Many patients are searching for an alternative to warfarin because of concerns about safety and the need for long-term monitoring. Nattokinase, a by-product of soybean fermentation, is purported to increase clot-dissolving actions in animals and human volunteers, as well as to suppress clot formation and enhance clot resolution in animals. This substance has not been appropriately studied in humans, however, and it should not be considered as a substitute for warfarin. It also has not been studied in combination with warfarin or aspirin. The FDA concluded in 2002 that there is "no adequate basis to conclude that NKCP (natto extract) containing 0.01% of nattokinase enzyme is reasonably expected to be safe." Patients should be advised that there are no oral alternatives to warfarin available at this time, and there is no evidence to support nattokinase as a therapeutic alternative.