Altered nonrenal drug clearance in ESRD:

Impact of renal function on Ticagrelor-induced antiplatelet effects in coronary artery disease patients

Background

Chronic renal failure (CKD) is associated with the presence of increased platelet reactivity and lower clinical benefit of clopidogrel. Ticagrelor has a more favorable pharmacodynamic and pharmacokinetic profile compared to clopidogrel, which has translated into better clinical outcomes in patients with acute coronary syndrome (ACS). We conducted a prospective mechanistic cohort study in order to investigate the impact of renal failure on the pharmacokinetics and pharmacodynamics of ticagrelor in patients with acute ACS.

Methods

Patients were divided into two groups based on their estimated renal clearances (eGFR ≥ 60 mL/min and eGFR < 60 mL/min). Platelet function was determined using the VerifyNow system at baseline, after the ticagrelor loading dose and at discharge. In addition, levels of ticagrelor and its active metabolite (AR-C124910XX) were determined in the first hour after loading dose.

Results

48 patients were recruited (eGFR ≥ 60 mL/min: 35 and eGFR < 60 mL/min: 13). There were no significant differences between the groups in terms of platelet inhibition after the loading or after 7 days of treatment (p = 0.219). However, the levels of ticagrelor and its active metabolite were lower in subjects with normal renal function than in CKD, especially at 4 (p = 0.02 and 0.04 respectively) and 6 h of loading (p = 0.042 and 0.08 respectively).

Conclusion

No differences in platelet inhibition were observed after treatment with ticagrelor in patients with different renal function, although patients with renal impairment showed higher levels of ticagrelor and AR-C124910XX after 4 h of the loading dose.

Olaparib in an ovarian cancer patient with end-stage renal disease and hemodialysis

PURPOSE

For patients with severe renal impairment (CrCl ≤ 30 ml/min) or end-stage renal disease (ESRD), olaparib intake is not recommended as the pharmacokinetics and safety of olaparib have not been evaluated in this patient group. Therefore, this valuable patient group is generally excluded from poly(ADP-ribose) polymerase inhibitor (PARPi) therapy. Here we report the pharmacokinetics (PK), efficacy, safety and tolerability of olaparib capsules 200 mg BID in a patient with recurrent epithelial ovarian cancer (EOC) and ESRD requiring hemodialysis.

METHODS

Blood and dialysate samples of the patient were collected on a dialysis and non-dialysis day. Olaparib total plasma concentrations were determined through high-performance liquid chromatography with tandem mass spectrometric detection. Actual scheduled sample times were used in the PK analysis to determine multiple dose PK parameters at steady state.

RESULTS

Maximum concentration was achieved 1.5 h after drug administration on non- dialysis and after 1 h on dialysis day. The steady-state trough concentration and the maximal plasma concentration were similar on dialysis and non- dialysis day. On non-dialysis day, the AUC_ss was 30% higher (24.0 µg.h/mL vs. 16.9 µg.h/ml) than on dialysis day. The plasma clearance CL_ss/F was lower on non-dialysis day. Olaparib was not detectable in the dialysate samples.

CONCLUSION

A total dose of olaparib 200 mg BID capsule formulation was well tolerated by our patient with ESRD and hemodialysis. Moreover, this maintenance therapy led to 16 months of progression free survival. Further trials on PARPi therapy in patients with hemodialysis are warranted.

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Effect of renal impairment on the pharmacokinetics and safety of dorzagliatin, a novel dual-acting glucokinase activator

Dorzagliatin is a novel allosteric glucokinase activator targeting both pancreatic and hepatic glucokinase currently under clinical investigation for treatment of type 2 diabetes (T2D). This study aimed to investigate the effect of renal impairment (RI) on dorzagliatin’s pharmacokinetics (PKs) and safety, and to guide appropriate clinical dosing in patients with diabetic kidney disease, including end‐stage renal disease (ESRD). Based on the results from physiologically‐based pharmacokinetic modeling, the predicted outcome of RI on dorzagliatin PK property would be minimum that the plasma exposure area under concentration (AUC) of dorzagliatin in patients with ESRD would increase at about 30% with minimal change in peak concentration (C_max) comparing to those in healthy volunteers (HVs). To definitively confirm the prediction, a two‐part RI study was designed and conducted based on regulatory guidance starting with the patients with ESRD matched with HVs. Results of the RI study showed minimum difference between patients with ESRD and HVs with respect to dorzagliatin exposure with geometric mean ratio of ESRD to HV at 0.81 for C_max and 1.11 for AUC. The elimination half‐life, volume of distribution, and systemic clearance for dorzagliatin were similar between the two groups. Dorzagliatin was well‐tolerated in patients with ESRD during the study. Therefore, RI showed no significant impact on dorzagliatin PK, suggesting that dorzagliatin can be readily used in patients with T2D at all stages of RI without need for dose adjustment.

Application of Individualized PBPK Modeling of Rate Data to Evaluate the Effect of Hemodialysis on Nonrenal Clearance Pathways

The aim of this study was to apply individualized, physiologically based pharmacokinetic modeling of ¹⁴ CO₂ production rates (iPBPK-R) measured by the erythromycin breath test to characterize the effect of hemodialysis on the function of nonrenal clearance pathways in patients with end-stage renal disease. Twelve patients previously received ¹⁴ C-erythromycin intravenously pre- and post-hemodialysis. Serial breath samples were collected after each dose over 2 hours. Eight PBPK parameters were co-estimated across periods, whereas activity of cytochrome P450 (CYP) 3A4 clearance was independently estimated for each period. Inhibition coefficients for organic anion transporting polypeptide (OATP), P-glycoprotein, and multidrug resistance-associated protein 2 activities were also estimated. Nonrenal clearance parameter estimates were explored regarding sex differences and correlations with uremic toxins and were used in hierarchical cluster analysis (HCA). Relationships between the function of nonrenal clearance pathways and uremic toxin concentrations were explored. Mean CYP 3A4 clearance increased by 2.2% post-hemodialysis. Uptake transporter activity was highly intervariable across hemodialysis. Females had 22% and 30% higher median CYP3A4 activity than males pre- and post-hemodialysis, respectively. Exploratory HCA indicated that using both CYP3A4 and OATP activity parameters at pre- and post-hemodialysis best identifies heterogeneous patients. This is the first study to use the iPBPK-R approach to simultaneously estimate multiple in vivo nonrenal elimination pathways in individual patients with kidney disease and to assess the effect of hemodialysis.

Dose Optimization in Kidney Disease: Opportunities for PBPK Modeling and Simulation

Kidney disease affects pharmacokinetic (PK) profiles of not only renally cleared drugs but also nonrenally cleared drugs. The impact of kidney disease on drug disposition has not been fully elucidated, but describing the extent of such impact is essential for conducting dose optimization in kidney disease. Accurate evaluation of kidney function has been a clinical interest for dose optimization, and more scientists pay attention and conduct research for clarifying the role of drug transporters, metabolic enzymes, and their interplay in drug disposition as kidney disease progresses. Physiologically based pharmacokinetic (PBPK) modeling and simulation can provide valuable insights for dose optimization in kidney disease. It is a powerful tool to integrate discrete knowledge from preclinical and clinical research and mechanistically investigate system- and drug-dependent factors that may contribute to the changes in PK profiles. PBPK-based prediction of drug exposures may be used a priori to adjust dosing regimens and thereby minimize the likelihood of drug-related toxicity. With real-time clinical studies, parameter estimation may be performed with PBPK approaches that can facilitate identification of sources of interindividual variability. PBPK modeling may also facilitate biomarker research that aids dose optimization in kidney disease. U.S. Food and Drug Administration guidances related to conduction of PK studies in kidney impairment and PBPK documentation provide the foundation for facilitating model-based dose-finding research in kidney disease.

Inflammation is a major regulator of drug metabolizing enzymes and transporters: Consequences for the personalization of drug treatment

Inflammation is an evolutionary process that allows survival against acute infection or injury. Inflammation is also a pathophysiological condition shared by numerous chronic diseases. In addition, inflammation modulates important drug-metabolizing enzymes and transporters (DMETs), thus contributing to intra- and interindividual variability of drug exposure. A better knowledge of the impact of inflammation on drug metabolism and its related clinical consequences would help to personalize drug treatment. Here, we summarize the kinetics of inflammatory mediators and the underlying transcriptional and post-transcriptional mechanisms by which they contribute to the inhibition of important DMETs. We also present an updated overview of the effect of inflammation on the pharmacokinetic parameters of most of the drugs that are DMET substrates, for which therapeutic drug monitoring is recommended. Furthermore, we provide opinions on how to integrate the inflammatory status into pharmacogenetics, therapeutic drug monitoring, and population pharmacokinetic strategies to improve the personalization of drug treatment for each patient.

Pharmacotherapeutic Management of Neuropathic Pain in End-Stage Renal Disease

Background

Chronic noncancer pain is pervasive throughout the general patient population, transcending all chronic disease states. Patients with end-stage renal disease (ESRD) present a complicated population for which medication management requires careful consideration of the pathogenesis of ESRD and intimate knowledge of pharmacology. The origin of pain must also guide treatment options. As such, the presentation of neuropathic pain in ESRD can present a challenging case. The authors aim to provide a review of available classes of medications and considerations for the treatment of neuropathic pain in ESRD.

Summary

In this narrative review, the authors discuss important strategies and considerations for the treatment of neuropathic pain in ESRD, including the pathogenesis of neuropathic pain, physiological changes for consideration in ESRD patients, and disease-specific consideration for medication selection. Pharmacotherapeutic classes discussed include: anticonvulsants, antiarrhythmics, antidepressants, topicals, and opioids.

Key Message

Pain management in ESRD patients requires careful assessment of drug-specific properties, accumulation, metabolism (presence of active/toxic metabolites), extraction by dialysis, and presence of drug - drug interactions. In the absence of pharmacokinetic data in ESRD patients, therapeutic window and potential risks should be factored in the decision making along with continued monitoring throughout therapy.

Simultaneous Assessment of Hepatic Transport and Metabolism Pathways with a Single Probe Using Individualized PBPK Modeling of 14CO2 Production Rate Data

Erythromycin is a substrate of cytochrome P4503A4 (CYP3A4) and multiple drug transporters. Although clinical evidence suggests that uptake transport is likely to play a dominant role in erythromycin's disposition, the relative contributions of individual pathways are unclear. Phenotypic evaluation of multiple pathways generally requires a probe drug cocktail. This approach can result in ambiguous conclusions due to imprecision stemming from overlapping specificity of multiple drugs. We hypothesized that an individualized physiologically based pharmacokinetic modeling approach incorporating 14CO2 production rates (iPBPK-R) of the erythromycin breath test (ERMBT) would enable us to differentiate the contribution of metabolic and transporter pathways to erythromycin disposition. A seven-compartmental physiologically based pharmacokinetic (PBPK) model was built for 14C-erythromycin administered intravenously. Transporter clearance and CYP3A4 clearance were embedded in hepatic compartments. 14CO2 production rates were simulated taking the first derivative of by-product 14CO2 concentrations. Parameters related to nonrenal elimination pathways were estimated by model fitting the ERMBT data of 12 healthy subjects individually. Optimized iPBPK-R models fit the individual rate data well. Using one probe, nine PBPK parameters were simultaneously estimated per individual. Maximum velocity of uptake transport, CYP3A4 clearance, total passive diffusion, and others were found to collectively control 14CO2 production rates. The median CYP3A4 clearance was 12.2% of the input clearance. Male subjects had lower CYP3A4 activity than female subjects by 11.3%. We applied iPBPK-R to ERMBT data to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways in healthy subjects. The iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. SIGNIFICANCE STATEMENT: Our developed individualized physiologically based pharmacokinetic modeling approach incorporating rate data (iPBPK-R) enabled us to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways of erythromycin in healthy subjects. A new interpretation of erythromycin breath test (ERMBT) data was also obtained via iPBPK-R. We found that rate data have rich information allowing estimation of per-person PBPK parameters. This study serves as proof of principle that the iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. iPBPK-R can be applied to other rate-derived data beyond ERMBT. Potential areas of application include drug-drug interaction, pathophysiological effects on drug disposition, and the role of biomarkers on hemodialysis efficiency utilizing estimated adjustment factors with correlation analysis.

Development of a physiologically-based pharmacokinetic model for cyclosporine in Asian children with renal impairment

This study aimed to assess the pharmacokinetics of cyclosporine A (CsA) in Asian children with renal impairment (RI) by developing a physiologically-based pharmacokinetic (PBPK) model with Simcyp Simulator. The PBPK model of Asian children with RI was developed by modifying the physiological parameters of the built-in population libraries in Simcyp Simulator. The ratio of healthy and RI populations was obtained for each parameter showing a difference between the populations. Each ratio was multiplied by the corresponding parameter in healthy Asian children. The model verification was performed with published data of Korean children with kidney disease given multiple CsA administrations. Simulations were performed with different combinations of ethnicity, age, and renal function to identify the net impact of each factor. The simulated results suggested that the effect of RI was higher in children than adults for both Caucasian and Asian. In conclusion, the constructed model adequately characterized CsA pharmacokinetics in Korean children with RI. Simulations with populations categorized by ethnicity, age, and renal function enabled to assess the net impact of each factor on specific populations.

The effect of chronic kidney disease on CYP2B expression and activity in male Wistar rats

Chronic kidney disease (CKD) is characterized by progressive reduction in kidney function over time. CKD affects greater than 10% of the population and its incidence is on the rise due to the growing prevalence of its risk factors. Previous studies demonstrated CKD alters nonrenal clearance of drugs in addition to reducing renal clearance. We assessed the function and expression of hepatic CYP2B enzymes using a rat model of CKD. CKD was induced in Wistar rats by supplementing their chow with adenine and confirmed through the detection of elevated uremic toxins in plasma. Liver enzymes AST and ALT were unchanged by the adenine diet. Bupropion was used as a probe substrate for hepatic CYP2B function using rat liver microsomes. The resulting metabolite, hydroxy-bupropion, and bupropion were quantified by ultra-performance liquid chromatography coupled to time-of-flight mass spectrometry. Level of mRNA and protein were determined by RT-PCR and Western blot, respectively. The results of our study demonstrate that CYP2B1 is downregulated in a rat model of CKD. CYP2B1 mRNA level was significantly decreased (88%, P < 0.001) in CKD relative to control. Similarly, maximal enzymatic velocity (Vmax) for CYP2B was decreased by 46% in CKD relative to control (P < 0.0001). Previous studies involving patients with CKD demonstrated altered bupropion pharmacokinetics compared to control. Hence, our results suggest that these alterations may be mediated by attenuated CYP2B hepatic metabolism. This finding may partially explain the alterations in pharmacokinetics and nonrenal drug clearance frequently observed in patients with CKD.

Medication Safety Principles and Practice in CKD

Ensuring patient safety is a priority of medical care because iatrogenic injury has been a primary concern. Medications are an important source of medical errors, and kidney disease is a thoroughfare of factors threatening safe administration of medicines. Principal among these is reduced kidney function because almost half of all medications used are eliminated via the kidney. Additionally, kidney patients often suffer from multimorbidity, including diabetes, hypertension, and heart failure, with a range of prescribers who often do not coordinate treatments. Patients with kidney disease are also susceptible to further kidney injury and metabolic derangements from medications, which can worsen the disease. In this review, we will present the key issues and threats to safe medication use in kidney disease, with a focus on predialysis CKD, as the scope of medication safety in ESKD and transplantation are unique and deserve their own consideration. We discuss drugs that need to be avoided or dose modified, and review the complications of a range of medications routinely administered in CKD, as these also call for cautious use.

The critical interaction between valproate sodium and warfarin: case report and review

BACKGROUND

Valproic acid (VPA) and warfarin are commonly prescribed for patients with epilepsy and concomitant atrial fibrillation (AF). When VPA and warfarin are prescribed together, clinically important interactions may occur. VPA may replace warfarin from the protein binding sites and result in an abnormally increased anticoagulation effect. This is commonly underrecognized.

CASE PRESENTATION

In our case, we report a 78-year-old woman with a glioma who presented with status epilepticus. The patient was on warfarin to prevent cardiogenic embolism secondary to AF. Intravenous loading dose of VPA was administered, but international normalized ratio (INR) increased significantly to 8.26. Intravenous vitamin K1 was then given and the patient developed no overt bleeding during the hospitalization.

CONCLUSION

By reviewing the literature and discussing the critical interaction between valproate sodium and warfarin, we conclude that intravenous VPA and the co-administrated warfarin may develop critical but underrecognized complications due to effects on the function of hepatic enzymes and displacement of protein binding sites.

Microbiota-derived uremic retention solutes: perpetrators of altered nonrenal drug clearance in kidney disease

INTRODUCTION

Scientific interest in the gut microbiota is increasing due to improved understanding of its implications in human health and disease. In patients with kidney disease, gut microbiota-derived uremic toxins directly contribute to altered nonrenal drug clearance. Microbial imbalances, known as dysbiosis, potentially increase formation of microbiota-derived toxins, and diminished renal clearance leads to toxin accumulation. High concentrations of microbiota-derived toxins such as indoxyl sulfate and p-cresol sulfate perpetrate interactions with drug metabolizing enzymes and transporters, which provides a mechanistic link between increases in drug-related adverse events and dysbiosis in kidney disease. Areas covered: This review summarizes the effects of microbiota-derived uremic toxins on hepatic phase I and phase II drug metabolizing enzymes and drug transporters. Research articles that tested individual toxins were included. Therapeutic strategies to target microbial toxins are also discussed. Expert commentary: Large interindividual variability in toxin concentrations may explain some differences in nonrenal clearance of medications. Advances in human microbiome research provide unique opportunities to systematically evaluate the impact of individual and combined microbial toxins on drug metabolism and transport, and to explore microbiota-derived uremic toxins as potential therapeutic targets.

Phase I trial to investigate the effect of renal impairment on isavuconazole pharmacokinetics

Purpose

The purpose of the study is to evaluate the effect of renal impairment (RI) and end-stage renal disease (ESRD) on the pharmacokinetics (PK) of isavuconazole and the inactive cleavage product, BAL8728.

Methods

A single intravenous dose of the prodrug isavuconazonium sulfate (372 mg, equivalent to 200 mg isavuconazole and 75 mg of BAL8728 cleavage product) was administered to healthy controls (parts 1 and 2) and participants with mild, moderate, or severe RI (part 2) or ESRD (part 1); ESRD participants received two doses of 200 mg isavuconazole, 1 h post-dialysis (day 1) and prior to dialysis (day 15). Plasma PK parameters for isavuconazole included maximum concentration (C_max), area under the concentration–time curve (AUC) from time of dose to 72 h (AUC₇₂), AUC extrapolated to infinity (AUC_∞), AUC to last measurable concentration (AUC_last), half-life (t_½ h), volume of distribution (V_z), and total clearance (CL), for the healthy control group versus those with mild, moderate, or severe RI or ESRD.

Results

Isavuconazole C_max values were 4% higher in mild RI and 7, 14, and 21% lower in participants with moderate RI, severe RI, or ESRD versus the healthy control group, respectively. When hemodialysis occurred post-dose (day 15), participants with ESRD had a 30% increase in AUC₇₂ for isavuconazole in parallel with reduction of extracellular volume induced by dialysis. Exposure (AUC_∞ and AUC_last) was not significantly different for participants with mild, moderate, or severe RI versus healthy controls although there was considerable variability. The t_1/2 (day 1) was 125.5 ± 63.6 h (healthy control group), 204.5 ± 82.6 h (ESRD group) in part 1, and 140.5 ± 77.7 h (healthy control group), 117.0 ± 66.2 h (mild RI), 158.5 ± 56.4 h (moderate RI), and 145.8 ± 65.8 L/h (severe RI) in part 2. CL was 2.4 ± 0.8 L/h (healthy control group) and 2.9 ± 1.3 L/h (ESRD group) in part 1 and 2.4 ± 1.2 L/h (healthy control group), 2.5 ± 1.0 L/h (mild RI), 2.2 ± 0.8 L/h (moderate RI), and 2.4 ± 0.8 L/h (severe RI) in part 2. The V_z was 382.6 ± 150.6 L in the healthy control group and 735.6 ± 277.3 L in ESRD patients on day 1 in part 1 of the study. In part 2 of the study, V_z was 410.8 ± 89.7 L in the healthy control group, 341.6 ± 72.3 L in mild RI, 509.1 ± 262.2 L in moderate RI, and 439.4 L in severe RI.

Conclusions

Based on the findings of this study, dose adjustments of isavuconazole are unlikely to be required in individuals with RI or in those with ESRD who receive hemodialysis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-017-2213-7) contains supplementary material, which is available to authorized users.

Influence of chronic kidney disease and haemodialysis treatment on pharmacokinetics of nebivolol enantiomers

AIM

The present study evaluated the pharmacodynamics and pharmacokinetics of nebivolol enantiomers in patients with chronic kidney disease (CKD) and in patients undergoing haemodialysis.

METHODS

Forty-three adult patients were distributed into three groups: healthy volunteers and hypertensive patients with normal kidney function (n = 22); patients with stage 3 and 4 CKD (n = 11); and patients with stage 5 CKD undergoing haemodialysis (n = 10). The subjects received a single oral dose of 10 mg racemic nebivolol. Serial blood samples were collected up to 48 h after administration of the drug and heart rate variation was measured over the same interval during the isometric handgrip test. The nebivolol enantiomers in plasma were analysed by liquid chromatography-tandem mass spectrometry.

RESULTS

The pharmacokinetics of nebivolol is enantioselective, with a greater plasma proportion of l-nebivolol. CKD increased the area under the concentration-time curve (AUC) of l-nebivolol (6.83 ng.h ml(-1) vs. 9.94 ng.h ml(-1) ) and d-nebivolol (4.15 ng.h ml(-1) vs. 7.30 ng.h ml(-1) ) when compared with the control group. However, the AUC values of l-nebivolol (6.41 ng.h ml(-1) ) and d-nebivolol (4.95 ng.h ml(-1) ) did not differ between the haemodialysis and control groups. The administration of a single dose of 10 mg nebivolol did not alter the heart rate variation induced by isometric exercise in the investigated patients.

CONCLUSIONS

Stage 3 and 4 CKD increases the plasma concentrations of both nebivolol enantiomers, while haemodialysis restores the pharmacokinetic parameters to values similar to those observed in the control group. No significant difference in heart rate variation induced by isometric exercise was observed between the investigated groups after the administration of a single oral dose of 10 mg nebivolol.

Effect of diseases on response to vitamin K antagonists

INTRODUCTION

The purpose of this review article is to summarize the literature on diseases that are documented to have an effect on response to warfarin and other VKAs.

METHODS

We searched the English literature from 1946 to September 2015 via PubMed, EMBASE, and Scopus for the effect of diseases on response vitamin K antagonists including warfarin, acenocoumarol, phenprocoumon, and fluindione.

DISCUSSION

Among many factors modifying response to VKAs, several disease states are clinically relevant. Liver disease, hyperthyroidism, and CKD are well documented to increase response to VKAs. Decompensated heart failure, fever, and diarrhea may also elevate response to VKAs, but more study is needed. Hypothyroidism is associated with decreased effect of VKAs, and obese patients will likely require higher initial doses of VKAs.

CONCLUSION

In order to minimize risks with VKAs while ensuring efficacy, clinicians must be aware of the effect of disease states when prescribing these oral anticoagulants.

The pharmacokinetics and safety of darapladib in subjects with severe renal impairment

AIM

Darapladib is a potent and reversible orally active inhibitor of lipoprotein-associated phospholipase A2 (Lp-PLA2 ). The aim of the study was to assess the effects of severe renal impairment on the pharmacokinetics and safety/tolerability of darapladib compared with normal renal function.

METHODS

This was an open label, parallel group study of darapladib following 10 day once daily 160 mg oral dosing in subjects with normal (n = 8) and severe renal impairment (estimated glomerular filtration rate <30 ml min(-1) 1.73 m(-2) , n = 8). Plasma concentrations of total and unbound darapladib as well as total darapladib metabolites were determined in samples obtained over 24 h on day 10.

RESULTS

Plasma concentrations of total and unbound darapladib as well as all three metabolites were higher in subjects with severe renal impairment. Area under the plasma concentration vs. time curve between time zero and 24 h (AUC(0,24 h) and maximum plasma concentration (Cmax ) of total darapladib in severely renally impaired subjects were 52% and 59% higher than those in the matched healthy subjects, respectively. Similar results were found with the darapladib metabolites. Darapladib was highly plasma protein bound with 0.047% and 0.034% unbound circulating in plasma in severely renally impaired and healthy subjects, respectively. Unbound plasma darapladib exposures were more than two-fold higher in severely renally impaired subjects than in healthy controls. Adverse events (AE) were reported in 38% of healthy subjects and 75% of severely renally impaired subjects, most of which were mild or moderate in intensity.

CONCLUSIONS

The results of this study showed that darapladib exposure was increased in subjects with severe renal impairment compared with healthy controls. However, darapladib was generally well tolerated in both groups.

A Synopsis of Clinical Pharmacokinetic Alterations in Advanced CKD

Unrecognized alterations in pharmacokinetics, which quantitatively describes the time course of drug disposition in the body, may lead to clinically significant changes in systemic exposure and corresponding response to drugs in patients with chronic kidney disease (CKD). Clinicians must take pharmacokinetic changes into consideration when selecting and dosing medications in CKD patients to optimize the risk:benefit ratio. Pharmacokinetic changes in absorption, distribution, and renal clearance are well characterized and generally predictable for most drugs. Conversely, changes in nonrenal clearance are less well understood and corresponding clinical implications are still being elucidated. This review provides a synopsis of alterations in each of these pharmacokinetic parameters observed in patients with advanced CKD.

Effect of hepatic or renal impairment on the pharmacokinetics of canagliflozin, a sodium glucose co-transporter 2 inhibitor

PURPOSE

Canagliflozin is a sodium-glucose cotransporter 2 inhibitor approved for the treatment of type 2 diabetes mellitus (T2DM). Because T2DM is often associated with renal or hepatic impairment, understanding the effects of these comorbid conditions on the pharmacokinetics of canagliflozin, and further assessing its safety, in these special populations is essential. Two open-label studies evaluated the pharmacokinetics, pharmacodynamics (renal study only), and safety of canagliflozin in participants with hepatic or renal impairment.

METHODS

Participants in the hepatic study (8 in each group) were categorized based on their Child-Pugh score (normal hepatic function, mild impairment [Child-Pugh score of 5 or 6], and moderate impairment [Child-Pugh score of 7-9]) and received a single oral dose of canagliflozin 300 mg. Participants in the renal study (8 in each group) were categorized based on their creatinine clearance (CLCR) (normal renal function [CLCR ≥80 mL/min]; mild [CLCR 50 to <80 mL/min], moderate [CLCR 30 to <50 mL/min], or severe [CLCR <30 mL/min] renal impairment; and end-stage renal disease [ESRD]) and received a single oral dose of canagliflozin 200 mg; the exception was those with ESRD, who received 1 dose postdialysis and 1 dose predialysis (10 days later). Canagliflozin's pharmacokinetics and pharmacodynamics (urinary glucose excretion [UGE] and renal threshold for glucose excretion [RTG]) were assessed at predetermined time points.

FINDINGS

Mean maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to infinite (AUC)0-∞ values differed by <11% between the group with normal hepatic function and those with mild and moderate hepatic impairment. In the renal study, the mean Cmax values were 13%, 29%, and 29% higher and the mean AUC0-∞ values were 17%, 63%, and 50% higher in participants with mild, moderate, and severe renal impairment, respectively; values were similar in the ESRD group relative to the group with normal function, however. The amount of UGE declined as renal function decreased, whereas RTG was not suppressed to the same extent in the moderate to severe renal impairment groups (mean RTG, 93-97 mg/dL) compared with the mild impairment and normal function groups (mean RTG, 68-77 mg/dL).

IMPLICATIONS

Canagliflozin's pharmacokinetics were not affected by mild or moderate hepatic impairment. Systemic exposure to canagliflozin increased in the renal impairment groups relative to participants with normal renal function. Pharmacodynamic response to canagliflozin, measured by using UGE and RTG, declined with increasing severity of renal impairment. A single oral dose of canagliflozin was well tolerated by participants in both studies. ClinicalTrials.gov identifiers: NCT01186588 and NCT01759576.

Consequences of renal failure on non-renal clearance of drugs

Kidney disease not only alters the renal elimination but also the non-renal disposition of drugs that are metabolized by the liver. Indeed, modifications in the expression and activity of intestinal and hepatic drug metabolism enzymes and uptake and efflux transporters have been reported. Accumulated uremic toxins, inflammatory cytokines, and parathyroid hormones may modulate these proteins either directly or by inhibiting gene expression. This can lead to important unintended variations in exposure and response when drugs are administered without dose adjustment for reduced renal function. This review summarizes our current understanding of non-renal clearance in circumstances of chronic and acute renal failure with experimental but also clinical studies. It also evaluates the clinical impact on drug disposition. Predicting the extent of the drug disposition modification is difficult first because of the complex interplay between metabolic enzymes and transport proteins but also because of the differential effects in the different organs (liver, intestines). Recommendations of the US FDA are presented as they may be potentially helpful tools to predict these modifications when no specific pharmacokinetic studies are available.

The organic anion transporter (OAT) family: a systems biology perspective

The organic anion transporter (OAT) subfamily, which constitutes roughly half of the SLC22 (solute carrier 22) transporter family, has received a great deal of attention because of its role in handling of common drugs (antibiotics, antivirals, diuretics, nonsteroidal anti-inflammatory drugs), toxins (mercury, aristolochic acid), and nutrients (vitamins, flavonoids). Oats are expressed in many tissues, including kidney, liver, choroid plexus, olfactory mucosa, brain, retina, and placenta. Recent metabolomics and microarray data from Oat1 [Slc22a6, originally identified as NKT (novel kidney transporter)] and Oat3 (Slc22a8) knockouts, as well as systems biology studies, indicate that this pathway plays a central role in the metabolism and handling of gut microbiome metabolites as well as putative uremic toxins of kidney disease. Nuclear receptors and other transcription factors, such as Hnf4α and Hnf1α, appear to regulate the expression of certain Oats in conjunction with phase I and phase II drug metabolizing enzymes. Some Oats have a strong selectivity for particular signaling molecules, including cyclic nucleotides, conjugated sex steroids, odorants, uric acid, and prostaglandins and/or their metabolites. According to the "Remote Sensing and Signaling Hypothesis," which is elaborated in detail here, Oats may function in remote interorgan communication by regulating levels of signaling molecules and key metabolites in tissues and body fluids. Oats may also play a major role in interorganismal communication (via movement of small molecules across the intestine, placental barrier, into breast milk, and volatile odorants into the urine). The role of various Oat isoforms in systems physiology appears quite complex, and their ramifications are discussed in the context of remote sensing and signaling.

Early non-steady-state population pharmacokinetics of oral cyclosporine in renal transplant recipients

This study aimed to evaluate the change in the pharmacokinetics (PK) of cyclosporine in the non-steady-state period in the first week after renal transplantation; the factors influencing this change, including genetic variability; and the time point concentration that correlated best with drug exposure. Data were obtained from 69 patients, and PK studies were conducted on postoperative days (PODs) 2, 3, and 7. Samples were taken pre-dose and at 1, 2, 3, 4, 6, 8, and 12 hours after drug administration. MDR1, CYP3A4, and CYP3A5 were genotyped. A population PK analysis and correlational analysis between the concentration at each time point and the area under the time-concentration curve were performed. A two-compartment model with first-order absorption was chosen. The rate and extent of drug absorption showed a significant increase on POD3, followed by a slight decrease on POD7. Until POD3, 8 hours post-dose was the single time point concentration that correlated best with drug exposure and 3 hours was the best time point on POD7. In both analyses, the MDR1 genotype showed potential as a factor influencing PK change. We conclude that oral administration of cyclosporine and dose adjustment based on a single concentration measurement might result in unexpected drug exposure during this early posttransplantation period.

Pharmacokinetics of tedizolid in subjects with renal or hepatic impairment

Two open-label, single-dose, parallel-group studies were conducted to characterize the pharmacokinetics of the novel antibacterial tedizolid and the safety of tedizolid phosphate, its prodrug, in renally or hepatically impaired subjects. Tedizolid pharmacokinetics in subjects with severe renal impairment without dialysis support was compared with that of matched control subjects with normal renal function. Effects of hemodialysis on tedizolid pharmacokinetics were determined in a separate cohort of subjects undergoing long-term hemodialysis. Effects of hepatic impairment on tedizolid pharmacokinetics were determined in subjects with moderate or severe hepatic impairment and compared with those of matched control subjects with normal hepatic function. Each participant received a single oral (hepatic impairment) or intravenous (renal impairment) dose of tedizolid phosphate at 200 mg; hemodialysis subjects received two doses (separated by 7 days), before and after dialysis, in a crossover fashion. The pharmacokinetics of tedizolid was similar in subjects with severe renal impairment and controls (∼8% lower area under the concentration-time curve [AUC], with a nearly identical peak concentration) and in subjects undergoing hemodialysis before and after tedizolid phosphate administration (∼9% lower AUC, with a 15% higher peak concentration); <10% of the dose was removed during 4 h of hemodialysis. Tedizolid pharmacokinetics was only minimally altered in subjects with moderate or severe hepatic impairment; the AUC was increased approximately 22% and 34%, respectively, compared with that of subjects in the control group. Tedizolid phosphate was generally well tolerated in all participants. These results suggest that tedizolid phosphate dose adjustments are not necessary in patients with any degree of renal or hepatic impairment. (This study has been registered at ClinicalTrials.gov under registration numbers NCT01452828 [renal study] and NCT01431833 [hepatic study].).

The influence of kidney function on dapagliflozin exposure, metabolism and pharmacodynamics in healthy subjects and in patients with type 2 diabetes mellitus

AIM(S)

This study assessed the effect of differences in renal function on the pharmacokinetics and pharmacodynamics of dapagliflozin, a renal sodium glucose co-transporter-2 (SGLT2) inhibitor for the treatment of type 2 diabetes mellitus (T2DM).

METHODS

A single 50 mg dose of dapagliflozin was used to assess pharmacokinetics and pharmacodynamics in five groups: healthy non-diabetic subjects; patients with T2DM and normal kidney function and patients with T2DM and mild, moderate or severe renal impairment based on estimated creatinine clearance. Subsequently, 20 mg once daily multiple doses of dapagliflozin were evaluated in the patients with T2DM. Formation rates of dapagliflozin 3-O-glucuronide (D3OG), an inactive metabolite, were evaluated using human isolated kidney and liver microsomes.

RESULTS

Plasma concentrations of dapagliflozin and D3OG were incrementally increased with declining kidney function. Steady-state Cmax for dapagliflozin were 4%, 6% and 9% higher and for D3OG were 20%, 37% and 52% higher in patients with mild, moderate and severe renal impairment, respectively, compared with normal function. AUC(0,τ) was likewise higher. D3OG formation in kidney microsomes was three-fold higher than in liver microsomes and 109-fold higher than in intestine microsomes. Compared with patients with normal renal function, pharmacodynamic effects were attenuated with renal impairment. Steady-state renal glucose clearance was reduced by 42%, 83% and 84% in patients with mild, moderate or severe renal impairment, respectively.

CONCLUSIONS

These results indicate that both kidney and liver significantly contribute to dapagliflozin metabolism, resulting in higher systemic exposure with declining kidney function. Dapagliflozin pharmacodynamics in diabetic subjects with moderate to severe renal impairment are consistent with the observation of reduced efficacy in this patient population.

Glucose-lowering drugs in patients with chronic kidney disease: a narrative review on pharmacokinetic properties

The achievement of a good glycaemic control is one of the cornerstones for preventing and delaying progression of microvascular and macrovascular complications in patients with both diabetes and chronic kidney disease (CKD). As for other drugs, the presence of an impaired renal function may significantly affect pharmacokinetics of the majority of glucose-lowering agents, thus exposing diabetic CKD patients to a higher risk of side effects, mainly hypoglycaemic episodes. As a consequence, a reduction in dosing and/or frequency of administration is necessary to keep a satisfactory efficacy/safety profile. In this review, we aim to summarize the pharmacology of the most widely used glucose-lowering agents, discuss whether and how it is altered by a reduced renal function, and the recommendations that can be made for their use in patients with different degrees of CKD.

Effects of chronic kidney disease and uremia on hepatic drug metabolism and transport

The pharmacokinetics of non-renally cleared drugs in patients with chronic kidney disease is often unpredictable. Some of this variability may be due to alterations in the expression and activity of extra-renal drug metabolizing enzymes and transporters, primarily localized in the liver and intestine. Studies conducted in rodent models of renal failure have shown decreased mRNA and protein expression of many members of the cytochrome P450 enzyme (CYP) gene family and the ATP-Binding Cassette (ABC) and Solute Carrier (SLC) gene families of drug transporters. Uremic toxins interfere with transcriptional activation, cause down-regulation of gene expression mediated by proinflammatory cytokines, and directly inhibit the activity of the cytochrome P450s and drug transporters. While much has been learned about the effects of kidney disease on non-renal drug disposition, important questions remain regarding the mechanisms of these effects, as well as the interplay between drug metabolizing enzymes and drug transporters in the uremic milieu. In this review, we have highlighted the existing gaps in our knowledge and understanding of the impact of chronic kidney disease on non-renal drug clearance, and identified areas of opportunity for future research.

Pharmacokinetics of tofacitinib, a janus kinase inhibitor, in patients with impaired renal function and end-stage renal disease

The pharmacokinetics (PK) of tofacitinib were assessed in patients with mild (Cockcroft-Gault creatinine clearance >50 and ≤80 mL/min), moderate (≥30 and ≤50 mL/min), and severe (<30 mL/min) renal impairment, and end-stage renal disease (ESRD) requiring dialysis. Six patients each with normal, mild, moderate, or severely impaired renal function, and 12 patients with ESRD, received single tofacitinib doses of 10 mg. PK data were obtained from blood and dialyzate (patients with ESRD only) samples prior and subsequent to dosing and/or hemodialysis (patients with ESRD only). Relative to patients with normal renal function, mean (90% CI) AUC(0-∞) ratios were 137% (97-195), 143% (101-202), and 223% (157-316) in patients with mild, moderate, and severe renal impairment, respectively. Maximum plasma concentrations (Cmax ) were similar across the four treatment groups. Terminal phase half-life (t1/2 ) increased with severity of renal impairment. Mean AUC(0-∞) in patients with ESRD on a non-dialysis day was similar to that in patients with moderate renal impairment and approximately 40% greater than healthy volunteer data. Mean (SD) dialyzer efficiency (ratio of dialyzer clearance/blood flow entering the dialyzer) was 0.73 (0.15). However, due to extensive non-renal clearance, dialysis procedure is unlikely to result in significant elimination of tofacitinib.

A Nonlinear Mixed Effects Pharmacokinetic Model for Dapagliflozin and Dapagliflozin 3-O-glucuronide in Renal or Hepatic Impairment

Dapagliflozin is a sodium–glucose co-transporter 2 inhibitor in development for the treatment of type 2 diabetes mellitus. A semi-mechanistic population pharmacokinetic (PK) model was developed for dapagliflozin and its inactive metabolite dapagliflozin 3-O-glucuronide (D3OG) with emphasis on renal and hepatic contribution to dapagliflozin metabolism. Renal and hepatic impairment decreased the clearance of dapagliflozin to D3OG and the clearance of D3OG. The fraction of D3OG formed via the renal route decreased from 40–55% in subjects with normal renal function (creatinine clearance (CLcr) > 80 ml/min) to 10% in subjects with severe renal insufficiency (CLcr = 13 ml/min). The model-based simulations suggested that the increase of systemic exposure (AUC_ss) of dapagliflozin and D3OG was less than twofold in subjects with mild or moderate renal impairment. This population modeling analysis presents a useful approach to evaluate the impact of renal and hepatic function on the PK of dapagliflozin.

Evaluation of exposure change of nonrenally eliminated drugs in patients with chronic kidney disease using physiologically based pharmacokinetic modeling and simulation

Chronic kidney disease, or renal impairment (RI) can increase plasma levels for drugs that are primarily renally cleared and for some drugs whose renal elimination is not a major pathway. We constructed physiologically based pharmacokinetic (PBPK) models for 3 nonrenally eliminated drugs (sildenafil, repaglinide, and telithromycin). These models integrate drug-dependent parameters derived from in vitro, in silico, and in vivo data, and system-dependent parameters that are independent of the test drugs. Plasma pharmacokinetic profiles of test drugs were simulated in subjects with severe RI and normal renal function, respectively. The simulated versus observed areas under the concentration versus time curve changes (AUCR, severe RI/normal) were comparable for sildenafil (2.2 vs 2.0) and telithromycin (1.6 vs 1.9). For repaglinide, the initial, simulated AUCR was lower than that observed (1.2 vs 3.0). The underestimation was corrected once the estimated changes in transporter activity were incorporated into the model. The simulated AUCR values were confirmed using a static, clearance concept model. The PBPK models were further used to evaluate the changes in pharmacokinetic profiles of sildenafil metabolite by RI and of telithromycin by RI and co-administration with ketoconazole. The simulations demonstrate the utility and challenges of the PBPK approach in evaluating the pharmacokinetics of nonrenally cleared drugs in subjects with RI.

Current understanding of drug disposition in kidney disease

Patients with chronic kidney disease (CKD) represent 13% of the American population. CKD has been shown to significantly alter drug disposition of nonrenally eliminated drugs. Indeed, modifications in the expression and function of intestinal and hepatic drug metabolism enzymes and uptake and efflux transporters have been reported. Uremic toxins, inflammatory cytokines, and parathyroid hormone have been implicated as causes. These changes can have an important clinical impact on drug disposition and lead to unintended toxicity if they are administered without dose adjustment in patients with impaired kidney function. This review summarizes recent preclinical and clinical studies and presents the current understanding of the effect of CKD on drug absorption, distribution, metabolism, and excretion.

Brivaracetam disposition in renal impairment

Brivaracetam is a novel high-affinity SV2A ligand currently in clinical development for epilepsy. The objective was to characterize its disposition in patients with renal impairment. A single oral dose of 200 mg brivaracetam was administered to 9 patients with severe renal impairment not requiring dialysis (creatinine clearance <15 mL/min, n = 6; 15-29 mL/min, n = 3) and 9 matched healthy controls. Plasma and urinary concentrations of brivaracetam and 3 pharmacologically inactive metabolites (acid, hydroxy, and hydroxyacid) were determined up to 72 hours postdose, and noncompartmental pharmacokinetic parameters were derived. The C(max) of brivaracetam was unchanged relative to healthy controls, whereas AUC was slightly increased (mean ratio, 1.21; 90% confidence interval, 1.01-1.45). Nonrenal and renal clearances of brivaracetam decreased from 47 and 4.5 to 41 and 1.7 mL/min/1.73 m(2). Exposure to the acid, hydroxy, and hydroxyacid metabolites was markedly increased: C(max) by 2.4-, 2.0-, and 11.7-fold and AUC by 3.2-, 4.1-, and 21.5-fold. Renal clearance of these rapidly cleared metabolites was decreased 10-fold in patients with severe renal impairment. Nonclinical toxicology studies concluded to the absence of safety issues related to the increased levels of metabolites. These observations suggest that dose adjustment of brivaracetam should not be required at any stage of renal dysfunction.

Factors that affect concentrations of cyclosporine during the induction period of kidney transplantation: multivariate analysis

OBJECTIVE

The pharmacokinetics of cyclosporine (CsA) depend on numerous factors over the transplantation course. The aim of this study was to evaluate the impact of several clinical variables on CsA concentrations during the induction period after kidney transplantation.

METHODS

Potential variables were contrasted with CsA concentrations at 2 hours postdose (C(2)) and with the area under the concentration curve of CsA (AUC) at days 3 and 10 after transplantation. Evaluated variables were: recipient age, gender, body mass index (BMI), type/duration of previous dialysis, pretransplant serum creatinine (sCr), donor type, CsA dose, cold ischemia time, reduction of sCr, and use of other immunosuppressive drugs.

RESULTS

This series included 112 patients who displayed an average age of 43 ± 13 years, including 62 men and 31 recipients of living donor organs. The induction dose of CsA was 8.36 ± 1.53 mg/kg. On day 3, the C(2) was related to the reduction of sCr (P = 0.034) and to the BMI (P = 0.033). There was an inverse correlation with pretransplant sCr (P = 0.012). The AUC correlated with BMI (P = 0.027) and living donor category (P = .002). Patients receiving rapamycin or a locally procured kidney showed a trend toward higher AUC values. On day 10, the CsA dose and use of rapamycin showed a trend to higher values of C(2); the AUC was related to the CsA dose (P = .034). None of the other variables showed significant effects. Analysis between variables showed that time on dialysis correlated with the pretransplant sCr (P = .002) and that the CsA dose was negatively associated with BMI (P = .009).

CONCLUSION

Pretransplant sCr, BMI, living donor kidney category, better functional recovery, and the dose of CsA were predictors of CsA concentrations of clinical interest during this induction period. The effect of BMI was not related to higher doses of CsA.

Effects of uremic toxins on transport and metabolism of different biopharmaceutics drug disposition classification system xenobiotics

Chronic kidney disease (CKD) is recognized to cause pharmacokinetic changes in renally excreted drugs; however, pharmacokinetic changes are also reported for drugs that are nonrenally eliminated. Few studies have investigated how uremic toxins may affect drug transporters and metabolizing enzymes and how these may result in pharmacokinetic/metabolic changes in CKD. Here, we investigated the effects of uremic toxins and human uremic serum on the transport of the prototypical transporter substrate [(3) H]-estrone sulfate and three Biopharmaceutics Drug Disposition Classification System (BDDCS) drugs, propranolol, losartan, and eprosartan. We observed a significant decrease in [(3) H]-estrone sulfate, losartan, and eprosartan uptake with some uremic toxins in both transfected cells and rat hepatocytes. The uptake of losartan was decreased in rat and human hepatocytes (28% and 48%, respectively) in the presence of hemodialysis (HD) serum. Time-course studies of losartan showed a 27%, 65%, and 68% increase in area under the curve (AUC) in the presence of HD serum, rifampin, and sulfaphenazole, respectively. Intracellular losartan AUC decreased significantly in the treatment groups, and the metabolite AUC decreased by 41% and 26% in rifampin- and sulfaphenazole-treated group, respectively. The intracellular AUC of eprosartan increased 190% in the presence of HD serum. These studies indicate that the uremic toxins contained in HD serum play an important role in drug disposition through drug transporters, and that there would be differential effects depending on the BDDCS classification of the drug.

Warfarin dosing in patients with impaired kidney function

BACKGROUND

In patients with kidney impairment, warfarin, a drug metabolized primarily by the cytochrome P-450 system, is initiated at similar doses and managed similarly as in the general medical population. Unfortunately, few data exist to guide dose adjustment in patients with decreased kidney function. Here, we determine the degree of warfarin dose reduction associated with kidney impairment and make recommendations for warfarin dosing.

STUDY DESIGN

Cross-sectional analysis.

SETTING & PARTICIPANTS

Long-term warfarin users followed up at anticoagulation clinics (n = 980); 708 participants from the University of Alabama (UAB) and 272 participants from the University of Chicago (UIC).

PREDICTOR

No/mild (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73 m(2)), moderate (eGFR, 30-59 mL/min/1.73 m(2)), and severe (eGFR < 30 mL/min/1.73 m(2)) kidney impairment; CYP2C9 and VKORC1 genotype; age; race; sex; body mass; sociodemographic factors; smoking status; alcohol; vitamin K intake; comorbid conditions (eg, congestive heart failure); and drug interactions (eg, amiodarone and statins).

OUTCOME & MEASUREMENT

Warfarin dose (milligrams per day) was evaluated using linear regression after adjustment for clinical, demographic, and genetic factors.

RESULTS

Prevalences of moderate (31.8% and 27.6%) and severe kidney impairment (8.9% and 6.6%) were similar in the UAB and UIC cohorts. Warfarin dose requirements were significantly lower in patients with moderate and severe kidney impairment compared with those with no/mild kidney impairment in the UAB (P < 0.001) and UIC (P < 0.001) cohorts. Compared with patients with no/mild kidney impairment, patients with moderate kidney impairment required 9.5% lower doses (P < 0.001) and patients with severe kidney impairment required 19% lower doses (P < 0.001).

LIMITATIONS

No measurement of warfarin, serum albumin, vitamin K, and coagulation factors; no evaluation of other markers (eg, cystatin).

CONCLUSION

Moderate and severe kidney impairment were associated with a reduction in warfarin dose requirements.

Down-regulation of liver drug-metabolizing enzymes in a murine model of chronic renal failure

Drug metabolism could be altered in patients with chronic renal failure (CRF). In rats, this phenomenon is related to a decrease in liver cytochrome P450 (P450) and phase II enzymes, particularly N-acetyltransferase 2 (NAT2). This study attempted to determine the effects of CRF on liver P450 isoforms and NAT2 expressions by using a CRF mouse model. Two groups of mice were studied: CRF induced by 3/4 nephrectomy and control. Liver protein expression and mRNA levels of the major P450 isoforms involved in drug metabolism (CYP1A2, 2C29, 2D, 2E1, and 3A11) and NAT2 were measured by Western blot and real-time polymerase chain reaction (PCR), respectively. CYP3A activity was also assessed by the N-demethylation of erythromycin. Results showed a significant reduction in the protein expression of CYP1A2 (56%), 2C29 (31%), and 3A11 (37%) in CRF mice compared with control animals. Real-time PCR revealed a similar reduction in mRNA levels of CYP1A2, 2C29, and 3A11 (59, 56, and 37%, respectively), in CRF mice. There was no significant modification in protein expression and mRNA of CYP2D and 2E1. Compared with control animals, CRF mice displayed a 25% reduction in N-demethylation of erythromycin. For NAT2, protein expression decreased by 33% and mRNA levels decreased by 23%. In conclusion, this study demonstrates that protein expression of liver CYP1A2, CYP2C29, and CYP3A11 is down-regulated in CRF mice, secondary to reduced gene expression. Phase II enzymes are similarly affected by CRF. Our results will allow the use of knockout mice to determine the mechanism underlying CRF-induced down-regulation of liver drug-metabolizing enzymes.

Hepatic clearance, but not gut availability, of erythromycin is altered in patients with end-stage renal disease

Nonrenal clearance of drugs can be significantly lower in patients with end-stage renal disease (ESRD) than in those with normal renal function. Using erythromycin (ER) as a probe compound, we investigated whether this decrease in nonrenal clearance is due to reduced hepatic clearance (CL(H)) and/or gut metabolism. We also examined the potential effects of the uremic toxins 3-carboxy-4-methyl-5-propyl-2-furan propanoic acid (CMPF) and indoxyl sulfate (Indox) on ER disposition. Route-randomized, two-way crossover pharmacokinetic studies of ER were conducted in 12 ESRD patients and 12 healthy controls after oral (250 mg) and intravenous (125 mg) dosing with ER. In patients with ESRD, CL(H) decreased 31% relative to baseline values (0.35 +/- 0.14 l/h/kg vs. 0.51 +/- 0.13 l/h/kg, P = 0.01), with no change in steady-state volume of distribution. With oral dosing, the bioavailability of ER increased 36% in patients with ESRD, and this increase was not related to changes in gut availability. As expected, plasma levels of CMPF and Indox were significantly higher in the patients than in the healthy controls. However, no correlation was observed between CL(H) of ER and the levels of uremic toxins.

Pharmacokinetics and safety of sunitinib malate in subjects with impaired renal function

This phase I, open-label, single-dose study evaluates the effects of severe renal impairment and end-stage renal disease (ESRD) requiring hemodialysis on the pharmacokinetics, safety, and tolerability of sunitinib and its primary active metabolite, SU12662. Subjects with normal renal function (creatinine clearance > 80 mL/min), severe renal impairment (creatinine clearance < 30 mL/min), and ESRD requiring hemodialysis receive a single dose of sunitinib 50 mg. Serial blood samples are collected for quantification of plasma concentrations using a validated liquid chromatography with tandem mass spectrometry assay. Safety is monitored. Twenty-four subjects complete the study. Pharmacokinetics in subjects with severe renal impairment appear similar to those with normal renal function. Plasma exposure to sunitinib and SU12662 appears lower in subjects with ESRD compared with subjects with normal renal function or severe renal impairment. Single-dose sunitinib 50 mg is well tolerated regardless of renal function. The currently approved starting dose of sunitinib 50 mg on Schedule 4/2 is expected to be appropriate for patients with renal impairment; any subsequent dose modifications should be based on patients' ability to tolerate treatment.