose accompanied by an initial one-third decrease in the CsA dose, while 24 received CsA alone (non- ketoconazole group). All of the patients were children (below 18 years), and the male-to-female ratio was 3:1. The mean duration of treatment was 22.9 months. The characteristics of both groups were comparable. RESULTS: Co-administration of ketoconazole significantly reduced mean doses of CsA by 48% with a net cost savings of 38%. It also resulted in a significant improvement in the CsA response and a more successful steroid withdrawal as well as a decrease in the frequency of renal impairment. Liver function tests remained normal in both groups up to and including the final follow-up (mean of 33.6 months). CONCLUSIONS: The co-administration of ketoconazole to CsA in children with idiopathic steroid-dependent nephrotic syndrome safely results in a significant reduction in CsA cost, which causes great concern in developing countries. It may also improve CsA response.

Assessment of the hepatic and intestinal first-pass metabolism of midazolam in a CYP3A drug-drug interaction model rats.

In the current study, to understand the characteristics of dexamethasone (DEX)-treated female rats as an animal model for drug-drug interactions, a double-cannulation method was applied and separately assessed for the intestinal and hepatic first-pass metabolism of midazolam. Midazolam was administered intravenously or orally to the animals, and midazolam concentrations in the portal and systemic plasma were simultaneously determined. Next, the rates of elimination from the intestine and liver were estimated using the AUC values. After oral administration of midazolam, the entire drug was absorbed without intestinal first-pass metabolism, and 93% of the administered midazolam was extracted in the liver of the DEX-treated female rats. Seven per cent of the midazolam administered reached the systemic circulation. When ketoconazole was given orally to the animals, in conjunction with midazolam, the extraction ratio in the liver decreased from 93% to 77% in the control rats, and the bioavailability of midazolam increased to 23%. On the other hand, after intravenous administration, the elimination half-life of midazolam was not changed by ketoconazole pretreatment. These results indicated that midazolam is only extracted in the liver of DEX-treated female rats and that ketoconazole inhibits the hepatic first-pass metabolism, but not the systemic metabolism. In conclusion, DEX-treated female rats can be used as a drug-drug interaction model via CYP3A4 enzyme inhibition, especially for the hepatic first-pass metabolism of orally administered drugs.