Direct oral anticoagulant concentrations and adherence in stroke patients

No therapeutic ranges linking drug concentrations of apixaban and rivaroxaban to clinical outcomes have been defined. We investigated whether direct oral anticoagulant (DOAC) concentrations among patients admitted to hospital with symptoms of stroke differed between those later verified to suffer an ischaemic cerebrovascular event (stroke or transient ischaemic attack) and those having other diagnoses (control group). Serum concentrations in 102 patients on DOAC for atrial fibrillation (84%) and thromboembolic disease (16%) were measured within 24 h of the acute event, employing ultra-high performance liquid chromatography with tandem mass spectrometry. We converted all concentrations to standardized trough levels. DOAC concentrations were lower in the 64 patients with verified ischaemic cerebrovascular event than in the 30 controls, 255 ± 155 versus 329 ± 144 nmol/L (p = 0.029), despite no statistically significant difference in self-reported adherence and daily dosages. Calculated concentrations were 5.4-596 nmol/L (median = 229 nmol/L) in the ischaemic stroke group and 41-602 nmol/L (median = 316 nmol/L) in controls. CHA₂ DS₂ -VASc score was significantly higher in the ischaemic stroke group than in controls (4.9 ± 1.6 versus 4.1 ± 1.7; p = 0.007). These results may suggest that patients with high cerebrovascular risk might benefit from higher DOAC levels than those with a lower risk.