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U.S. Department of Health and Human Services


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Information for Consumers: What You Should Know about Changes to Heparin


This information has been updated. FDA Drug Safety Communication: Change in Heparin USP Monograph (4/7/2010)


On October 1, 2009, the United States Pharmacopeia (USP) changed the standard for how the amount of heparin (the "USP unit") is determined in products used in the United States. USP is an organization that sets standards for the quality, purity, strength, and consistency for medicines sold in the United States. These changes will make the amount of heparin available in a single "USP unit" dose the same as the "International Unit" that is used in most other countries.  As a result, overall, heparin in the U.S. will be about 10% less potent, unit for unit, than it is today. 

The other changes in the USP monograph (the document that lists the standards for a medicine) are very important because they will help make heparin more pure and less likely to be contaminated.

What to Expect

These changes will start affecting the heparin used in healthcare settings on or after October 8, 2009. If you receive heparin as part of any treatment, such as part of kidney dialysis or to prevent blood clots, the changes may affect your treatment in two ways.

  • Your doctor may prescribe a higher dose of heparin than you normally receive.  Specifically, you may notice that the dose or number of units of heparin you receive is slightly higher than before. If you have any questions about the dose of heparin you receive, you should ask your doctor or other healthcare provider (nurse, pharmacist) to explain the change to you.  As has always been the case, your doctor will use his or her best judgment in deciding what dose of heparin you should receive.
  • You may receive more monitoring after your heparin treatment than what was typical.  This monitoring may include blood testing that is commonly used to monitor heparin treatment. This will likely be temporary as the newer product becomes the standard across the healthcare system.

What Else You Should Know

The new heparin will be available in healthcare settings on or after October 8, 2009. At this time, your healthcare facility will probably have heparin stocked in the pharmacy made under the old system as well. Having heparin available that is made under both the old and new systems is necessary to ensure that there is no heparin shortage and you can continue to receive your treatments as scheduled.

Because it is possible that you will be treated with heparin made under the old or new system, we have recommended that your healthcare provider closely monitor your treatment. Some tests that may be affected include your aPTT or ACT monitoring. We and other organizations, institutes, and agencies have alerted all healthcare facilities to make them aware of the change. The manufacturers of heparin are also taking steps to lessen the likelihood that there is confusion when using heparin made under the old and new system. However,

We encourage you to ask your healthcare provider questions if you have concerns about your heparin treatment.


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