Clinical pharmacokinetics and pharmacodynamics of the oral direct thrombin inhibitor dabigatran etexilate

Differences in coagulation responses to vascular injury between uninterrupted dabigatran and apixaban: A clinical prospective randomized study

BACKGROUND

The coagulation response during vascular injury with uninterrupted administration of direct oral anticoagulants has not been elucidated.

OBJECTIVE

Our aim was to evaluate differences in coagulation responses after vascular injury between uninterrupted direct thrombin inhibitor and direct factor Xa inhibitor recipients.

METHODS

Patients scheduled for catheter ablation for atrial fibrillation were randomly assigned to receive dabigatran or apixaban in this prospective, randomized, comparative, parallel-group study. Venous blood was collected 3 times: 180 minutes after taking the anticoagulant on the day before the procedure, before vascular punctures of the ablation procedure, and 10-15 minutes after the start of vascular punctures.

RESULTS

Forty-two patients were enrolled. The prothrombin fragment 1+2 level, the primary end point, was much larger after vascular puncture in the uninterrupted dabigatran recipients (median, 83 pmol/L; interquartile range, 56-133 pmol/L) than in the uninterrupted apixaban recipients (median, 1 pmol/L; interquartile range, -3 to 19 pmol/L; P < .001). Antithrombin levels decreased after vascular puncture in dabigatran recipients, and both protein C and antithrombin levels decreased after vascular puncture in apixaban recipients.

CONCLUSION

Unlike uninterrupted apixaban, uninterrupted dabigatran does not inhibit thrombin generation in response to vascular injury.

Direct-Acting Oral Anticoagulant Dabigatran as a Bridging Therapy while Optimizing Warfarin Dosage for Cardioembolic Stroke

INTRODUCTION

Parenteral heparin is widely used as bridging therapy while optimizing oral anticoagulation (OAC). Newer direct-acting OACs (DOACs) attain therapeutic effect very quickly. We report the use of dabigatran as bridging therapy during warfarin optimization for cardioembolic stroke in two patients who opted to receive warfarin for long-term anticoagulation for secondary stroke prevention.

CASE PRESENTATIONS

Patient A was a 60-year-old man with hypertension, hyperlipidaemia, and gout who was admitted with a sudden onset of left-sided weakness. Clinically, he was alert but had right gaze preference and left-sided hemiplegia. The clinical diagnosis was of a right cortical stroke. He underwent intravenous tPA augmented with sonothrombolysis - the National Institute of Health Stroke Scale (NIHSS) score fell from 7 to 0. Repeat brain scan showed infarcts in the right frontal and parietal lobes. He was found to have atrial fibrillation (AF) and advised anticoagulation. He opted for warfarin with dabigatran bridging which was started on day 2 of his hospital admission. His International Normalized Ratio (INR) exceeded 2 by day 6 of anticoagulation, at which time the bridging dabigatran was stopped, fixed-dose warfarin was continued, and he was discharged well. On subsequent reviews in the clinic, his INR was in the therapeutic range of 2.0-3.0. He had no bleeding or recurrent ischaemic events during follow-up. Patient B was a 78-year-old man with a hypertension, hyperlipidaemia, and diabetes mellitus. He was admitted after he developed difficulty talking and mild right-sided weakness. Clinically, he was alert but had expressive aphasia and mild right-sided upper limb weakness (NIHSS 6). The clinical diagnosis was of a left cortical stroke. The brain scan showed a left posterior frontal and parietal infarct. He was out of the time window for recanalization therapy and was treated conservatively. He was found to have AF and advised anticoagulation. He opted for warfarin with dabigatran bridging which was started on day 1 of his hospital admission. His INR was almost 2 by day 5 of anticoagulation, at which time the bridging dabigatran was stopped and fixed-dose warfarin continued. He declined daily blood taking - his INR 4 days later was in the therapeutic range of 2.0-3.0. He had no bleeding or recurrent ischaemic events. He underwent rehabilitation uneventfully and was discharged well.

CONCLUSIONS

The use of DOACs such as dabigatran as bridging therapy during optimization of OAC is feasible. Compared to heparin as bridging therapy, DOAC has the advantage of oral administration, lower cost, and possibly lower bleeding risks. This novel practice may be applicable in thrombosis in arterial and venous circulations, e.g., ischaemic stroke, deep venous thrombosis, pulmonary embolism.

Dabigatran Attenuates the Binding of Thrombin to Platelets-A Novel Mechanism of Action

BACKGROUND

 Thrombin is a multifunctional regulatory enzyme of the haemostasis and has both pro- and anticoagulant roles. It has, therefore, been a main target for drug discovery over many decades. Thrombin is a serine protease and possesses two positively charged regions called exosites, through which it is known to bind to many substrates. Dabigatran is a thrombin inhibitor and is widely used as an oral anticoagulant for the antithrombotic treatment of atrial fibrillation and venous thromboembolism. The mechanism by which dabigatran inhibits thrombin is the blockage of the active site, however, its effect on thrombin binding to its substrates has not been studied thoroughly and is thus poorly understood.

MATERIAL AND METHODS

 The effect of dabigatran on thrombin binding to platelets was evaluated by flow cytometry using fluorescently labelled thrombin and washed platelets. Further, to confirm the results we utilized modern techniques for biomolecular binding studies, microscale thermophoresis (MST) and surface plasmon resonance (SPR), which validated the results.

RESULTS

 Dabigatran inhibited thrombin binding to platelets as analysed by flow cytometry. The inhibition was dose dependent with IC50 of 118 nM which was slightly lower than for inhibition of platelet activation and is close to the clinically relevant plasma concentration of dabigatran. MST and SPR also confirmed inhibitory effect of dabigatran on thrombin binding to platelets.

CONCLUSION

 Apart from blocking the active site, dabigatran also inhibits thrombin binding to platelets. Since thrombin has numerous functions beyond the cardiovascular system, this finding may have important implications.

The pharmacokinetics of dabigatran in a rat model of hyperlipidaemia induced by poloxamer 407

Various pharmacokinetic changes have been reported in experimental hyperlipidemic (HL) animal models. To evaluate whether P-glycoprotein (P-gp) activity was affected in HL rats, we assessed the pharmacokinetics of dabigatran after oral administration of dabigatran etexilate (DABE); this is a dabigatran prodrug and a well-known P-gp substrate.HL and control rats exhibited similar area under the plasma concentration-time curve (AUC), total body clearance (CL), and steady state volume of distribution (Vss) values following intravenous administration of dabigatran (1 mg/kg). This suggested that the distribution and elimination of dabigatran were similar in control and HL rats.The hepatic and intestinal P-gp protein levels did not differ significantly between control and HL rats. The dabigatran AUC and extent of absolute oral bioavailability (F) values were similar in control and HL rats following oral administration of DABE (10 mg/kg as dabigatran). Therefore, there was no apparent change in intestinal P-gp activity in HL rats compared to control rats.This study revealed no significant change in P-gp expression or activity in the intestine or liver of HL rats, and similar pharmacokinetics of dabigatran. Hyperlipidaemia may not directly affect the oral absorption of P-gp substrate drugs.

Atrial fibrillation and ischemic heart disease: (un)solved therapeutic dilemma?

Concomitant presence of atrial fibrillation and coronary artery disease requiring percutaneous coronary intervention is a frequent occurrence. The choice of optimal antithrombotic therapy, in this context, is still challenging. To offer the best protection both in terms of stroke and stent thrombosis, triple therapy with oral anticoagulation and dual antiplatelet therapy would be required. Several drug combinations have been tested in recent years, including direct oral anticoagulants, with the aim of balancing ischemic and bleeding risk. Both pharmacokinetic aspects of the molecules and patient's characteristics should be analyzed in choosing oral anticoagulation. Then, as suggested by guidelines, triple therapy should start with a seven-day duration and the aim to prolong to thirty days in high thrombotic risk patients. Dual therapy should follow to reach twelve months after coronary intervention. Even not fully discussed by the guidelines, in order to balance ischemic and bleeding risk it should also be considered: 1) integrated assessment of coronary artery disease and procedural complexity of coronary intervention; 2) appropriateness to maintain the anticoagulant drug dosage indicated in technical data sheet; the lack of data on the suspension of antiplatelet drugs one year after percutaneous intervention; 3) the possibility of combination therapy with ticagrelor; and 4) the need to treat the occurrence of paroxysmal atrial fibrillation during acute coronary syndrome. With data provided clinician should pursue a therapy as personalized as possible, both in terms of drug choice and treatment duration, in order to balance ischemic and bleeding risk.

Efficacy and safety of direct oral anticoagulants in patients with atrial fibrillation combined with chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Currently published studies have not observed consistent results on the efficacy and safety of direct oral anticoagulants (DOACs) use in patients with chronic kidney disease (CKD) combined with atrial fibrillation (AF). Therefore, this study conducted a meta-analysis of the efficacy and safety of DOACs for patients with AF complicated with CKD.

METHODS

Database literature was searched up to May 30, 2023, to include randomized controlled trials (RCT) involving patients with AF complicated with CKD DOACs and vitamin K antagonists (VKAs). Stroke, systemic embolism (SE), and all-cause mortality were used as effectiveness indicators, and major bleeding, intracranial hemorrhage (ICH), fatal bleeding, gastrointestinal bleeding (GIB), and clinically relevant non-major bleeding (CRNMB) were used as safety outcomes.

RESULTS

Nine RCT studies were included for analysis according to the inclusion criteria. Results of the efficacy analysis showed that compared with VKAs, DOACs reduced the incidence of stroke/SE (OR = 0.75, 95% CI 0.67-0.84) and all-cause deaths (OR = 0.84, 95% CI 0.75-0.93) in patients with AF who had comorbid CKD. Safety analyses showed that compared with VKAs, DOACs improved safety by reducing the risk of major bleeding (OR = 0.76, 95%CI 0.65-0.90), ICH (OR = 0.46, 95%CI 0.38-0.56), and fatal bleeding (OR = 0.75, 95%CI 0.65-0.87), but did not reduce the incidence of GIB and CRNMB.

CONCLUSION

Compared with VKAs, DOACs may increase efficacy and improve safety in AF patients with CKD (90 ml/min> Crcl≥15 ml/min), and shows at least similar efficacy and safety in AF patients with Kidney failure (Crcl<15 ml/min).

Assessing the relative contribution of CYP3A-and P-gp-mediated pathways to the overall disposition and drug-drug interaction of dabigatran etexilate using a comprehensive mechanistic physiological-based pharmacokinetic model

Dabigatran etexilate (DABE) is a clinical probe substrate for studying drug-drug interaction (DDI) through an intestinal P-glycoprotein (P-gp). A recent in vitro study, however, has suggested a potentially significant involvement of CYP3A-mediated oxidative metabolism of DABE and its intermediate monoester BIBR0951 in DDI following microdose administration of DABE. In this study, the relative significance of CYP3A- and P-gp-mediated pathways to the overall disposition of DABE has been explored using mechanistic physiologically based pharmacokinetic (PBPK) modeling approach. The developed PBPK model linked DABE with its 2 intermediate (BIBR0951 and BIBR1087) and active (dabigatran, DAB) metabolites, and with all relevant drug-specific properties known to date included. The model was successfully qualified against several datasets of DABE single/multiple dose pharmacokinetics and DDIs with CYP3A/P-gp inhibitors. Simulations using the qualified model supported that the intestinal CYP3A-mediated oxidation of BIBR0951, and not the gut P-gp-mediated efflux of DABE, was a key contributing factor to an observed difference in the DDI magnitude following the micro-versus therapeutic doses of DABE with clarithromycin. Both the saturable CYP3A-mediated metabolism of BIBR0951 and the solubility-limited DABE absorption contributed to the relatively modest nonlinearity in DAB exposure observed with increasing doses of DABE. Furthermore, the results suggested a limited role of the gut P-gp, but an appreciable, albeit small, contribution of gut CYP3A in mediating the DDIs following the therapeutic dose of DABE with dual CYP3A/P-gp inhibitors. Thus, a possibility exists for a varying extent of CYP3A involvement when using DABE as a clinical probe in the DDI assessment, across DABE dose levels.

Bioavailability of Orally Administered Drugs After Bariatric Surgery

PURPOSE OF REVIEW

Oral drug absorption after bariatric surgery is likely to be altered, but the impact of different bariatric surgery procedures on individual drugs is not uniform. The aim of this article is to describe factors influencing the bioavailability of orally administered drugs after bariatric surgery and to provide readers with practical recommendations for drug dosing. We also discuss the medications that may be harmful after bariatric surgery.

RECENT FINDINGS

The fundamental factors for enteral drug absorption are the production of gastric acid; the preserved length of the intestine, i.e., the size of the absorption surface and/or the preserved enterohepatic circulation; and the length of common loop where food and drugs are mixed with digestive enzymes and bile acids. Bypassing of metabolizing enzymes or efflux pumps and changes in intestinal motility can also play an important role. Significant changes of drug absorption early after the anatomic alteration may also be gradually ameliorated due to gradual intestinal adaptation. The most affected drugs are those with low or variable bioavailability and those undergoing enterohepatic circulation. Attention should also be paid to oral drug formulations, especially in the early postoperative period, when immediate-release and liquid formulations are preferred. The changes in oral bioavailability are especially clinically meaningful in patients treated with drugs possessing narrow therapeutic index (e.g., oral anticoagulants, levothyroxine, and anticonvulsants) or in acute conditions (e.g., anti-infectives); nevertheless, it may also influence the therapeutic value of chronic therapy (e.g., antidepressants. antihypertensives, antiplatelets, statins, PPIs, contraceptives, and analgesics); therapeutic effect of chronic therapy is further influenced by pharmacokinetic alterations resulting from weight loss. Therapeutic drug monitoring, periodical clinical evaluation, and adequate dose adjustments are necessary. Due to safety reasons, patients should avoid oral bisphosphonates, regular use of non-steroidal anti-inflammatory drugs, and, if possible, corticosteroids after bariatric surgery.

Comparisons between diluted thrombin time, ecarin chromogenic assays, and UPLC-MS for plasma level dabigatran quantification: Results from DRIVING study

INTRODUCTION

The knowledge of dabigatran levels is helpful for decision-making in specific situations such as urgent surgery or when the question of reversal arises (uncontrolled bleeding, eligibility for thrombolysis). However, a limited number of observational studies are available regarding comparisons between quantification methods. The objective of the study was to compare dabigatran plasma levels using three assays including the reference method (high-performance liquid chromatography coupled with mass spectrometry), focusing on the agreement around the 30-50 ng/mL clinically relevant thresholds.

METHODS

Sixty healthy volunteers from DRIVING trial (NCT01627665) were given a single 300-mg dabigatran etexilate dose. Serial blood samplings were performed at pre-defined time points (0 to 24 h). We analyzed plasma samples using ultra-performance-liquid chromatography coupled with tandem mass spectrometry (UPLC-MS) (dabigatran reference method); ii/diluted thrombin time (dTT) (Hemoclot-DTI-Hyphen-Biomed); iii/ecarin-based chromogenic assay (ECA-II-Stago).

RESULTS

Nine hundred sixty samples were analyzed using the three assays (2759 values). dTT and ECA-II values were highly correlated with those of UPLC-MS (Deming regression). Most values >50 ng/mL were higher using dTT and ECA-II compared to UPLC-MS: biases were constant, +14% and +16% with dTT and ECA-II, respectively (Bland-Altman plots), suggesting that active metabolites accounted for ~15% of thrombin inhibition. Regarding values <30 ng/mL, 30-50 ng/mL, or ≥50 ng/mL, the agreement probability between dTT and ECA-II was of 90.6% [88.4-92.5] (Cohen's kappa coefficient 0.84).

CONCLUSION

dTT and ECA-II assays rapidly provide accurate dabigatran-level results for clinical practice, both assays being suitable in emergency, taking into account the thrombin inhibitory effect of dabigatran metabolites.

An Analysis of Delayed Bleeding in Cases of Colorectal Endoscopic Submucosal Dissection Due to Types of Direct Oral Anticoagulants in Japan

BACKGROUND & AIMS

Reported rates of delayed bleeding (DB) after endoscopic resection using direct oral anticoagulants (DOACs) are high and heterogeneous. This large-scale multicenter study analyzed cases of DB after colorectal endoscopic submucosal dissection related to various types of DOACs in Japan (the ABCD-J study) with those associated with warfarin.

METHODS

We retrospectively reviewed 1019 lesions in patients treated with DOACs and 459 lesions in patients treated with warfarin among 34,455 endoscopic submucosal dissection cases from 47 Japanese institutions between 2012 and 2021. The DB rate (DBR) with each DOAC was compared with that with warfarin. Risk factors for DB in patients treated with DOACs or warfarin were also investigated.

RESULTS

The mean tumor sizes in the DOAC and warfarin groups were 29.6 ± 14.0 and 30.3 ± 16.4 mm, respectively. In the DOAC group, the DBR with dabigatran (18.26%) was significantly higher than that with apixaban (10.08%, P = .029), edoxaban (7.73%, P = .001), and rivaroxaban (7.21%, P < .001). Only rivaroxaban showed a significantly lower DBR than warfarin (11.76%, P = .033). In the multivariate analysis, heparin bridging therapy (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.27-3.73, P = .005), rectal location (2.01, 1.28-3.16, P = .002), and procedure time ≥55 minutes (2.43, 1.49-3.95, P < .001) were significant risk factors for DB in the DOAC group. The DB risk in the DOAC group (OR, (95% CI)) was 2.13 (1.30-3.50) and 4.53 (2.52-8.15) for 1 and 2 significant risk factors, respectively.

CONCLUSIONS

Dabigatran was associated with a higher DBR than other DOACs, and only rivaroxaban was associated with a significantly lower DBR than warfarin.

Comparative Intra-Subject Analysis of Gene Expression and Protein Abundance of Major and Minor Drug Metabolizing Enzymes in Healthy Human Jejunum and Liver

First pass metabolism by phase I and phase II enzymes in the intestines and liver is a major determinant of the oral bioavailability of many drugs. Several studies analyzed expressions of major drug-metabolizing enzymes (DMEs), such as CYP3A4 and UGT1A1 in the human gut and liver. However, there is still a lack of knowledge regarding other DMEs (i.e., "minor" DMEs), although several clinically relevant drugs are affected by those enzymes. Moreover, there is very limited intra-subject data on hepatic and intestinal expression levels of minor DMEs. To fill this gap of knowledge, we analyzed gene expression (quantitative real-time polymerase chain reaction) and protein abundance (targeted proteomics) of 24 clinically relevant DMEs, that is, carboxylesterases (CES), UDP-glucuronosyltransferases (UGT), and cytochrome P450 (CYP)-enzymes. We performed our analysis using jejunum and liver tissue specimens from the same 11 healthy organ donors (8 men and 3 women, aged 19-60 years). Protein amounts of all investigated DMEs, with the exception of CYP4A11, were detected in human liver samples. CES2, CYP2C18, CYP3A4, and UGT2B17 protein abundance was similar or even higher in the jejunum, and all other DMEs were found in higher amounts in the liver. Significant correlations between gene expression and protein levels were observed only for 2 of 15 jejunal, but 13 of 23 hepatic DMEs. Intestinal and hepatic protein amounts only significantly correlated for CYP3A4 and UGT1A3. Our results demonstrated a notable variability between the individuals, which was even higher in the intestines than in the liver. Our intrasubject analysis of DMEs in the jejunum and liver from healthy donors, may be useful for physiologically-based pharmacokinetic-based modeling and prediction in order to improve efficacy and safety of oral drug therapy.

Treatment of dabigatran intoxication in critically ill patients with Acute Kidney Injury: The role of Sustained Low-Efficiency Dialysis

The use of dabigatran in patients with non-valvular atrial fibrillation (AF) has widely increased in the last decades, due to its positive effects in terms of safety/efficacy. However, because of the risk of major bleeding, a great degree of attention has been suggested in elderly patients with multiple comorbidities. Notably, dabigatran mainly undergoes renal elimination and dose adjustment is recommended in patients with Chronic Kidney Disease (CKD). In this regard, the onset of an abrupt decrease of kidney function may further affect dabigatran pharmacokinetic profile, increasing the risk of acute intoxication. Idarucizumab is the approved antagonist in the case of dabigatran-associated major bleeding or concomitant need of urgent surgery, but its clinical use is limited by the lack of data in patients with Acute Kidney Injury (AKI). Thus, the early start of Extracorporeal Kidney Replacement Therapy (EKRT) could be indicated to remove the drug and to reverse the associated excess anticoagulation. Sustained Low-Efficiency Dialysis (SLED) could represent an effective therapeutic option to reduce the dabigatran plasma levels rapidly while avoiding post-treatment rebound. We present here a case series of three AKI patients with acute dabigatran intoxication, effectively and safely resolved with a single SLED session.

A ratiometric electrochemical probe for the quantification of apixaban in unprocessed plasma samples using carbon aerogel/BFO modified glassy carbon electrodes

A novel electrochemical probe was established for the quantification of apixaban (APX) in unprocessed plasma samples. Efficiently oxidized graphene oxide aerogels (EEGO-AGs) and nano-sized Bi2Fe4O9 (BFO) particles were electrodeposited on the surface of a glassy carbon electrode (GCE). In this work, a ratiometric electrochemical method was introduced for APX detection to enhance the specificity of the probe in plasma samples. The fabricated ratiometric probe was employed for the indirect detection determination of APX using K3[Fe(CN)6]/K4[Fe(CN)6] as the redox pair. The differential pulse voltammetry technique was used to record the current alteration of the BFO/EEGO-AG-functionalized GCE probe at various APX concentrations. The probe response was proportional to the APX concentrations from 10 ng mL-1 to 10 μg mL-1 with a low limit of quantification (LLOQ) of 10 ng mL-1. After validation, this method was successfully utilized for the determination of APX in patients' plasma samples who have taken APX regularly. The fabricated chemosensor detected APX concentrations in unprocessed plasma samples with high selectivity, resulting from the physical filtering antifouling activity of aerogels.

Clinical outcomes and predictors of a gap in direct-acting oral anticoagulant therapy in the elderly: A time-varying analysis of a nationwide cohort study

INTRODUCTION

As direct-acting oral anticoagulants (DOACs) have short half-lives of around 12 h, even a short gap in DOAC therapy may diminish anticoagulation effects, increasing risks of adverse clinical outcomes. We aimed to evaluate clinical consequences of a gap in DOAC therapy with atrial fibrillation (AF) and to identify its potential predictors.

MATERIALS AND METHODS

In this retrospective cohort study, we included DOAC users aged over 65 years with AF from the 2018 Korean nationwide claims database. We defined a gap in DOAC therapy as no claim for a DOAC one or more days after the due date of a refill prescription. We used a time-varying-analysis method. The primary outcome was a composite of death and thrombotic events including ischemic stroke/transient ischemic attack or systemic embolism. Potential predictors of a gap included sociodemographic and clinical factors.

RESULTS AND CONCLUSIONS

Among 11,042 DOAC users, 4857 (44.0 %) patients had at least one gap. Standard national health insurance, non-metropolitan locations of medical institutions, history of liver disease, chronic obstructive pulmonary disease, cancer, or dementia, and use of diuretics or non-oral agents were associated with increased risks of a gap. In contrast, history of hypertension, ischemic heart disease, or dyslipidemia were associated with a decreased risk of a gap. A short gap in DOAC therapy was significantly associated with a higher risk of the primary outcome compared to no gap (hazard ratio 4.04, 95 % confidence interval 2.95-5.52). The predictors could be utilized to identify at-risk patients to provide additional support to prevent a gap.

Direct Oral Anticoagulants: An Updated Systematic Review of Their Clinical Pharmacology and Clinical Effectiveness and Safety in Patients With Nonvalvular Atrial Fibrillation

Direct oral anticoagulants have been an increasingly used class of drugs in the setting of nonvalvular atrial fibrillation, defying vitamin K antagonists' monopoly when it comes to anticoagulation due to its several limitations. Direct oral anticoagulants (DOACs) have entered the market as a noninferior and safer option in comparison with vitamin K antagonists, as their respective phase III clinical trials proved. The aim of this article was to update and summarize data on their clinical pharmacology and to review real-world data to know their comparative effectiveness and safety. We performed a systematic review using PubMed, Google Scholar, Embase, and Web of Science as search engines. Regarding pharmacodynamics, there were no substantial changes reported from their original profile. There were many advances in the knowledge about clinical pharmacokinetics of DOACs that have had a direct impact on their clinical use, mainly related to drug-drug interactions. In a real-world setting, DOACs have shown to be noninferior in preventing thromboembolic events compared to vitamin K antagonists. In regards to safety, DOACs have shown a lower bleeding risk relative to warfarin. Comparison between DOACs has demonstrated rivaroxaban to have the highest bleeding risk. Overall, the evidence gathered showed few changes from the original data presented in phase III clinical trials, concluding that their real-world use coincides greatly with them.

General Framework to Quantitatively Predict Pharmacokinetic Induction Drug-Drug Interactions Using In Vitro Data

INTRODUCTION

Metabolic inducers can expose people with polypharmacy to adverse health outcomes. A limited fraction of potential drug-drug interactions (DDIs) have been or can ethically be studied in clinical trials, leaving the vast majority unexplored. In the present study, an algorithm has been developed to predict the induction DDI magnitude, integrating data related to drug-metabolising enzymes.

METHODS

The area under the curve ratio (AUC_ratio) resulting from the DDI with a victim drug in the presence and absence of an inducer (rifampicin, rifabutin, efavirenz, or carbamazepine) was predicted from various in vitro parameters and then correlated with the clinical AUC_ratio (N = 319). In vitro data including fraction unbound in plasma, substrate specificity and induction potential for cytochrome P450s, phase II enzymes and uptake, and efflux transporters were integrated. To represent the interaction potential, the in vitro metabolic metric (IVMM) was generated by combining the fraction of substrate metabolised by each hepatic enzyme of interest with the corresponding in vitro fold increase in enzyme activity (E) value for the inducer.

RESULTS

Two independent variables were deemed significant and included in the algorithm: IVMM and fraction unbound in plasma. The observed and predicted magnitudes of the DDIs were categorised accordingly: no induction, mild, moderate, and strong induction. DDIs were assumed to be well classified if the predictions were in the same category as the observations, or if the ratio between these two was < 1.5-fold. This algorithm correctly classified 70.5% of the DDIs.

CONCLUSION

This research presents a rapid screening tool to identify the magnitude of potential DDIs utilising in vitro data which can be highly advantageous in early drug development.

Impact of amiodarone on plasma concentration of direct oral anticoagulant in patients with atrial fibrillation

BACKGROUND/PURPOSE

Amiodarone increases exposure of direct oral anticoagulants (DOACs). We aimed to analyze the effects of concurrent amiodarone use on DOAC concentrations and clinical outcomes.

METHODS

Patients who were ≥20 years of age, had atrial fibrillation, and took DOAC were enrolled to provide trough and peak samples for DOAC concentration measurements using ultra-high-performance liquid chromatography-tandem mass spectrometry. The results were compared with concentrations reported in clinical trials to define above, within, or under the expected range. The outcomes of interest were major bleeding and any gastrointestinal bleeding. Multivariate logistic regression and Cox proportional hazards model were used to determine the impact of amiodarone on above-range concentration and clinical outcomes, respectively.

RESULTS

A total of 722 participants (420 men, 58.2%) were enrolled to provide 691 trough samples and 689 peak samples. Among them, 21.3% concurrently used amiodarone. The proportion of patients with above-range trough and peak concentrations was 16.4% and 30.2%, respectively, for amiodarone users, in contrast to 9.4% and 19.8% for amiodarone non-users. The use of amiodarone was associated with above-range trough and peak concentrations (odds ratio [OR] = 2.00 [1.16, 3.47] and 1.82 [1.19, 2.79], respectively). However, amiodarone was not a significant predictor of major bleeding or any gastrointestinal bleeding.

CONCLUSION

Concurrent amiodarone use led to increased DOAC concentration but was not associated with a higher risk of major bleeding or any gastrointestinal bleeding. Therapeutic monitoring of DOAC users concurrently taking amiodarone may be recommended for patients with an additional risk of increased DOAC exposure.

Insights into the Pharmacokinetics and Pharmacodynamics of Direct Oral Anticoagulants in Older Adults with Atrial Fibrillation: A Structured Narrative Review

Older adults, the fastest growing population, represent almost 50% of all users of direct oral anticoagulants (DOACs). Unfortunately, we have very little relevant pharmacological and clinical data on DOACs, especially in older adults with geriatric profiles. This is highly relevant as pharmacokinetics and pharmacodynamics (PK/PD) often differ substantially in this population. Hence, we need to obtain a better understanding of the PK/PD of DOACs in older adults, to ensure appropriate treatment. This review summarises the current insights into PK/PD of DOACs in older adults. A search was undertaken up to October 2022 to identify PK/PD studies of apixaban, dabigatran, edoxaban, and rivaroxaban, that included older adults aged ≥ 75 years. This review identified 44 articles. Older age alone did not influence exposure of edoxaban, rivaroxaban and dabigatran, while apixaban peak concentrations were 40% higher in older adults than in young volunteers. Nevertheless, high interindividual variability in DOAC exposure in older adults was noted, which can be explained by distinctive older patient characteristics, such as kidney function, changes in body composition (especially reduced muscle mass), and co-medication with P-gp inhibitors, which is in line with the current dosing reduction criteria of apixaban, edoxaban, and rivaroxaban. Dabigatran had the largest interindividual variability among all DOACs since its dose adjustment criterion is only age, and thus it is not a preferable option. Additionally, DOAC exposure, which fell outside of on-therapy ranges, was significantly related to stroke and bleeding events. No definite thresholds linked to these outcomes in older adults have been established.

Analysis of the clinical characteristics of dabigatran-induced oesophagitis

OBJECTIVES

Dabigatran-induced oesophagitis has emerged in recent years. However, the incidence and clinical characteristics of patients with dabigatran-induced oesophagitis have not yet been clarified. The aim of this study was to examine the clinical characteristics of the disease.

METHODS

A retrospective analysis was undertaken of the literature on dabigatran-induced oesophagitis in Chinese and English from 2008 onwards.

RESULTS

There were 20 men (74.07%) and seven women (25.93%) in the study; their median age was 75 years (range 37-90). The main clinical symptoms were dysphagia (42.31%), odynophagia (26.92%), retrosternal pain (23.08%) and heartburn (23.08%). Endoscopy mainly showed sloughing mucosal casts (14 cases, 56%), ulcers (8 cases, 32%) and erosion (6 cases, 24%). The main injury sites were the mid to lower oesophagus (32%) and the mid oesophagus (32%). Withdrawal of dabigatran or giving the correct medication regimen resulted in rapid recovery of clinical symptoms from 1 day in some patients and up to 4 weeks, and mucosal recovery (2-5 weeks) in a median time of 3 weeks (range 0.29-48) in all patients.

CONCLUSIONS

Oesophagitis is a rare complication of dabigatran with a good prognosis. Patients should be given proper medication instructions to prevent the occurrence of dabigatran-induced oesophagitis.

Dabigatran etexilate is efficacious in consumptive coagulopathy and pain associated with venous malformations

OBJECTIVE

Consumptive coagulopathy treatment and pain management are crucial for patients with venous malformations (VMs). Dabigatran etexilate, a non-vitamin K antagonist oral anticoagulant, has known advantages compared with low-molecular-weight heparin and vitamin K antagonists, including oral administration, a more consistent pharmacokinetics/pharmacodynamics profile, a better safety profile, and no need for coagulation surveillance. In the present study, we tested the efficacy and safety of dabigatran etexilate for consumptive coagulopathy treatment and pain management for patients with VMs.

METHODS

To investigate the efficacy and safety of dabigatran etexilate in treating localized intravascular coagulation (LIC) associated with VM, we retrospectively collected data for 19 outpatients with VM and LIC, who had been treated with dabigatran etexilate from September 2019 to June 2021. The patients provided oral informed consent and underwent biologic blood testing, routine examinations, and determination of coagulation function before and after treatment. The dosage of dabigatran etexilate was 110 mg twice daily for adults and 55 mg twice daily for children.

RESULTS

All 19 patients had benefited from dabigatran etexilate treatment with coagulation improvement and pain relief. Pain had improved in all 16 evaluable patients. The fibrinogen and D-dimer levels had improved in 18 of 19 patients. The fibrin degradation product level had improved in 10 of 14 patients. None of patients reported lesion regression, appearance changes, or improvement in mobility. No significant differences were found in the D-dimer, fibrinogen, and fibrin degradation product levels between the short-term (<10 days) and long-term (≥10 days) use of the medication. Dabigatran etexilate was well tolerated by all patients. No bleeding event had occurred during follow-up.

CONCLUSIONS

The results of our study have confirmed the efficacy and safety of dabigatran etexilate in treating pain and LIC in patients with VMs. Dabigatran etexilate is a suitable choice preoperatively to modify coagulation function and pain in patients with VMs.

Interactions Between Direct Oral Anticoagulants (DOACs) and Antiseizure Medications: Potential Implications on DOAC Treatment

The use of direct oral anticoagulants (DOACs) is increasing because of their superior efficacy and safety compared with vitamin K antagonists. Pharmacokinetic drug interactions, particularly those involving cytochrome P450- mediated metabolism and P-glycoprotein transport, significantly affect the efficacy and safety of DOACs. In this article, we assess the effects of cytochrome P450- and P-glycoprotein-inducing antiseizure medications on DOAC pharmacokinetics in comparison to rifampicin. Rifampicin decreases to a varying extent the plasma exposure (area under the concentration-time curve) and peak concentration of each DOAC, consistent with its specific absorption and elimination pathways. For apixaban and rivaroxaban, rifampicin had a greater effect on the area under the concentration-time curve than on peak concentration. Therefore, using peak concentration to monitor DOAC concentrations may underestimate the effect of rifampicin on DOAC exposure. Antiseizure medications that are cytochrome P450 and P-glycoprotein inducers are commonly used with DOACs. Several studies have observed a correlation between the concomitant use of DOACs and enzyme-inducing antiseizure medications and DOAC treatment failure, for example, ischemic and thrombotic events. The European Society of Cardiology recommends avoiding this combination, as well as the combination of DOACs with levetiracetam and valproic acid, owing to a risk of low DOAC concentrations. However, levetiracetam and valproic acid are not cytochrome P450 or P-glycoprotein inducers, and the implications of their use with DOACs remain to be elucidated. Our comparative analysis suggests DOAC plasma concentration monitoring as a possible strategy to guide dosing owing to the predictable correlation between DOACs' plasma concentration and effect. Patients taking concomitant enzyme-inducing antiseizure medications are at risk for low DOAC concentrations and subsequently, treatment failure and thus can benefit from DOAC concentration monitoring to prophylactically identify this risk.

Effects of Simvastatin on Pharmacokinetics and Anticoagulant Effects of Dabigatran in Healthy Subjects

Higher risk of major hemorrhage associated with concomitant use of dabigatran and simvastatin compared to other statins was previously reported with a suggestion of P-glycoprotein-mediated interaction. The aim of this study was to evaluate the effects of simvastatin on pharmacokinetics and anticoagulant effects of dabigatran, a direct oral anticoagulant. A total of 12 healthy subjects were enrolled in an open-label, two-period, single sequence study. Subjects were given 150 mg of dabigatran etexilate followed by 40 mg of once-daily simvastatin for seven days. Dabigatran etexilate was administered with simvastatin on the seventh day of simvastatin administration. Blood samples for pharmacokinetic and pharmacodynamic analyses were obtained until 24 h post-dose of dabigatran etexilate with or without co-administration of simvastatin. Pharmacokinetic parameters were derived from noncompartmental analysis for dabigatran etexilate, dabigatran, and dabigatran acylglucuronide. When simvastatin was co-administered, geometric mean ratios of area under time-concentration curves for dabigatran etexilate, dabigatran, and dabigatran acylglucuronide were 1.47, 1.21, and 1.57, respectively, compared to when dabigatran etexilate was administered alone. Thrombin generation assay and coagulation assay showed similar profiles between before and after co-administration of simvastatin. This study provides evidence that simvastatin treatment plays a minor role in modulating pharmacokinetics and anticoagulant effects of dabigatran etexilate.

Clinical conundrums involving statin drug-drug interactions

Statins are the cornerstone of pharmacologic therapy for the prevention and treatment of atherosclerotic cardiovascular disease. While they are generally considered safe, statins can be affected by drug-drug interactions (DDIs) that increase their systemic exposure increasing the risk for statin-associated muscle symptoms. These interactions are primarily mediated through metabolizing enzymes such as cytochrome P450 isoenzymes and membrane-bound drug transporting proteins including P-glycoprotein and organic ion transporting polypeptide. Recognition and avoidance of clinically significant statin DDIs is important to ensure their safe use. Conversely, concern over statin DDIs that are not clinically significant may lead to inappropriate underutilization or avoidance of statins in patients who would benefit from them. While many statin DDIs are well-characterized, we present several others that are less-well-established which may warrant clinical attention.

Twice- or once-daily dosing of direct oral anticoagulants and gastrointestinal bleeding in patient with atrial fibrillation

Aims

Direct oral anticoagulant (DOAC) is widely used for the prevention of embolic stroke in non-valvular atrial fibrillation (NVAF) patients. However, the gastrointestinal bleeding risk in several DOAC regimens was higher than warfarin, especially in once-daily regimens.

Methods and results

We conducted a single-center prospective registry of patients with NVAF treated with DOACs: the DIRECT registry (N = 2216; follow-up duration 650 [IQR 103-1574] days, UMIN000033283). All patients were divided into 2 groups: the twice-daily (BID) regimen group (dabigatran and apixaban) versus the once-daily (QD) regimen group (rivaroxaban and edoxaban). Out of 2216 patients, we successfully matched 904 patients in the QD group and 904 patients in the BID group using propensity score. The primary endpoint was gastrointestinal bleeding defined as any bleeding in the gastrointestinal tract that was identified through medical records regardless of bleeding site or severity. The BID group showed a significantly lower gastrointestinal bleeding rate than the QD group (3.5/100 person-year vs. 6.2/100 person-year, log-rank P < 0.0001). The secondary endpoints were all death, stroke, major bleeding, and any bleeding. The rate of major bleeding was significantly lower in patients with BID regimen group (log-rank P = 0.040). In contrast, all death, stroke, and any bleeding did not differ between both groups (log-rank P = 0.280, 0.520 and 0.066, respectively).

Conclusions

The BID regimen as compared with the QD regimen was associated with reduced risk of gastrointestinal bleeding.

Direct oral anticoagulants after bariatric surgery-What is the evidence?

BACKGROUND

Obesity is a global epidemic and bariatric surgery is used with increasing frequency to treat its complications. The extent to which bariatric surgery alters the efficacy, safety, and pharmacokinetics of direct oral anticoagulants (DOACs) is unknown.

AIMS

In this review, we summarize the evidence supporting the use of DOACs after bariatric surgery and apply our findings to resolve several clinical cases.

MATERIALS & METHODS

We systematically searched MEDLINE, EMBASE, Cochrane Library, CINAHL and ClinicalTrials.gov from January 1, 2000, to June 15, 2021 for randomized and non-randomized studies evaluating the use of DOACs for any indication after bariatric surgery. Two reviewers independently screened titles, abstracts, and full-text articles. Clinical and pharmacokinetic outcomes were pooled by random-effects meta-analysis with inverse variance weighting. We used the Newcastle-Ottawa scale to assess risk of bias in non-randomized studies and assessed the certainty of evidence with GRADE.

RESULTS

From 2519 records, we included 28 studies (n = 3229 patients): no randomized trials, 7 cohort studies, 6 case series, and 15 case reports. Incidence rates for arterial thromboembolism, venous thromboembolism and major bleeding were: 0.73 (95% confidence interval [CI]: 0.01-5.10), 2.45 (95% CI: 0.40-7.94), and 3.40 (95% CI: 0.80-9.36) events per 100 patient-years, respectively. The pooled proportion of peak direct oral anticoagulant drug levels within the expected range was 58% (95% CI: 39%-74%).

CONCLUSION

There appears be substantial risk of DOAC malabsorption after bariatric surgery that could affect clinical outcomes, however the certainty of evidence was very low.

PROSPERO

CRD42020202636.

Anticoagulant Effects of Dabigatran on Coagulation Laboratory Parameters in Pediatric Patients: Combined Data from Five Pediatric Clinical Trials

Background  Dabigatran etexilate, a direct oral thrombin inhibitor, is approved to treat venous thromboembolism (VTE) in both adults and children.

Objectives  This population analysis characterized relationships between dabigatran total plasma concentrations and coagulation laboratory parameters (activated partial thromboplastin time [aPTT]; diluted thrombin time [dTT]; ecarin clotting time [ECT]).

Methods  Data from three phase 2a and one single-arm and one randomized, comparative phase 2b/3 pediatric studies (measurements: aPTT 2,925 [ N  = 358]; dTT 2,348 [ N  = 324]; ECT 2,929 [ N  = 357]) were compared with adult data (5,740 aPTT, 3,472 dTT, 3,817 ECT measurements; N  = 1,978). Population models were fitted using nonlinear mixed-effects modeling. Covariates (e.g., sex, age) were assessed on baseline and drug-effect parameters, using a stepwise covariate model-building procedure.

Results  Overall, relationships between dabigatran, aPTT, dTT, and ECT were similar in children and adults. For children aged <6 months, a higher proportion of baseline samples were outside or close to the upper aPTT and ECT adult ranges. No age-related differences were detected for dTT. With increasing dabigatran concentration, aPTT rose nonlinearly (half the maximum effect at 368 ng/mL dabigatran) while dTT and ECT increased linearly (0.37 and 0.73% change per ng/mL dabigatran, respectively). Mean baseline aPTT (45 vs. 36 seconds) and ECT (40 vs. 36 seconds) were slightly increased for those aged <6 months versus older children.

Conclusion  The similar relationships of laboratory parameters observed across pediatric age groups suggests that developmental changes in the hemostatic system may have little effect on response to dabigatran.

Safety of Non-Vitamin K Antagonist Oral Anticoagulant Treatment in Patients with Chronic Kidney Disease and Kidney Transplant Recipients

The use of novel oral anticoagulants in patients with impaired renal function or undergoing immunosuppressive therapy is limited due to the risk of drug-to-drug interactions and anticoagulation-related adverse events. This article aims to assess the current data on the safety of direct-acting oral anticoagulant-based therapy in the population of kidney transplant recipients and patients with impaired renal function. The most important factors affecting the safety of treatment are the incidence of bleeding events, thromboembolic events, deaths and drug-to-drug interactions. The available data were compared to the findings on warfarin-based anticoagulation. Findings on the use of novel oral anticoagulants in kidney transplant recipients are limited yet promising in terms of safety and efficacy of use. However, current recommendations state that the co-administration of non-vitamin K antagonist oral anticoagulants with several immunosuppressive agents is contraindicated.

Development and Validation of UPLC-MS/MS Method for Quantifying of Free and Total Dabigatran in Human Plasma: An Application for a Bioequivalence Study

Dabigatran etexilate mesylate (DABE), a prodrug, quickly changes in our bodies after its oral administration into dabigatran (DAB). Accordingly, detecting DABE in plasma is practically unmanageable. A UPLC-MS/MS technique was developed and validated to compute free DAB in participants. For the first time, the central composite design- a type of response surface methodology- was utilized for optimizing variables affecting the cleavage of glucuronide bond. Additionally, the pharmacokinetic parameters of generic medication (okanadab) were determined, and the obtained outcomes were compared to those of branded drug (pradaxa®). The sample preparation was done using methanol as a protein precipitant and the separation was achieved via ACQUITY UPLC BEH C18 column (2.1x50mm, 1.7μm). The elution was isocratically conducted using 10mM ammonium formate: methanol (72:28, v/v) as a mobile phase (MP) and the flow rate was 0.25mL/min. Multiple reaction monitoring (MRM) and positive electrospray ionization (ESI) were used. The determination was performed within 1min, and the calibration growth curve was established over a range of (1.19 - 475) ng/mL using dabigatran-d3 as a tagged internal standard (IS). Bioequivalence research was validated following FDA guidelines for bio-analytical procedures and acceptable outcomes were achieved. The outcomes for okanadab and pradaxa® did not differ significantly.

Biopharmaceutics considerations for direct oral anticoagulants

Vitamin K antagonists (VKA) and direct oral anticoagulants (DOACs) have been clinically used in the treatment of coagulation disorders. There are four DOACs approved since 2010 (dabigatran etexilate, rivaroxaban, apixaban, and edoxaban), and they were designed to overcome the practical limitations of VKA. This review summarized biopharmaceutics considerations about DOACs, which are critically discussed, applying risk analyses to subside the further classification of these drugs according to the Biopharmaceutics Classification System (BCS). These discussions included data compiled about physicochemical properties, equilibrium solubility, permeability, and drug dissolution of DOACs. From the biopharmaceutics characteristics is possible to identify critical variables related to the absorption process, which can help in the design of new formulations. The data were compared with the criteria recommended by regulatory agencies for the biopharmaceutics classification according to the BCS. From that, these data may be used to discuss the approval of generic medicines by the BCS-based biowaiver, and the clinical risks arising from novel formulations with DOACs. However, although there are indications of biopharmaceutics classifications for DOACs, conclusive information to classify these compounds according to the BCS is lacking, requiring more experimental studies to achieve this aim. Conclusive information is essential for a safe decision about the biowaiver, as well as to guide the development of new formulations containing the DOACs.

The value and limitations of new oral anticoagulant plasma level assessments

The class of new oral anticoagulants (NOACs) has been developed to provide reliable oral anticoagulation without the need for therapeutic drug monitoring. Based on phase I and II trials and pharmacokinetic and pharmacodynamic modeling, fixed drug doses have been selected for large phase III clinical trials for each currently available NOAC. In these trials, the use of the fixed dose without plasma level assessments was shown to be at least as effective and at least as safe as vitamin K antagonists with continuous therapeutic drug monitoring. Real world evidence reaffirms that the use of a fixed NOAC dose without plasma level assessment is safe and effective in a large variety of patients. Nevertheless, measurement of NOAC plasma levels can add information that may be useful in some clinical scenarios. This review discusses the possible use cases, the limitations, and the practical implementation of measuring NOAC plasma concentrations.

Low Exposure to Direct Oral Anticoagulants Is Associated with Ischemic Stroke and Its Severity

Background and purpose

In acute stroke patients, plasma concentrations of direct oral anticoagulants (DOAC) at hospital admission only poorly mirror DOAC exposure or the coagulation status at the time of the event. Here, we evaluated whether DOAC exposure and DOAC plasma concentration at the time of transient ischemic attacks (TIA) and ischemic strokes correlate with their likelihood of occurrence.

Methods

Prospectively, consecutive DOAC patients with acute ischemic stroke or TIA were included. Admission DOAC plasma concentrations were measured by ultraperformance liquid chromatography– tandem mass spectrometry. Individual DOAC exposure (area under the curve) and DOAC concentrations at event onset were derived from population pharmacokinetic analyses.

Results

DOAC exposure was successfully modeled in 211 patients (ischemic stroke 74.4%, TIA 25.6%). Compared to published values, 63.0% had relatively lower DOAC exposure and they more often received lower DOAC doses than recommended (odds ratio [OR], 2.125; 95% confidence interval [CI], 1.039 to 4.560; P=0.044). These patients more likely suffered ischemic strokes than TIA (OR, 2.411; 95% CI, 1.254 to 4.638; P=0.008) and their strokes were more severe (slope, 3.161; 95% CI, 0.741 to 5.58; P=0.011). Low relative DOAC concentrations at event onset were likewise associated with ischemic strokes (OR, 4.123; 95% CI, 1.834 to 9.268; P=0.001), but not to stroke severity (P=0.272). DOAC exposure had a higher explanatory value for stroke severity than concentrations at event.

Conclusions

Low DOAC exposure is strongly associated to ischemic stroke and its severity. By monitoring DOAC plasma concentrations, patients prone to ischemic stroke might be identified.

Effects of direct oral anticoagulants dabigatran and rivaroxaban on the blood coagulation function in rabbits

The aim of this study was to explore the effects of dabigatran and rivaroxaban on the activities of various coagulation factors. To achieve that, 60 rabbits were randomly divided into experimental groups that received different doses of dabigatran or rivaroxaban. The effects of dabigatran and rivaroxaban on the activities of FII, FV, FVIII, FX, and activated protein C (APC) were analyzed. In the dabigatran groups, activated partial thromboplastin time and thromboplastin time (TT) were prolonged after drug administration, and the activities of FII, FV, FVIII, and FX were inhibited as the drug concentration increased. Low doses of dabigatran inhibited APC activity. In the rivaroxaban groups, APTT and TT were not significantly prolonged after drug administration. In contrast, the high-dose rivaroxaban group exhibited prolonged PT, and the degree of inhibition of the activities of FII, FV, FVIII, and FX increased as the drug concentration increased. Rivaroxaban had no significant effect on APC activity regardless of dosage. As the drug concentration increased, both NOACs had more significant inhibitory effects on the activities of FII, FV, FVIII, and FX. Low concentrations of dabigatran generated an inhibitory effect on APC activity, while high concentrations of dabigatran had no significant effect. Rivaroxaban had no significant effect on APC activity.

Dabigatran Acylglucuronide, the Major Metabolite of Dabigatran, Shows a Weaker Anticoagulant Effect than Dabigatran

Dabigatran (DAB) is an orally administered thrombin inhibitor. Both DAB and its main metabolite dabigatran acylglucuronide (DABG) have established anticoagulant effects. Here, we aimed to compare the relative anticoagulant effects of DABG and DAB in humans. Anticoagulant effects of DAB and DABG were measured in vitro using a thrombin generation assay. Additionally, their effects on other coagulation assays including PT, aPTT, TT, and fibrinogen were compared. Both DAB and DABG showed inhibitory effects on thrombin generation in a dose-dependent manner, but DABG exhibited a weaker inhibitory effect than that of DAB. The IC₅₀ values of DAB and DABG on thrombin generation AUC were 134.1 ng/mL and 281.9 ng/mL, respectively. DABG also exhibited weaker anticoagulant effects than DAB on PT, aPTT, and TT. The results of the present study indicate that the anticoagulant effect of DABG, a main active DAB metabolite, is weaker than that of DAB.

Impact of different renal function equations on direct oral anticoagulant concentrations

The purpose of this study is to investigate the correlation between glomerular filtration rate (GFR) estimated by different renal function equations and non-vitamin K antagonist oral anticoagulant concentration. Atrial fibrillation patients who aged ≥ 20 years and used dabigatran, rivaroxaban, or apixaban for thromboembolism prevention were enrolled to collect blood samples and measure drug concentrations using ultra-high-performance liquid chromatography with tandem mass spectrometry. The GFR was estimated using the Cockroft–Gault formula (abbreviated as creatinine clearance, CrCL), Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI) featuring both creatinine and cystatin C, and the Modification of Diet in Renal Disease Study equation (MDRD). Multivariate regression was used to investigate the associations of different renal function estimates with drug concentrations. A total of 511 participants were enrolled, including 146 dabigatran users, 164 rivaroxaban users and 201 apixaban users. Compared to clinical trials, 35.4% of dabigatran, 4.9% of rivaroxaban, and 5.5% of apixaban concentrations were higher than the expected range (p < 0.001). CKD-EPI and MDRD estimates classified fewer patients as having GFR < 50 mL/min than CrCL in all 3 groups. Both CrCL and CKD-EPI were associated with higher-than-expected ranges of dabigatran or rivaroxaban concentrations. Nevertheless, none of the renal function equations was associated with higher-than-expected apixaban concentrations. For participants aged ≥ 75 years, CKD-EPI may be associated with higher-than-expected trough concentration of dabigatran. In conclusion, CrCL and CKD-EPI both can be used to identify patients with high trough concentrations of dabigatran or rivaroxaban. Among elderly patients who used dabigatran, CKD-EPI may be associated with increased drug concentration.

Assessment of exposure to direct oral anticoagulants in elderly hospitalised patients

It is unclear whether elderly patients established on direct oral anticoagulants (DOACs) have greater exposure to these drugs, which could subsequently increase their risk of bleeding. We assessed DOAC exposure and factors affecting it in a real-world elderly cohort of patients. For this, 151 medically stable hospital inpatients (76 established on apixaban, 61 on rivaroxaban, 14 on dabigatran) with a median [interquartile range (IQR)] age of 84 (78-89) years were recruited. Patients provided blood samples for measurement of peak and trough plasma DOAC concentrations. There was up to 48-fold and 13-fold variation in trough and peak plasma drug concentrations respectively. A significantly greater proportion of patients on apixaban had peak plasma drug concentrations within the reported ranges compared to those on either rivaroxaban or dabigatran (82·9% vs. 44·3% vs. 64·3% respectively; P < 0·001). A third of the variability in DOAC plasma concentrations was attributed to the influences of DOAC dosage, renal function and gender. To what extent the observed increases in DOAC exposure in the older patients is the cause of their increased risk of bleeding, which could potentially be ameliorated by dosing titration, requires further investigation.

Nonvalvular atrial fibrillation patients anticoagulated with rivaroxaban compared with warfarin exhibit reduced circulating extracellular vesicles with attenuated pro-inflammatory protein signatures

BACKGROUND

Rivaroxaban, a direct oral factor Xa inhibitor, mediates anti-inflammatory and cardiovascular-protective effects besides its well-established anticoagulant properties; however, these remain poorly characterized. Extracellular vesicles (EVs) are important circulating messengers regulating a myriad of biological and pathological processes and may be highly relevant to the pathophysiology of atrial fibrillation as they reflect alterations in platelet and endothelial biology. However, the effects of rivaroxaban on circulating pro-inflammatory EVs remain unknown.

OBJECTIVES

We hypothesized that rivaroxaban's anti-inflammatory properties are reflected upon differential molecular profiles of circulating EVs.

METHODS

Differences in circulating EV profiles were assessed using a combination of single vesicle analysis by Nanoparticle Tracking Analysis and flow cytometry, and proteomics.

RESULTS

We demonstrate, for the first time, that rivaroxaban-treated non-valvular atrial fibrillation (NVAF) patients (n=8) exhibit attenuated inflammation compared with matched warfarin controls (n=15). Circulating EV profiles were fundamentally altered. Moreover, quantitative proteomic analysis of enriched plasma EVs from six pooled biological donors per treatment group revealed a profound decrease in highly pro-inflammatory protein expression and complement factors, together with increased expression of negative regulators of inflammatory pathways. Crucially, a reduction in circulating levels of soluble P-selectin was observed in rivaroxaban-treated patients (compared with warfarin controls), which negatively correlated with the patient's time on treatment.

CONCLUSION

Collectively, these data demonstrate that NVAF patients anticoagulated with rivaroxaban (compared with warfarin) exhibit both a reduced pro-inflammatory state and evidence of reduced endothelial activation. These findings are of translational relevance toward characterizing the anti-inflammatory and cardiovascular-protective mechanisms associated with rivaroxaban therapy.

Strategies for the prevention and treatment of bleeding in patients treated with dabigatran: an update

INTRODUCTION

Although dabigatran is safer than vitamin K antagonists, bleeding still occurs. Bleeding is an important cause of short-term morbidity and rarely mortality and can also have long-term consequences that are often under-appreciated. After bleeding, patients often do not restart treatment or are poorly adherent, which is associated with increased thromboembolism and mortality. Consequently, we need strategies to prevent and treat bleeding in patients with atrial fibrillation treated with dabigatran.

AREAS COVERED

We review a) relevant dabigatran pharmacology, b) the burden and consequences of bleeding, c) how to identify patients at high risk of bleeding; and d) existing and novel approaches to prevent and treat bleeding in dabigatran-treated patients.

EXPERT OPINION

Concerns about the risk of bleeding associated with anticoagulant therapy and emerging evidence of increased risk of thromboembolism and mortality after bleeding highlight the need for improved approaches to prevention and treatment of bleeding. Future research priorities should focus on improving our ability to prevent bleeding by identifying modifiable risk factors and the development of safer agents. The current front runners include drugs that selectively target the contact pathway of coagulation (e.g. factor XI). Targeting upstream drivers of thrombosis (e.g. inflammation) could help to further reduce the risk of thromboembolism.

The Clinical Significance of Drug-Food Interactions of Direct Oral Anticoagulants

Cardiovascular diseases are the most common cause of death in the world. For almost 60 years, vitamin K antagonists (VKAs) were the mainstay of anticoagulation therapy, but in recent years direct oral anticoagulants (DOACs) have become the anticoagulant treatment of choice. DOACs were initially considered drugs with no significant food interactions; however, clinical observations from daily practice have proved otherwise as interactions with food ingredients have been reported. Food, dietary supplements or herbs may contain substances that, when administered concomitantly with DOACs, can potentially affect the plasma concentration of the drugs. The aim of this paper was to evaluate the clinical significance of drug-food interactions of DOACs, such as dabigatran, rivaroxaban, apixaban, edoxaban and betrixaban. Patients treated with anticoagulants should avoid products containing St. John's wort and take special care with other food ingredients. As the interest in dietary supplements is on the rise, healthcare providers can contribute to the development of well-designed clinical trials on interactions between DOACs and food, and distribute sufficient knowledge about the proper use of these supplements among patients.

Reduced physiologically-based pharmacokinetic model of dabigatran etexilate-dabigatran and its application for prediction of intestinal P-gp-mediated drug-drug interactions

BACKGROUND

Dabigatran etexilate (DABE) has been suggested as a clinical probe for intestinal P-glycoprotein (P-gp)-mediated drug-drug interaction (DDI) studies and, as an alternative to digoxin. Clinical DDI data with various P-gp inhibitors demonstrated a dose-dependent inhibition of P-gp with DABE. The aims of this study were to develop a joint DABE (prodrug)-dabigatran reduced physiologically-based-pharmacokinetic (PBPK) model and to evaluate its ability to predict differences in P-gp DDI magnitude between a microdose and a therapeutic dose of DABE.

METHODS

A joint DABE-dabigatran PBPK model was developed with a mechanistic intestinal model accounting for the regional P-gp distribution in the gastrointestinal tract. Model input parameters were estimated using DABE and dabigatran pharmacokinetic (PK) clinical data obtained after administration of DABE alone or with a strong P-gp inhibitor, itraconazole, and over a wide range of DABE doses (from 375 µg to 400 mg). Subsequently, the model was used to predict extent of DDI with additional P-gp inhibitors and with different DABE doses.

RESULTS

The reduced DABE-dabigatran PBPK model successfully described plasma concentrations of both prodrug and metabolite following administration of DABE at different dose levels and when co-administered with itraconazole. The model was able to capture the dose dependency in P-gp mediated DDI. Predicted magnitude of itraconazole P-gp DDI was higher at the microdose (predicted vs. observed median fold-increase in AUC_+inh/AUC_control (min-max) = 5.88 (4.29-7.93) vs. 6.92 (4.96-9.66) ) compared to the therapeutic dose (predicted median fold-increase in AUC_+inh/AUC_control = 3.48 (2.37-4.84) ). In addition, the reduced DABE-dabigatran PBPK model predicted successfully the extent of DDI with verapamil and clarithromycin as P-gp inhibitors. Model-based simulations of dose staggering predicted the maximum inhibition of P-gp when DABE microdose was concomitantly administered with itraconazole solution; simulations also highlighted dosing intervals required to minimise the DDI risk depending on the DABE dose administered (microdose vs. therapeutic).

CONCLUSIONS

This study provides a modelling framework for the evaluation of P-gp inhibitory potential of new molecular entities using DABE as a clinical probe. Simulations of dose staggering and regional differences in the extent of intestinal P-gp inhibition for DABE microdose and therapeutic dose provide model-based guidance for design of prospective clinical P-gp DDI studies.

Human Variability in Carboxylesterases and carboxylesterase-related Uncertainty Factors for Chemical Risk Assessment

Carboxylesterases (CES) are an important class of enzymes involved in the hydrolysis of a range of chemicals and show large inter-individual variability in vitro. An extensive literature search was performed to identify in vivo probe substrates for CES1 and CES2 together with their protein content and enzymatic activity. Human pharmacokinetic (PK) data on Cmax, clearance, and AUC were extracted from 89 publications and Bayesian meta-analysis was performed using a hierarchical model to derive CES-related variability distributions and related uncertainty factors (UF). The CES-related variability indicated that 97.5% of healthy adults are covered by the kinetic default UF (3.16), except for clopidogrel and dabigatran etexilate. Clopidogrel is metabolised for a small amount by the polymorphic CYP2C19, which can have an impact on the overall pharmacokinetics, while the variability seen for dabigatran etexilate might be due to differences in the absorption, since this can be influenced by food intake. The overall CES-related variability was moderate to high in vivo (<CV 50%), which might be due to possible polymorphism in the enzyme but also to the small sample size available per chemical. The presented CES-related variability can be used in combination with in vitro data to derive pathway-specific distributions.

Pharmacokinetics and Safety of Dabigatran Etexilate after Single and Multiple Oral Doses in Healthy Chinese Subjects

Background and Objective

Dabigatran etexilate is a non-vitamin K antagonist oral anticoagulant (NOAC) that is used to prevent stroke and systemic embolism in adults with nonvalvular atrial fibrillation (NVAF) and one or more risk factors. Pharmacokinetic data on this anticoagulant in Chinese subjects are limited. This study aimed to provide further information on the pharmacokinetic profile of dabigatran in healthy Chinese subjects, together with its safety profile.

Methods

This was an open-label, single-centre, phase I study. Subjects were randomized into 110 and 150 mg dabigatran etexilate treatment groups. Each subject received 7 days of treatment: a single dose on day 1, no dose on days 2–3, and then multiple doses on days 4–10. Blood samples were collected to analyze the pharmacokinetic profile of dabigatran. All adverse events (AEs) were recorded. Routine clinical laboratory tests, a physical examination, vital signs, and 12-lead electrocardiogram (ECG) measurements were performed.

Results

A total of 28 subjects (14 males and 14 females) were randomized in this trial. The plasma concentration of total dabigatran reached its maximum measured concentration at a median time of 3–4 h from the dose of interest (either the initial single dose on day 1 or the final dose on day 10) under fed conditions, and declined with an elimination half-life of 10.7–10.9 h following the dose of interest. There was a modest difference in pharmacokinetic profile between male and female subjects. None of the subjects experienced a serious adverse event (SAE) or an AE of moderate or severe intensity. The investigator reported that 17 of the 28 subjects had mild treatment-emergent AEs that resolved without any concomitant treatment or intervention. No clinically significant changes in vital signs or ECG parameters were observed.

Conclusions

This study revealed the pharmacokinetic characteristics and good safety profile of dabigatran in healthy Chinese subjects.

Electronic supplementary material

The online version of this article (10.1007/s13318-020-00626-4) contains supplementary material, which is available to authorized users.

Development and validation of LC-MS/MS method for simultaneous determination of dabigatran etexilate and its active metabolites in human plasma, and its application in a pharmacokinetic study

Dabigatran is a direct thrombin inhibitor widely used for preventing various thrombotic events. Although there are several established LC-MS/MS based methods for quantification of plasma dabigatran etexilate and its active metabolites (dabigatran and dabigatran acylglucuronide), so far, there are no studies for simultaneous quantification of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. In the present study, a novel and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for assessment of dabigatran pharmacokinetics in human plasma samples according to FDA guidelines. We used the new method to simultaneously quantify dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. After deproteinization using acetonitrile, the supernatants were evaporated, dissolved in a mobile phase, and finally injected onto an HPLC system with a silica-based C₁₈ reverse-phase column. Mass spectrometer system was operated in multiple reaction monitoring mode (MRM) (dabigatran etexilate: m/z 629.464→290.100; dabigatran: m/z 472.300→289.100, and dabigatran acylglucuronide: m/z 648.382→289.100) and all the components were confirmed using positive electrospray ionization (ESI). Correlation coefficients > 0.999 were achieved for all the calibration curves with linear regression. The intra-day and inter-day accuracies of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide were 95.84-109.44 %, 99.4-103.42 %, and 98.37-104.42 %, respectively, while their corresponding precisions were 3.84-9.79, 1.07-8.76 %, and 2.56-4.51 %, respectively. We successfully applied the new method to determine the pharmacokinetic profiles of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in humans. Our findings demonstrated the method as robust, reliable, and sensitive.

Adherence to direct oral anticoagulant treatment for atrial fibrillation in the Netherlands: A surveillance study

BACKGROUND

Adherence to direct oral anticoagulants (DOACs) in patients with atrial fibrillation in every day practice may be less than in clinical trials.

AIMS

To assess adherence to DOACs in atrial fibrillation patients in every day practice and identify predictors for non-adherence.

METHODS

Individual linked dispensing data of atrial fibrillation patients who used DOACs were obtained from the Foundation for Pharmaceutical Statistics covering the Netherlands between 2012 and 2016. One year adherence to DOAC was calculated for initial DOAC as proportion of days covered (PDC) ≥80% and the association between clinical variables and adherence was assessed using logistic regression. In addition, we measured non-persistence, that is, patients who completely stopped their initial DOAC within 1 year follow-up.

RESULTS

A total of 4797 apixaban-, 20 454 rivaroxaban- and 18 477 dabigatran users were included. The mean age was 69 years (n = 43 910), which was similar for the DOAC types. The overall proportion of patients with PDC ≥80% was 76%, which was highest for apixaban- (87%), followed by dabigatran- (80%) and rivaroxaban (69%) users. Multivariable analyses revealed that age ≤60 years, no concomitant drug use were predictors for non-adherence. Of atrial fibrillation patients who continued treatment, 97% had a PDC ≥80%, compared with only 56% for those who discontinued their DOAC treatment within 1 year.

CONCLUSIONS

Non-adherence to DOACs was associated with age ≤60 years and no concomitant drugs use. Non-adherence was higher in patients who later discontinued DOAC treatment. Results of our study support research into interventions to improve adherence.

Pharmacokinetic modeling and simulation support for age- and weight-adjusted dosing of dabigatran etexilate in children with venous thromboembolism

BACKGROUND

Dabigatran etexilate (DE), a direct oral thrombin inhibitor, has been evaluated in children with venous thromboembolism (VTE) using oral solution, pellets, or capsules.

OBJECTIVES

This study evaluated DE pharmacokinetics (PK) in children with VTE and the appropriateness of a DE pediatric age- and weight-based dosing algorithm.

PATIENTS/METHODS

A population PK model was fitted to data from four single-arm and one randomized, comparative pediatric VTE studies (358 children aged birth to <18 years; 2748 PK observations) and one healthy-adult study (32 males aged <40 years; 1523 PK observations) using nonlinear mixed-effects modeling. A stepwise, covariate, model-building procedure evaluated the influence of covariates (e.g., age, body weight, body surface area [BSA]-normalized renal function, and sex). The final model was used to evaluate the pediatric dosing algorithm, with simulations comparing pediatric trough exposure with reference exposure defined for the pediatric studies.

RESULTS

The population PK of dabigatran was adequately described by a two-compartment model with first-order elimination and absorption. Age, weight, BSA-normalized renal function, and sex were statistically significant covariates (all P < .05). Apparent clearance increased with age (independently of body weight), diminished with decreasing BSA-normalized renal function, and was lower in females than males. All disposition parameters increased with body weight escalation (allometric scaling). Simulations confirmed that for all DE formulations, the final pediatric dosing algorithms achieved reference exposure without dose adjustment.

CONCLUSIONS

Using a population PK model of DE for children with VTE, simulations showed that the final dosing algorithms were appropriate for all DE formulations; no dose titration was needed.

Advances in reconstructing intestinal functionalities in vitro: From two/three dimensional-cell culture platforms to human intestine-on-a-chip

Standard two/three dimensional (2D/3D)-cell culture platforms have facilitated the understanding of the communications between various cell types and their microenvironments. However, they are still limited in recapitulating the complex functionalities in vivo, such as tissue formation, tissue-tissue interface, and mechanical/biochemical microenvironments of tissues and organs. Intestine-on-a-chip platforms offer a new way to mimic intestinal behaviors and functionalities by constructing in vitro intestinal models in microfluidic devices. This review summarizes the advances and limitations of the state-of-the-art 2D/3D-cell culture platforms, animal models, intestine chips, and the combined multi-organ chips related with intestines. Their applications to studying intestinal functions, drug testing, and disease modeling are introduced. Different intestinal cell sources are compared in terms of gene expression abilities and the recapitulated intestinal morphologies. Among these cells, cells isolated form human intestinal tissues and derived from pluripotent stem cells appear to be more suitable for in vitro reconstruction of intestinal organs. Key challenges of current intestine-on-a-chip platforms and future directions are also discussed.

Using Pharmacogenetics of Direct Oral Anticoagulants to Predict Changes in Their Pharmacokinetics and the Risk of Adverse Drug Reactions

Dabigatran, rivaroxaban, apixaban, and edoxaban are direct oral anticoagulants (DOACs) that are increasingly used worldwide. Taking into account their widespread use for the prevention of thromboembolism in cardiology, neurology, orthopedics, and coronavirus disease 2019 (COVID 19) as well as their different pharmacokinetics and pharmacogenetics dependence, it is critical to explore new opportunities for DOACs administration and predict their dosage when used as monotherapy or in combination with other drugs. In this review, we describe the details of the relative pharmacogenetics on the pharmacokinetics of DOACs as well as new data concerning the clinical characteristics that predetermine the needed dosage and the risk of adverse drug reactions (ADRs). The usefulness of genetic information before and shortly after the initiation of DOACs is also discussed. The reasons for particular attention to these issues are not only new genetic knowledge and genotyping possibilities, but also the risk of serious ADRs (primarily, gastrointestinal bleeding). Taking into account the effect of the carriership of single nucleotide variants (SNVs) of genes encoding biotransformation enzymes and DOACs metabolism, the use of these measures is important to predict changes in pharmacokinetics and the risk of ADRs in patients with a high risk of thromboembolism who receive anticoagulant therapy.