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10-06-2010 | Cardiology | Article

Risk for newer OAC drug–drug interactions highlighted


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MedWire News: The risk for interactions between new oral anticoagulant (OAC) agents and foods, drugs, and dietary supplements has been flagged in a review published in the International Journal of Clinical Practice.

Jeanine Walenga and Cafer Adiguzel, from Loyla University Medical Center in Maywood, Illinois, USA, highlight known interactions and contraindicated drugs in patients using dabigatran, rivaroxaban, and apixaban.

However, they emphasize that “real world” use of these agents is limited, and that caution is required given the numerous interactions now known for warfarin, including those with antibiotics, garlic, fish oils, and St John’s wort.

“The new OACs offer significant potential advantages to the field of venous thromboembolism (VTE) prophylaxis, but their lack of extensive clinical experience should not be underestimated,” the researchers comment.

Walenga and Adiguzel report that the direct thrombin inhibitor dabigatran has been shown so far to interact with nonsteroidal anti-inflammatory drugs (NSAIDs) and clopidogrel.

Furthermore, dabigatran is a substrate for P-glycoprotein and should therefore be used with caution alongside drugs that inhibit or induce this transporter, such as clarithromycin, while quinidine is contraindicated for this reason.

The factor (F)Xa inhibitor rivaroxaban also interacts with NSAIDs, clopidogrel, and P-glycoprotein inhibitors or inducers, as well as agents that inhibit the cytochrome CYP3A4 metabolic pathway. It is contraindicated with HIV protease inhibitors and azole antimycotics that inhibit both CYP3A4 and P-glycoprotein.

Less is known about apixaban, a FXa inhibitor under current investigation, but this should be used with clopidogrel and aspirin only under caution due to the increased antithrombotic effect and risk for bleeding.

“The US population, in general, has a high-frequency of use of over-the-counter medication and supplements, as well as long-term use of drugs for cardiovascular disease, arthritis, and other disorders,” Walenga and Adiguzel conclude.

“In addition, the elderly population often has comorbid illnesses and clinical conditions (eg, diabetes, orthopedic surgery) that require frequent or long-term drug treatments.

“Thus, these combinations of factors will add to the complexity of drug interactions in these patient populations,” they say.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Lynda Williams

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