#39 Dabigatran versus Warfarin in Atrial Fibrillation
CLINICAL QUESTION
What are the benefits and risks of dabigatran (Pradaxa®) compared to warfarin, in patients with atrial fibrillation?
BOTTOM LINE
Dabigatran offers some advantages over warfarin (example ~0.6%/year fewer strokes), but benefits decline as warfarin time in INR range improves. If using Dabigatran 150mg bid is generally recommended.
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EVIDENCE
Randomized Controlled Trial (RCT)1,2 of 18,113 patients given dabigatran 110 mg BID or 150 mg BID, or warfarin. Primary outcome: Stroke or systemic embolism. Net benefit outcome: Stroke, systemic or pulmonary embolism, MI, death, or major hemorrhage.
- 63% male, mean age 71 years, mean CHADS2 2.1. INR in range 64% of time for warfarin patients.
- Dabigatran 150mg BID versus warfarin (events per year):
- Dabigatran improved primary outcome (1.1% vs. 1.7%), Number Needed to Treat (NNT)=167.
- Dabigatran improved net benefit (6.9% vs. 7.6%), NNT=137.
- No difference in death or major bleed, but trend favoured dabigatran.
- Dabigatran had non-statistically significant increase in myocardial infarctions (0.8% vs. 0.6%).
- Dabigatran 110 mg BID vs. warfarin (events per year):
- No difference in primary outcome, death, myocardial infarction, or net benefit.
- Dabigatran had fewer major bleeds (2.9% vs 3.6%) NNT=143.
- More patients stopped dabigatran (21%) than warfarin (17%) at two years.
- Early RCT of dabigatran versus warfarin was too short (12 weeks) with too few patients (502) to assess meaningful clinical outcomes.3
- Potential risk of myocardial infarction: Number Needed to Harm ~400-500/year.4,5
- Dabigatran increases the risk of bleeding and thromboembolism in mechanical heart valves.6
- Benefits of dabigatran over warfarin declined (or disappeared) the more INR was in range (in the warfarin group).7
- Prescribing considerations:8,9
- Dabigatran contraindicated: Creatinine clearance (CrCl) <30 ml/minute, patients on ketoconazole.
- Drug interactions can occur with P-glycoprotein inhibitors (including verapamil, amiodarone, and quinidine).
- Dabigatran 150 mg BID recommended but consider 110 mg bid for patients >80 years, or patients >75 years old with risk factors for bleeding, diminished renal function (CrCl 30-50 ml/ minute).
- If switching from warfarin to dabigatran, do when INR <2.0.
- Cost effectiveness analysis suggest dabigatran 150 mg is cost effective.10,11
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