Direct oral anticoagulant failure in stroke/transient ischaemic attack: neurologic and pharmacokinetic considerations

Pharmacokinetics and pharmacodynamics of direct oral anticoagulants

INTRODUCTION

Direct oral anticoagulants (DOACs) have overtaken vitamin K antagonists to become the most widely used method of anticoagulation for most indications. Their stable and predictable pharmacokinetics combined with relatively simple dosing, and the absence of routine monitoring has made them an attractive proposition for healthcare providers. Despite the benefits of DOACs as a class, important differences exist between individual DOAC drugs in respect of their pharmacokinetic and pharmacodynamic profiles with implications for dosing and reversal in cases of major bleeding.

AREAS COVERED

This review summarizes the state of knowledge relating to the pharmacokinetics of dabigatran (factor IIa/thrombin inhibitor) and apixaban, edoxaban and rivaroxaban (factor Xa) inhibitors. We focus on pharmacokinetic differences between the drugs which may have clinically significant implications.

EXPERT OPINION

Patient-centered care necessitates a careful consideration of the pharmacokinetic and pharmacodynamic differences between DOACs, and how these relate to individual patient circumstances. Prescribers should be aware of the potential for pharmacokinetic drug interactions with DOACs which may influence prescribing decisions in patients with multiple comorbidities. In order to give an appropriate dose of DOAC drugs, accurate estimation of renal function using the Cockcroft-Gault formula using actual body weight is necessary. An increasing body of evidence supports the use of DOACs in patients who are obese, and this is becoming more routine in clinical practice.

Direct Oral Anticoagulant Failures in Atrial Fibrillation With Stroke: Retrospective Admission Analysis and Novel Classification System

Introduction

Breakthrough acute ischemic stroke (AIS) in patients with known, nonvalvular Atrial Fibrillation (AF), on Direct Oral Anticoagulants (DOAC), is an ongoing clinical conundrum. Switching anticoagulants was shown to be ineffective in preventing recurrent AIS. Systematic, patient-level chart review of so-called "DOAC failures" may offer insight into this phenomenon.

Methods

We conducted an IRB-approved, 6-year, retrospective study of AIS admissions, already prescribed DOAC for known AF. We sought plausible, alternative reasons for the AIS using a novel classification schema, CLAMP: C for Compliance concerns, L for Lacunes (small-vessel disease), A for Arteriopathy (atherosclerosis, web, or vasculitis), M for Malignancy, and P for Patent Foramen Ovale (PFO). These categories were labeled as DOAC "Pseudo-failures." Conversely, absence of CLAMP variables were labeled as DOAC "Crypto-failures" conceivably from AF itself ("atriopathy") or pharmacokinetic/pharmacogenomic dysfunction (ie, altered DOAC absorption, clearance, metabolism, or genetic polymorphisms). Forward logistic regression analysis was performed on prespecified DOAC subgroups.

Results

Of 4890 AIS admissions, 606 had AF, and 87 were previously prescribed DOAC (14.4% overall DOAC failure rate, 2.4% annualized over 6 years). Pseudo-failures comprised 77%: Compliance concerns (48.9%), Lacunes (5.7%), Arteriopathy (17.0%), Malignancy (26.1%), and PFO (2.3%). Crypto-failures comprised 23%, had lower CHADSVASc scores (AOR = .65, P = .013), and occurred more with rivaroxaban (41%) than apixaban (16%) or dabigatran (5.6%).

Conclusion

In AIS patients with known AF, DOAC Pseudo-failures, with identified alternate etiologies, are 3 times more likely than DOAC Crypto-failures. The CLAMP schema represents a novel approach to diagnostic classification and therapeutic adjustments in patients already prescribed DOAC for AF.

No Time to Lose: Cases of Anticoagulant Reversal Before Thrombolysis in Acute Ischemic Stroke Patients

Direct oral anticoagulant (DOAC) reversal before intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients is well-documented in Europe, specifically for dabigatran: the selective humanized monoclonal antibody fragment idarucizumab, given to neutralize dabigatran prior to IVT, was associated with improved outcomes post-IVT. However, in the United States, this approach is rarely reported and not endorsed by guidelines. Therefore, further reporting on this is needed and neuroradiographic correlation may help validate this concept. At our hospital in Tampa, Florida, two octogenarians with atrial fibrillation, adherent with the DOAC dabigatran, presented with AIS shortly after symptom onset. Both received idarucizumab, then IVT. Clinical outcomes, treatment times, and perfusion-based neuroradiographic parameters were assessed. Patient A had a 41 ml penumbra on computed tomography perfusion (CTP) scan that decreased to 15 ml in final infarct volume on follow-up imaging, resulting in a 26 ml penumbral salvage (63.4%), and National Institutes of Health Stroke Scale (NIHSS) improved from 11 to 9 . Patient B had a 23 ml penumbra on CTP that decreased to 0.5 ml on follow-up imaging, resulting in a 22.5 ml penumbral salvage (97.8%), and NIHSS improved from 9 to 4. Neither developed bleeding complications. Both had delayed door-to-needle times but nevertheless demonstrated clinical neurological improvements. In our limited experience, IVT after immediate DOAC reversal in AIS patients on dabigatran was associated with clinical improvement in NIHSS by 2 to 5 points (with no neuroworsening), and penumbral salvage of ischemic brain tissue on neuroimaging ranging from 63.4% to 97.8%. Further reporting on this may lead to greater IVT use and better outcomes in "DOAC failures", especially for patients without other acute treatment options such as mechanical thrombectomy. Research into other anticoagulant reversal agents pre-IVT in AIS is also warranted.