Comparative pharmacokinetic interaction profiles of pravastatin, simvastatin, and atorvastatin when coadministered with cytochrome P450 inhibitors

The Effect of Inflammatory Bowel Disease and Irritable Bowel Syndrome on Pravastatin Oral Bioavailability: In vivo and in silico evaluation using bottom-up wbPBPK modeling

The common disorders irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) can modify the drugs' pharmacokinetics via their induced pathophysiological changes. This work aimed to investigate the impact of these two diseases on pravastatin oral bioavailability. Rat models for IBS and IBD were used to experimentally test the effects of IBS and IBD on pravastatin pharmacokinetics. Then, the observations made in rats were extrapolated to humans using a mechanistic whole-body physiologically-based pharmacokinetic (wbPBPK) model. The rat in vivo studies done herein showed that IBS and IBD decreased serum albumin (> 11% for both), decreased PRV binding in plasma, and increased pravastatin absolute oral bioavailability (0.17 and 0.53 compared to 0.01) which increased plasma, muscle, and liver exposure. However, the wbPBPK model predicted muscle concentration was much lower than the pravastatin toxicity thresholds for myotoxicity and rhabdomyolysis. Overall, IBS and IBD can significantly increase pravastatin oral bioavailability which can be due to a combination of increased pravastatin intestinal permeability and decreased pravastatin gastric degradation resulting in higher exposure. This is the first study in the literature investigating the effects of IBS and IBD on pravastatin pharmacokinetics. The high interpatient variability in pravastatin concentrations as induced by IBD and IBS can be reduced by oral administration of pravastatin using enteric-coated tablets. Such disease (IBS and IBD)-drug interaction can have more drastic consequences for narrow therapeutic index drugs prone to gastric degradation, especially for drugs with low intestinal permeability.

Proposing a framework to quantify the potential impact of pharmacokinetic drug-drug interactions caused by a new drug candidate by using real world data about the target patient population

Drug development teams must evaluate the risk/benefit profile of new drug candidates that perpetrate drug-drug interactions (DDIs). Real-world data (RWD) can inform this decision. The purpose of this study was to develop a predicted impact score for DDIs perpetrated by three hypothetical drug candidates via CYP3A, CYP2D6, or CYP2C9 in type 2 diabetes mellitus (T2DM), obesity, or migraine. Optum Market Clarity was analyzed to estimate use of CYP3A, CYP2D6, or CYP2C9 substrates classified in the University of Washington Drug Interaction Database as moderate sensitive, sensitive, narrow therapeutic index, or QT prolongation. Scoring was based on prevalence of exposure to victim substrates and characteristics (age, polypharmacy, duration of exposure, and number of prescribers) of those exposed. The study population of 14,163,271 adults included 1,579,054 with T2DM, 3,117,753 with obesity, and 410,436 with migraine. For T2DM, 71.3% used CYP3A substrates, 44.3% used CYP2D6 substrates, and 44.3% used CYP2C9 substrates. For obesity, 57.1% used CYP3A substrates, 34.6% used CYP2D6 substrates, and 31.0% used CYP2C9 substrates. For migraine, 64.1% used CYP3A substrates, 44.0% used CYP2D6 substrates, and 28.9% used CYP2C9 substrates. In our analyses, the predicted DDI impact scores were highest for DDIs involving CYP3A, followed by CYP2D6, and CYP2C9 substrates, and highest for T2DM, followed by migraine, and obesity. Insights from RWD can be used to estimate a predicted DDI impact score for pharmacokinetic DDIs perpetrated by new drug candidates currently in development. This score can inform the risk/benefit profile of new drug candidates in a target patient population.

Physiologically based pharmacokinetic modeling to assess the drug-drug interactions of anaprazole with clarithromycin and amoxicillin in patients undergoing eradication therapy of H. pylori infection

OBJECTIVE

This study aimed to assess the pharmacokinetic (PK) interactions of anaprazole, clarithromycin, and amoxicillin using physiologically based pharmacokinetic (PBPK) models.

METHODS

The PBPK models for anaprazole, clarithromycin, and amoxicillin were constructed using the GastroPlus™ software (Version 9.7) based on the physicochemical data and PK parameters obtained from literature, then were optimized and validated in healthy subjects to predict the plasma concentration-time profiles of these three drugs and assess the predictive performance of each model. According to the analysis of the properties of each drug, the developed and validated models were applied to evaluate potential drug-drug interactions (DDIs) of anaprazole, clarithromycin, and amoxicillin.

RESULTS

The developed PBPK models properly described the pharmacokinetics of anaprazole, clarithromycin, and amoxicillin well, and all predicted PK parameters (Cmax,ss, AUC0-τ,ss) ratios were within 2.0-fold of the observed values. Furthermore, the application of these models to predict the anaprazole-clarithromycin and anaprazole-amoxicillin DDIs demonstrates their good performance, with the predicted DDI Cmax,ss ratios and DDI AUC0-τ,ss ratios within 1.25-fold of the observed values, and all predicted DDI Cmax,ss, and AUC0-τ,ss ratios within 2.0-fold. The simulated results show no need to adjust the dosage when co-administered with anaprazole in patients undergoing eradication therapy of H. pylori infection since the dose remained in the therapeutic range.

CONCLUSION

The whole-body PBPK models of anaprazole, clarithromycin, and amoxicillin were built and qualified, which can predict DDIs that are mediated by gastric pH change and inhibition of metabolic enzymes, providing a mechanistic understanding of the DDIs observed in the clinic of clarithromycin, amoxicillin with anaprazole.

Covalent Conjugates of Allylbenzenes and Terpenoids as Antibiotics Enhancers with the Function of Prolonged Action

The drug resistance of pathogenic bacteria is often due efflux pumps-specific proteins that remove foreign compounds from bacterial cells. To overcome drug resistance, adjuvants are often used that can inhibit efflux pumps or other systems that ensure the resistance of bacteria to the action of antibiotics. We assumed that a new level of effectiveness with the use of an antibiotic + an adjuvant pair could be achieved by their joint delivery into the pathogen. To test this hypothesis, we constructed a series of molecular carriers based on poly-(olygo-, dendry)mers based on cyclodextrin-grafted PEI or mannan, as well as glycol chitosan, covalently bound to antibiotic, adjuvant, and the oligosaccharide ligand to the macrophage mannose receptor (CD206), which we studied earlier and showed high efficiency and selectivity of delivery of a therapeutic "cargo" to macrophages. Moxifloxacin was used as an antibiotic, and terpenoid and allylbenzene compounds were used as adjuvants, for which we previously discovered the ability to inhibit bacterial efflux pumps. We show that: (a) the resulting structures were stable in vitro for a long time (up to 10 days); (b) they were adsorbed on bacterial cells, providing a local increase in the concentration of the antibiotic and adjuvant in pathogen cells; (c) they were internalized by bacterial cells, ensuring the accumulation of both antibiotic and adjuvant inside bacterial cells; (d) the adjuvant, after entering the bacterial cell, provided inhibition of the efflux pumps; (e) due to this action of the adjuvant, combined with the targeted delivery by the carrier, the antibiotic's half-life in rats increased by more than 2 times, the effective concentration of the drug in the blood plasma (AUC) increased up to 8-10 times; (f) a significant increase in the effectiveness of the antibacterial action against Gram+ and Gram- cells was achieved (up to 3 times). Potentially, such an approach would significantly increase the effectiveness of therapies for a number of infectious and other diseases, reduce the dosage of antibiotics, shorten the duration of treatment, and reduce the risk of developing bacterial resistance. Moreover, the use of a polymer carrier with covalently bound organic molecules of different structures will avoid problems linked to different (suboptimal) solubility and bio-distribution of the administered molecules, which would be almost inevitable when using the same compounds separately. It would be very difficult to find antibiotic/adjuvant pairs that simultaneously achieve optimal concentrations in the same target cells. In our case, terpenoids and alkylbenzenes used as adjuvants are practically insoluble as individual compounds, and their unacceptable pharmacological properties would not allow them to be used as efflux pump inhibitors.

Differential Preincubation Effects of Nicardipine on OATP1B1- and OATP1B3-Mediated Transport in the Presence and Absence of Protein: Implications in Assessing OATP1B1- and OATP1B3-Mediated Drug-Drug Interactions

Impaired transport activity of hepatic OATP1B1 and OATP1B3 due to drug-drug interactions (DDIs) often leads to increased systemic exposure to substrate drugs (e.g., lipid-lowering statins). Since dyslipidemia and hypertension frequently coexist, statins are often concurrently used with antihypertensives, including calcium channel blockers (CCBs). OATP1B1/1B3-related DDIs in humans have been reported for several CCBs. To date, the OATP1B1/1B3-mediated DDI potential of CCB nicardipine has not been assessed. The current study was designed to assess the OATP1B1- and OATP1B3-mediated DDI potential of nicardipine using the R-value model, following the US-FDA guidance. IC50 values of nicardipine against OATP1B1 and OATP1B3 were determined in transporter-overexpressing human embryonic kidney 293 cells using [3H]-estradiol 17β-D-glucuronide and [3H]-cholecystokinin-8 as substrates, respectively, with or without nicardipine-preincubation in protein-free Hanks' Balanced Salt Solution (HBSS) or in fetal bovine serum (FBS)-containing culture medium. Preincubation with nicardipine for 30 min in protein-free HBSS buffer produced lower IC50 and higher R-values for both OATP1B1 and OATP1B3 compared to in FBS-containing medium, yielding IC50 values of 0.98 and 1.63 µM and R-values of 1.4 and 1.3 for OATP1B1 and OATP1B3, respectively. The R-values were higher than the US-FDA cut-off value of 1.1, supporting that nicardipine has the potential to cause OATP1B1/3-mediated DDIs. Current studies provide insight into the consideration of optimal preincubation conditions when assessing the OATP1B1/3-mediated DDIs in vitro.

Identification of polypharmacy patterns in new-users of metformin using the Apriori algorithm: A novel framework for investigating concomitant drug utilization through association rule mining

PURPOSE

With increased concomitant chronic diseases in type 2 diabetes mellitus (T2DM), the use of multiple drugs increases as well as the risk of drug-drug interactions (DDI) and adverse drug reactions (ADR). Nevertheless, how medication patterns vary in T2DM patients across different sex and age groups is unclear. This study aims to identify and quantify common drug combinations in first-time metformin users with polypharmacy (≥5 co-medications).

METHODS

New users of metformin were identified from the IQVIA Medical Research Data incorporating data from THIN, A Cegedim Database (2016-2019). A descriptive cohort study explored prescription patterns in patients with polypharmacy. The Apriori algorithm, used to find frequent item-sets in databases, was first-time applied to identify and quantify drug combinations of up to seven drugs to investigate potential harmful polypharmacy patterns.

RESULTS

The cohort included 34 169 new-users of metformin, of which 20 854 (61.0%) received polypharmacy. Atorvastatin was the most frequently co-prescribed drug with metformin overall (38.7%), in women (34.3%) and men (42.6%). In the stratified analysis, a higher proportion of women received polypharmacy (65.6%) compared to men (57.4%). Moreover, the proportion of patients receiving polypharmacy increased with age (18-39 years = 30.4%, 40-59 years = 50.5%, 60-74 years = 70.9%, and ≥75 years = 84.3%).

CONCLUSION

This study is the first to identify and quantify commonly prescribed combinations of drugs compounds in patients with polypharmacy using the Apriori algorithm. The high polypharmacy prevalence at all strata indicates the need to optimize polypharmacy to minimize DDI and ADR.

Evaluation of the drug-drug interaction potential of the novel hepatitis B and D virus entry inhibitor bulevirtide at OATP1B in healthy volunteers

Introduction: Bulevirtide is a first-in-class antiviral drug to treat chronic hepatitis B/D. We investigated the drug-drug interaction potential and pharmacokinetics of high-dose subcutaneous bulevirtide (5 mg twice daily) with organic anion transporting polypeptide 1B1 (OATP1B1) and cytochrome P450 (CYP) 3A4. Methods: This was a single-center, open-label, fixed-sequence drug-drug interaction trial in 19 healthy volunteers. Before and at bulevirtide steady state, participants ingested a single 40 mg dose of pravastatin. A midazolam microdose was applied to quantify CYP3A4 activity. Results: At bulevirtide steady state, pravastatin area under the concentration-time curve (AUC_0-∞) increased 1.32-fold (90% CI 1.08-1.61). The 5 mg bulevirtide twice-daily treatment resulted in a mean AUC_0-12 of 1210 h*ng/ml (95% CI 1040-1408) and remained essentially unchanged under the influence of pravastatin. CYP3A4 activity did not change to a clinically relevant extent. As expected, total bile acids increased substantially (35-fold) compared to baseline during bulevirtide treatment. All study medication was well tolerated. Discussion: The study demonstrated that high-dose bulevirtide inhibited OATP1B-mediated hepatic uptake of the marker substrate pravastatin but the extent is considered clinically not relevant. Changes in CYP3A4 activity were also not clinically relevant. In conclusion, this study suggests that OATP1B substrate drugs as well as CYP3A4 substrates may safely be used without dose adjustment in patients treated with bulevirtide. However, in patients using high statin doses and where concomitant factors potentially further increase statin exposure, caution may be required when using bulevirtide.

Predicting disruptions to drug pharmacokinetics and the risk of adverse drug reactions in non-alcoholic steatohepatitis patients

The liver plays a central role in the pharmacokinetics of drugs through drug metabolizing enzymes and transporters. Non-alcoholic steatohepatitis (NASH) causes disease-specific alterations to the absorption, distribution, metabolism, and excretion (ADME) processes, including a decrease in protein expression of basolateral uptake transporters, an increase in efflux transporters, and modifications to enzyme activity. This can result in increased drug exposure and adverse drug reactions (ADRs). Our goal was to predict drugs that pose increased risks for ADRs in NASH patients. Bibliographic research identified 71 drugs with reported ADRs in patients with liver disease, mainly non-alcoholic fatty liver disease (NAFLD), 54 of which are known substrates of transporters and/or metabolizing enzymes. Since NASH is the progressive form of NAFLD but is most frequently undiagnosed, we identified other drugs at risk based on NASH-specific alterations to ADME processes. Here, we present another list of 71 drugs at risk of pharmacokinetic disruption in NASH, based on their transport and/or metabolism processes. It encompasses drugs from various pharmacological classes for which ADRs may occur when used in NASH patients, especially when eliminated through multiple pathways altered by the disease. Therefore, these results may inform clinicians regarding the selection of drugs for use in NASH patients.

Prevention of Adverse Outcomes and Treatment Side Effects in Patients with Neuromuscular Disorders

In this article, we review prevention of serious adverse clinical outcomes and treatment side effects in patients with neuromuscular disorders including myopathies and myasthenia gravis. While neither of these entities is preventable, their course can often be modified, and severe sequelae may be prevented, with the identification of risk factors and proactive attention toward treatment planning.

Drug-Drug Interactions With Over-The-Counter Medicines: Mind the Unprescribed

BACKGROUND

This review provides a summary of the currently available clinical data on drug-drug interactions (DDIs) involving over-the-counter (OTC) medicines. It aims to educate and increase awareness among health care providers and to support decisions in daily practice.

METHODS

An extensive literature search was performed using bibliographic databases available through PubMed.gov. An initial structured search was performed using the keywords "drug-drug-interaction AND (over-the-counter OR OTC)," without further restrictions except for the language. The initial results were screened for all described DDIs involving OTC drugs, and further information was gathered specifically on these drugs using dedicated database searches and references found in the bibliography from the initial hits.

RESULTS

From more than 1200 initial hits (1972-June 2021), 408 relevant publications were screened for DDIs involving OTC drugs, leading to 2 major findings: first, certain types of drug regimens are more prone to DDIs or have more serious DDI-related consequences, such as antiretroviral, anti-infective, and oral anticancer therapies. Second, although most DDIs involve OTC drugs as the perpetrators, some prescription drugs (statins or phosphodiesterase-5 inhibitors) that currently have OTC status can be identified as the victims in DDIs. The following groups were identified to be frequently involved in DDIs: nonsteroidal anti-inflammatory drugs, food supplements, antacids, proton-pump inhibitors, H2 antihistamines, laxatives, antidiarrheal drugs, and herbal drugs.

CONCLUSIONS

The most significant finding was the lack of high-quality evidence for commonly acknowledged interactions. High-quality interaction studies involving different phenotypes in drug metabolism (cytochrome P450) and distribution (transporters) are urgently needed. This should include modern and critical drugs, such as oral anticancer medications and direct oral anticoagulants.

Geriatric Pharmacology Case Series: Direct Oral Anticoagulants for Older People With Cancer

This case study focuses on the treatment of a patient with cancer-associated venous thromboembolism (VTE). This is a common complication of cancer that can result in substantial morbidity and mortality. The case reviews the approach of analyzing older people with cancer-associated VTE and its treatment options.

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.

Promising effects of atorvastatin on mortality and need for mechanical ventilation in patients with severe COVID-19; a retrospective cohort study

PURPOSE

Considering the anti-inflammatory effect of atorvastatin and the role of medical comorbidities such as hypertension and coronary artery disease on the prognosis of the COVID-19 patients, we aimed to assess the effect of atorvastatin add-on therapy on mortality caused by COVID-19.

METHODS

We conducted a retrospective cohort study, including patients who were hospitalised with confirmed diagnosis of severe COVID-19. Baseline characteristics and related clinical data of patients were recorded. Clinical outcomes consist of in-hospital mortality, need for invasive mechanical ventilation and hospital length of stay. COX regression analysis models were used to assess the association of independent factors to outcomes.

RESULTS

Atorvastatin was administered for 421 of 991 patients. The mean age was 61.640 ± 17.003 years. Older age, higher prevalence of hypertension and coronary artery disease reported in patients who received atorvastatin. These patients have shorter hospital length of stay (P = .001). Based on COX proportional hazard model, in-hospital use of atorvastatin was associated with decrease in mortality (HR = 0.679, P = .005) and lower need for invasive mechanical ventilation (HR = 0.602, P = .014).

CONCLUSIONS

Atorvastatin add-on therapy in patient with severe COVID-19 was associated with lower in-hospital mortality and reduced the risk of need for invasive mechanical ventilation which supports to continue the prescription of the medication.

Evaluation of Pharmacokinetic Drug Interactions of the Direct-Acting Antiviral Agents Elbasvir and Grazoprevir with Pitavastatin, Rosuvastatin, Pravastatin, and Atorvastatin in Healthy Adults

BACKGROUND

Many people infected with hepatitis C virus have comorbidities, including hypercholesterolemia, that are treated with statins. In this study, we evaluated the drug-drug interaction potential of the hepatitis C virus inhibitors elbasvir (EBR) and grazoprevir (GZR) with statins. Pitavastatin, rosuvastatin, pravastatin, and atorvastatin are substrates of organic anion-transporting polypeptide 1B, whereas rosuvastatin and atorvastatin are also breast cancer resistance protein substrates.

METHODS

Three open-label, phase I clinical trials in healthy adults were conducted with multiple daily doses of oral GZR or EBR/GZR and single oral doses of statins. Trial 1: GZR 200 mg plus pitavastatin 10 mg. Trial 2: Part 1, GZR 200 mg plus rosuvastatin 10 mg, then EBR 50 mg/GZR 200 mg plus rosuvastatin 10 mg; Part 2, EBR 50 mg/GZR 200 mg plus pravastatin 40 mg. Trial 3: EBR 50 mg/GZR 200 mg plus atorvastatin 10 mg.

RESULTS

Neither GZR nor EBR pharmacokinetics were meaningfully affected by statins. Coadministration of EBR/GZR did not result in clinically relevant changes in the exposure of pitavastatin or pravastatin. However, EBR/GZR increased exposure to rosuvastatin (126%) and atorvastatin (94%). Coadministration of statins plus GZR or EBR/GZR was generally well tolerated.

CONCLUSIONS

Although statins do not appreciably affect EBR or GZR pharmacokinetics, EBR/GZR can impact the pharmacokinetics of certain statins, likely via inhibition of breast cancer resistance protein but not organic anion-transporting polypeptide 1B. Coadministration of EBR/GZR with pitavastatin or pravastatin does not require adjustment of either dose of statin, whereas the dose of rosuvastatin and atorvastatin should be decreased when coadministered with EBR/GZR.

Pharmacokinetic Estimation Models-based Approach to Predict Clinical Implications for CYP Induction by Calcitriol in Human Cryopreserved Hepatocytes and HepaRG Cells

Calcitriol, a vitamin D₃ metabolite, is approved for various indications because it is the bioactive form of vitamin D in the body. The purpose of this study was to predict the clinical significance of cytochrome P450 (CYP) induction by calcitriol using in vitro human cryopreserved hepatocytes, HepaRG experimental systems, and various pharmacokinetic estimation models. CYP2B6, 3A4, 2C8, and 2C9 mRNA levels increased in a concentration-dependent manner in the presence of calcitriol in human cryopreserved hepatocytes and HepaRG cells. Using the half maximal effective concentration (EC₅₀) and maximum induction effect (E_max) obtained from the in vitro study, a basic kinetic model was applied, suggesting clinical relevance. In addition, a static mechanistic model showed the improbability of a clinically significant effect; however, the calculated area under the plasma concentration-time curve ratio (AUCR) was marginal for CYP3A4 in HepaRG cells. To clarify the effect of CYP3A4 in vivo, physiologically based pharmacokinetic (PBPK) modeling was applied as a dynamic mechanistic model, revealing a low clinically significant effect of CYP3A4 induction by calcitriol. Therefore, we conclude that CYP induction by calcitriol treatment would not be clinically significant under typical clinical conditions.

Assessing OATP1B1- and OATP1B3-Mediated Drug-Drug Interaction Potential of Vemurafenib Using R-Value and Physiologically-Based Pharmacokinetic Models

Organic anion transporting polypeptides (OATP) 1B1 and OATP1B3 are important determinants of transporter-mediated drug-drug interactions (DDIs). Current studies assessed the OATP1B1 and OATP1B3-mediated DDI potential of vemurafenib, a kinase inhibitor drug with high protein binding and low aqueous solubility, using R-value and physiologically-based pharmacokinetic (PBPK) models. The total half-maximal inhibitory concentration (IC50,total) values of vemurafenib against OATP1B1 and OATP1B3 were determined in 100% human plasma in transporter-overexpressing human embryonic kidney 293 stable cell lines. The unbound fraction of vemurafenib in human plasma before (fu,plasma) and after addition into the uptake assay plate (fu,plasma,inc) were determined by rapid equilibrium dialysis. There was no statistically significant difference between fu,plasma and fu,plasma,inc. Vemurafenib IC50,total values against OATP1B1 and OATP1B3 are 175 ± 82 and 231 ± 26 μM, respectively. The R-values [R = 1 + fu,plasma × Iin,max/(fu,plasma,inc × IC50,total)] were then simplified as R = 1+Iin,max/IC50,total, and were 1.76 and 1.57 for OATP1B1 and OATP1B3, respectively. The simulated pravastatin AUC ratio was 1.28 when a single dose of pravastatin (40 mg) was co-administered with vemurafenib (960 mg, twice daily) at steady-state, compared to pravastatin alone. Both R-value and PBPK models predict that vemurafenib has the potential to cause OATP1B1- and OATP1B3-mediated DDIs.

Cholesterol-lowering drugs the simvastatin and atorvastatin change the protease activity of pepsin: An experimental and computational study

In this study, the effect of long-term use drugs of cholesterol-lowering atorvastatin and simvastatin on the activity and molecular structure of pepsin as important gastric enzyme was investigated by various experimental and computational methods. Based on the results obtained from fluorescence experiments, both drugs can bond to pepsin and quench the fluorescence intensity of protein through the static quenching mechanism. Also analysis of the thermodynamic parameters of binding the drugs to pepsin showed that the main forces in the complex formation for both are hydrophobic interactions and van der Waals forces. The effects of the drugs on the enzymatic activity of pepsin were then investigated and results showed that in the presence of both drugs the catalytic activity of the enzyme was significantly increased in lower (0.3-0.6 mM) concentrations however about the atorvastatin, increasing the concentration (0.9 mM) decreased the protease activity of pepsin. Also as a result of the FTIR studies, it was found that binding of the drugs to protein did not significant alteration in the structure of the protein. In order to obtain the atomic details of drug-protein interactions, the computational calculations were performed. The results in good agreement with those obtained from the experimental for interaction; confirm that the drugs both are bind to a cleft near the active site of the protein without any change in the structure of pepsin. Overall from the results obtained in this study, it can be concluded that both simvastatin and atorvastatin can strongly bond to a location close to the active site of pepsin and the binding change the enzymatic activity of protein.

Statin Intolerance in Clinical Practice

PURPOSE OF REVIEW

In our pilot study, we aimed to determine how many patients with the statin intolerance history referred to the specialized center for the diagnostics and treatment of lipoprotein metabolism disorders really suffer from a complete statin intolerance. The purpose of the study was to prove that complete statin intolerance is overestimated and overdiagnosed, and with the detailed knowledge of the issue and patient approach, it is possible to find an appropriate statin treatment for the most of patients.

RECENT FINDINGS

With the increasing number of statin users worldwide, the issue of statin intolerance has been a frequently discussed topic in recent years. There are many factors that play a role in the manifestation of statin intolerance (predisposing factors as age, sex, and some diseases), genetic factors leading to a different metabolism, drug-drug interactions, psychological reasons, and the negative influence of the mass media. However, it is estimated that true complete statin intolerance, defined by an intolerance of at least three statins at their usual lowest daily doses, occurs in approximately 3-6% of all statin users. In our pilot study, we conducted a retrospective analysis of 300 patients who were referred to the Center of Preventive Cardiology with a history of statin intolerance. During the follow-up treatment, 222 patients (74%) were able to use some statin (rosu-, atorva-, simva-, fluvastatin), and in 21% of the cases (63 patient), the target values according their CV risk level were even achieved. Only 78 patients (26%) were confirmed as being complete statin intolerant following a thorough therapeutic effort. The most tolerated statin was rosuvastatin.

Interpretation of Drug Interaction Using Systemic and Local Tissue Exposure Changes

Systemic exposure of a drug is generally associated with its pharmacodynamic (PD) effect (e.g., efficacy and toxicity). In this regard, the change in area under the plasma concentration-time curve (AUC) of a drug, representing its systemic exposure, has been mainly considered in evaluation of drug-drug interactions (DDIs). Besides the systemic exposure, the drug concentration in the tissues has emerged as a factor to alter the PD effects. In this review, the status of systemic exposure, and/or tissue exposure changes in DDIs, were discussed based on the recent reports dealing with transporters and/or metabolic enzymes mediating DDIs. Particularly, the tissue concentration in the intestine, liver and kidney were referred to as important factors of PK-based DDIs.

Repurposing of Existing Statin Drugs for Treatment of Microbial Infections: How Much Promising?

Today's microbial infections' resistance to approved drugs, the emergence of new infectious diseases and lack of vaccines, create a huge threat to human health. Thus, there is an urgent need to create novel antimicrobial agents, but the high cost and prolonged timeline of novel drug discovery and development is the major barrier to make new drugs. Therefore, there is a need for specific cost effective approaches in order to identify new drugs for the treatment of various microbial infections. Drug repurposition is an alternative technique to find existing clinically approved drugs for other indications. This approach may enhance the portfolio of Pharmaceutical companies by reducing the time and money required for the development of new chemical entity. In literature, various studies have reported some encouraging results regarding the antimicrobial use of existing statin drugs. Further, some clinical studies have also shown the protective effect of statin drugs in reduction of the morbidity and mortality due to many infectious diseases but complete understanding is still lacking. Thus, there is a need for better understanding of the use of statin drugs, especially in the context of antimicrobial effects. In this review, we try to summarize the use of statin drugs in various infectious diseases and their proposed antimicrobial mechanism of action. Further, current challenges and future perspectives of repurposition of statin drugs as antimicrobial agents have also been discussed.

A Drug-Drug Interaction Study to Evaluate the Effect of TAS-303 on CYP3A Activity in the Small Intestine and Liver

TAS‐303 (4‐piperidinyl 2,2‐diphenyl‐2‐[propoxy‐1,1,2,2,3,3,3‐d₇] acetate hydrochloride) is a novel selective noradrenaline reuptake inhibitor being developed for the treatment of stress urinary incontinence. An in vitro study and a physiologically based pharmacokinetic model simulation showed that TAS‐303 had inhibitory potential against cytochrome P450 (CYP) 3A. This open‐label, single‐group study investigated the effect of TAS‐303 on CYP3A activity by evaluating the pharmacokinetics (PK) of single‐dose oral simvastatin 5 mg or intravenous midazolam 1 mg after repeated oral administration of TAS‐303 3 mg in 12 healthy participants. TAS‐303 plus simvastatin resulted in a 1.326‐fold and a 1.420‐fold increase of simvastatin in peak plasma concentration and area under the plasma concentration‐time curve from time zero to time t, where t is the final time of detection (AUC_0‐t), respectively. The addition of midazolam resulted in a 1.090‐fold increase in the midazolam AUC_0‐t. TAS‐303 had a weak PK interaction with simvastatin but no apparent interaction with midazolam. TAS‐303 at 3 mg/day is a weak inhibitor of intestinal but not hepatic CYP3A activity. No clinically important safety concerns related to TAS‐303 were raised.

Interaction potential between clarithromycin and individual statins-A systematic review

The high prevalence of statin and clarithromycin utilization creates potential for overlapping use. The objectives of this MiniReview were to investigate the evidence base for drug-drug interactions between clarithromycin and currently marketed statins and to present management strategies for these drug combinations. We conducted a systematic literature review following PRISMA guidelines with English language studies retrieved from PubMed and EMBASE (from inception through March 2019). We included 29 articles (16 case reports, 5 observational, 5 clinical pharmacokinetic and 3 in vitro studies). Based on mechanistic/clinical studies involving clarithromycin or the related macrolide erythromycin (both strong inhibitors of CYP3A4 and of hepatic statin uptake transporters OATP1B1 and OATP1B3), clarithromycin is expected to substantially increase systemic exposure to simvastatin and lovastatin (>5-fold increase in area under the plasma concentration-time curve (AUC)), moderately increase AUCs of atorvastatin and pitavastatin (2- to 4-fold AUC increase) and slightly increase pravastatin exposure (≈2-fold AUC increase) while having little effect on fluvastatin or rosuvastatin. The 16 cases of statin-clarithromycin adverse drug reactions (rhabdomyolysis (n = 14) or less severe clinical myopathy) involved a CYP3A4-metabolized statin (simvastatin, lovastatin or atorvastatin). In line, a cohort study found concurrent use of clarithromycin and CYP3A4-metabolized statins to be associated with a doubled risk of hospitalization with rhabdomyolysis or other statin-related adverse events as compared with azithromycin-statin co-administration. If clarithromycin is necessary, we recommend (a) avoiding co-administration with simvastatin, lovastatin or atorvastatin; (b) withholding or dose-reducing pitavastatin; (c) continuing pravastatin therapy with caution, limiting pravastatin dose to 40 mg daily; and (d) continuing fluvastatin or rosuvastatin with caution.

Transporter-Mediated Drug-Drug Interactions and Their Significance

Drug transporters are considered to be determinants of drug disposition and effects/toxicities by affecting the absorption, distribution, and excretion of drugs. Drug transporters are generally divided into solute carrier (SLC) family and ATP binding cassette (ABC) family. Widely studied ABC family transporters include P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), and multidrug resistance proteins (MRPs). SLC family transporters related to drug transport mainly include organic anion-transporting polypeptides (OATPs), organic anion transporters (OATs), organic cation transporters (OCTs), organic cation/carnitine transporters (OCTNs), peptide transporters (PEPTs), and multidrug/toxin extrusions (MATEs). These transporters are often expressed in tissues related to drug disposition, such as the small intestine, liver, and kidney, implicating intestinal absorption of drugs, uptake of drugs into hepatocytes, and renal/bile excretion of drugs. Most of therapeutic drugs are their substrates or inhibitors. When they are comedicated, serious drug-drug interactions (DDIs) may occur due to alterations in intestinal absorption, hepatic uptake, or renal/bile secretion of drugs, leading to enhancement of their activities or toxicities or therapeutic failure. This chapter will illustrate transporter-mediated DDIs (including food drug interaction) in human and their clinical significances.

Variability in In Vitro OATP1B1/1B3 Inhibition Data: Impact of Incubation Conditions on Variability and Subsequent Drug Interaction Predictions

As the research into the organic anion transporting polypeptides (OATPs) continues to grow, it is important to ensure that the data generated are accurate and reproducible. In the in vitro evaluation of OATP1B1/1B3 inhibition, there are many variables that can contribute to variability in the resulting inhibition constants, which can then, in turn, contribute to variable results when clinical predictions (R-values) are performed. Currently, the only experimental condition recommended by the US Food and Drug Administration (FDA) is the inclusion of a pre-incubation period.¹ To identify other potential sources of variability, a descriptive analysis of available in vitro inhibition data was completed. For each of the 21 substrate/inhibitor pairs evaluated, cell type and pre-incubation were found to have the greatest effect on half-maximal inhibitory concentration (IC₅₀ ) variability. Indeed, when only HEK293 cells and co-incubation conditions were included, the observed variability for the entire data set (highest IC₅₀ /lowest) was reduced from 12.4 to 5.2. The choice of probe substrate used in the study also had a significant effect on inhibitor constant variability. Interestingly, despite the broad range of inhibitory constants identified, these two factors showed little effect on the calculated R-values relative to the FDA evaluation cutoff of 1.1 triggering a clinical evaluation for the inhibitors evaluated. However, because of the small data set available, further research is needed to confirm these preliminary results and define best practice for the study of OATPs.

The clinical significance of statins-macrolides interaction: comprehensive review of in vivo studies, case reports, and population studies

The objectives of this article were to review the mechanism and clinical significance of statins-macrolides interaction, determine which combination has the highest risk for the interaction, and identify key patients' risk factors for the interaction in relation to the development of muscle toxicity. A literature review was conducted in PubMed and Embase (1946 to December 2018) using combined terms: statins - as group and individual agents, macrolides - as group and individual agents, drug interaction, muscle toxicity, rhabdomyolysis, CYP3A4 inhibitors, and OAT1B inhibitors, with forward and backward citation tracking. Relevant English language in vivo studies in healthy volunteers, case reports, and population studies were included. The interaction between statins and macrolides depends on the type of statin and macrolide used. The mechanism of the interaction is due to macrolides' inhibition of CYP3A4 isoenzyme and OAT1B transporter causing increased exposure to statins. The correlation of this increased statin's exposure to the development of muscle toxicity could not be established, unless the patient had other risk factors such as advanced age, cardiovascular diseases, renal impairment, diabetes, and the concomitant use of other CYP3A4 inhibitors. Simvastatin, lovastatin, and to lesser extent atorvastatin are the statins most affected by this interaction. Rosuvastatin, fluvastatin, and pravastatin are not significantly affected by this interaction. Telithromycin, clarithromycin, and erythromycin are the most "offending" macrolides, while azithromycin appears to be safe to use with statins. This review presented a clear description of the clinical significance of this interaction in real practice. Also, it provided health care professionals with clear suggestions and recommendations on how to overcome this interaction. In conclusion, understanding the different characteristics of each statin and macrolide, as well as key patients' risk factors, will enable health care providers to utilize both groups effectively without compromising patient safety.

Pharmacokinetics of the Novel, Selective, Non-steroidal Mineralocorticoid Receptor Antagonist Finerenone in Healthy Volunteers: Results from an Absolute Bioavailability Study and Drug-Drug Interaction Studies In Vitro and In Vivo

BACKGROUND AND OBJECTIVES

Finerenone is a selective, non-steroidal mineralocorticoid receptor antagonist. In vivo and in vitro studies were performed to assess absolute bioavailability of finerenone, the effect of metabolic enzyme inhibitors on the pharmacokinetics of finerenone and its metabolites, the quantitative contribution of the involved enzymes cytochrome P450 (CYP) 3A4 and CYP2C8 and the relevance of gut wall versus liver metabolism.

METHODS

The pharmacokinetics, safety and tolerability of finerenone (1.25-10 mg orally or 0.25-1.0 mg intravenously) were evaluated in healthy male volunteers in four crossover studies. Absolute bioavailability was assessed in volunteers receiving finerenone orally and by intravenous infusion (n = 15) and the effects of erythromycin (n = 15), verapamil (n = 13) and gemfibrozil (n = 16) on finerenone pharmacokinetics were investigated. Finerenone was also incubated with cryopreserved human hepatocytes in vitro in the presence of erythromycin, verapamil or gemfibrozil.

RESULTS

Finerenone absolute bioavailability was 43.5% due to first-pass metabolism in the gut wall and liver. The geometric mean AUC_0-∞ ratios of finerenone (drug + inhibitor/drug alone) were 3.48, 2.70 and 1.10 with erythromycin, verapamil and gemfibrozil, respectively. The contribution ratio of CYP3A4 to the metabolic clearance of finerenone derived from these values was 0.88-0.89 and was consistent with estimations based on in vitro data, with the remaining metabolic clearance due to CYP2C8 involvement.

CONCLUSION

Finerenone is predominantly metabolized by CYP3A4 in the gut wall and liver. Increases in systemic exposure upon concomitant administration of inhibitors of this isoenzyme are predictable and consistent with in vitro data. Inhibition of CYP2C8, the second involved metabolic enzyme, has no relevant effect on finerenone in vivo.

Clinical Aspects of Transporter-Mediated Drug-Drug Interactions

Drug transporters play an essential role in disposition and effects of multiple drugs. Plasma concentrations of the victim drug can be modified by drug-drug interactions occurring in enterocytes (e.g., P-glycoprotein), hepatocytes (e.g., organic anion-transporting polypeptide 1B1 (OATP1B1)), and/or renal proximal tubular cells (e.g., organic cation transporter 2 (OCT2)/multidrug and toxin extrusion 1 and 2-K (MATE1/MATE2-K)). In addition, transporter-mediated drug-drug interactions can cause altered local tissue concentrations and possibly altered effects/toxicity (e.g., in liver and kidneys). During drug development, there is now an intensive in vitro screening of new molecular entities as transporter substrates and inhibitors, followed if necessary by drug-drug interaction studies in healthy volunteers. Nevertheless, there are still unresolved issues, which will also be discussed in this review article (e.g., the clinical significance of transporter-mediated drug-drug interactions of particular relevance to the elderly who are prescribed multiple drugs, with additional impaired liver or kidney function, and the extent to which medication safety in real life could be improved by a reduction of those interactions).

Impact of Genetic Variation on Pravastatin Systemic Exposure in Pediatric Hypercholesterolemia

This study investigated the impact of SLCO1B1 genotype on pravastatin systemic exposure in children and adolescents with hypercholesterolemia. Participants (8-20 years) with at least one allelic variant of SLCO1B1 c.521T>C (521TC, n = 15; 521CC, n = 2) and wild-type controls (521TT, n = 15) completed a single oral dose pharmacokinetic study. Interindividual variability of pravastatin acid (PVA) exposure within SLCO1B1 genotype groups exceeded the approximately twofold difference in mean PVA exposure observed between SLCO1B1 genotype groups (P > 0.05, q > 0.10). The 3'α-iso-pravastatin acid and lactone isomer formation in the acidic environment of the stomach prior to absorption also was variable and affected PVA exposure in all genotype groups. The SLCO1B1 c.521 gene variant contributing to variability in systemic exposure to PVA in our pediatric cohort was comparable to previous studies in adults. However, other demographic and physicochemical factors seem to also contribute to interindividual variability in the dose-exposure relationship.

Trends and variations in outpatient coprescribing of simvastatin or atorvastatin with potentially interacting drugs in Thailand

Background:

The aim of this study was to assess trends and variations in coprescribing of simvastatin or atorvastatin with interacting drugs in Thailand.

Methods:

Outpatient prescriptions between 2013 and 2015 in 26 tertiary care hospitals were analyzed for statin coprescribing. The proportion of patients exposed to coprescribing was estimated for semi-annual changes, using a time-series analysis and for hospital variations, using an interquartile range (IQR).

Results:

The coprescribing of simvastatin with all contraindicated drugs in 10 university and 16 general hospitals, respectively, was 3.6 and 3.1% in 2013, then decreased to 3.2 and 2.6% in 2014 and to 2.6 and 2.0% in 2015. The drug most frequently coprescribed with simvastatin, on a decreasing trend (by 0.19 percentage points) was gemfibrozil (in 2013, 2014 and 2015, respectively; 2.9, 2.3 and 2.0% in university hospitals, and 2.5, 2.0 and 1.6% in general hospitals). A similar trend was found in atorvastatin-gemfibrozil coprescribing. Patients coprescribed simvastatin with the rest of the contraindicated drugs were relatively stable at 0.6–0.8%. No protease inhibitors were coprescribed with simvastatin and atorvastatin. The IQR of simvastatin coprescribing in the university hospitals was smaller than that in the general hospitals and decreased over time.

Conclusions:

Coprescriptions potentially leading to drug interactions with simvastatin in Thailand were observed although the contraindicated drugs were acknowledged. Mutual awareness among health professionals and the implementation of electronic prescribing should be strengthened as zero drug interaction was possible as in the case of protease inhibitors in the present study.

Safety assessment of concurrent statin treatment and evaluation of drug interactions in China

Objectives

Acute muscle injury and potentially fatal rhabdomyolysis may occur with the use of statins and certain enzyme inhibitors, but data on this topic from China are quite limited. This study aimed to measure the concomitant exposure of patients to different statins and their enzyme inhibitors or interacting medications in 76 hospitals in six Chinese cities.

Methods

Prescription database was retrieved from Hospital Prescription Analysis Cooperation Project from January 2015 to December 2015, covering 76 tertiary facilities in six cities in China. Every evidence-based enzyme inhibitor was included, and labeled enzyme inhibitors and other relevant information were identified and obtained using the Drug Safety Update from the UK Medicines and Healthcare Products Regulatory Agency. The proportions of different statin types among all patients and those co-medicated with their inhibitors were examined.

Results

A total of 296,765 patients exposed to statins were included in this study. 80% of patients (n = 144,863, 80.5%) were concomitantly prescribed a CYP3A4-metabolized statin with an interacting drug during the study period. Among those prescribed a non-CYP3A4-metabolized statin, 40.0% of patients were concomitantly given an interacting drug, and approximately 20% of patients were concomitantly given a labeled inhibitor, predominantly calcium channel blockers, other statins, and fibrates. Rates of co-prescription were higher in patients aged over 65 years and in patients taking high-dose statins.

Conclusion

Statins were frequently co-prescribed with metabolic inhibitors in China, where drug safety strategy on highlighting warnings and contraindications of statins are still lacking. For high-dose statins patients who are over 65 years and co-administered with any metabolic inhibitors, prescribers and pharmacists should be more concerned in order to prevent adverse drug reactions.

Update on colchicine, 2017

Colchicine is an ancient medication that is currently approved for the treatment of gout and FMF. However, colchicine has a wide range of anti-inflammatory activities, and studies indicate that it may be beneficial in a variety of other conditions. This paper reviews the evidence for the well-established use of colchicine in gout, as well as several other rheumatic diseases. In addition, we highlight the potential benefit of colchicine in cardiac disease, including coronary artery disease in patients both with and without gout.

A cooperation project between hospital pharmacists and general practitioners about drug interactions in clinical practice

Objectives

(1) To evaluate drug-drug interactions (DDIs) in general practitioners' (GPs) prescriptions; (2) to implement a cooperation project between pharmacists and GPs to improve DDI management and patient care.

Methods

In 2013, pharmacists from the Community Drug Assistance ASL TO1 launched a cooperation project involving 48 GPs. As a first step, GPs were asked to select, from a list, drug associations for which they recommended analysis of occurrence in their prescriptions. The pharmacists (1) analysed GPs' prescriptions dated 2012-2014, according to the list of DDIs selected (n= 9); (2) evaluated solutions for DDI management, using the Micromedex DDI checker database and literature analysis; they then (3) disseminated DDI-related information to GPs through training meetings and (4) assessed the efficacy of these actions through a questionnaire submitted to the GPs in 2013.

Results

(1) Prescriptions analysis: a reduction in the number of DDIs was observed (-14% in 2013 vs 2012, -9% in 2014 vs 2012); in some cases these reductions were statistically significant (calcium carbonate + proton pump inhibitors (PPIs) -50%, p<0.0041, amoxicillin+lansoprazole -42%, p<0.0088). (2) Questionnaire: this was completed by 75% of GPs. The literature analysis was considered interesting by 94% of GPs; solutions were adopted by 89% of GPs and 34% of GPs affirmed that clinical improvements after application of the measures were observed in their patients, even if they could not provide quantitative data for this outcome.

Conclusion

The cooperation project between pharmacists and GPs was effective because it established a professional exchange between the two health professionals. The pharmacist gave support to GPs, which benefited the patients, who gained clinical improvements and improved satisfaction with their medical care, as declared by the GPs in answers to the questionnaire.

Pretreatment With Rifampicin and Tyrosine Kinase Inhibitor Dasatinib Potentiates the Inhibitory Effects Toward OATP1B1- and OATP1B3-Mediated Transport

Present studies determined the effects of pretreatment with rifampicin, an organic anion-transporting polypeptide (OATP) inhibitor, and the tyrosine kinase inhibitor dasatinib on OATP1B1- and OATP1B3-mediated transport, and evaluated the OATP-mediated drug-drug interaction potential of dasatinib using the static R-value and dynamic physiologically based pharmacokinetic models. Rifampicin and dasatinib pretreatment significantly decreased OATP1B1- and OATP1B3-mediated transport. Rifampicin pretreatment also significantly decreased [3H]-pitavastatin and [3H]-CCK-8 accumulation in human sandwich-cultured hepatocytes. Present studies revealed that estrone-3-sulfate is a less-sensitive OATP1B1 substrate than estradiol-17β-glucuronide in assessing rifampicin pretreatment effects. Pretreatment with rifampicin and dasatinib reduced the inhibition constant (Ki) values against OATP1B1 by 3 and 2.1 fold and against OATP1B3 by 2.4 and 2.1 fold, respectively. The in vitro rifampicin Ki values after preincubation are comparable to the estimated in vivo Ki reported previously. Models predict that dasatinib has a low potential to cause OATP1B1- and OATP1B3-mediated drug-drug interactions. Time-lapse confocal microscopy demonstrated that rifampicin and dasatinib pretreatment did not affect plasma membrane localization of green-fluorescent protein-tagged OATP1B1 (GFP-OATP1B1) and GFP-OATP1B3 in human embryonic kidney 293 stable cell lines. In summary, we report novel findings that pretreatment with rifampicin and dasatinib potentiates the inhibitory effects toward OATP1B1 and OATP1B3 without affecting plasma membrane levels of the transporters.

Simvastatin modulates gene expression of key receptors in zebrafish embryos

Nuclear receptors (NR) are involved in the regulation of several metabolic processes and it is well known that these constituents may be modulated by different chemicals classes, including pharmaceuticals that may activate or antagonize NR. In mammals, some pharmaceuticals modulate the transcription of pregnane X receptor, Pxr, peroxisome proliferator activated receptor, Ppars, and aryl hydrocarbon receptor, Ahr, affecting mRNA expression of genes belonging to various regulatory pathways, including lipid metabolism and detoxification mechanisms. The aim of this study was to determine the effects of simvastatin (SIM), an anticholesterolemic drug, on selected NR and AhR mRNA transcription levels during zebrafish early development. Embryos were collected at different development stages (0, 2, 6, 14, 24, 48, and 72 hr post fertilization (hpf)) and mRNA of all target NR was detected at all time points. Embryos (1 and 24 hpf) were exposed to different concentrations of SIM (5 or 50 μg/L) in two differing assays with varying exposure times (2 or 80 hr). The transcription levels of ahr2, raraa, rarab, rarga, pparαa, pparβ1, pparγ, pxr, rxraa, rxrab, rxrbb, rxrga, rxrgb, as well as levels of cholesterol (Chol) were measured after exposure. SIM exerted no marked effect on Chol levels, and depending upon exposure duration mRNA levels of NR and AhR either increased or decreased. After 2 hr SIM treatment in 24 hpf embryos, transcription of ppars, pxr, and ahr was up-regulated, while after 80 hr mRNA levels of pxr and ahr were decreased with no marked changes in ppars. Data demonstrate that SIM produced alterations in gene expression of NR which are involved in varying physiological functions and that may disturb regulation of different physiological processes which might impair fish survival and ecosystems regeneration.

Cardiovascular Ion Channel Inhibitor Drug-Drug Interactions with P-glycoprotein

P-glycoprotein (Pgp) is an ATP-binding cassette (ABC) transporter that plays a major role in cardiovascular drug disposition by effluxing a chemically and structurally diverse range of cardiovascular therapeutics. Unfortunately, drug-drug interactions (DDIs) with the transporter have become a major roadblock to effective cardiovascular drug administration because they can cause adverse drug reactions (ADRs) or reduce the efficacy of drugs. Cardiovascular ion channel inhibitors are particularly susceptible to DDIs and ADRs with Pgp because they often have low therapeutic indexes and are commonly coadministered with other drugs that are also Pgp substrates. DDIs from cardiovascular ion channel inhibitors with the transporter occur because of inhibition or induction of the transporter and the transporter's tissue and cellular localization. Inhibiting Pgp can increase absorption and reduce excretion of drugs, leading to elevated drug plasma concentrations and drug toxicity. In contrast, inducing Pgp can have the opposite effect by reducing the drug plasma concentration and its efficacy. A number of in vitro and in vivo studies have already demonstrated DDIs from several cardiovascular ion channel inhibitors with human Pgp and its animal analogs, including verapamil, digoxin, and amiodarone. In this review, Pgp-mediated DDIs and their effects on pharmacokinetics for different categories of cardiovascular ion channel inhibitors are discussed. This information is essential for improving pharmacokinetic predictions of cardiovascular therapeutics, for safer cardiovascular drug administration and for mitigating ADRs emanating from Pgp.