Antiplalet and anticoagulants

Question 1

Warfarin

• Mechanism
• Monitoring
• Reversal

Answer 1

Vitamin K oral antagonist
- Inhibits gamme carboxylation of factors 2, 7, 9, 10= affects extrinsic pathway

Monitoring

• Citrated blood tubes to measure clotting test
• Check INR
• 2.5 for DVT/PE and AF
• 3.5 for VTE/ heart valves

Reversal
- Vitamin K, 10mg IV

Question 2

Heparin

• Mechanism
• Formulations
• Examples

Answer 2

Mucopolusaccharide, potentiates anti-thrombin

• Inactivates 2a and 10a
• Administered parenterally

Formulations

• Unfractioned (IV infusion)
• Low molecular weight (Subcut injection)

Examples

• Tinzaparin
• Enoxaparin
• Dalteparin

Question 3

Unfractionated heparin

• Monitoring
• Use
• Reversal
• Indications
• Side effects

Answer 3

Given less often than LNW heparin

• Usually used in renal failure
• Load with bolus, then hourly infusion

Monitored by APTT (1.5-2.5x

Can be partially reversed with protamine sulphate

Indications
- Treatment of VTE in renal failure, pregnancy

Side effect
- Heparin induced thrombocytopenia (HIT)

Question 4

Hirudin

Answer 4

Anticoagulant derived from snake venom

Agratroban is derived from this
- Used in patients with heparin induced thrombocytopenia

Question 5

Danaparoid

Answer 5

Heparinoid

- Heparin like compound

Question 6

Arixtra

Answer 6

Fondaparinx

- Potentiates antithrombin, inhibits 10x

Question 7

DVT treatment

Answer 7

1. LMW heparin
   - Enoxaparin
   - Dalteparin
2. Warfarin for 6 months
   - Monitor INR within

Or just DOACs

• Rivaroxaban
• Dabigatrain
• Epixaban
• Edoxaban

Question 8

Genetic conditions that predispose to clotting

Answer 8

Protein S, Protein C deficiency

Factor V Leiden
- Affects around 10% of population

Anti-phospholipid syndrome

Question 9

DOACs

• Classes and examples
• Monitoring

Answer 9

Direct oral anticoagulants

Direct thrombin inhibitor
- Dabigatran

Direct factor 10a inhibitors

• Rivaroxaban
• Epixaban
• Edoxaban

Monitor
- Renal function

Question 10

Rivaroxaban

• Mechanism
• Indications
• Dosin

Answer 10

Direct factor Xa inhibitor
- Irreversible

Indications

• VTE prophylaxis
• Prophylaxis for DVT and PEs
• Stroke prevention in AFib

Dosin

• 15mg bd for 3 weeks, then 20mg OD
• 15mg OD if CrCl is 15-50ml/min

Question 11

Dabigatran

• Mechanism
• Indication
• Antidote
• Dosing

Answer 11

Direct thrombin inhibitor

Indications

• VTE prophylaxis
• DVT and PE
• Stroke prevention in AFib

Antidote
- Praxbind (idarucizumab)

Dosing

• 150mg BD
• Prophylactic dose 110mg BD
• Creatinine clearance >30ml/min

Question 12

Octaplex

Answer 12

Given in reversal of warfarin overdose

Contains protein clotting complexes
- Factors 2,7,9,10.

Question 13

Antiplatelet drug classes and examples

Answer 13

COX inhibitors
- Aspirin

ADP receptor inhibitor
- Clopidogrel

Phosphodiesterase inhibitor
- Dipyridamole

Potentiator of adenylate cyclase
- Prostacyclin

Glycoprotein 2a/b inhibitor

• Abciximab
• Epitifibatide
• Tirofiban

Question 14

Fibrinolytic agents

• Mechanism
• Classes
• Route

Answer 14

Lyses fresh arterial thrombi
- Convert plasminogen to plasmin

Classes

• Tissue plasminogen activator (alteplase)
• Streptokinase

Adminstration
- Systemically: Acute MI, thrombotic stroke, Major PE, iliofemoral thrombosis

Question 15

Glycoprotein 2a/2b inhibitors

- Mechanism

Answer 15

Glycoprotein 2a/b are receptors involved in platelet aggregation.
- Inhibiting this prevents platelet aggregation, hence blot clotting.

Examples

• Abciximab
• Eptifibatide
• Tirofiban

Question 16

Warfarin interactions

Answer 16

Cytochrome P450 interaction

Examples

• Alcohol
• Erythromycin
• Carbamazepine

Question 17

Warfarin side effects

Answer 17

Teratongenic

Bleeding risk

• Intracranial bleeds
• Minor bleeds (up to 20% a year)

Skin necorsis

Alopecia