Apixaban pharmacodynamic activity in umbilical cord, paediatric, and adult plasma

Exposure Matching-Based Pediatric Dose Selection for Drugs with Renal Excretion - Lessons Learned from Pediatric Development of Direct Oral Anticoagulants

The pediatric clinical development programs of the direct oral anticoagulants (DOACs) edoxaban, rivaroxaban, and dabigatran have recently been completed, with apixaban close to the finish line. One common pharmacokinetic (PK) characteristic of these four DOACs is that renal excretion contributes 27% or more in their elimination, resulting in age-dependent drug clearance in both pediatric and adult subjects. Several lessons have been learned from adult exposure matching and pediatric dose selection for DOACs. The main goal of this tutorial is to provide an informed perspective on pediatric dose selection for renally excreted drugs, using these four DOACs as case examples. This tutorial is organized into seven steps: (1) consideration of age-related differences in disease and response to treatment; (2) consideration of age-related differences in drug absorption, distribution, metabolism, and excretion; (3) selection of the reference adult population and exposure for pediatric exposure matching; (4) prediction of pediatric clearance and pediatric dose selection based on data from young adults; (5) conduct and design of efficient pediatric PK and pharmacodynamic (PD) studies that inform dose selection; (6) assessment of exposure matching and dose adjustment using population PK simulation; (7) evaluation of the need for dose adjustment in pediatric sub-populations.

Direct oral anticoagulants versus standard anticoagulation in children treated for acute venous thromboembolism

Direct oral anticoagulants (DOACs) are widely used to treat venous thromboembolism (VTE) in adults. Little attention is given to pediatric VTE (PVTE). The objective of this study is to study the efficacy and safety of DOACs in published PVTE randomized control trials (RCTs). PubMed, Embase, China National Knowledge Infrastructure, the Cochrane Library, SinoMed, and ClinicalTrials.gov were searched until 2021, to identify RCTs that enrolled patients with VTE <18 years of age who received DOACs versus standard anticoagulation. Outcomes were evaluated using the Mantel-Haenszel method of random-effects model. Our study evaluated seven RCTs that included 1139 cases of PVTE, which had a low risk of publication and assessment bias. Compared with standard anticoagulation, patients receiving DOACs presented a lower rate of recurrent VTE (relative risk [RR], 0.42 [confidence interval {CI}, 0.20 to 0.89]), similar mortality rate (RR, 0.50 [CI, 0.07 to 3.57]), major bleeding (RR, 0.46 [CI, 0.14 to 1.57]), and higher clinically relevant nonmajor bleeding (RR, 2.71 [CI, 1.05 to 7.02]) with low heterogeneity. Limiting to subgroups, dabigatran and rivaroxaban yielded similar findings, except for a higher incidence of nonmajor bleeding during rivaroxaban use. DOACs could be an alternative to standard anticoagulation in PVTE. Dabigatran and rivaroxaban have similar effects. IMPACT: In venous thromboembolism (VTE), direct oral anticoagulants (DOACs) are widely used as a substitution for standard anticoagulation in most situations for adults; however, little attention is paid to the pediatric population. For pediatric VTE, previous meta-analyses have emphasized the epidemiology, risk factors, and the use of traditional anticoagulants, and seldom reported the use of novel oral anticoagulants. This is the first meta-analysis of randomized controlled trials that focuses on the efficacy outcomes and safety endpoints of DOACs compared with standard anticoagulation in pediatric VTE.

Apixaban: A Clinical Pharmacokinetic and Pharmacodynamic Review

Apixaban is an oral, direct factor Xa inhibitor that inhibits both free and clot-bound factor Xa, and has been approved for clinical use in several thromboembolic disorders, including reduction of stroke risk in non-valvular atrial fibrillation, thromboprophylaxis following hip or knee replacement surgery, the treatment of deep vein thrombosis or pulmonary embolism, and prevention of recurrent deep vein thrombosis and pulmonary embolism. The absolute oral bioavailability of apixaban is ~ 50%. Food does not have a clinically meaningful impact on the bioavailability. Apixaban exposure increases dose proportionally for oral doses up to 10 mg. Apixaban is rapidly absorbed, with maximum concentration occurring 3–4 h after oral administration, and has a half-life of approximately 12 h. Elimination occurs via multiple pathways including metabolism, biliary excretion, and direct intestinal excretion, with approximately 27% of total apixaban clearance occurring via renal excretion. The pharmacokinetics of apixaban are consistent across a broad range of patients, and apixaban has limited clinically relevant interactions with most commonly prescribed medications, allowing for fixed dosages without the need for therapeutic drug monitoring. The pharmacodynamic effect of apixaban is closely correlated with apixaban plasma concentration. This review provides a summary of the pharmacokinetic, pharmacodynamic, biopharmaceutical, and drug–drug interaction profiles of apixaban. Additionally, the population-pharmacokinetic analyses of apixaban in both healthy subjects and in the target patient populations are discussed.

Pharmacokinetics and pharmacodynamics of oral anticoagulants used in atrial fibrillation

INTRODUCTION

The availability of non-vitamin K antagonist oral anti-coagulants alongside vitamin K antagonists has offered a variety of options for anti-coagulation, but has also necessitated a good understanding of the pharmacological properties of each of these drugs prior to their use, to maximise the therapeutic benefit and minimise patient harm Areas covered: This review article outlines the pharmacokinetic and pharmacodynamic profiles of the currently licensed VKAs and NOACs that are most commonly used in clinical practice, with the aim of demonstrating how variations in these characteristics influence their use in clinical practice. A literature search was conducted on PubMed using keywords and relevant articles published by the 31^st of December 2018 were included. Expert opinion: The effect of a drug is determined by a combination of elements which include patient characteristics and external factors, in addition to its pharmacokinetic and pharmacodynamic properties. A good understanding of these is essential. Despite the wealth of information available, particularly on VKAs, our knowledge on the pharmacology responsible for certain drug effects and inter-individual variations is still limited. Increasing efforts are being made to understand these and include focus on pharmacogenomics and drug transporter proteins.

Anticoagulant prophylaxis and therapy in children: current challenges and emerging issues

This review is aimed at describing the unique challenges of anticoagulant prophylaxis and treatment in children, and highlighting areas for research for improving clinical outcomes of children with thromboembolic disease. The evidence presented demonstrates the challenges of advancing the evidence base informing optimal management of thromboembolic disease in children. Recent observational studies have identified risk factors for venous thromboembolism in children, but there are few interventional studies assessing the benefit-risk balance of using thromboprophylaxis in risk-stratified clinical subgroups. A risk level-based framework is proposed for administering mechanical and pharmacological thromboprophylaxis. More research is required to refine the assignment of risk levels. The anticoagulants currently used predominantly in children are unfractionated heparin, low molecular weight heparin, and vitamin K antagonists. There is a paucity of robust evidence on the age-specific pharmacology of these agents, and their efficacy and safety for prevention and treatment of thrombosis in children. The available literature is heterogeneous, reflecting age-specific differences, and the various clinical settings for anticoagulation in children. Monitoring assays and target ranges are not well established. Nevertheless, weight-based dosing appears to achieve acceptable outcomes in most indications. Given the limitations of the classical anticoagulants for children, there is great interest in the direct oral anticoagulants (DOACs), whose properties appear to be particularly suitable for children. All DOACs currently approved for adults have Pediatric Investigation Plans ongoing or planned. These are generating age-specific formulations and systematic dosing information. The ongoing pediatric studies still have to establish whether DOACs have a positive benefit-risk balance in the various pediatric indications and age groups.