Study Warns of Potential Adverse Drug Interactions from New Using Blood Thinners

May 31, 2010

(PhysOrg.com) -- Three new oral blood-thinning drugs nearing approval by the Food and Drug Administration are more convenient than the standard drug Coumadin because they do not require monthly visits to adjust doses.

But the promising drugs also could be subject to dangerous interactions when taken alongside widely used prescription drugs, over-the-counter medicines such as aspirin and even herbal supplements such as St. John's Wort, according to a Loyola University Health System study.

"Many unknowns remain as to how the new anticoagulants will behave in the real world patient population," researchers conclude in a review article in the June issue of the .

While the new drugs offer "significant potential advantages," their lack of extensive clinical experience "should not be underestimated," researchers wrote.

Lead author is blood clot specialist Jeanine Walenga, PhD, a professor in the Cardiovascular Institute and departments of Thoracic and Cardiovascular Surgery and Pathology at Loyola University Chicago Stritch School of Medicine. Co-author is Cafer Adiguzel, MD, who completed a fellowship at Loyola.

Coumadin reduces the risk of life-threatening blood clots in patients who have chronic conditions such as irregular heart rhythms or have undergone recent surgeries such as hip and knee replacements.

Coumadin (generic name, warfarin) must be carefully monitored. If the dose is too high, a patient could experience excessive bruising and be at higher risk for brain hemorrhages. If the dose is too low, the drug would be ineffective in preventing life-threatening blood clots. Patients typically must come in every month for a blood test to determine whether the dose needs to be adjusted.

The three new drugs do not need to be monitored every month, according to their manufacturers. They are rivaroxaban (Xarelto), dabigatran etexilate (Pradaxa) and apixaban. Rivaroxaban and dabigatran etexilate have been approved in Europe and apixaban is under development. Manufacturers of all three drugs have asked for or are expected to seek approval from the U.S. .

Interactions with other drugs can make the new blood-thinning drugs either ineffective or too effective. For example, St. John's wort, typically taken for depression, can make the drugs less effective, while aspirin can make them more potent and thereby increase the risk of bleeding.

One study found that one-third of older adults use aspirin. A second study found that 29 percent of adults ages 57 to 85 take at least five prescription drugs.

"A high proportion of adults in the United States consume at least one of the drugs known to have some level of interaction with one of the new oral anticoagulants," the Loyola researchers write.

So far, most of what's known about potential drug interactions comes from animal studies or clinical trials that included relatively healthy patients who were carefully monitored. Less is known about elderly patients who have multiple health problems and might miss doses or take incorrect doses.

"The impact of any drug interaction will only become known with increasing clinical experience of these new oral anticoagulants," researchers wrote.

Explore further: FDA OKs Merck tablet to reduce ragweed allergies

add to favorites email to friend print save as pdf

Related Stories

Older adults at high risk for drug interactions

Dec 23, 2008

At least one in 25 older adults, about 2.2 million people in the United States, take multiple drugs in combinations that can produce a harmful drug-drug interaction, and half of these interactions involve a non-prescription ...

Warfarin: patient knows best

Apr 23, 2010

(PhysOrg.com) -- An Oxford-led review published last week in the Cochrane Library - that gold-standard source for the best evidence-based medical care - showed how empowering people at risk of blood clots ...

Study shows experimental drug cuts stroke risk

Aug 30, 2009

(AP) -- An experimental drug reduces the stroke risk in patients with irregular heartbeats by more than three times, compared with the popular drug warfarin - but possibly at a cost, according to new research released Sunday.

Recommended for you

Study recalculates costs of combination vaccines

11 hours ago

One of the most popular vaccine brands for children may not be the most cost-effective choice. And doctors may be overlooking some cost factors when choosing vaccines, driving the market toward what is actually a more expensive ...

Drug watchdog urges vigilance in cancer drug theft

14 hours ago

Europe's medicine watchdog urged doctors Thursday to be vigilant in administering the cancer drug Herceptin, vials of which had been stolen in Italy and tampered with before being sold back into the supply chain.

Pyridoxine-doxylamine drug safety data lacking

Apr 16, 2014

(Medical Xpress)—The most commonly prescribed drug for pregnant women suffering from morning sickness in their first trimester does not prevent birth defects even though drug safety data says it does, according to research ...

User comments : 0

More news stories

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

White House updating online privacy policy

A new Obama administration privacy policy out Friday explains how the government will gather the user data of online visitors to WhiteHouse.gov, mobile apps and social media sites. It also clarifies that ...

Six Nepalese dead, six missing in Everest avalanche

At least six Nepalese climbing guides have been killed and six others are missing after an avalanche struck Mount Everest early Friday in one of the deadliest accidents on the world's highest peak, officials ...