Some Common But Severe Drug Interactions Involving Coumadin (Warfarin)
Beware Of "G" Herbs and Supplements: Garlic, Ginseng, Ginkgo Biloba, and Ginger
In April 2006 Douglas S. Paauw, M.D., a University of Washington medical investigator, spoke at an American College of Physicians meeting about adverse events associated with Coumadin (warfarin) therapy which are caused by drug interactions.
As explained in an April 9, 2006 MedPage Today article by Peggy Peck:
Adverse events associated with Coumadin therapy continue to be a leading cause of hospitalizations for drug-related adverse events, and many times the problem can be traced to those herbs and supplements, he said. Dr. Paauw ran through those and other hazards during a session titled, "Ten Common Prescribing Errors: Drug Interactions and Side Effects."
Starting with the herbs and supplements, Dr. Paauw had an easy-to-remember bit of advice: be particularly careful with herbs and supplements beginning with the letter "G". Garlic, ginger, and gingko biloba, all increase the anticoagulation of Coumadin (warfarin). Meanwhile, ginseng decreases the anticoagulation of Coumadin (warfarin).
According to the April 9, 2006 MedPage Today article, Dr. Paauw told the audience of doctors that "the most severe Coumadin adverse events are often traced to Bactrim aka Septra (TMP/sulfa), a frequently prescribed antibiotic in elderly patients who are also the most likely users of Coumadin."
During his presentation, Dr. Paauw listed several other prescription drugs that are likely to interact with Coumadin, including these:
- erythromycin,
- amiodarone,
- Diflucan (fluconazole),
- Nizoral (keotoconazole),
- Sporanox (itraconazole), and
- mentronidazole.
Dr. Paauw also mentioned that the use of Prilosec (omeprazole) or Tylenol (acetaminophen) while using Coumadin at the same time can affect a patient's INR.
As pointed out in the MedPage Today article, Dr. Paauw's presentation emphasized these two lessons concerning drug safety:
- Patients need to know that herbs, supplements, and vitamins can react with prescription drugs: and,
- Patients should, on a regular basis, tell their doctor(s) about all prescription and non-prescription drugs that they are using in order to reduce the risk of adverse events caused by drug interactions.
(Posted by: Tom Lamb)
