A case report of recurrent transient ischaemic attacks on dabigatran for atrial fibrillation: real-world insight into treatment failure

Non-valvular atrial fibrillation (AF) is an important risk factor for acute ischaemic stroke. There has been an increase in the use of direct-acting oral anticoagulants (DOAC therapy) in stroke prophylaxis due to their convenience and rapid action of onset. However, there is a lack of information in the literature regarding management options and possible mechanisms with the apparent failure of DOAC therapy.

We present a clinical case of a 51-year-old man presenting with transient ischaemic attacks on a background of AF on therapeutic doses of dabigatran. His medication box suggested 100% compliance and his admission coagulation studies showed a marginally prolonged activated partial thromboplastin time and thrombin time (TT). While in hospital, our patient had supervised doses of dabigatran (150 mg b.i.d.). Despite this, his peak dabigatran level was undetectable (<40 ng/mL). With the apparent failure of therapy, he was switched to apixaban 5 mg b.i.d., which showed subsequent peak levels in the target range.

There are a number of isolated case reports of DOAC failure in stroke prophylaxis and management has simply involved switching to another DOAC or warfarin. This case is unique as we have discovered undetectable levels of dabigatran providing a mechanism for failure.