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Atrial fibrillation: Amiodarone linked to increased stroke and systemic embolism risk when used with Warfarin


Amiodarone ( Cordarone ) is an effective medication in preventing atrial fibrillation ( AF ), but it interferes with the metabolism of Warfarin ( Coumadin ).

A study has examined the association of major thrombotic clinical events and bleeding with the use of Amiodarone in the ARISTOTLE ( Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation ) trial.

Baseline characteristics of patients who received Amiodarone at randomization were compared with those who did not receive Amiodarone.

In ARISTOTLE, 2,051 ( 11.4% ) patients received Amiodarone at randomization. Patients on Warfarin and Amiodarone had time in the therapeutic range that was lower than patients not on Amiodarone ( 56.5% vs. 63.0%; p less than 0.0001 ).

More Amiodarone-treated patients had a stroke or a systemic embolism ( 1.58%/year vs 1.19%/year; adjusted hazard ratio [ HR ]: 1.47, 95% confidence interval [ CI ]: 1.03 to 2.10; p = 0.0322 ).

Overall mortality and major bleeding rates were elevated, but were not significantly different in Amiodarone-treated patients and patients not on Amiodarone.

When comparing Apixaban ( Eliquis ) with Warfarin, patients who received Amiodarone had a stroke or a systemic embolism rate of 1.24%/year versus 1.85%/year ( HR: 0.68, 95% CI: 0.40 to 1.15 ), death of 4.15%/year versus 5.65%/year ( HR: 0.74, 95% CI: 0.55 to 0.98 ), and major bleeding of 1.86%/year versus 3.06%/year ( HR: 0.61, 95% CI: 0.39 to 0.96 ).

In patients who did not receive Amiodarone, the stroke or systemic embolism rate was 1.29%/year versus 1.57%/year ( HR: 0.82, 95% CI: 0.68 to 1.00 ), death was 3.43%/year versus 3.68%/year ( HR: 0.93, 95% CI: 0.83 to 1.05 ), and major bleeding was 2.18%/year versus 3.03%/year ( HR: 0.72, 95% CI: 0.62 to 0.84 ).

The interaction p values for amiodarone use by Apixaban treatment effects were not significant.

In conclusion, Amiodarone use was associated with significantly increased stroke and systemic embolism risk and a lower time in the therapeutic range when used with Warfarin.
Apixaban consistently reduced the rate of stroke and systemic embolism, death, and major bleeding compared with Warfarin in Amiodarone-treated patients and patients who were not on Amiodarone. ( Xagena )

Flaker G et al, J Am Coll Cardiol 2014;64:1541-1550

XagenaMedicine_2014



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