Thursday night on "World News," we asked for your questions regarding the new genetic testing recommendations on the labeling of the common blood thinner warfarin, often sold under the brand name Coumadin.
For help in answering your questions, we sought the expertise of Dr. Brian Gage, an associate professor of medicine at the Washington University School of Medicine, who is involved with clinical trials of these genetic tests.
How does the test work?
Question from Kathy of Sloansville, N.Y.:
I started Coumadin about three weeks ago for a blood clot in my calf. Can you explain what is entailed by "genetic testing?" What are they looking for?
Genetic testing can help predict someone's therapeutic dose of warfarin or Coumadin. However, if you've already been taking the anticoagulant for three weeks, then your doctor already knows your approximate therapeutic dose, so genetic testing would not be helpful at this point in your therapy.
How can I find out what genetic tests are needed?
Question from Kim of Tucson, Ariz.:
I am 49 years old and had a blood clot in my leg that moved to my lung a year and a half ago. I have been on warfarin since then and have my blood checked almost every week. I have had a hard time getting adjusted, though, and I have only stayed on a particular dose for two months before having to change doses. How can I find out if this genetic test can help and what tests to get?
Because you've been taking warfarin for so long, genetic testing would not be helpful. Warfarin is affected by changes in your diet and by other medications. I recommend that you get a pill dispenser, which will help ensure that you don't miss a dose, a common reason why it's difficult to regulate warfarin.
What are the long-term side effects of Coumadin?
Question from Diane of Keene, N.H.:
I have been on and off warfarin or Coumadin since I was 20 years old. I am currently on warfarin and will probably be for the rest of my life, as it was determined that I have a blood clotting disorder. My question is, will I have long-term side effects? And if so, should I talk to my doctor about having the genetic testing?
Except for a risk of bleeding, warfarin is remarkably free of side effects. However, we have found that long-term warfarin use can be associated with osteoporosis in elderly men. Although we did not observe this trend in women, as a precaution you should get enough exercise, calcium, and vitamin D to keep your bones strong.
Is long-term use of Coumadin dangerous, and how can I limit the risk?
Question from Bobette of Wildomar, Calif.:
My husband is on 8 mg of warfarin each day after getting DVTs from knee replacement surgery. Should we be concerned at the amount? Will he be on it the rest of his life? There were no details about the use of this drug in the news report. Is long-term use dangerous?
Deep venous thrombosis (DVT) is common after joint replacement surgery and is usually treated with 6-12 weeks of warfarin therapy. However, in certain circumstances, longer duration of anticoagulant therapy is indicated, so your husband should speak with his physician. You should not be concerned about his daily dose of 8 mg as long as his doctor is monitoring his warfarin therapy regularly with an INR blood test.
How do doctors currently determine the proper dose of Coumadin?