CLINICAL LABORATORY MONITORING AND ASSESSMENT OF AND ANTIPLATELET DRUGS USED FOR THE MANAGEMENT OF CARDIOVASCULAR DISORDERS

Jeanine M. Walenga, Ph.D. Professor Thoracic & Cardiovascular Surgery Pathology & Laboratory Medicine, and Physiology Loyola University Chicago ~~ Clinical Laboratory Director Loyola University Medical Center Blood Coagulation and Platelet Activation Leads to Thrombotic Cardiovascular Disorders Laboratory Assessment of Drugs

• The therapeutic range of a drug is the dose that provides the desired effect without side effects. – For antithrombotic drugs, the side effects are bleeding and thrombosis.

Anticoagulant Drugs and their Mechanism of Action

Mechanism of Legend Class Example Action

Vitamin K Inhibit synthesis of antagonists Warfarin II, VII, IX, X # (VKA)

UFH Indirectly inhibit Xa, IIa via AT; indirectly # inhibit VIIa via TFPI LMWH release

Indirectly inhibit Xa Pentasaccharide via AT

Argatroban Direct acting inhibitors Inhibit II (DTI)

Apixaban

Rivaroxaban Direct acting Inhibit Xa Xa inhibitors

Betrixaban Drug: Warfarin Assay: Prothrombin Time (PT)

XIIa VIIa XIa Extrinsic Pre-K HMWK TF IXa VIIIa Intrinsic

PT Reagent Xa Va (Thromboplastin ) Common TF, PL, Ca++ Pro Thr XIIIa (II) (IIa)

Fibrinogen Fibrin Crosslinked Polymer Fibrin Prothrombin Time (PT) Assay

• Assesses the function of the coagulation factors of the extrinsic and common pathways • Used to monitor warfarin therapy

Assay endpoint = clotted blood plasma Near Patient Testing Warfarin Monitoring – PT/INR Drug: (UFH) Assay: Activated Partial Thromboplastin Time (APTT, PTT)

XIIa VIIa XIa HMW Extrinsic Pre-K TF K IXaIXa VIIIa Intrinsic

Xa Va APTT Reagent (Partial Common thromboplastin) ++ Thr XIIIa PL, NCS, Ca Pro (IIa) (II)

Fibrinogen Fibrin Crosslinked Polymer Fibrin Activated Partial Thromboplastin Time (APTT) Assay

• Assesses the function of the coagulation factors of the intrinsic and common pathways • Used to monitor heparin (UFH) therapy

Assay endpoint = clotted blood plasma Near Patient Testing Heparin Monitoring – ACT ACT = Activated Clotting Time (a test similar to the APTT)

iSTAT Hemochron Jr. Signature

HemoTec

Hemochron Anticoagulant Drugs and their Mechanism of Action

Mechanism of Legend Class Example Action

Vitamin K Inhibit synthesis of antagonists Warfarin II, VII, IX, X # (VKA)

UFH Indirectly inhibit Xa, IIa via AT; indirectly # Heparins inhibit VIIa via TFPI LMWH release

Indirectly inhibit Xa Pentasaccharide Fondaparinux via AT

Argatroban Direct acting thrombin inhibitors Bivalirudin Inhibit II (DTI) Dabigatran

Apixaban

Rivaroxaban Direct acting Inhibit Xa Xa inhibitors Edoxaban

Betrixaban Drugs: Heparins (UFH, LMWH, fondaparinux) Assay: Anti-FXa (Synthetic Substrate or Chromogenic Assay)

1) Heparin-AT-FXa + excess FXa

2) Chromogenic substrate specific for FXa (CLEAR, no COLOR)

+ excess FXa

Enzymatic activity of FXa releases a chromophore more enzyme = more yellow color (YELLOW) Anticoagulant Drugs and their Mechanism of Action

Mechanism of Legend Class Example Action

Vitamin K Inhibit synthesis of antagonists Warfarin II, VII, IX, X # (VKA)

UFH Indirectly inhibit Xa, IIa via AT; indirectly # Heparins inhibit VIIa via TFPI LMWH release

Indirectly inhibit Xa Pentasaccharide Fondaparinux via AT

Argatroban Direct acting thrombin inhibitors Bivalirudin Inhibit II (DTI) Dabigatran

Apixaban

Rivaroxaban Direct acting Inhibit Xa Xa inhibitors Edoxaban

Betrixaban Direct Acting Thrombin Inhibitor Drugs (DTIs) Each DTI has its own dose-response effect 350

300

250

200 Assay: APTT

150 Argatroban

100 Lepirudin 50 Bivalirudin 0 0 2 4 6 8 10 12 Heparin Concentration (ug/mL)

For near patient testing, such as during percutaneous coronary intervention (PCI), the ACT assay (as used for UFH) is used for monitoring DTIs. Anticoagulant Drugs and their Mechanism of Action

Mechanism of Legend Class Example Action

Vitamin K Inhibit synthesis of antagonists Warfarin II, VII, IX, X # (VKA)

UFH Indirectly inhibit Xa, IIa via AT; indirectly # Heparins inhibit VIIa via TFPI LMWH release

Indirectly inhibit Xa Pentasaccharide Fondaparinux via AT

Argatroban Direct acting thrombin inhibitors Bivalirudin Inhibit II (DTI) Dabigatran

Apixaban

Rivaroxaban Direct acting Inhibit Xa Xa inhibitors Edoxaban

Betrixaban Laboratory Assessment of DOACs

• DOACs do not require routine laboratory monitoring because they have a wider safety margin. • However, there are medical circumstances when laboratory assessment of the DOAC is needed to know how much drug is onboard. • The DOACs respond differently than warfarin and heparin in the conventional PT and APTT. Laboratory Assessment of DOACs Drugs that Effect Platelet Function

– , non-reversible block of platelet cyclooxygenase – NSAIDS (non-steroidal anti- inflammatory drugs) reversible inhibition – ADP receptor blockers () – GP IIb/IIIa blockers () – PAR-1 (thrombin receptor) antagonists () – Phosphodiesterase inhibitor () Laboratory Assessment of Anti-Platelet Drugs

• Anti-platelet drugs are typically not monitored. • If there is a medical reason to determine the level of activity of the drug, assays are available. Platelet Aggregation Functional Test

Platelet Rich Plasma (PRP)

Blood specimen PRP showing platelet aggregates after agonist added

Platelet Aggregometer Laboratory Assessment of Anti-Platelet Drugs •Verify Now • Individual test cartridges for 3 anti-platelet drug classes: 1. Aspirin 2. ADP receptor inhibitors (clopidogrel, Plavix) 3. GP IIb/IIIa inhibitors (ReoPro) FIN