The Interruption of Anticoagulation section of our article on Treatment of Atrial Fibrillation cited the recommendations of the American College of Chest Physicians on perioperative management of antithrombotic therapy (JD Douketis et al. Chest 2022; 162:e207). A reader suggested that our general statement on when to discontinue an oral anticoagulant would have benefited from inclusion of the recommendations of the American College of Cardiology/American Heart Association (JA Joglar et al. Circulation 2024; 149:e1). Recommendations for periprocedural management of oral anticoagulant therapy vary with the anticoagulant, the bleeding risk of the patient and the procedure, the patient’s thromboembolic risk (CHA₂DS₂-VASc score), the presence of a mechanical valve, and for some anticoagulants, the patient’s renal function. These recommendations are provided in detail in both of the above-cited guidelines.

Atrial fibrillation (AF) is the most common arrhythmia in the world. Risk factor modification, anticoagulation, rhythm control, and rate control are the four pillars of its management. American College of Cardiology/American Heart Association (ACC/AHA) guidelines on management of AF were updated recently.

Anticoagulants are the drugs of choice for treatment and prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE), collectively referred to as venous thromboembolism (VTE). US guidelines for treatment of VTE were updated in 2020 and 2021.

View the Comparison Table: Some Parenteral Anticoagulants for VTE

View the Comparison Table: Some Oral Anticoagulants for VTE

A synthetic form of the protein apoaequorin is the active ingredient in the over-the-counter dietary supplement Prevagen (Quincy Bioscience), which is heavily marketed to improve memory.

Treatment of atrial fibrillation includes anticoagulation, rate control, and rhythm control. US guidelines were recently updated.

Anticoagulants are the drugs of choice for treatment and prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE), collectively referred to as venous thromboembolism (VTE). Updated US guidelines for treatment of VTE were published in 2016.

View the Comparison Table: Some Oral Anticoagulants for VTE

View the Comparison Table: Some Parenteral Anticoagulants for VTE

The FDA has approved betrixaban (Bevyxxa – Portola), a once-daily, oral, direct factor Xa inhibitor, for prophylaxis of venous thromboembolism (VTE) in adults hospitalized for an acute medical illness who have moderately or severely restricted mobility and other risk factors for VTE. Betrixaban is the first oral anticoagulant to be approved in the US for this indication.

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 results of a recently published study suggest that taking the oral direct thrombin inhibitor dabigatran etexilate (Pradaxa) with either simvastatin (Zocor, and others) or lovastatin (Altoprev, and others) increases the risk of major hemorrhage.

Direct-to-consumer advertisements continue to urge patients who take warfarin (Coumadin, and others) for atrial fibrillation to ask their doctors about the benefits of one or another of the newer oral anticoagulants.

The FDA has approved edoxaban (Savaysa – Daiichi Sankyo), a once-daily, oral, direct factor Xa inhibitor, for treatment of venous thromoboembolism (VTE) and for prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. It is the fourth new oral anticoagulant to be approved for VTE and nonvalvular atrial fibrillation.

Antiplatelet drugs are the drugs of choice for prevention and treatment of arterial thrombosis. Anticoagulants are the drugs of choice for prevention and treatment of venous thromboembolism and for prevention of cardioembolic events in patients with atrial fibrillation.

The treatment of atrial fibrillation includes anticoagulation, rate control, and rhythm control. New US guidelines for the management of atrial fibrillation have recently been published.

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.

Arterial thrombi are composed mainly of platelet aggregates held together by small amounts of fibrin. Antiplatelet drugs are the drugs of choice for prevention and treatment of arterial thrombosis, but anticoagulants are also effective, and their effects can add to those of antiplatelet drugs. Venous thrombi are composed mainly of fibrin and trapped red blood cells, with relatively few platelets. Anticoagulants are the agents of choice for prevention and treatment of venous thromboembolism and for prevention of cardioembolic events in patients with atrial fibrillation.

The FDA has approved prasugrel (Effient - Lilly/Daiichi Sankyo), an oral antiplatelet drug, for use with aspirin to reduce the rate of thrombotic cardiovascular events in patients with acute coronary syndromes (ACS) being managed with percutaneous coronary intervention (PCI). It will compete with clopidogrel (Plavix) for such use.

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.2

Patient susceptibility varies, possibly on a genetic basis; occasional use of acetaminophen generally has little or no effect on the international normalized ratio (INR) in patients on chronic warfarin therapy, but in some, even a few grams of the drug may cause a dramatic increase in INR. One study in healthy subjects found no effect of acetaminophen 4 g per day for 2 weeks, while another study in patients with the same acetaminophen dose for the same period of time found a moderate increase in INR.3,4 It might be prudent to monitor INR in patients on chronic warfarin therapy more closely than usual when they take more than 2 g per day of acetaminophen for more than a few days.

1. Pharmacogenetic-based dosing of warfarin. Med Lett Drugs Ther 2008; 50:39.
2. HH Thijssen et al. Paracetamol (acetaminophen) warfarin interaction: NAPQI, the toxic metabolite of paracetamol, is an inhibitor of enzymes in the vitamin K cycle. Thromb Haemost 2004; 92:797.
3. D Kwan et al. The effects of acetaminophen on pharmacokinetics and pharmacodynamics of warfarin. J Clin Pharmacol 1999; 39:68.
4. I Mahe et al. Paracetamol: A haemorrhagic risk factor in patients on warfarin. Br J Clin Pharmacol 2005; 59:371.

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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.

Arterial and venous thrombosis are major causes of morbidity and mortality. Arterial thrombi consist of platelet aggregates held together by small amounts of fibrin. Antiplatelet drugs are the drugs of choice for prevention and treatment of arterial thrombosis, but anticoagulants are also effective, and their effects can add to those of antiplatelet drugs. Venous thrombi are composed mainly of fibrin and trapped red blood cells, with relatively few platelets. Anticoagulants are the agents of choice for prevention and treatment of venous thromboembolism and for prevention of cardioembolic events in patients with atrial fibrillation.

The drugs of choice for treatment of some fungal infections are listed in the table that begins on page 8. Some of the indications and dosages recommended here have not been approved by the FDA.

Percutaneous coronary intervention (PCI), such as balloon angioplasty or stent placement, predisposes to subsequent thrombosis. The current pharmacologic approach to prevention of this problem combines an anticoagulant with one or more antiplatelet drugs.

Several recent case reports suggest that oral sildenafil may be effective for treatment of pulmonary arterial hypertension (PAH). Sildenafil is currently marketed as Viagra for treatment of erectile dysfunction (Medical Letter 1998; 40:51).

Fondaparinux (Arixtra - Organon Sanofi-Synthelabo), a synthetic analog of heparin, has been approved by the FDA for prevention of deep vein thrombosis (DVT) after hip fracture surgery or knee or hip replacement.

Bivalirudin is being promoted as an intravenous (IV) anticoagulant that can be used instead of heparin in patients with unstable angina undergoing coronary angioplasty.

Micronized fenofibrate (Tricor - Abbott), a fibric acid derivative structurally similar to clofibrate (Atromid-S, and others) and gemfibrozil (Lopid, and others), has been approved by the FDA for treatment of hypertriglyceridemia. Increased serum triglyceride concentrations have been associated with an increased risk of coronary heart disease (J Jeppesen et al, Circulation, 97:1029, 1998).

The drugs of choice for treatment of deep fungal infections are listed in the table below. Some of the indications and dosages recommended here have not been approved by the FDA.

The drugs of choice for treatment of deep fungal infections are listed in the table on page 101. Some of the indications and dosages recommended here have not been approved by the US Food and Drug Administration. More detailed guidelines are available from the Infectious Diseases Society of America (J Sobel et al, Clin Infect Dis, volume 30, April 2000).

Nizatidine (Axid - Lilly), a new H2-receptor antagonist similar to cimetidine (Tagamet), ranitidine (Zantac) and famotidine (Pepcid), was recently approved by the US Food and Drug Administration for treatment of active duodenal ulcer and for maintenance therapy after healing. Cimetidine, ranitidine and famotidine are also approved for treatment of pathological hypersecretory conditions such as Zollinger- Ellison syndrome; cimetidine is approved in addition for treatment of gastric ulcers.