Anticoagulation for Dentists Flashcards
How does Aspirin work as an anti platelet
- Inhibits cyclo-oxygenase irreversibly for lifetime of platelet 7-10 days
- Dose: 75-300mg per day
How does clopidogrel work as an anti platelet
- Blocks ADP receptor (on platelet surface) irreversibly
- Acts for lifetime of platelet i.e. 7-10 days
- Dose 75mg per day
How does Prasugrel work as an anti platelet
- Blocks ADP receptor irreversibly
- Acts for lifetime of the platelet (7-10days)
- More rapid and consistent inhibition than clopidogrel
Do antiplatelet medications have tone stopped before primary care dental surgeries?
NO
What are the three different types of anticoagulants?
INTRAVENOUS:
- Unfractionated heparin
SUBCUTANEOUS:
- Low molecular weight heparins e.g.) enoxaparin, tinzaparin, dalteparin
ORAL:
- Warfarin, dabigatran, rivaroxaban, apixaban, edoxaban
What is Heparin?
- Glycosaminoglycan derived from porcine mucosa
- Binds to antithrombin and increases its activity (thrombin causes clotting)
- Indirect thrombin inhibitor (since it acts by enhancing the activity of antithrombin)
- Given by continuous infusion
- Hospital patients only
- Monitor with APTT test
- Aim for ratio 1.8-2.8
What is low molecular weight heparin?
- Smaller molecule made from unfractionated heparin
- Given subcutaneously
- Renally excreted
- Given once daily. Weight adjusted dosing
- No monitoring necessary
- Used for treatment and prophylaxis
- Dalteparin used in sheffield
- For dental work give last dose 24 hours before dental surgery
- Next dose 4 hours after dental surgery
Describe the pharmacology of Warfarin
- Given by mouth completely and rapidly absorbed
- 99% plasma protein bound
- Inhibits the production of :
- Factors II, VII, IX, X (2, 7, 9, 10)
- Protein C and Protein S
- Metabolised by the liver via cytochrome P450
- Peak effect 3-4 days after starting, and effect still present 4-5 days after stopping
Describe the potentiation of anticoagulation with Warfarin (Interactions)
• Reduced warfarin binding to albumin
- e.g.) Phenytoin
• Inhibition of hepatic microsomal degradation of warfarin
- e.g.) Erythromycin
Describe the inhibition of anticoagulation with Warfarin (Interactions)
• Acceleration of hepatic microsomal degradation of Warfarin
- e.g.) Carbamazepine
• Enhanced synthesis of clotting factors
- e.g.) Vitamin K
How do we monitor Warfarin
- INR test
- Dose of warfarin based on INR
- Frequency of monitoring depends on stability of patients INR
- INR must be before surgery of invasive procedures
- Uses a drop of blood, similar to blood glucose measurement
What does an INR of 2.0 - 3.0 indicate
- Treatment of DVT/PE (6 months)
* Atrial fibrillation
What does an INR of 3.0-4.5 indicate
- Recurrent DVT/PE on warfarin (life-long)
* Mechanical heart valves (life-long)
What are the side effects of warfarin
• Bleeding:
- 3% any bleeding
- 1% serious
- 0.3% death due to bleeding
- Skin necrosis
- Embryopathy
Reversal of Warfarin
• Stop Warfarin:
- Takes 2-3 days
• Vitamin K
- with iv preparation 80% correction 6 hours
• Fresh Frozen Plasma (FFP):
- Only partial correction
• Clotting factor concentrate:
- Contains factors II, VII, IX, X
- Complete correction in 10 minutes
