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RBF > Anticoagulant drugs > Flashcards

Anticoagulant drugs Flashcards

1
Q

What are three indications for anticoagulants

A

Coronary artery disease
Cerebrovascular disease
Peripheral vascular disease

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2
Q

What are three thrombo-embolic disease indications for anticoagulants

A

Atrial fibrillation
Venous thrombo embolism (PE, DVT)
Prosthetic cardiac valves

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3
Q

Three indications for heparin use

A

Acute coronary syndromes (MI)
Thromboembolus (prophylaxis and treatment)
Warfarin replacement (pregnancy)

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4
Q

What is the mechanism of action of unfractionated heparin

A

Binds to and increases the activity of Anti-Thrombin III.

Anti-Thrombin III inactivates Thrombin and factor Xa. Also IXa, XIa and XIIa.

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5
Q

What test is used to monitor UH and why is it necessary to do so vigilantly

A

aPPT.

Because UH has variable bio-availability due to unpredictable patterns of binding to cells and plasma proteins.

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6
Q

What biometric measurement should UH dosage be titrated against

A

Weight

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7
Q

How do you reverse UH therapy

A

Protamine sulphate

Irreversibly binds to heparin

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8
Q

Mechanism of action of LMWH

A

Binds to anti-thrombin. Smaller chains and more predictable structure c/w UH.
Does not inactivate Thrombin, specifically affects Xa.

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9
Q

Three advantages and three disadvantages of LMWH compared with UH

A
  • Higher bioavailiability
  • More predictable- monitoring not usually required
  • Less thrombocytopenia
  • Community SC administration
  • Cannot be monitored with aPPT
  • Not fully reversible with protamine
  • Care in renal failure (different metabolism)
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10
Q

What is an adverse effect related to UH use and platelet count

A

Thrombocytopenia. Due to an autoimmune phenomenon.

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11
Q

Prophylaxis dosing of LMWH (e.g. post C/S)

A

2o-40mg SC OD

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12
Q

Treatment regime of PE/DVT

A

Initially give LMWH, then warfarin, continue LMWH until INR therapeutic (5-7 days)

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13
Q

Mechanism of action of Warfarin

A

Antagonist of Vitamin K synthesis in the liver. Vitamin K required for synthesis of clotting factors II, VII, IX, and X.

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14
Q

Uses of warfarin

A

Treatment of venous or arterial thrombosis- DVT/ PE.

Prevention of venous or arterial thromboembolism- mechanical heart valves, AF.

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15
Q

Describe two instance when lifelong warfarin therapy is indicated

A

If more than one episode of DVT/ PE

If mechanical valves of AF (preventative)

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16
Q

How is warfarin metabolised and what is the clinical relevance of this

A

In the liver by cytochrome P450 enzyme. Many drugs decrease P450 efficacy and thus subject to drug interactions.

17
Q

Describe the half life and clinical implications

A

Very long half life- takes several days for the drug to have clinical effect so in treatment requires initial dual therapy with another anti-coagulant

18
Q

Two unwanted effects of warfarin

A

Haemorrhage (intracranial and GI)

Teratogenic in pregnancy (first trimester bone and CNS, third intracranial bleeds)

19
Q

Contraindications to warfarin

A

Situations where the risk of bleeding is greater than potential clinical benefits of therapy: substance abuse, dementia, falls.
Pregnancy

20
Q

Describe monitoring of warfarin

A

Use the INR. PR which adjusts for lab differences in thromboplastin. Initially monitor INF every 2-3 days. Long term therapy every 4-12/52.

21
Q

Describe target INR

A

Rx of VTE/ PE/ AF 2-3

Rx heart valve replacement/ anti-phospholipid syndrome/ recurrent thrombosis 3-4.5

22
Q

Four factors that affect warfarin metabolism

A

Absorption- diarrhoea and vomiting
Metabolism- liver disease
Nutrition/dietary (Vit K reduction)
Drugs

23
Q

Name five drugs that are inhibitors of the P450 enzyme and describe what effect this has on warfarin therapy.

A

Amioderone
Antimicrobials (erythromycin, metronidazole, ceprofloxacin)
Sodium valporate
Simvistatin
NSAIDs
Omeprazole
Decrease warfarin metabolism/excretion so potentiate its effects.

24
Q

Drugs that inhibit warfarin

A

Barbituates
OCP
Carbamazepine
Azithioprine

25
Q

Describe management of high INR coupled with bleeding

A

Stop warfarin
Give FFP/Prothrombin X and blood PRN
Give Vitamin K (slow onset so clotting factors need to be given PRN)

26
Q

Describe the mechanism of action and PK of dabigatran

A

Direct thrombin inhibitor
Prodrug; liver and gut enzymes cleave it to its active form.
Renal excretion

27
Q

Uses of dabigatran

A

Similar to warfarin- PE/DVT/AF. Not used in metal prosthetic heart valves.

28
Q

What drug is used to reverse the effects of dabigatran

A

Idarucizumab

RBF (8 decks)

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