The reason warfarin is tolerated longterm is that it doesn't require special breaking down by the liver or kidneys that these newer, experimental drugs do. Warfarin is referred to in some research papers as a Vitamin-K agonist (VKA). What this means, basically, is that the body 'thinks' it IS Vitamin K, but it has no effects on clotting. (Think if it like a credit card -- you want three credit cards in your wallet, and make sure that you have three - but one of those (a Warfarin card) looks like a credit card but will always have a 0 credit limit -- when you go to use the card, it has no effect). So - in other words, the body regulates the Vitamin K in the system - but some of the K (actually Warfarin) has no effect - so the coagulation isn't as good -- and you get the anticoagulation effect. Also - because the body wants to keep a steady state of Vitamin K, any dosing changes you make won't become effective very rapidly - these changes are gradually adjusted by the body - and that's why a dose today may not show much anticoagulation effect for a few days - it takes that long for the body to change the amount of K that is replaced by Warfarin. Warfarin, when properly managed, is safe, has no longterm effects on the liver or kidneys, and as has been seen by many on this forum, can be taken for decades without ill effects. (I've been taking it for 19 years, and there are people like Dick who have more than 40 years of history with warfarin).
The newer drugs don't seem to be as easily processed by the body, have different modes of action -- and although it would be great if we could get away with a pill a day and no testing, this probably won't happen for a LONG time. (Also, FWIW - I'm not sure I'd be happy paying a few bucks a day for a new coagulation management pill (which I assume the drug company that develops it would charge) so I can avoid paying a dime or two each day, and maybe $10-$20 a month for self-tests).
