💊370: Anticoagulants Flashcards
What is the mechanism of action of Heparin?
Stops clotting progression by suppressing fibrin formation
What are dosing considerations for Heparin?
- Dosing by weight
- Can overlap with Warfarin
- Safe in pregnancy
What are the two types of Heparin?
- Unfractionated Heparin (UFH)
2. Low Molecular Weight Heparin (LMWH)
What is the mechanism of action of Unfractionated Heparin?
- Long chains bing to antithrombin, making more effective
- Impacts factor Xa, IX, XI, XII
Wraps around “hugs” thrombin
What are side effects of UFH?
- Bleeding
2. Heparin-induced Thrombocytopenia (HIT)
What is Heparin-induced Thrombocytopenia (HIT)?
Immune response leading to platelet activation and aggregation
- Platelet levels drop
- x30 risk Thrombosis
= Stop Heparin, use different anticoags (NOT LMWH)
What should a nurse monitor for a patient on UFH?
- Hemoglobin, platelet counts
- Activated partial thromboplastin time (aPTT, goal 1.5-2x control)
- Nomagram
- Anti-Xa
What is a prototype of Low Molecular Weight Heparin?
Dalteparin (Fragmin)
“-parin”
What are advantages of LMWH?
- More predictable
- Less bleeding
- Less HIT
- No monitoring required
- Fixed dose schedule due to longer half life
- Easy to give as SC for outpatients
What are disadvantages of LMWH?
- Drug price $$$
- Lower reversal of anticoagulation
- Dosing for renal/obesity uncertain
What are side effects of LMWH?
- Bleeding
- HIT (Heparin-induced Thrombocytopenia)
- Spinal/epidural hematoma
- Antiplatelet drugs
What is the mechanism of action of Fondaparinux (Arixtra)?
Small molecule, highly selective Xa inactivation
= similar to LMWH without HIT
What are dosing considerations for Fondaparinux (Arixtra)?
- Safe in pregnancy
- Renal dose adjustment needed
- SC injection once daily
What is the mechanism of action for Warfarin (Coumadin)?
Vitamin K antagonist - blocks synthesis of VII, IX, X, and prothrombin
What are therapeutic uses for Warfarin (Coumadin)?
- VTE treatment and prophylaxis
- Thrombosis in artificial heart valves
- Stroke in AFib
- Recurrent TIA and MI
What are side effects of Warfarin (Coumadin)?
- Bleeding
- Spinal/epidural hematoma
- UNSAFE for pregnancy and breastfeeding
- Liver disease, alcoholism
➡️ Vitamin K to reverse effects
What are drug interactions with Warfarin?
*Highly protein bound
- CYP450 metabolized
- Increased bleeding with antiplatelets/acetaminophen/aspirin/Vitamin E
- Cholestyramine ⬇️ PO absorption
- Alcohol (liver)
- Gut bacteria - synthesize Vit K
What are therapeutic uses for for Direct Oral Anticoagulants (DOACs)?
- Stroke (AFib)
2. VTE prophylaxis (ortho surgery)
What are side effects of DOACs?
- Bleeding
2. Renal dysfunction (GFR < 30mL/min)
What are drug interactions with DOACs?
P-glycoprotein (P-gp) pumps out DOACs in gut ➡️ Drugs inhibit P-gp
= azoles, verapamil, protease inhibitors
Anti platelets ⬆️ bleeding risk
What are prototypes of Direct Thrombin inhibitors?
Dabigatran Etexilate (Pradax)
What is the antidote to Dabigatran?
Idarucizumab
What are side effects of Dabigatran?
- Dysplesia/gastritis
Take with food, antacids/PPIs
What is a prototype of Direct Factor Xa inhibitors?
Rivaroxaban (Xaralto)
“-aban”
=Metabolized by CYP450
What is the mechanism of action for Low Dose Aspirin (ASA)?
Suppress platelet aggregation by irreversible inhibition of COX enzyme
Effects persist for platelet lifespan (7-10 days)
What is the dose of ASA for acute MIs?
160mg - 325mg
What are side effects of ASA?
- Bleeding
2. GI upset/irritation (use enteric-coated ASA, ECASA)
What is the mechanism of action of Clopidogrel (Plavix)?
Prodrug
Irreversible blockade of ADP Receptor on platelets
= prevention of platelet aggregation
What are the therapeutic uses for Clopidogrel (Plavix)?
- Coronary stenting
- Stroke prophylaxis
- MI and other vascular event prophylaxis
What are drug interactions with Clopidogrel (Plavix)?
- Bleeding
2. Proton Pump inhibitors (PPIs, omeprazole) ⬇️ efficacy
What are side effects of Clopidogrel (Plavix)?
- Bleeding
- GI (pain, dyspepsia, diarrhea, n/v)
- Rash
- Headache
What is a prototype of Thrombolytics?
Alteplade (tPA)
“-plase”
What is the mechanism of action for Thrombolytics?
Increased conversion of plasminogen to plasmin, which then digests fibrin clots and degraded fibrinogen + clotting factors
- Short half life (5min)
- Rapid hepatic inactivation
What are the therapeutic uses for Thrombolytics?
- Ischemic stroke
- Pulmonary embolism
- Acute MI
What are side effects of Thrombolytics?
High risk of bleeding
= injections/wounds/procedures contraindicated
What are contraindications for Thrombolytics?
- Prior intracranial hemorrhage
- Cerebro vascular lesión
- Ischemic stroke
- Internal bleeding
- Intracranial neoplasm
- Aortic dissection
- Sever HTN
What is the mechanism of action for Alteplase?
tPA = tissue plasminogen activator
Conversion of plasminogen to plasmin ➡️ digests fibrin meshwork, degrades fribunigen ajd clotting Factors
