RISK FACTORS, MONITORING
RISK FACTORS
| Enhanced warfarin effect: | |
| – Weight loss
– Acute illness – Thyroxine – Alcohol – Amiodarone |
– Antibiotics
– SSRIs/SNRIs – NSAIDs – Aspirin |
Decreased warfarin effect:
- Weight gain
- Enzyme inducers (carbamazepine, rifampicin, phenytoin, phenobarbital, St John’s Wort).
MONITORING
Warfarin monitoring:
- Daily monitoring at the start
- Therapeutic range: INR 2-3 (2.5)
- Recurrent DVT/PE range: INR 3-4 (3.5)
- Two positive results on separate occasions needed
- Then twice weekly for 1-2 weeks
- Can extend to 12-weekly thereafter
- Close monitoring of thyroid issues
- Watch out for bleeding risk interactions like for DOACs
Apixaban monitoring:
- Initial: Clotting, FBC, LFT, U&Es
- Review at 1 month, then 3-monthly
- Yearly blood tests
- avoid certain drug combinations: NASIDs, other anticoagulants, antiplatelets, SSRIs, SNRIs = increased bleeding risk.
