Hematology & Anticoagulant Drugs Flashcards
Hemophilia A involves a deficiency in:
factor VIII
hemophilia B involves a deficiency in:
factor IX
What % of hemoglobin is normal in mild hemophilia? In moderate? In severe?
mild = 6-49% is normal
moderate = 1-5% is normal
severe <1% is normal
Medications for treating hemophilia A
factor VIII concentrate
DDAVP
antibody therapy
gene therapy
B12 deficiency causes:
bone marrow suppression
decreased GI tract mucosa
*neuronal demyelination of the CNS
When are B12 injections preferred?
If neurologic deficits (d/t neuronal demyelination of the CNS)
Consequences of folic acid deficiency
bone marrow suppression
GI tract mucosa decrease
fetal neural tube defects
is folic acid or folinic acid replacement preferred
folic acid (the folinic acid active form is more expensive & not any more effective)
Why is B12 given in severe folic acid deficiency?
B12 is utilized in converting folic acid to its active form
**folic acid can also be converted to its active form via a different pathway too!
erythropoietin (EPO) results in:
stimulation of RBC production in one marrow
adverse effects of exogenous EPO
HTN
CV events
what increases the risk of CV events with exogenous EPO?
Hgb>11
or
Hgb increase >1 in 2 weeks
formulations of exogenous EPO
epoetin alfa
darbepoetin (longer 1/2 life)
What are leukopoietic growth factors?
substances that stimulate WBC proliferation
adverse effects of leukopoietic growth factors?
leukocytosis
bone pain
formulations of leukopoietic growth factors
G-CSF: filgrastim
GM-CSF: sargramostim
What do thrombopoietin receptor agonists do?
stimulate platelet production
Two main steps in forming a clot
- platelet plug
- fibrin mesh
fibrinogen connects activated platelets by binding:
GPIIb/IIIa receptors
platelet activation occurs upon exposure to an agonist such as:
ADP
TXA2
thrombin
collagen
platelet activation factor
What is fibrin?
threadlike protein that reinforces the platelet plug
What does antithrombin do?
inhibits some of the coagulation factors so clotting doesn’t get out of control
Which factors depend on vitamin K for their synthesis?
II, VII, IX, X
what degrades the fibrin mesh?
plasmin
What happens with arteriole thrombosis formation?
Lack of adequate blood flow (oxygenation) to distal tissues
What happens with venous thrombosis formation?
Possibility of pieces breaking off (emboli) and traveling to lungs/brain.
Which drugs activate antithrombin?
heparin
LMWH (enoxaparin, dalteparin)
How does heparin work?
activates antithrombin –>
increased inhibition of some clotting factors
–> decreased ability to create fibrin mesh
Which major step in coagulation does heparin inhibit?
Fibrin mesh formation
What type of drug is warfarin?
Anticoagulant
Vitamin K antagonist
How does warfarin work?
inhibits VKORC1 (vitK epoxie reductase complex 1)
vitK cannot be converted to active form
factors II, VII, IX, X are decreased = fibrin mesh formation is decreased
Which major step in coagulation does warfarin inhibit?
fibrin mesh formation
How do direct thrombin inhibitors work?
Bind & inhibit thrombin
Thus fibrin can’t be formed & factor XIII can’t be activated.
Decreased fibrin mesh formation
What major step in coagulation do direct thrombin inhibitors inhbit?
Fibrin mesh formation
Name a couple direct thrombin inhibitors
dapigatran
desirudin
bivalrudin
argatroban
How do direct factor Xa inhibitors work?
bind & inhibit factor Xa = decreased thrombin production
= decreased fibrin mesh formation
What major step in coagulation do direct factor Xa inhibitors inhibit?
fibrin mesh formation
List a couple direct factor Xa inhibitors
rivaroxaban
apixaban
What is the primary source of thrombi in veins?
fibrin
*thus anti-fibrin drugs are especially helpful for preventing DVTs
How is heparin administered?
IV or subQ
Why do IV infusions of heparin have to be monitored with PTT checks?
widely variable protein binding, so effects amongst various patients are unpredictable
What is normal PTT
40 sec
What is often the therapeutic goal of heparin infusion?
PTT 60-80sec
antidote for heparin
protamine
How does protamine work?
binds heparin, inactivating it
adverse effects of high dose heparin?
hemorrhage
heparin induced thrombocytopenia
hypersensitivity reactions
What is HIT (heparin induced thrombocytopenia)?
immune response against heparin: antibodies are produced against heparin-platelet complexes
What does HIT result in?
consumption of platelets (decreased platelets available to clot) = thrombocytopenia
increased platelet activation = increased thromboembolic events
What lab values might you expect to change in heparin induced thrombocytopenia?
PTT increase
platelet decrease (drastically)
Treatment for heparin induced thrombocytopenia?
d/c heparin
use alternative anticoagulant
Why don’t LMWH require PTT monitoring?
decreased protein binding & slower clearance: predictable pharmacokinetics
How is warfarin given?
PO only
What might occur if another highly protein bound drug is given to your patient on warfarin?
Increased free warfarin = overdose
Increased bleeding risk
What lab value is monitored during warfarin administration?
PT/INR
What is the normal INR value?
0.8-1.1
What is the goal INR in warfarin therapy?
2-3
Why is warfarin not used for acute clotting issues?
Doesn’t inhibit the vitK factors that are already synthesized - thus effects take a few days
(just inhibits the formation of future vitK factors)
Adverse effects of warfarin
hemorrhage
fetal hemorrhage (contraindicated in pregnancy)
infant hemorrhage (caution in breasfeeding)
antidote of warfarin
vitamin K (phenytonadione)
FFP
plasma concentrates of factor II, VII, IX, X
Dietary guidance for a patient being prescribed warfarin:
caution with excessive dietary vitK:
- leafy green veggies
- mayo
- canola oil
What is unique about bivalrudin (compared with the other direct thrombin inhibitors)?
IV only (continuous infusion)
rapid onset
short duration
adverse effects of direct thrombin inhibitors
hemorrhage (less than warfarin)
GI disturbances
bivalrudin can cause back pain, hypotension, and headache
Do you need to monitor lab values for direct thrombin inhibitors or direct factor Xa inhibitors?
no
adverse effects of rivaroxaban
hemorrhage (less than warfarin)
maternal hemorrhage risk + fetal effects (avoid in pregnancy)
How does aspirin decrease clotting?
irreversibly inhibits cyclooxygenase = decreased thromboxane A2 (TXA2) formation
(TXA2 agonizes platelet activation & aggregation)
What major step in clotting does aspirin inhibit?
platelet activation & aggregation
what class of medication is aspirin?
COX inhibitor
How do P2Y12 ADP receptor antagonists work?
block P2Y12 ADP receptors on platelet surface –> decreased activation and aggregation
What major step in clotting do P2Y12 ADP receptor antagonists inhibit?
platelet activation & aggregation
List some P2Y12 ADP receptor antagonists
clopidogrel
prasugrel
ticagrelor
How do PAR-1 antagonists work?
inhibit PAR1 receptors on platelet surface = decreased platelet activation/aggregation
What major step in coagulation do PAR1 antagonists inhibit?
platelet activation/aggregation
Name a PAR1 antagonist
vorapaxar
How do GP IIb/IIIa receptor antagonists work?
block GPIIb/IIIa receptors on platelet surface = inhibit FINAL COMMON STEP in platelet aggregation
(thus making them the MOST effective antiplatelet drug)
list some GPIIb/IIIa receptor antagonists
abciximab
tirofiban
eptifibatide
Which antiplatelet drug is most effective
GP IIb/IIIa receptor antagonists
(like abciximab)
duration of action of single dose of aspirin
7-10 days (lifetime of platelet due to irreversible binding)
duration of action of single dose clopidogrel (Plavix)
7-10 days (lifetime of platelet due to irreversible binding)
Why are GPIIb/IIIa receptor antagonists the most powerful antiplatelet drug?
all other platelet activating/aggregating agonists (TXA2, etc.) require the GP IIb/IIIa receptor
What do thrombolytic drugs do?
break down thrombi that have already formed
list some thrombolytics
alteplase (tPA)
reteplase
tenecteplase
how do thrombolytic drugs work?
activate plasmin which breaks down fibrin mesh
also degrades clotting factors
route of administration of thrombolytic drugs
IV
uses for thrombolytic drugs
acute MI, CVA, PE
adverse effects of thrombolytic drugs
hemorrhage!
How to prevent hemorrhage when administering thrombolytic drugs
- minimize patient manipulations
- avoid invasive procedures (even PIV placement!)
- avoid subQ/IM injections
- minimize concurrent use of other blood thinners