Poor Compliance with Coumadin® (Warfarin) Therapies

In 2007, a study was conducted at three anticoagulation clinics to determine the effect of adherence on anticoagulation control. Patients were monitored with electronic Medication Event Monitoring System (MEMS) medication bottle caps.


  • 92% had at least 1 missed or extra bottle opening; 36% missed more than 20% of their bottle openings; and 4% had more than 10% extra bottle openings.
  • For each 10% increase in missed pill bottle openings, there was a 14% increase in the odds of under-anticoagulation
  • Participants with more than 20% missed bottle openings (1-2 missed days each week) had more than a 2-fold increase in the odds of under-anticoagulation
  • Participants who had extra pill bottle openings on more than 10% of days had a statistically significant increase in over-anticoagulation


Patients have substantial difficulties maintaining adequate adherence with warfarin regimens, and this poor adherence has a significant effect on anticoagulation control.

Source: International Normalized Ratio Adherence and Genetics (IN-RANGE) Study, Archives of Internal Medicine, Volume 167, FEB. 12, 2007