Anticoagulants Flashcards
Define Anticoagulants
Drugs used to prevent coagulation
What are the two main types of anticoagulants?
Injectable anticoagulants ie. Heparins
Oral anticoagulants ie. Warfarin
What are the two main types of heparins?
Unfractionated Heparin
Low Molecular Weight Heparins (Enoxaparin, Tinzaparin)
How do heparins work?
Activate Antithrombin III
AIII inactivates clotting factors/thrombin by complexing w/ serine protease of the factors
When should heparin be used?
Immediate action
Used while Warfarin takes effect
Used to prevent thrombosis/clotting on collecting
What marker should be monitored during the use of unfractionated heparins?
Activated Partial Thromboplastin Time (APTT)
Which pathway does APTT examine?
Intrinsic pathway
Altered by changes in F XII, XI, IX, VIII, X, V, II, I
Do LMWHs require monitoring?
No
What effect does treatment with heparin have on platelets?
> 5 days heparin can lead to thrombocytopenia
Define DVTs
Deep Vein Thrombosis
What is a major secondary risk of DVTs
Pulmonary Embolism
What is a major cause of DVTs
Immobility in hospital
What are the signs/symptoms of DVTs?
Painful swelling in calf
What is diagnosis of DVT based on?
Ultrasound scan
D-dimer blood test
What are D-dimers?
Product of fibrinolysis raised in thrombosis
What are the risk factors for DVT/PE?
Surgery Pregnancy Oestrogens Malignancy MI/Heart Failure Obesity Age >40 Coagulation Disorders Immobility History of VTE Trauma
What is the regular drug treatment for DVTs in hospital?
Enoxaparin s.c.
How does Warfarin work?
Vitamin k antagonist (blocks Vit. K reductase)
Vit K essential for prothrombin AND F X, IX, VI (1972) production
When is Warfarin used?
Patients w/ replaced heart valves
Atrial Fibrillation
DVT/PE
What are the problems with using Warfarin?
Many drug interactions
Narrow therapeutic window
Several days to act
What is the INR?
International Normalised Ratio
Measure of clotting time based on prothrombin time
Ideally I
What is the Prothrombin Time?
Time for coagulation following addition of thromboplastin
What abnormalities prolong the Prothrombin Time?
Abnormalities of F VII, X, V, II, I
Liver Disease
Warfarin
What is the effect of increased Warfarin action?
Bleeding:
- Gastric
- Cererbral
- Haemoptysis
- Blood in faeces
- Blood in urine
- Easy bruising
How should Warfarin dosing/monitoring take place?
INR frequently monitored at start (2/wk) then increase interval (max 12 wks)
How can Warfarin dosing be reversed?
Vitamin K
When should Warfarin dosing be reversed?
Patient is bleeding
Very high INR (>8-10)
Warfarin overdose
How should patients be counselled about taking Warfarin?
Stick to regimen Take at 6 pm If dose missed DON'T take two, inform Dr Don't take when pregnant Consume alcohol in moderation
What dietary modifications should be made when treated with Warfarin?
Avoid excessive green vegetables
Avoid high levels of Vit K
What symptoms should patients be aware of and notify their doctors over?
Haemoptysis Blood in faeces Blood in urine Nose bleeds (>20-30 mins) Easy bruising Skin changes (necrosis) Diarrhoea/Vomiting >2days
What factors affect anticoagulant treatment in pregnant women?
Pregnancy produces thrombophilic state to prevent post partum haemmorhage
Thrombophilia - decreased venous return (gravid uterus/immobility)
Why should Wafarin be avoided in pregnant women?
Teratogenic (Chondroplasia punctata, optic atrophy, mental retardation)
Avoid in T1/3
Favour LMWHs
What is Dabigatran?
Oral thombin inhibitor
What are the benefits of Dabigatran over Warfarin?
Less bleeding
Fewer interactions
Does not require monitoring
EQUALLY EFFECTIVE
What is Rivaroxaban?
Oral inhibitor of activated F X
What is Dipyridamole?
Antiplatelet drug
Phosphodiesterase inhibitor
How does Dipyridamole work?
Phosphodiesterase inhibitor
Prevents cAMP/cGMP breakdown
Inhibits aggregation
What is Streptokinase?
Thrombolytic medication
Fibrinolysis
How does Streptokinase work?
Activates endogenous fibrinolysis system
When is Streptokinase used?
Breakdown clots immediately after MI
