Antidotes for Warfarin are those agents which reverse the effects of toxicity of warfarin.
Warfarin is an oral anticoagulant that is commonly used to treat and prevent blood clots. Warfarin has more clinical applications approved by the FDA and off label.
It can be used for the prophylaxis and treatment of
- Venous thrombosis and pulmonary embolism.
- Thromboembolic complications due to atrial fibrillation or valvular cardiac replacement.
- Heart attack
- Reduction of the risk of death.
- Stroke, systemic embolization after myocardial infarction.
The possible side effects are:
- Unusual bruises
- Bleeding from the gums
- Bleeding from cuts that take a long time to stop.
- Menstrual bleeding or vaginal bleeding more intense than normal
- Urine pink or brown
- Red or black stools
- Blood coughed
- Vomit blood.
While Serious side effects include
- Death of skin tissue.
- Purple cornea syndrome
Warfarin works by preventing your body from forming blood clots. This is done by blocking the formation of coagulation factors necessary for coagulation.
Warfarin inhibits vitamin KO reductase and, therefore, limits the availability of vitamin K in the cyclic response. This reduces the blood’s clotting activity by reducing the production of vitamin K-dependent factors. The effect of warfarin can be overestimated by the administration of vitamin K1 (phytonadione) as a medication or through diet.
Therefore, vitamin KH2 is available for carboxylation without the need for vitamin KO reductase. It can also be stored in the liver when it is administered in large amounts that confer warfarin resistance to the patient for several periods of time.
Warfarin also prevents the carboxylation of other proteins produced in the bone, which explains its teratogenic effects in the formation of fetal bone when used in pregnancy. However, this does not appear to affect normal bone metabolism after birth.
Warfarin competitively inhibits Vitamin K 1 epoxide reductase complex (VKORC1), an enzyme essential for activating the vitamin k available in the body. Through this mechanism, warfarin can deplete the functional stores of vitamin K and, therefore, reduce the synthesis of active coagulation factors.
In people who require a rapid reversal of warfarin due to severe bleeding or emergency surgery, the effect of warfarin on vitamin K, prothrombin complex concentrate (PCC) or fresh frozen plasma (PFF) may reverse.
Antidotes for warfarin
1. Vitamin K1
To reverse the effects of warfarin, vitamin K1 can be given. This is one of the best antidote for warfarin. Vitamin K1 is available as an oral tablet or as an ampoule for intravenous (IV) or oral administration. Ampoules are not recommended for intramuscular or subcutaneous use. Intramuscular vitamin K1 Antidotes for warfarin is not recommended as it has sedimentation properties that may interfere with the reuptake of anticoagulant therapy. In addition, intramuscular injection poses a significant risk of hematoma formation in patients with anticoagulant therapy (especially if anticoagulant). Studies have also shown that the response to intramuscular or subcutaneous vitamin K1 is unpredictable and sometimes delayed.
Ideally, unless the patient is bleeding actively, vitamin K1 is administered at a dose that rapidly reduces INR to a safe area, but not to a therapeutic area without causing resistance when warfarin is restored.
Oral vitamin K1 is the treatment of choice Antidotes for warfarin unless a very rapid reversal of anticoagulation is required. For most patients, 1.0 to 2.0 mg oral vitamin K1 is sufficient. If INR is particularly high, 5 mg may be required orally. Although the injectable vitamin K1 formulation (Konakion MM, Roche Products Pty Ltd) is not approved for oral use of government agencies in Australia and New Zealand, it is favored for elimination of anticoagulation due to its flexible dose.
Although the IV injection causes a faster response, it may be associated with anaphylactic reactions. There is no evidence that this rare but serious complication can be avoided using low doses.
Antidotes for warfarin Dose (Vitamin K)
The optimal intravenous dose of vitamin K1 for partial relief of excessive anticoagulation with warfarin is 0.5 to 1.0 mg. If an INR correction is desired (instead of just returning to the usual therapeutic area), higher doses of vitamin K1 are required. In general, INR can be normalized within 24 hours with an intravenous dose of 5 to 10 mg vitamin K1.
Large doses of vitamin K1 can lead to some resistance to warfarin reanticoagulation. This can be avoided by administering lower doses. Larger doses are appropriate when a clinical decision is taken to complete treatment with additional warfarin.
2. Prothrombin concentrate and fresh frozen plasma.
Full effect of vitamin K1 by reducing INR lasting up to 24 hours, even when administered in larger doses to achieve complete reversal. For immediate reversal of clinically significant bleeding, the combination of Prothrombin Complex Concentrate (PCC) and Fresh Frozen Plasma (FFP) period is covered before vitamin K1 has reached full effect.
Vitamin K1 is important in maintaining the reversal achieved by PCC and FFP.
Prothrombinx-HT is the only PCC approved for reversal of warfarin in Australia and New Zealand. It is a concentrate of three factors that contain Factors II, IX and X, but only small amounts of Factor VII. Therefore, additional use of the FFP should be considered as the source of factor VII.
In 2013, FDA approves Prothrombin Complex Concentrate (Kcentra, CSL Behring). It is one of the first CCPs of four unactivated factors indicated for the acute reversal of vitamin K antagonist anticoagulation (warfarin) in patients with acute, severe bleeding.