Full-page newspaper advertisements and a series of television commercials have urged patients with atrial fibrillation to "rethink warfarin" in favor of Eliquis (apixaban – Bristol-Myers Squibb). Apixaban is the latest of 3 new oral anticoagulants now competing with warfarin (Coumadin, and others) for the oral anticoagulant market.

Warfarin sodium (Coumadin, and others) and other coumarin anticoagulants prevent thrombosis, but patient response is highly variable and overanticoagulation can lead to hemorrhage. Genotyping patients for single nucleotide polymorphisms (SNPs) that affect coumarin metabolism and sensitivity may help clinicians estimate the therapeutic warfarin dose. The FDA has added a note to warfarin labeling recommending lowrange doses for patients with such genetic variations. Commercial tests for these variants are now available and cost about $500 per test.

A reader expressed disappointment that our recent listing of “Some Warfarin Drug Interactions”1 did not include acetaminophen. Perhaps it should have. Acetaminophen can increase the anticoagulant effect of warfarin, particularly with continued use, but it does so inconsistently. The mechanism of this interaction has not been established, but may be related to an acetaminophen metabolite inhibiting vitamin K-epoxide reductase, the target for warfarin’s anticoagulant effect.2Patient susceptibility varies, possibly on a genetic basis; occasional use of acetaminophen generally has little or...

Balfaxar (Octapharma), a human plasma-derived four-factor prothrombin complex concentrate (PCC), has been approved by the FDA for rapid reversal of warfarin anticoagulation in adults who require an urgent surgical/invasive procedure. It is the second four-factor PCC to become available in the US; Kcentra, which has been available since 2013, is approved for the same indication and for urgent reversal of warfarin anticoagulation in adults with acute major bleeding. Balfaxar is marketed in Canada and Europe as Octaplex.

Warfarin-related bleeding, especially intracranial hemorrhage, can be catastrophic. Several products are available to reverse warfarin’s anticoagulant effect.

The FDA has approved use of Kcentra (CSL Behring), a human-derived 4-factor prothrombin complex concentrate (PCC), for urgent reversal of warfarin anticoagulation in adults with acute major bleeding. It is the only 4-factor PCC available in the US.

With the widespread adoption of the CHA₂DS₂-VASc scoring system, oral anticoagulation therapy is now recommended for all patients ≥75 years old with nonvalvular atrial fibrillation. Atrial fibrillation has, however, been associated with an increased risk of falls, and older patients starting warfarin for atrial fibrillation have a high rate of hospitalization for intracranial bleeding. Many practitioners are reluctant, therefore, to prescribe an oral anticoagulant for elderly patients who are at high risk for falls.

The FDA has approved the oral direct thrombin inhibitor dabigatran (da big’ a tran) etexilate (Pradaxa – Boehringer Ingelheim) for prevention of thromboembolic stroke in patients with non-valvular atrial fibrillation. It has been available in Canada (Pradax) since 2008 for prevention of thromboembolism in patients undergoing knee or hip replacement surgery and was recently approved there for use in atrial fibrillation.

Atrial fibrillation increases the risk of thromboembolic stroke. Anticoagulant therapy can reduce this risk and is recommended for patients with atrial fibrillation and one or more of the following: congestive heart failure, hypertension, age ≥75 years, diabetes, or prior stroke or transient ischemic attack (CHADS₂ score ≥1).

The FDA has approved apixaban (Eliquis – Bristol-Myers Squibb/Pfizer), an oral direct factor Xa inhibitor, for prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. It is the third new oral anticoagulant to be approved for this indication as an alternative to warfarin.