Anti coag drugs Flashcards
indications of anticoagulant drugs
venous thrombosis
atrial fibrillation
what do anti coagulants target
formation of the fibrin clot
heparin
warfarin
ATTP
PT
heparin potentiates what
effect
how is it given
forms
potentiates antithrombin
immediate effect
parenteral - IV or SC
2 forms - unfractionated IV, low molecular weight (LMWH) - SC
why can AFib lead to a stroke
Stasis in the left atrium – fibrin clot can be formed on the wall – blood clot can break off and go straight up the caroti artery into the brain and can lead to a very severe stroke
other indications for anti coag
valve replacements - metal valves
heparin stops what
breaking apart of the thrombin/factor 10 and antithrombin complex
how do the two types of heparin work and which is monitored more
LMWH – antthrombin and factor 10 – needs less monitering
Unfractionated – antithrombin and thrombin
monitoring of heparin
APTT for unfractionated
anti 10 assay for LMWH but not really monitored as more predictable response
when is LMWH monitered
kidney disease
obesity
pregnancy
why APTT for heparin
more sensitive than PT
heparin complications
bleeding
heparin induced thrombocytopenia (with thrombosis) - HITT - monster FBC in patients on heparin
osteoporosis with long term - higher risk with unfractionated
heparin reversal
stop the heparin - short half life
in severe bleeding - protamine sulphate, reverses antithrombin effect
complete reversal for unfractionated
partial reversal for LMWH
coumarin anticoag
mechanism of action
warfarin, phenindione, acenocoumarin, phenprocoumon
inhibition of vit K
vit K is what
where is it absorbed
requires what for absorption
final carboxylation of what
fat soluble vitamin
upper intestine
requires bile salts
of clotting factors 2, 7, 9, 10
what proteins w bit K
where synthesised
protein C and protein S
synthesised in liver
vit K and platelets pos and neg what
vit k makes the factors neg
and the platelets release calcium which is pos
warfarin initiatiation
window
maintanence
metabolised where
rapid and slow
narrow therapeutic window
maintanence - dose should be taken at the same time every day
stabilise them
metabolised in the liver w cytochrome p450
what should the INR be between
1-3
warfarin prolongs what
PT - better test
APTT is also prolonged
what is the INR
patients PT time (sec) / mean normal PT time in seconds all to the power of ISI
major risk factor with warfarin
haemorrhage
factors that influence bleeding risk w warfarin
intensity of anti coag concomitant clinical disorders concomitant use to of other medications drug interactions quality of management
bleeding complications
mild - skin bruising, epistaxis, haematuria
severe - GI, intracerebarl, drop in HB
warfarin reversal
no action
omit warfarin dose(s) - takes a few days for warfarin to come down
oral Vit K - 6 hours
clotting factors (FFP or factor concentrates 2 7 9 and 10) - immediately warfarin comes down
clinical and lab assessment of response
type of new anticoagulants
oral direct thrombin inhibitors - dabigatran PO
oral factor 10 inhibitors - riveroxaban, apixaban
con of new anticoag
no specific antidote – have been developed
who are new anti coag drugs used in
instead of LMWH as prophylaxis in elective hip and knee replacement surgery
stroke prevention in AFIb in some px
treatment for DVT/PE
