...it's a competitive antagonist, a permanent disabler for the enzymes involved in the Vitamin K cycle, who are vital for the coagulation system. There's a rather narrow therapeutic dosage frame which depends on your body size and composition a lot, below which you get no noticeable effect at all, above which you bleed to death (antidote is vit. K). It's common to need to adjust it's dosage based on how effective you see it being in a person.