Drug use in thrombotic diseases

Vasoconstriction

The initial stage of hemostasis where the blood vessel narrows.

Platelet aggregation

The second stage of hemostasis resulting in a platelet plug.

Blood coagulation

The third stage of hemostasis leading to a fibrin clot.

Fibrinolysis

The fourth stage of hemostasis responsible for clot breakdown.

Antiplatelet agents

Drug class that inhibits platelet activation, adhesion, and aggregation.

Anticoagulants

Drug class that inhibits blood clotting factors to prevent or extend fibrin clots.

Thrombolytic agents

Drug class that dissolves existing clots by converting plasminogen to plasmin.

Hemostatic agents

Drug class that stops excessive bleeding by inhibiting plasminogen activation and preserving clots.

Aspirin

Irreversibly inhibits COX-1 to decrease Thromboxane A2 (TXA2) synthesis for the 7-10 day lifespan of a platelet.

Aspirin adverse effects

GI bleeding, hemorrhagic stroke, and increased risk of inhibiting prostacyclin at higher doses.

Abciximab

Noncompetitive, irreversible GP IIb/IIIa receptor antagonist given IV during PCI.

Eptifibatide

Competitive, reversible GP IIb/IIIa receptor antagonist rapidly cleared by the kidneys.

Tirofiban

Competitive, reversible GP IIb/IIIa receptor antagonist that blocks fibrinogen binding to platelets.

Glycoprotein IIb/IIIa Antagonists MOA

Blocks GP IIb/IIIa receptors on platelets to prevent fibrinogen binding and cross-linking.

Clopidogrel

Irreversible P2Y12 prodrug bioactivated by CYP2C19; efficacy is reduced in poor metabolizers or with omeprazole use.

Ticlopidine

P2Y12 antagonist associated with a high incidence of neutropenia, agranulocytosis, and TTP.

Prasugrel

Irreversible P2Y12 antagonist carrying a black box warning for bleeding and strictly contraindicated in patients with a history of TIA or stroke.

Ticagrelor

Reversible, non-competitive P2Y12 antagonist acting outside the receptor site, carrying a black box warning for bleeding.

P2Y12 Antagonists MOA

Inhibits ADP receptors on platelets, blocking ADP-mediated conformational changes and aggregation.

Thrombotic Thrombocytopenic Purpura (TTP)

Condition characterized by microthrombi formation in small blood vessels, organ ischemia, and purpura.

Dipyridamole

PDE inhibitor that increases cAMP to cause vasodilation and reduced platelet aggregation; used with aspirin for stroke prevention but contraindicated in unstable angina due to coronary steal.

Cilostazol

PDE-3 inhibitor metabolized by hepatic CYPs used for intermittent claudication; absolutely contraindicated in Heart Failure.

Phosphodiesterase (PDE) Inhibitors MOA

Inhibits PDE enzymes to increase intracellular cAMP levels in platelets and vascular smooth muscle.

Unfractionated Heparin (UFH)

AT III activator with a 1:1 Thrombin-to-Xa inhibition ratio; administered IV, monitored via aPTT, and reversed by Protamine Sulfate.

Low Molecular Weight Heparins (LMWH)

Subcutaneous AT III activators (like Enoxaparin) that selectively inhibit Factor Xa over Thrombin and do not require routine lab monitoring.

Heparin-Induced Thrombocytopenia (HIT)

Immune-mediated adverse reaction causing low platelet count and paradoxical thrombosis; requires switching to Argatroban.

Protamine Sulfate

Specific reversal agent that forms a 1:1 inactive complex with UFH to neutralize its anticoagulant effect.

Fondaparinux

Synthetic pentasaccharide that selectively binds AT III to inhibit Factor Xa only; renally eliminated and contraindicated in severe renal impairment.

Warfarin

Oral Vitamin K Antagonist that inhibits VKOR, preventing gamma-carboxylation of Factors II, VII, IX, X, and Proteins C/S.

Warfarin Monitoring

Monitored routinely using International Normalized Ratio (INR), with a standard therapeutic target of 2.0-3.0.

Warfarin Reversal

Managed with oral Vitamin K1 for minor bleeding, or IV Vitamin K1, FFP, or PCC for severe hemorrhage.

Warfarin Adverse Effects

Severe risk of hemorrhage, high plasma protein displacement interactions, and teratogenicity (contraindicated in pregnancy).

Dabigatran

Oral direct thrombin inhibitor administered as a prodrug (etexilate) for stroke prevention in nonvalvular AF, reversed by Idarucizumab.

Idarucizumab

Monoclonal antibody fragment acting as the specific reversal agent for Dabigatran.

Argatroban

IV direct thrombin inhibitor metabolized by the liver; drug of choice for VTE prophylaxis/treatment in patients with HIT.

Bivalirudin

IV direct thrombin inhibitor used as an alternative to heparin in PCI patients who are at risk for HIT.

Rivaroxaban & Apixaban

Oral direct Factor Xa inhibitors metabolized by CYP3A4 and P-gp; contraindicated if CrCl < 15 mL/min and reversed by Andexanet alfa.

Andexanet alfa

Reversal agent for direct Factor Xa inhibitors (Rivaroxaban, Apixaban).

Alteplase (t-PA)

Fibrin-specific thrombolytic agent that converts plasminogen to plasmin to dissolve clots in acute ischemic stroke within 3 to 4.5 hours.

Streptokinase

Fibrin non-specific thrombolytic agent with high antigenicity that can induce allergic reactions and antibody formation.

Thrombolytic Contraindications

Active internal bleeding, history of hemorrhagic stroke, head trauma, intracranial neoplasm, recent surgery, severe uncontrolled hypertension, and pregnancy.

Tranexamic Acid (TXA)

Hemostatic agent that competitively inhibits plasminogen activation to prevent fibrin degradation; used to stop excessive bleeding.