BOSTON, MASSACHUSETTS. Warfarin (Coumadin) therapy is a major cause of internal bleeding and hemorrhagic stroke. The risk increases substantially with higher doses (elevated INR value) and with the concomitant use of other anticoagulants or medications that potentiate warfarin's action. Researchers at the Harvard Medical School now report that the incidence of warfarin-related major bleeding and intracranial hemorrhage (hemorrhagic stroke) among patients admitted to the Brigham and Women's Hospital has increased substantially from the 4-year period 1995-1998 to the 4-year period 1999-2002. Among the highlights of the findings are:
Sixty-two per cent of the warfarin-treated patients also received medications that are known to potentiate the
effect of warfarin. Among the more common ones were quinolone antibiotics (32%), levothyroxine (15%),
simvastatin (10%), and amiodarone (10%). The use of more than one potentiating medication increased
from 24% in the first period to 41% in the second period. If aspirin, clopidogrel and other antiplatelet agents
and anticoagulants are included, then a full 86.6% of warfarin-treated patients received one or more
medications that would increase the effect of warfarin and make them susceptible to major bleeding.
Editor's comment: It is indeed ironic that several recent articles in mainstream medical journals warn against taking certain herbs when on warfarin. Perhaps an article warning against taking warfarin with many commonly prescribed medications would be more appropriate.