Anticoagulaiton drugs Flashcards
indications for antiocoagulants?
venous thrombosis
Afib
MofA- anticoagulants?
target formation of fibrin clot
naturally occuring anticoagulants?
-serine protease inhibitors
-Protein C and Protein S
mofa heparin?
-activates antithrombin
Unfractioned heparin:
-antithrombin binds to thrombin + Xa
LMWH:
-antithrombin binds to Xa
how long does it take for heparin to work?
immediate effect
2 forms of heparin?
- unfractioned
- LMWH
mofa unfractioned heparin?
Activates antithrombin and predominantly inhibits thrombin (but also works on Xa )
mofa LMWH heparin?
Activates antithrombin (binds to it) and inhibits Xa
how to monitor unfractioned heparin?
Activated partial thromboplastin time (APTT) for unfractionated
how to monitor LMWH?
Anti-Xa assay for LMWH – but usually no monitoring of LMWH required
As factor 10a is in centre of haemostasis – will affect PT and APTT, but much more sensitive to APTT
why use unfracitionated over LMWH?
unfractionated easier to reverse so may use if patient is more prone to bleeding
complications of heparin?
Bleeding – as more anticoagulated
Heparin induced thrombocytopenia (with thrombosis) - monitor FBC in patients on heparin (more common in unfractionated)
Osteoporosis with long term use
what to do if patient is on heparin and starts bleeding?
Stop heparin – has short half life (will take longer to disappear in LMWH)
If severe bleeding:
-Protamine sulphate (antidote)
-Reverses antithrombin effect, complete reversal for unfractionated and partial reversal for LMWH
examples of coumarin anticoagulants?
warfarin, phenindione, acenocoumarin, phenprocoumon
where are clotting factors made?
usually in liver
Role of Vitamin K?
-Fat soluble vitamin, absorbed in jejeunum + ileum of intestine, requires bile salts for absorption
Final carboxylation of clotting factors 2 (prothrombin), 7, 9, 10 – all key components in secondary haemostasis
-also affect protein C and protein S (natural anticoagulants)– these drop initially on warfarin therapy, so always give heparin initially too
-Synthesised in liver
MofA of warfarin?
inhibition of vitamin K:
-vitamin K helps make clotting factors 2 (prothrombin), 7, 9, 20
-also affect protein C and protein S (natural anticoagulants)
what should be done in the initiation of warfarin?
should give heparin too
-as Warfarin also affect protein C and protein S (natural anticoagulants)– these drop initially on warfarin therapy, so always give heparin initially too
rapid- acute thrombosis
slow- in community, so not big affect on protein C or S
how is warfarin monitored?
-INR
-PT and APTT prolonged (due to factor 2, 7, 9 and 10 being affected)
-clotting factor 7 has shortest has life and so PT prolonged the most
what clotting factor has the shortest half life and what effect does that have?
o Shortest half-life is factor 7, so PT prolonged the most
calculation for INR?
Complications of Warfarin?
Haemorrhage
Bleeding complications:
Mild – skin bruising, epistaxis, haematuria
Severe – GI, intracerebral, significant drop in Hb
risk factors for complications of a haemorrhage when on warfarin?
Risk factors – intensity of anticoagulation, concomitant clinical disorders, concomitant use of other medications, drug interactions, quality of management
management of bleeding when patient is on warfarin?
Management depends on severity of bleeding and INR
Omit warfarin doses – hopefully bring INR down
If not, administer oral vitamin K – 6 hours to work
If severe :
-Give prothrombin complex concentrate (PTCC)
-If no PTCC available give FFP (takes longer to thaw so not first line)
