| August
1, 2007
Change Ordered to Warfarin Drug Label
Warfarin Label Says Dosage May Depend on Genetic Test
By Daniel J. DeNoon
WebMD Medical News
Reviewed By Louise Chang, MD
Aug. 1, 2007 – In a new trend, labels on the clot-fighting
drug warfarin will now warn that people with certain gene variations
may need lower doses of the drug.
It's the first time that the FDA has asked doctors to consider
a patient's genetic makeup when prescribing a widely used drug,
says Larry Lesko, PhD, director of clinical pharmacology at the
FDA.
"Today is a significant event for those who see the day
when medicine is tailored to the genetic makeup of each one of
its users," Lesko said at a news conference.
"We are continuing to engage in various projects that will
further evaluate the relationship between genetic variability
and treatment outcomes in patients," FDA Deputy Commissioner
and Chief Medical Officer Janet Woodcock, MD, said at the news
conference.
The change in the label for warfarin (originally sold under the
brand name Coumadin) does not require that patients get genetic
tests. But the new label suggests that genetic testing can help
doctors find the correct dosage of the drug.
Each year, about 2 million Americans start taking warfarin to
prevent blood clots, heart attacks, and strokes. It is notoriously
difficult to find the right warfarin dosage for an individual
patient. Factors such as age, diet, use of other medications,
and use of vitamins and supplements affect the dosage.
Because of this, warfarin is the second most common drug (after
insulin) that sends patients to the emergency room.
Researchers have noticed that about a third of patients who start
warfarin need much lower doses than expected. This difference
appears to be due to variations in two genes. One of the genes,
VKORC1, affects a patient's sensitivity to warfarin. The other
gene, CYP2C9, affects how quickly a person clears warfarin from
the body.
The new warfarin label suggests that doctors starting a patient
on warfarin might want to have that patient tested for variations
in these genes. Most major laboratories already offer the test.
Lesko says the cost of testing ranges from $125 to $500; a patient
would need to be tested only once.
Patients already taking warfarin probably will not need genetic
testing if they already have found the warfarin dosage that works
best for them.
SOURCES: News release, FDA. Warfarin drug information label,
Aug. 16, 2007. FDA news conference, Aug. 16, 2007, with Janet
Woodcock, MD, deputy commissioner and chief medical officer, FDA;
and Larry Lesko, PhD, director, office of clinical pharmacology,
Center for Drug Evaluation and Research, FDA.
© 2007 WebMD Inc. All rights reserved.
Source: www.medicinenet.com
Comments:
Warfarin, also sold under the brand name Coumadin, is prescribed
to about 2 million people every year for the prevention
of blood clots that could cause heart attack or stroke.
Warfarin is a dangerous drug with a very narrow safety margin.
It is usually prescribed to elderly people, and is the second
most common drug that sends people to emergency rooms due
adverse events. The dose of Warfarin has to be meticulously
determined and closely monitored with periodic tests. The
researchers of this study noted that currently people are
getting two to three times higher doses than they require,
putting them at a risk of life threatening side effect of
bleeding. While doctors are prescribing Warfarin at much
higher doses than required, they do not indicate the importance
of nutrients, and sometimes deter their patients from taking
vitamins while taking Warfarin. It is never emphasized that
the doses of dangerous medications should be closely monitored
and reduced as much as possible and the nutrients intake
should be increased. Pharmaceutical drugs do not address
root cause of the disease and produce adverse effects, while
nutrients are opposite. Dr. Rath has been fighting against
pharma industry for promoting drugs that generate side effects,
do not treat diseases, and deplete the body of many essential
nutrients. You can read more about this on www.drrathresearch.org
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