Weekly missing dose (“6/7” SSU Protocol): A rational approach in warfarin use

Abstract

Warfarin is still used as a standard drug for long term oral anticoagulation. We hypothesized that chronic warfarin use six days a week (“6/7” SSU protocol) is a safe and effective method in order to minimize the burden of frequent blood testing. Our unpublished data indicated that weekly missing dose of warfarin a day per week could attain an ideal therapeutic goal with a need to less frequent blood samplings without the risk of warfarin toxicity (bleeding) or significant drop in therapeutic serum level. Our rationale was rather a high half-life of warfarin (20-60 hours) with more than 97% protein bounding. So, disruption of daily oral prescription of warfarin by off-days (a day each week) can effectively halt the risk of bleeding without considerable impact on its anticoagulation effects. We hypothesized that due to unappreciated long elimination half-life, this mode of dosing (six days a week) could be more justified than the continuous daily oral prescription. This fact has been experienced for years regarding practice with digoxin (with 36-48 hours half-life). Similarly this concept could be true for every drug with “more than a day” half-life like warfarin.