Among other indications, Coumadin is often given to patients with an
irregular heartbeat called atrial fibrillation to reduce the risk of blood clots
and stroke. A blood test called the INR is measured on a regular basis to ensure
that the dose being given is not thinning the blood too much or too little.
"The first evidence of a possible interaction between ginseng and (Coumadin)
came from a widely cited case report published in 1997," study author Dr.
Chun-Su Yuan, from The University of Chicago, told Reuters Health. In that
report, a patient on Coumadin "experienced a significant drop in the INR after
using ginseng for 2 weeks. When the ginseng was stopped, the patient's INR
returned to the desired level."
Still, Yuan said that some subsequent studies in humans and animals have not
supported an interaction between the two agents.
To clarify the association, Yuan's team conducted a study involving 20
healthy volunteers. In the 4-week study, the subjects took Coumadin during the
first week, took American ginseng or placebo for the second and third weeks, and
then took Coumadin during the fourth week.
The researchers' findings appear in the Annals of Internal Medicine.
In agreement with the case report, ginseng use for two weeks was tied to a
significant reduction in the INR, meaning that the blood was now less thin and
more prone to clotting.
Yuan said that past studies may have failed to show a drug interaction
because ginseng was not used long enough. "One week of ginseng therapy is
probably not enough to" turn on the liver enzymes that break down Coumadin --
the apparent reason why the herb and the drug interact.
Yuan favors not using ginseng at all for people on Coumadin treatment. When
people take ginseng and the Coumadin dose is adjusted to compensate, "it's
possible that the INR could go dangerously high if the patient suddenly stops
the ginseng."
SOURCE: Annals of Internal Medicine, July 6,2004.
