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DNA Tests now Available Determine Safe Dosage for Dangerous Drugs, Coumadin and Warfarin

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25 million prescriptions were written for the popular blood thinner Coumadin and warfarin last year. Patients will soon notice a new FDA label attached to their prescription. The warning: The patient's genes may dictate the safe dosage level for the drug.

This is important because Coumadin affects the blood's ability to clot. If the dose is too low, deadly clots may form; too high, a patient may bleed to death.

Historically, physicians have used the "trial and error" method when prescribing Coumadin because it was never known how the patient would process the drug.

Would it metabolize quickly, or stay in the bloodstream at dangerous levels? The only way to determine the correct dosage was to subject patients to frequent (often daily) blood tests.

Dosage levels were then juggled until the patient's blood reflected "safe levels," which could sometimes take weeks or months to determine - leaving the patient vulnerable to stroke, heart attack, or deadly bleeding.

According to research cited by the FDA, warfarin alone is responsible for 15% of severe drug side effects.

A DNA test that determines the proper and safe dosage for Coumadin (within 1.5 mg/day) is now available to the public.

The test reveals data from two specific genes that forecast how the patient would respond to Coumadin.

Gene CYP2C9 reveals how quickly - or slowly - Coumadin is metabolized. Gene VKORC1 is the genetic "site of action" for Coumadin.

Information gathered from these two genes determines the prescription needed for the drug to be effective.

According to Genelex founder Howard Coleman, this is the perfect example of how DNA testing can be used to determine proper drug dosage.

"The future of health care is all about customizing medicines to be safely prescribed to the individual, rather than treating patients as though they are all alike."

"Patients starting Coumadin should learn how the drug will be processed in their bodies, before or soon after they begin the medicine. Knowing this information and sharing it with their health care provider can be life- saving."

The test is available online or by calling toll- free (800) 523-3080. Patients who order receive a DNA collection kit, and send in either a blood sample or a cheek swab.

Once Genelex completes the testing, patients receive their results, which they may then share with their physicians and pharmacists. Typically, results are available within four or five days.

Next month, FDA-funded researchers will begin enrolling hundreds of warfarin patients in a study designed to determine if the genetics testing gets them to the safest dosage faster.

One local Seattle attorney said the Coumadin dosage he received was "all over the board." In his early 50's and in excellent shape, the attorney was surprised when he developed a DVT (deep vein thrombosis).

He was prescribed Coumadin, but it took over a month before physicians could determine the correct dosage level.

"It was very scary. Had I taken this test early on, the correct dosage levels could have been determined without the ordeal that I endured," he said.

"I actually was in trial in San Francisco when my doctor's office in Seattle phoned and told me to immediately stop taking the medicine, because my blood test revealed a level that was several times too high."

"Thank God I didn't have a serious adverse reaction, because at those levels, I certainly could have."

He was fascinated by the Genelex test results. "Instead of shooting blindly, my physician would have had information about the way I personally respond to Coumadin. I wish I'd have done this before I ever took the drug."