vit K?

[preetin]

Hi I dont just want to memorize that give warfarin will deplete protein C and S which will lead to vascular necrosis, so its better to start off with Heparin.
can somebody explain why?

[Dr. X]

while i agree that warfarin will deplete protein c and s, and in its excess could lead to v. necrosis, i dont think this is the reason to start with heparin.

heparin is usually used for acute conditions, for example the famous MI, stroke, DVT, pulmonary embolism, etc. it has a rapid onset (seconds) as well as short half life. their mechanism is to activate antithrombin III.

warfain is usually used for chronic condions, for example, prophylaxis of stroke (kinda like baby aspirin) in a rhd pxt, atrial fibrillation, and also articial heart valve pxts, etc. Their mechanism is to interfere with Vit K-dependent clottin factors, 2, 7, 9, 10. They also inhibit protein C and S, which in turn stops factors 8, 5. They have a slow onset and longer half life.

both in excess could cause bleeding (leading to v. necrosis), but im guessing opportunities are more with warfarin due to avaliability and misuse of drug. (heparin is IV, where warfain is oral) Another imp. point is that warfarin crosses the placenta (terotogenic) whereas, heparin is safe in preg.

heparin - monitor PTT (intrinsic pathway)
warfarin - monitor PT (extrinsic pathway)

[Dr. X]

after this post, i was heading to the library listening to goljan and guess what he was talking about.. first word.. warfarin. lol. last 10 min of nutrition1 and few more min. in nutrition2 about vit. k. he mentioned how vit. E could enhance the effects of warfarin thus becoming toxic and several other good stuff. it might give u a better idea on the topic.

[bckwood]

so its better to start off with Heparin.
can somebody explain why?


Warfarin inhibits the procoagulants II, VII, IX, and X and the patient would remain Normal until the normal clotting factors created before warfarin was given are cleared by the liver. This could take 36-72 hours because of the long half life of factor II. That is why patients are started on heparin.

[preetin]

yah, i gotta listen to patho again, bu thanks for ur help.