Anticoagulant only effective in VIVO:

Ans. b (Coumarin). (Ref. Harrison's internal medicine 16th ed. 688)ANTICOAGULANTSA. Vitamin K antagonists:# The oral anticoagulants act by antagonizing the effects of vitamin K.# They take at least 48 to 72 hours for the anticoagulant effect to develop fully.# Generally, these anticoagulants are used to treat patients with- Deep-vein thrombosis (DVT),- Pulmonary embolism,- Atrial fibrillation, and- Mechanical prosthetic heart valves.# The most important oral anticoagulants are:- Warfarin (Coumarin).- Acenocoumarol- PhenindioneB. Heparin and its derivatives# Heparin is a biological substance, usually made from pig intestines.# It works by activating antithrombin III, which blocks thrombin from clotting blood.# Heparin can be used in vivo (by injection), and also in vitro to prevent blood or plasma clotting in medical devices.# Low molecular weight heparin is a more highly processed product that does not require monitoring of the APTT coagulation parameter (it has more predictable plasma levels) and has fewer side effects.# Fondaparinux is a synthetic sugar composed of the five sugars (pentasaccharide) in heparin that bind to anti- thrombin. It is a smaller molecule than low molecular weight heparin.C. Direct thrombin inhibitors# Include- Argatroban, Lepirudin, and Bivalirudin.- Oral direct thrombin inhibitor are Dabigatran, Rivaroxaban and ximelagatranPD. Anticoagulants outside the body# Apart from heparin, most of the chemicals added work by binding Ca++ ions, preventing the coagulation proteins from using them.- EDTA chemical strongly and irreversibly binds calcium.- Citrate is used for coagulation tests, as well as in blood transfusion bags. It gets rid of the calcium, but not as strongly as EDTA.* It can be in the form of Sodium citrate or ACD.- Oxalate has a similar mechanism to citrate.* It is the anticoagulant used in fluoride tubes.