Anticoagulants Flashcards

Question 1

Q

Transexamic acid (TXA)

Answer

A

CLASS
antifibrinolytic
lysine analong
procoagulant
USE
Blood loss and need for transfusion are reduced in surgical patients
MOA
directly inhibit plasmin at high doses
competitively inhibits plasminogen activation (binds to the kringle domain in place of lysine on plasminogen), reducing plasmin concentration and fibrinolytic activity.
PK
Onset: 5-15 min
DOA: 3 hours
E1/2 t: 2- 11 hours
PB: 3% (does not bind to albumin)
Vd: 9-12 liters
Elimination: 95% excreted unchanged
- Reduce dose in renal disease
SE
Seizures
GABA blockade in frontal cortex
Vision changes – particularly color vision
Ureteral obstruction and bleeding
Renal toxicity
No increase of risk for thromboembolic events based on current evidence

Question 2

Q

heparin: class, MOA

Answer

A

class
- anticoagulant
- highly sulfated glycosaminoglycan
use
- Pulmonary embolus
- DVT & DVT prevention
- acute MI & stroke
- dialysis
- cardio-pulmonary bypass
- disseminated intravascular coagulation
MOA
- acts as a co-actor when bound to anti-thrombin III (endogenous) and potentiates anti-thrombin III effects
- anti-thrombin inactivates thrombin and other coag factor (9, 10, 11, 12) and plasmin
- also prevents conversion of fibrinogen to fibrin (blocks stabilization of clot)
- heparin also binds to factor II which also inhibits thrombin
PK
Onset: minutes IV (SQ onset 1-2 hours)
E½ life: ~ 1 hr
Metabolism: hepatic
Exretion: 50% unchanged in urine after IV admin
precise mechanism of clearance/metabolism unclear
Baseline antithrombin activity can influence patient response
Temp (more active at higher body temperatures)
Highly polar and large MW
- Good choice in pregnancy and breast feeding
poor lipid soluble
Protein binding
- A lot of non-specific binding = variable free drug/unpredictable dose response

SIDE EFFECTS

Hemorrhage
HIT (heparin induced thrombocytopenia)
- 50% decrease in plt count <100,ooo cells/mm3 with thrombosis
Osteoporosis
Hypersensitivity
- Animal tissue extraction source
CAUTIONS/CI/DI
Liver or kidney disease
Indwelling epidural catheter
Traumatic placement of epidural or spinal anesthetic
Other anti-platelet or anti-coagulation medications
Peri-surgical: eye, brain or spinal cord
Patients at high risk for bleeding
- Hemophilia, aneurysm, severe HTN, GI bleed risk (i.e. PUD), thrombocytopenia

DOSE

DVT Prophylaxis: 5000 units SQ Q8-12 hrs
CPB: 300 units/kg, maintenance dose 100 units/kg/hr using ACT as a therapeutic guide
D/C infusion 4-5 hours prior to sx & check PTT
reversal agent: protamine
monitor Activated Partial Thromboplastin Time (aPTT)
- Typical goal: 1.5-2X normal (30-35 seconds)
- Activated clotting time (ACT) used with high dose (CPB)

Question 3

Q

Protamine

Answer

A

CLASS
unfractionated heparin antagonist
inhibitor of anticoagulation and fibrinolysis
USE
heparin overdose
reversal of heparin after CPB
mild anticoagulant effect alone
MOA
Protamine is alkaline and + charged, heparin is acidic and – charged
binds ionically with heparin to form an inactive compound with no anticoagulation effects
when used alone it acts on platelets & fibrinogen to produce mild anticoagulative effects
PK
DOA: ~2 hours (may need to redose)
Eliminated via reticuloendolthelial system within 20 min
clears faster than heparin→heparin rebound may occur
SE
HISTAMINE release = bronchoconstriction, hypotension, tachycardia, pulm HTN, facial flushing
anaphylaxis
acute pulmonary vasoconstriction
right ventricular failure
some SE are from protamine/heparin induced release of thromboxane A2 release from platelets and macrophages - may be attenuated by pretreatment with COX inhibitors
CAUTION/CONTRAINDICATIONS/DRUG INTERACTIONS
hypersensitivity
highest risk for allergic rx if:
- allergic to seafood
- DM if tx with insulin containing protamine (NPH)
DOSE
1 mg of protamine for every 100 units of heparin administered throughout the procedure - administer SLOWLY < or = 5 mg/min

Brainscape's Knowledge GenomeTM