Relationship between plasma dabigatran concentration and activated partial thromboplastin time in Japanese patients with non-valvular atrial fibrillation

Evaluation of Extended-Interval Dabigatran Dosing in Older Patients With Non-Valvular Atrial Fibrillation

OBJECTIVE

To evaluate the safety and efficacy of extended-interval dabigatran dosing in older Chinese patients with non-valvular atrial fibrillation.

METHODS

We conducted an observational study on non-valvular atrial fibrillation patients administered dabigatran at different dosing intervals at the Department of Geriatrics, Peking University First Hospital, China. We enrolled 121 consecutive non-valvular atrial fibrillation patients aged ≥60 years on dabigatran therapy (mean age, 79.6 ± 7.4 years); they were administered conventional low-dose dabigatran (110 mg twice daily) or extended-interval dosing with dabigatran (110 mg every 16 h or every 24 h). All patients received follow-up care, and we evaluated the presence of bleeding and thromboembolic events.

RESULTS

All patients exhibited creatinine clearance greater than 30 mL/min with an average of 56.6 ± 17.3 mL/min. Sixty-two patients received extended-interval dosing with dabigatran at a mean dose of 117.1 ± 18.6 mg daily. Patients on extended-interval dosing were older; they exhibited lower creatinine clearance and bodyweight and higher CHA₂DS₂-VASc and HAS-BLED scores. The mean follow-up time was 25.8 ± 15.6 months. No significant differences were observed in the trough and peak values of the activated partial thromboplastin time and in thromboembolic or bleeding events between the 2 groups.

CONCLUSION

Extended-interval dabigatran dosing in older patients with non-valvular atrial fibrillation and lower creatinine clearance can maintain activated partial thromboplastin time trough and peak values comparable to the conventional low dose. Physician-prescribed practices regarding dabigatran dosing intervals do not lead to worse outcomes in the above-mentioned population.

Concentrations of dabigatran administered after acute ischemic stroke

BACKGROUND AND PURPOSE

The aim of this study was to evaluate the anticoagulation intensity of dabigatran for acute ischemic stroke patients and hemorrhagic/ischemic events after early initiation of dabigatran.

METHODS

Acute ischemic stroke/transient ischemic attack (TIA) patients admitted to our hospital who started dabigatran from January 2012 to December 2017 were studied. Blood samples were drawn just before (0 h) and 4 h after dabigatran at a median of 5 days after starting dabigatran to measure dabigatran concentrations (C_0h, C_4h) based on the thrombin clotting time assay (Hemoclot®).

RESULTS

Of the 70 patients (54 men, 69 ± 9 y), 14 started dabigatran after a TIA, and 56 started it after an ischemic stroke a median of 5 days after onset. C_0h, C_4h was 82.5 ± 58.0, 143.1 ± 98.2 ng/dl (150 mg BID, 35 patients) and 50.6 ± 40.9, 91.2 ± 64.7 ng/ml (110 mg BID, 35 patients). During a median follow-up of 382 (IQR 109-688) days of all 70 patients, five had clinical events. Three patients had bleeding events, two with nasal bleeding (C_0h, C_4h: 50, 80 ng/ml, C_0h, C_4h: 91, 173 ng/ml) and one with GI bleeding (C_0h, C_4h: 5, 5 ng/ml). Two patients had ischemic events, one with ischemic stroke (C_0h, C_4h: 10, 50 ng/ml) and another with acute myocardial infarction (C_0h, C_4h: 40, 40 ng/ml).

CONCLUSIONS

There was no obvious relationship between dabigatran concentration and hemorrhagic/ischemic events in this study. Larger sample study will be needed to examine the relationship between the concentration and events in clinical practice.

Removal of dabigatran using sorbent hemadsorption

BACKGROUND

The Redual PCI trial has demonstrated the safety of dabigatran and ticagrelor or clopidogrel combination in preventing strokes in patients with atrial fibrillation. There was 15.4% risk of hemorrhage in the dabigatran/ticagrelor or clopidrogel arm, lower than that of triple therapy with warfarin, aspirin and ticagrelor or clopidogrel. While idarucizumab is an effective antidote for dabigatran, there is no good method for antagonizing both dabigatran and ticagrelor. We tested in this study a hemadsorbtion method for removing dabigatran that we had previously successfully applied in the removal of ticagrelor from human blood.

METHODS

100 mL 4% BSA solution pre-incubated with dabigatran was passed through 10, 20 and 40 mL sorbent columns and dabigatran concentration was measured from the affluent and effluent solution using LC-MS/MS. For testing the effect of dabigatran removal on the aPTT value one human volunteer was administered oral dabigatran etexilate mesilate 150 mg. Plasma was collected 4 h after dabigatran administration and then in three experiments 20 mL of collected plasma was circulated through three different 10 mL CytoSorb columns over a duration of 5 min. aPTT was measured from plasma at baseline prior to drug administration, then post blood collection (mixed plasma) and from the adsorbed plasma as well.

RESULTS

Dabigatran concentration, as measured by LC-MS/MS, decreased from 1456 ± 331 nM (greater than the therapeutic level of 743 nM) to 67 ± 59 nM (P = 0.002) with the 10 mL CytoSorb column, while with the 40 mL column it dropped to undetectable levels. In one human volunteer experiment the aPTT was on average 29.2 ± 0.4 in the 3 baseline samples, 34.7 ± 1.8 s after oral dabigatran (mixed plasma), and 25 ± 0.7 s after plasma was passed through CytoSorb (adsorbed plasma) (P = 0.000025 and 0.0000002 for comparison between baseline plasma and mixed plasma, as well as the dabigatran mixed plasma and post-adsorption values respectively).

CONCLUSION

Dabigatran is robustly removed by a sorbent hemadsorption method already proven successful for the P2Y12 receptor antagonist ticagrelor. Dabigatran removal restores the aPTT to below baseline values, suggesting that sorbent hemadsorption could clinically reverse the anticoagulant effect of this drug.