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Doctors Hope Better Blood Thinners Are On The Horizon

July 15, 2008

Doctors are hopeful three new experimental drugs will make treatment more accessible for millions of people at risk of lethal blood clots.

Two million patients currently use Coumadin, also known as warfarin, that causes an array of side effects and restrictions. The goal of the new drugs is to provide an alternative.

The first target is a pill option for people who now require daily blood-thinning shots for weeks after knee or hip replacement surgery.

Dr. Richard Becker, a hematology and cardiovascular specialist at Duke University Medical Center said the need is substantial for an easier alternative, “I don’t know of a drug that has the inherent complexities and potential for harm that Coumadin does.”

Thousands of Americans are in late stage testing for three pills that aim to prevent blood clots in ways that promise to be less arduous. One of the three pills – Boehringer Ingelheim’s Pradaxa – just started selling in Europe.

Meanwhile, Medicare is discussing plans to withhold payment from hospitals when at-risk patients develop clots in their veins – a common preventable cause of hospital deaths.

About a third of patients who need protective blood thinners while hospitalized get them, according to the National Quality Forum.

Recent estimates suggest that about 900,000 people a year suffer a vein clot, and nearly 300,000 die.

Medically DVT, or “deep vein thrombosis” is a clot that can kill quickly if it moves up from the legs to the lungs. Being sedentary for long periods, such as hospital stays or even long airplane flights, can cause a clot.

NBC journalist David Bloom died of DVT in 2003 after spending days in a cramped military vehicle while covering the invasion of Iraq. Vice President Cheney suffered a clot after a long trip last year. 

There are a variety of factors that lead to DVT which include increasing age, smoking, birth control pills, being overweight, and major surgeries like knee or hip replacements.

Orthopedic surgery patients are given faster-acting shots of the blood thinner enoxaparin for protection. However, warfarin is a favored treatment once a vein clot strikes. Warfarin is also the leading protection for other types of clots, such as strokes caused by the irregular heartbeat atrial fibrillation.

Wafarin does not come free of side effects that include dangerous bleeding. It also requires monthly blood checks because diet and other factors can change the needed dose.

In recent years, the highly anticipated blood thinner Exantra was pulled off the European market, and rejected in the U.S. due to surprising liver damage.

Early trial results have U.S. specialists optimistic about the three new drugs, but regulators are watching closely for any signs of problems.

Pharmacist John Fanikos of Boston’s Brigham and Women’s Hospital and the North American Thrombosis Forum said, “There are some huge benefits to these drugs, all three of them – if they play out.”

There are also a handful of other drugs in the pipeline including rivaroxaban, which regulates a key player in blood clotting, called Factor Xa.

The New England Journal of Medicine published two studies last month of more than 7,000 knee and hip replacement patients who took either a daily rivaroxaban pill or the current standard injections. Pill users were less likely to suffer fatal and nonfatal vein clots. However, the amount of bleeding and other side effects were similar with both drugs.

Bayer Healthcare AG and Johnson & Johnson (JNJ) are developing rivaroxaban. They plan to seek Food and Drug Administration approval later this summer.

European regulators said Pradaxa was as effective as standard shots in protecting orthopedic patients. Pradaxa, or dabigatran, interferes with another blood clotting agent, called thrombin.

Duke’s Becker said one U.S. study didn’t show as big an effect, but other research continues on the drug. Becker said it works similarly to the ill-fated Exantra, but so far there are no signs of liver toxicity.

Key studies are underway for Bristol-Myers Squibb’s apixaban; which works against the same clotting factor as rivaroxaban.

Stay tuned: Major studies comparing warfarin to each drug have started at hospitals nationwide. Fanikos said, if they work, they promise fewer side effects, dietary restrictions, or dose problems than warfarin.

He said warfarin will continue to play an important role, since the generic form sells for as little as $40 for a three-month supply.

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