By Dr. Brian McDonough

By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – One of the most unpredictable drugs that we prescribe as physicians is the blood thinner warfarin, well known as coumadin. 

Here’s the problem. It’s hard to figure out the correct dose because it can vary from person to person.  Too little, the drug won’t protect people from lethal blood clots.  Too much, and they bleed.

It even gets more complicated.  Other things can affect how the drug works. Something as simple as a big serving of spinach or stressful travel can alter how much of the drug stays in the body, putting patients in a danger zone. 

It had been thought that scientists had discovered two genes to help determine if someone can tolerate only a little warfarin or need a lot could help, but as of this point it has not panned out.

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