I could use some help with some basic research I'm putting together about how oral anticoagulants are used...
- When in an outpatient setting are oral anticoagulants used?
- Why or in what circumstances are various anticoagulants prescribed? (Why Warfarin over Plavix or vice versa). Basically what criteria are used to decide which anticoagulant to prescribe? I'm assuming the main competitors are warfarin, plavix, aspirin, and heparin?
- When are low molecular weight heparins used over high molecular weight and why?
Any help you can offer on some or all of these questions will be greatly appreciated... Thanks!
I work as a nurse in surgery so my pharmacology is pretty limited right now, since I don't deal with drugs first hand, however I will give it my best shot:
Coumadin, widely used for patients with A fib, PE, DVT or those with mechanical heart valves. There is a scale of INR levels which determines the dosage. I think for mechanical valves is pretty high up there, something like 2.5. You take the drug daily and get INR level constantly to adjust the dosage. Patients are very prone to bruising and bleeding. The drug prevents clotting factors from forming. This way clots don't form. It blocks conversion of several factors in the clotting cascade by inhibiting the final active clotting factor. It is reversed with an injection of Vitamin K. We have to do it once in a while in the hospital when the patients come with GI bleeds. It is used a long term drug for chronic patients, again like a mechanical valve.
Heparin, from what I understand is the IV form of coumadin and is easily reversed with protamine sulfate and is used for patients in the hospital for pretty much the same reasons as coumadin and also acute stroke or heart attack. It falls under platelet aggregation inhibitor. The advantage over coumadin is that heparin has a short half life I think after an hour the PT levels return to normal. Heparing is used as a short term drug until patients can be started on coumadin. For example you are on coumadin because a history of stroke. So you come to the hospital a couple of days early and get started on heparin and stopped on the coumadin. Then you do the procedure and afterwards you can start anticoagulation therapy again.
Plavix is used for CAD, PVD or cerebrovascular disease. I see it mostly used after caths when stents are placed or acute heart attacks. To us Plavix is nasty because causes a lot of bleeding in the OR. Plavix cannot be reversed because it blocks some sort of receptors on the platelets therefore making them not usable. The treatment for it give the patient a bunch of blood products. Under optimal conditions the patient should stop Plavix five days before surgery.
Usually, low molecular weight heparins come in a tiny TB syringe and can be given once daily for prophylaxis, under the skin, after surgery, especially surgical procedures where immobility is expected thus increasing the risk for clots to form. Patients can inject low molecular weight heparin like Lovenox by themselves, so it reduces their hospitalization time.
Finally, it seems like everyone is on ASA nowadays. It is used as prophylaxis for patients at high risk for CAD or strokes. Like patients that have high blood pressure or those with dyslipidemia. It also blocks platelet aggregation by I think changing a conformation of sorts. It is also irreversible and the patients going for surgery will have to stop a few days ahead of time.
This is pretty much the down and dirty on these drugs. Other people can chip in.
). So to those who have apparently been so heavily burdened by my asking these questions, don't worry, it won't happen again. 
