Anti-coagulants Flashcards
Which is a vit K antagonist ?
Warfarin
What is the problem of anti-coagulants having NARROW therapeutic windows?
- over anticoagulation==> bleeding problems
- under: reduced efficacy
When are anti-coagulants given?
venous thrombosis
ATRIAL fibrillation
Why are anti-coagulants given for atrial fibrillation?
- d.t irregular contraction of the atrium
- results in stasis in the atrium> BLOOD CLOT formed
- —-like venous thrombosis
- risk of STROKE (through common carotid > internal carotid arteries> brain)
What are two types of thromboembolic strokes?
- atheroma (platelet rich thrombus)
- embolic stroke if pt HAS Atrial fibrillation —give anticoagulants, check ECG
Thrombin role?
- converts fibrinogen to fibrin
- —switching it off; stops coagulation!
Why is warfarin effective against PC AND PS?
-they’re also VITK dependant blood clotting factors.
How does heparin work?
- causes the blood clot to disappear over a LONG period of time
- —-potentiates anti-thrombin
What are the 2 forms of heparin?
- unfractionated (alot of MONITORING) — shorter Half T1/2
- LMWH
- –given as IV / s.c : parentral ! (inpatient)
What is the MOA of heparin?
- heparin keeps the anti-thrombin BOUND to thrombin and Xa to potentiate anti-thrombin axn
What is the diff between unfractionated and LMWH?
- —–unfractionated keeps anti-thrombin and thrombin together
- —-LMWH - keeps both bound together (Xa and Thrombin) —affect stays for 12-24 hrs
How to monitor heparin?
Why does LMWH not require as much monitoring?
PT and APTT is prolonged
—-APTT is much more sensitive
- anti-Xa assay; MORE PREDICTABLE!
What is monitored in a pt who takes warfarin?
- INR
- PT
What is the risk of monitoring PT with heparin?
- may lead to OVER-COAGULATION
What are the risks of heparin?
- abs to platelets!—-(heparin induced thrombocytopenia)
- BLEEDING
- OSTEOPOROSIS
- s/c injections EVERYDAY
What to monitor if the pt has been on unfractionated heparin?
- monitor FBC
- check for the platelet Abs
How to reverse heparinn drug action?
- STOP the heparin (STOPS bioavailability of unfractionated heparin)
- –ANTIDote: PROTAMINE SULPHATE (reverses anti-thrombin effect)
How effective is PROTAMIN SULPHATE for reversing heparin axn?
- PARTIAL reversal for LMWH
- —complete reversal for unfractionated
Name coumarin anit-coagulants.
—INHIBIT vitamin K
warfarin. phenindione. acenocoumarin
phenprocoumon
What is affected with warfarin administration?
- PROTEIN C,S (reduces FIRST FEW DAYS)
2, 7, 9, 10 (3-5DAYS)
—–no longer have a negative charge (does not form a blood clot)
What should be noted when administering warfarin and heparin?
- ALWAYS GIVEN WARFARIN AND HEPARIN TOGETHER (KICK IN HEPARIN IN A WEEK)
What is an issue with Warfarin?
- NARROW therapeutic window
- –metabolised in the liver (need to personalise the dose to the individual; some need 1 mg or 15 mg)
What is recommended with warfarin administration?
dose to be taken at the SAME time every day
What is the INR?
normalizes the PT ratio by adjusting the variability in the sensitivity of the diff. thromboplastins.
—-standardizes reagents
What are the MAJOR adverse effects of haemorrhage?
- intensity of t anti-coagulation
- concomitant clinical d.o
- concomitant use of OTHER meds
- BEWARE drug interactions
- quality of management
What are some bleeding s.es of warfarin?
MILD: bruising/ epistaxis/ haematuria
SEVERE: GI/ intracerebral/ sign. DROP in Hb
What to do if INR is HIGH?
-DROP 1-2 doses
( 2-3 days of INR to drop)
- give VITAMIN K
—if MASSIVE hemorrhage (ADMINISTER clotting factors )
- clinical and lab assessment of response
Why is clotting factors reserved for life-threatening conditions?
- $$$
- risk of infection!
- in the 50s: Hep.C and HIV
How long does it take for vit K and clotting factors to act?
- Vit. K: 6 HRS
- CLOTTING FACTORS: immediate
DABIGATRAN
- targets THROMBIN (prevents fibrin clot forming)
In whom is dabigatran inhibited?
Name Xa inhibitors,
- EDOXABAN
- RIVAROXABAN
- APIXABAN
Why are anti-coagulants given for DVT/ PE and atrial fibrillation?
- don’t affect PC AND PS
What is warfarin used for?
- those on heart valves and phospholipid diseases
- —great for preventing arterial events
Why are new anti-coagulants preferred nowadays>
- oral
- NO monitoring needed
- LESS drug interactions
What are new anticoagulants used for?
- prophylaxis in hip and knee replacement surgery
What do the anti-coagulant drugs target?
- formation of fibrin clot
If pt comes in with a suspected stroke, an his ecg shows atrial fibrillation, what medication is he given?
- anti-coagulants (to dissolve the FIBRIN-rich clot)
—-not given anti-platelets (unless ecg is -ve and the pt has HIGH BP/ is a smoker/ has DM/ high cholestrol)
What does prolonged PT with normal APTT suggest?
Factor VII deficiency
WHat does prolonged APTT with NORMAL PT suggest?
Factor VIII, IX, XI, XII
vWF (resp. to transport VIII)
