Anticoagulation for dentists - Haematological disorders

Question 1

What do to regarding dental procedures when the pt is on antiplatelets?

Answer 1

Balance risk of bleeding vs risk of thrombosis if drugs are discontinued
Antiplatelets do NOT have to be stopped before primary care dental surgical procedures

Question 2

List the intravenous, subcutaneous and oral anticoagulants

Answer 2

Intravenous = unfractionated heparin

Subcutaneous = low molecular weight heparins e.g. enoxaparin, tinzaparin, delteparin

Oral = warfarin, dabigatran, rivaroxaban, apixaban, edoxaban

Question 3

How does prasugrel work?

Answer 3

Blocks ADP receptor irreversibly
Acts for lifetime of platelet 7-10days
More rapid and consistent inhibition than clopidogrel

Question 4

What is heparin?

How does it work?

Answer 4

Glycoseaminoglycan derived from porcine mucosa
Binds to antithrombin and increases its activity
Indirect thrombin inhibitor

Given by continuous infusion - hospital pts only

Question 5

How to monitor heparin?

Answer 5

Monitor with APTT test - aim for ratio 1.8-2.8

Question 6

What is low molecular weight heparin?

Answer 6

Smaller molecule made from unfractionated heparin

Question 7

How is low molecular weight heparin given?

Answer 7

Given subcutaneously and renally excreted
Once daily - weight adjusted dosing
No monitoring necessary

Question 8

Low molecular weight heparin and dentistry?

Answer 8

For dental work give last dose 24hrs before dental surgery

Next dose 4hrs after dental surgery

Question 9

How is warfarin given?

Answer 9

By mouth and rapidly absorbed

Question 10

What does warfarin do?

Answer 10

Inhibits production of:
Factors II, VII, IX, X
Protein C and protein S

Metabolised by the liver via cytochrome P450
Peak effect 3-4 days after starting
Effect present 4-5 days after stopping

Question 11

What drugs do warfarin interact with?

Answer 11

Potentiation of anticoagulation:

• Reduced warfarin binding to albumin
  e. g. Phenytoin
• Inhibition of hepatic microsomal degradation of warfarin
  e. g. Erythromycin

Inhibition of anticoagulation:

• Acceleration of hepatic microsomal degradation of warfarin
  e. g. Carbamazepine
• Enhanced synthesis of clotting factors e.g. vitamin K

Question 12

How to monitor warfarin?

Answer 12

INR
Dose of warfarin depends of INR
Frequency of monitoring depends on stability of INR
Measure before surgery or invasive procedure

Question 13

When is the INR of 2-3 a target?

Answer 13

Treatment of DVT/PE (6 months)
Atrial fibrillation (life-long)

Question 14

When is the INR of 3-4.5 a target?

Answer 14

Recurrent DVT/PE on warfarin

Mechanical heart valves

Question 15

Side effects of warfarin?

Answer 15

3% any bleeding
1% serious/life threatening
0.3% death due to bleeding
Skin necrosis
Embryopathy (if used in 1st trimester of pregnancy)

Question 16

How to reverse warfarin?

Answer 16

Stop warfarin - takes 2-3 days
Vitamin K - 80% correction in 6hrs
Fresh frozen plasma - only partial correction
Clotting factor concentrate 
- Containing factors II, VII, IX, X
- Complete correction in 10 mins

Question 17

What to warn pts on warfarin?

Answer 17

No IM injections
No aspirin, NSAID without consultation
No contact sports
Excessive alcohol intake is harmful
Significant changes in diet should be reported
Consult doctor or pharmacist before any new meds including OTC

Question 18

Evidence of issues with dental extractions when on warfarin?

Answer 18

Wahl 1998 - 12 episodes of serious bleeding

Question 19

When is it safe to extract teeth when on warfarin?

Answer 19

INR less than 4

Check INR within 24hrs of extraction

Question 20

Name the new oral anticoagulants

Answer 20

NOACs
DOACs

• Rivaroxaban, apixaban, edoxaban (Xa inhibitors)
  Dabigatran (thrombin inhibitor)

Question 21

Pros of DOACs

Answer 21

Standard oral doses
No alcohol or food interactions
Fewer drug interactions
No major adverse events other than bleeding
Half life 6-15hrs

Question 22

Negatives of DOACs

Answer 22

No antidote

More expensive than warfarin

Question 23

DOAC and dental surgery?

Answer 23

Use LA with vasoconstrictor
Use infiltration or intraligamentary injection
If IAN used - inject slowing with aspiration
If on short term anticoagulation treatment = delay dental work until not on meds if possible
Do not take anticoagulant on morning of dental work
Restart 4hrs post prcedure

Question 24

Taking apixaban, dabigatran, rivaroxaban and edoxaban before and after dental surgery?

Answer 24

Apixaban or dabigatran = miss morning dose, post treatment usual time in evening as long as at least 4hrs after haemostasis

Rivaroxaban = delay morning dose, evening = 4hrs after haemostasis
Edoxaban = not applicable in morning, usual time in evening if 4hrs after haemostasis