FDA May Block Xarelto Approval: Are There Enough Blood Thinners for Everyone?

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Recent news about Food and Drug Administration (FDA) reviewers accusing the pharmaceutical makers Bayer and Johnson & Johnson of misleading claims about their blood thinning drug Xarelto with respect to Xarelto’s benefits matching and possibly surpassing the effectiveness of Warfarin raises a “so-what” question: With at least five other blood thinning medications already available, so what if Xarelto is denied FDA approval as a blood thinning agent to use for preventing blood clots resulting from atrial fibrillation - don’t we already have enough blood thinning medications as it is?

Perhaps, for now, but according to a recent FDA report, a rise in the number of shortages of significant medications has nearly tripled between 2005 and 2010 - and is expected to reach a new record by the end of 2011. The shortages range from supply chain problems when active pharmaceutical ingredients (APIs) are scarce or unavailable to pharmaceutical companies discontinuing a product because it is no longer cost effective. This means that pharmaceutical companies must either be forced to continue production of a needed drug (which the FDA cannot currently do) or new, replacement drugs must be created and approved on a continual rotating basis.

A simple example is the sole drug used for treating Black Widow spider bites: Antevenin Latrodectus Marctans. Bites by Black Widow spiders are rarely fatal and at first hardly noticeable. However, several hours following a bite the symptoms are extremely painful and the Black Widow spider antivenin is needed to alleviate the pain. According to the American Society of Health-System Pharmacists’ web page listing drug shortages, the drug to treat Black Widow spider bites is difficult to come by. Emergency supplies are likely only available through the drug’s maker, Merck. Imagine if you will, a child bitten and having to wait a minimum of several hours to an entire day for relief until the drug is delivered to the hospital. As of last August the drug shortage list included almost 75 commonly prescribed medications.

To address the problem of the shortage of medications available, the Food and Drug Law Institute has created a proposed policy for the FDA, the pharmaceutical industry and the government. They determined that a lack of transparency and communication is to blame for a large part of the growing drug shortage problem. Their recommendations include measures such as:

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• Pharmaceutical companies alerting the FDA beforehand of shortages and/or plans to discontinue a drug to give the FDA ample time to prepare for and minimize the impact when a needed drug is no longer available.
• The FDA and Government must provide incentives to encourage companies to maintain a line of drug that are not cost-effective and/or encourage the creation of new replacement drugs.
• The FDA should work with the Drug Enforcement Agency (DEA), which imposes limitation quotas on controlled substances manufacturers. For example, if one company runs into production problems that results in a shortage, other companies should not be prevented from exceeding their quota to remedy the shortage.

The anti-bloodclotting drug Rivaroxaban (Xarelto) met FDA approval last July as a blood thinner for reducing the risk of blood clots, deep vein thrombosis (DVT), and pulmonary embolism (PE) following knee or hip replacement surgery. However, it has not yet been approved for the expanded use of preventing strokes by thinning blood clots resulting from atrial fibrillation. The FDA reviewers’ opinion is that the drug maker’s claims in a study meant to showcase the drug’s effectiveness as a blood thinner for conditions not related to knee and hip replacement is faulted in the studies design. The makers claim that Xarelto is at least as good as if not better than Warfarin (Coumadin), which is commonly used as a preferential blood thinner. However, the reviewers found that the testing may be faulted by not showing that Warfarin was used properly in comparison to Xarelto.

Currently, FDA approved drugs to prevent blood clotting include Lovenox (enoxaparin), generic versions of enoxaparin, Arixtra (fondaparinux), Fragmin (dalteparin) for hip replacement surgery only, Coumadin (warfarin) and heparin. Each has it uses and some are preferable over others depending on the medical condition and the patient’s response/tolerance to the drug.

Whether or not the FDA will approve Xarelto for its extended application remains to be seen. And although a lack of approval may not have an immediate effect on the public (unless you are an investor), in the long term it may affect the development of future drugs and their availability. Today, there is enough blood thinner to meet America’s needs. Tomorrow may be a different story.

This Thursday, the Cardiovascular and Renal Drugs Advisory Committee will meet to vote on whether Xarelto (rivaroxaban) should be approved by the FDA, and, if so, whether its label can state that it works better than Warfarin at preventing strokes.

Sources:
American Society of Health-System Pharmacists http://www.ashp.org/DrugShortages/Current/
Food and Drug Policy Forum Vol. 1, Issue 16, August 2011 http://www.ashp.org/DocLibrary/Policy/DrugShortages/FDLI-Article-on-Drug-Shortages.aspx

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