Some months ago, we published a blog to announce what we thought was important medical news about a new product called Pradaxa. That blog, entitled A New Blood Thinning Drug is Approved – Pradaxa – better than Coumadin?, was widely viewed by many readers since October, 2010. Following our posting, a number of those readers have sent us questions about this new drug. To better serve our readers, we have invited Dr. Steven M. Davis to be our guest blogger on Pradaxa, and to answer some of these important questions.
Dr. Davis is the Associate Professor of Pharmacy at the Campbell University College of Pharmacy and Health Sciences in Buies Creek, NC. He is also the Clinical Coordinator for Pharmacy Services at Wake Forest University Baptist Medical Center in Winston Salem, NC. Dr. Davis has a PharmD with a specialty certification in geriatric pharmacology.
Below are the most frequently asked reader questions:
- How does Pradaxa differ chemically to Coumadin (Warfarin)?
- Do things with high Vitamin K (like spinach, lettuces, and broccoli) interfere with Pradaxa?
- If one were to start Pradaxa, how long would it take the blood to thin? If one were already taking Coumadin (Warfarin), what is the recommended method of switching to Pradaxa?
- How long would it take to reverse the effects of Pradaxa? I have been told Coumadin (Warfarin) stays in the body and before any surgery a patient has to wait 5 days.
- Why doesn’t the blood coagulation need monitoring if Pradaxa thins out the blood? Why wouldn’t the blood protime (PT) need monitoring with Pradaxa?
- How would someone adjust Pradaxa to keep the protime (PT) at a desired level?
- Are there any restrictions to other medications such as Aspirin?
Dr. Davis’ responses are listed below:
Question 1: Pradaxa (Darbigatran) is a direct thrombin inhibitor. Thrombin is one of many clotting factors in the body necessary for coagulating blood. Coumadin (Warfarin) works by a completely different mechanism. Coumadin/Wafarin prevents the activation of 4 clotting factors that depend on Vitamin K .
Question 2: Since Pradaxa works by directly inhibiting the clotting factor thrombin, the amount of vitamin K in the diet does not matter.
Question 3: When switching from Coumadin to Pradaxa, a physician will usually wait for a patient’s INR to drop below 2 before starting Pradaxa. In most patients taking Pradaxa, blood will be appropriately thinned 2 to 3 days after starting the medication.
Question 4: Pradaxa is still a blood thinner and care must be used before surgery. Pradaxa has a shorter life in the body (that is why it is dosed twice daily) and it is cleared from the body quicker than Coumadin (Warfarin). It is recommended that a patient discontinue Pradaxa 1-2 days before surgery if they have normal kidney function and 3-5 days if they have impaired kidney function. Of course you would NEVER stop this medication without consulting your physician first.
Question 5: Prothrombin time (PT) and INR measure the ability of Coumadin (Warfarin) to prevent the activation of the Vitamin K dependant clotting factors. Again, since Pradaxa does not affect these factors, the prothrombin time does not change and, therefore, does not need to be monitored.
Question 6: The biggest advantage to Pradaxa is that there are fewer drug interactions, less food/drug interactions (Vit K containing foods), and thus no need to monitor prothrombin time or INR.
Question 7: Combining Pradaxa with aspirin will increase a patient’s risk of bleeding. Both medications are used together frequently but ONLY under the direction of a physician.
Dr. Davis offers the following advice to patients considering taking or taking the drug Pradaxa.
This is a new medication and as with all new medications, it has not been used in a large population of patients yet. New side effects and drug interactions may be discovered as this drug is used more frequently. The Food and Drug Administration (FDA) monitors these reports and will issue statements as necessary.
From Brian Nash: I want to take this opportunity to thank Dr. Steven Davis for providing us with this information for our readers.
To our readers: Please keep in mind that we, at Nash & Associates, are not physicians. While Dr. Davis was so kind to provide the information he did regarding Pradaxa, this is not the usual approach we would take to our blog postings. From time to time we try to make you aware of important and/or interesting medical news. However, if you have questions about Pradaxa, we strongly urge you to speak with your personal physician.
UPDATE: Interesting piece by Dr. Wes on Pradaxa just posted today. Thought you may want to read. The comments have been coming in fast and furious on this new “wonder drug.” Here’s the post by Dr. Wes – Pradaxa, Your Days are Numbered