Pharmacology Flashcards
What’s the mech of action for heparin?
Unfractionated heparin (UFH) will bind with antithrombin III (ATIII), and inactivated clotting factors such as IXa, Xa, and of course IIa (thrombin).
LMWH with ATIII can bind Xa, and some IIa
Fondaparinux is the unique pentasaccharide sequence that UFH and LMWH use to bind AT.
It can only bind Xa!
Can Anti-thrombin inactivate clotting factors by itself?
Yes but heparin acts as a catalyst.
A physician gives you a demonstration on how to administer an IV bolus of heparin which has a half life of 90 mins. How long until a steady state is reached?
He tells you that you should monitor the effect the drug is having on the patient so you can adjust the dose; what should you use to monitor the drugs effect?
4 half lives or 6 hrs.
aPTT activated partial thromboplastin time; this is a measure of anti-factor Xa levels.
You see a first year intern freaking out because they gave someone too much heparin and they’re not sure what to do; what reversal agent would you use, how long will it take to work?
Protamine which itself is an anticoagulant but in the presence of heparin they form a salf and become inactive.
5 mins
Explain the mechanism of heparin induced thrombocytopenia (HIT)
Platlet factor 4 inactivates heparin and this molecule is seen as an Ag and forms an immune complex with IgG. These immune complexes then are bound by platets on the Fc receptor, these are then removed by splenic MO and leads to thrombocytopenia (decreased platelet count).
This binding can also lead to platelet activation and aggregation causing thrombosis.
why should you check a patients platelet count during heparin therapy?
To monitor for a HIT.
How do you treat a DVT?
IV heparin asap
oral warfarin
stop heparin when theraputic warfarin effect is attained (3-4 days)
ourpatient warfarin therapy
What’s the vitamin K cycle and what role does warfarin play in it?
Vitamin K cycle is a process whereby Vitamin K is Reduced by an Oxide reductase, then used to fuel a carbodylase reaction of a glutamic acid (adds Carboxyl group, converting it into a clotting factor), the Vitamin K that is oxidized in the process is then reduced agin by oxide reductase in a cyclic manner.
Warfarin inhibits the oxide reductase and stops the manufacture of clotting factors (II, VII, IX, and X). In time those already in the blood deplete.
Why don’t we just lead with warfarin and leave heparin out of it?
Warfarin alone could initially result in clotting due to inhibition of protein C and S synthesis
Until warfarin is theraputic the patient should be on heparin also, because the vitamin K cycle also produces proteins C and S (which inhibit clotting factors VIIIa, and Va).
How do you monitor warfarin therapy? What are you monitoring?
PT prothrombin time, INR internationally normalized ratio.
This is really a measure of the extrinsic pathway, and aPTT is a measure of the intrinsic path.
Your monitoring the speed at which the blood can clot after having administered an anticoagulant (warfarin), as clotting time slows the drug is having an effect.
Warfarin is a racemic mix of R and S sterioisomers which works best?
S for Super warfarin
What’s the antidote for high warfarin administration?
What if they start a life threatening bleed?
Vitamin K
add Fresh frozen plasma, or VIIa
Which anticoagulant can be used during pregnancy and which can not?
NO WARFARIN= WAR WITH MOM
YES HEPARIN= HEALTHY FOR MOM
What’s warfarins half life?
1.5 days x 4 = 6 days for steady state
The LMWH mention in lecture end in ___________?
-parin;
add a ux and you have fondaparinux for the factor Xa inhibitor
