Anticoagulants

Heparin

• Obtained from hog intestines or beef lung

• Acts by activating plasma antithrombin III in turn leading to increased rate of inhibition of factor Xa and thrombin production

• Not plasma bound

• Immediate onset ( for acute tx)

• Must be given I.V. or S.C.

• Anticoagulant of chice in pregnant women

• For tx and prevention of venous thromobosis and pulmonary embolism

• risk of Thrombocytopenia, hypersensitivity, and transient hypercoagulability upon discontinuation

• Bleeding risk increases as the dose increases.

• Antidote: protamine sulfate

Coumarin

(Warfarin)

• Acts by interfering with synthesis of several factors (including 10a) necessary for the conversion of prothrombin to thrombin.

• Blocks Vitamin K

• Vitamin K is required for the production of factors VII, IX, prothrombin, and anticoagulant proteins c and s.

• 97% plasma bound, and metabolized by the liver

• ineffective in vitro

• For tx and prevention of venous thromobosis and pulmonary embolism

• Use one stage PT test to evaluate therapeutic effect (given via INR)

• Only effects the production of new clotting factors so there is a 2-3 day delay in therapeutic effect.

• First 30 days have an increased risk of bleeding complications

• Effect may be increased by any drug that inhibits P450 system (Erythromycin)

• Risk of drug interactions. Be sure to look at the the handout

• Antidote is Vit. K, or phenytonadione

Dicoumaral

• ?

• ?

• ?

Theraputic goals

• determined by INR score

• INR goal is 2.0-3.0(2.5 ideal) for everything except mechanical prosthetic valves, post-acute MI prophylaxis, where the range is 2.5-3.5(ideal 3.0)

• INR5.0-5.9 give .05 mg vit. K

• INR 6.0-9.9 give 2.5 mg vit K

• INR >10 give 5.0 mg vit K

• Warning signs: epitaxis, GI bleeding, hematuria, hemoptysis, hemorrhoids… anything with bleeding