Cardiovascular Meds: anticoagulants Flashcards
Specify 3 laboratory tests to monitor the effectiveness of anticoagulants
PT/INR: patients who are taking Warfarin
aPTT: those who are taking Heparin
Heparin Anti-Xa level: those who are on unfractionated (UF) heparin and sometimes with low molecular weight (LMW) heparin
Describe the mechanisms of action of
- anticoagulants
- antiplatelets
- thrombolytics
- anticoagulants: disrupt the coagulation cascade, less fibrin is produced
- antiplatelets: inhibit platelet aggregation
- thrombolytics: lyse the clot
Recognize 3 major emergencies for patients on anticoagulants, antiplatelets, and thrombolytics
- shortness of breath or chest pain
- vital signs–low BP and high HR
- changes in level of consciousness/mental status
What are 4 examples of serious thrombi?
- pulmonary emboli
- myocardial infarction (MI)
- deep vein thrombosis (DVT)
- embolic stroke
Compare arterial blood clots with venous blood clots
Arterial blood clots:
damage to BV or rupture of plaques
–> platelets adhere to the site
–> platelets secrete ADP and TXA2 which attracts more platelets
Venous blood clots:
when venous flow is slow and stagnant, coagulation cascade occurs and fibrin is produced
–> fibrin attracts RBCs and platelets to make a clot
Specify whether anticoagulants treat thrombosis in arteries or veins
Anticoagulants treats THROMBOSIS IN VEINS !!!
Classify anticoagulants into 3 groups according to their mechanisms of action and give examples of each
- activates antithrombin: LMW heparin, UF heparin, and Fondaparinux
- Vitamin K antagonists: Warfarin
- Direct thrombin inhibitors: Bivalirudin
Specify whether antiplatelet drugs treat thrombosis in arteries or veins
Antiplatelets treat THROMBOSIS IN ARTERIES !!!
Classify antiplatelet drugs into 3 groups
- Aspirin
- P2Y12ADP receptor antagonists
- GP llb/lla receptor antagonists
Describe the mechanism of action of warfarin
Warfarin stops activation of Vitamin K
So there is less VK-dependent clotting factors (VII, IX, X< and prothrombin)
Specify the laboratory test to monitor therapeutic warfarin levels
PT/INR
*** monitor the lab work and adjust dosage –> the goal is to reach & maintain therapeutic warfarin level
*** normal INR level for someone not receiving warfarin is 1.0
*** patients with DVT, pulmonary embolism: target INR is 2-3
***patients with prosthetic aortic heart valves: 2.5-3.5
Recognize the dietary restrictions for patients on warfarin
Severely limit vitamin K rich foods!
List 3 contraindications of warfarin therapy
- current severe bleeding
- poor compliance to medication, INR monitoring, or dietary restrictions
- pregnant women
Identify 4 groups of patients who should take warfarin with caution
- uncontrolled hypertension
- severe liver disease
- recent surgery on brain, spinal column, or eye
- patients who are also taking OTC aspirin and NSAIDs
Describe the mechanism of action of “direct thrombin inhibitors”
Direct thrombin inhibitors are oral produrg:
dabigatran etexilate –> converted to dabigatran in the body
–> binds and inhibit prothrombin in the blood
***Fast onset
No lab monitoring, dietary restrictions, dosage is not weight dependent
Lower risk of serious bleeding
Name an example of direct thrombin inhibitors and specify the drug approved for its reversal
dabigatran etexilate
antidote for overdose: Idarucizumab
3 therapeutic uses of direct thrombin inhibitors
- atrial fib
- knee/hip replacement (immobility –> risk of developing clots)
- DVT/PE
Recognize the rationale for giving unfractionated heparin (UFH) subcutaneous or intravenous (IV)
No oral route for UF heparin!
Reason: UF heparin is a large polymer with negative charge –> cannot cross membrane!
What is MOA of heparin?
Heparin is a helper to antithrombin, which inactivates factor Xa and thrombin)
Describe the common laboratory test that is used to monitor UFH therapy and state its normal value and therapeutic target
aPTT monitoring (activated partial thromboplastin time)
Normal values: 40 sec
Therapeutic target: 60-80 sec (1.5-2x times normal)
Identify 6 factors that affect the bioavailability of heparin
- aging
- obesity
- changes in heparin binding proteins
- liver diseases
- kidney diseases
- heparin resistance
***List 2 conditions that lead to prolonged activated partial thromboplastic (aPTT) without heparin
Lupus (autoimmune disease)
Deficiency in contact factors
Specify the patient group at a higher risk of developing HIT
Post-op patients
Define heparin-induced thrombocytopenia (HIT) type II and describe its pathophysiology
Type 2 HIT is an immune-mediated disorder (due to abnormal antibodies) that typically occurs 4-10 days after exposure to heparin and has life- and limb-threatening thrombotic complications
Identify 5 complications of HIT type II
Complications include clots–not bleeding!
- DVT
- PE
- skin necrosis
- MI
- venous gangrene
List an example of low-molecular weight heparin (LMWH)
enoxaparin
Sub Q administration
Recount 3 differences between LMWH and unfractionated heparin (UFH)
LMWH is:
- broken into smaller pieces
- more specific to factor Xa inactivation
- more predictable; they can be given as a weight based dose
What is the antidote for heparin overdosing?
Protamine sulfate
Describe the mechanism of action of aspirin and list the 2 therapeutic uses of aspirin
Aspirin suppresses platelet aggregation by inhibiting the isoenzyme “cyclooxygenase (COX)” which leads to pain relief and the reduction of inflammation, fever, and clots.
Therapeutic uses:
1. MI and angina
2. ischemic stroke and transient ischemic attacks (TIAs)
Describe the mechanism of action of clopidogrel and list the 2 therapeutic uses of clopidogrel
Clopidogrel is a prodrug –> metabolized in the liver into its’ active form –> suppresses platelet clumping by blocking P2Y12ADP receptors on the platelets
Therapeutic uses:
- keep coronary stents open
- reduce thrombotic events such as MI, stroke, or peripheral arterial disease
Name an example of glycoprotein IIB/IIIa (GPIIB/IIIa) receptor blockers
Amociximab
Two things to know:
1. Most effective antiplatelet drugs
2. Must be given IV
Nice to know:
Block the last step of platelet aggregation by blocking the receptor –> prevent fibrinogen & vWf factors from binding on platelets
State 2 indications of GPIIB/IIIa receptor blockers (Abciximab)
- Percutaneous Coronary Intervention (PCI)
- Acute Coronary Syndromes (unstable angina and non-STEMI)
List precautions for GPIIB/IIIa receptor blockers
- The elderly, patients with renal disease, and women
–> higher risk of bleeding - No reversal agent
What kind of lab work must be drawn for Abciximab administration?
- Platelet count
- Hb labs
Discuss the MOA of thrombolytic therapy and name 1 drug in this class
Alteplase (tPA)
converts plasminogen to plasmin –> dissolve clots!
tPA is for emergency use only!
