Anticoagulants Flashcards
Low molecular weight heparins
Enoxaparin (Lovenox), dalteparin (Fragmin), tinzaparin (innohep), Fondaparinux (Arixtra)
Direct thrombin inhibitors
Argatroban, lepirudin (Refludan) and bivalirudin (Angiomax)
Heparin MOA
Binds to the natural anticoagulant antithrombin and accelerates its enzymatic activity, complex inhibits thrombin as well as other factors
What molecules can form the bridge between AT and thrombin
heparin molecules at least 18 saccharide units
What will Heparin not do
It will not dissolve an existing blood clot
What does Heparin do
Only prevents propagation and growth
What is the T1/2 of heparin
it is dose dependent but it usually ranges from 30-90 mins mins
Heparin clearance is reduced in who
patients with renal and hepatic dysfunction
How do we monitor heparin?
aPTT, ACT, anti-factor Xa activity, or protamine titration assay, aPTT is the most widely used; ACT is most commonly used during coronary angioplasty and CABG surgery
ADR’s of Heparin
Bleeding, local irritation at injection site, thrombocytopenia, long-term use of heparin, alopecia, priapism, hyperkalemia, elevated ALT/AST and osteoporosis
The antidote is available and very effective
Protamine
HIT
severe, immune-mediated, drug-induced complication, usually indiacted by 50% drop in platelets or a platelet count ,150,000; typically the drop occurs 5-10 days into treatment
What do you do if a patient develops HIT
stop all forms of heparin, be sure to check for flushes, heparin in TPN, and heparin coated catheters, order heparin antibody lab, use a direct thrombin inhibitor or fondaparinux
What do you do if the heparin antibody lab is positive?
the patient should never get heparin ever, ever again
Heparin clinical uses
treatment of venous thromboembolism, atrial fibrillation, prevention of VTE, acute coronary syndromes, maintaining patent IV line, intraoperative coagulation
Low Molecular weight heparin
smaller molecular weight fragment obtained by chemical or enzymatic depolarization techniques of unfractionated heparin, similar to heparin, it prevents formation of thrombi
LMWH products commercially available in the US
Enoxaparin (Lovenox), Dalteparin (Fragmin), Tinzaparin (Innohep), last 2 not used
Smaller molecular weight prevents what
binding AT and thrombin simultaneously
For all three LMWH
routine monitoring is not necessary, T1/2 is 3-6 hours, dose independent renal elimination, subcutaneous bioavailability >90%
Routine efficacy monitoring of LMWH is
not recommended
What is the most accurated method to monitor efficacy?
Anti-factor Xa levels
how often do you measure LMWH
peak level 4 hours post dose at steady state
Patients to consider monitoring
weight> 150 kg or ,50 kg, CrCL ,30 ml/min pediatric patients, pregnant patients
Enoxaparin (Lovenox)
always adjust dose in renal failure, 1 mg/kg subcut Q12hr, always use actual body weight, don’t cap doses in obese
ADRs of Enoxaparin (Lovenox)
bleeding (monitor Hgb/HCT), HIT but not as common as heparin
Consider use of heparin over LMWH for pt with
obesity, renal failure, surgical candidates, or high risks for bleeding
Clinical uses of Enoxaparin (Lovenox)
treatment of VTE, prophylaxis of VTE, prevention of thrombus in Afib, STEMI, NSTEMI
Dalteparin (Fragmin)
LMWH, Prophylaxis and treatment of ACS, DVT/PE but not FDA approved for this
Tinzaparine (Innohep)
LMWH
Fondaparinux (Arixtra)
Factor Xa inhibitor, T1/2= 17-21 hours, will accumulate in renal impairment, no method of monitoring, no reversal agent
Clinical uses of Fondaparinux (Arixtra)
VTE prophylaxis, post op joint replacement or abdominal surgery, STEMI and NSTEMI, treatment of PE or DVT
Fondaparinux (Arixtra) serves as a great option for people who
have developed HIT
Argatroban
a direct thrombin inhibitor, treatment and prophylaxis of HIT, cardiovascular procedures in place of heparin with HIT or suspected HIT, monitor with aPTT and infusion rates adjusted accordingly, $$$, adjust in hepatic
Lepirudin (Refludan)
direct thrombin inhibitors, treatment and prophylaxis of HITT, cardiovascular procedures (in place of heparin) with HIT or suspected HIT, use is rare, adjust renal
Bivalirudin (Angiomax)
direct thrombin inhibitor, continuous infusion during PCI, IV only $$$$, adjust renal
Direct thrombin inhibitors
all given as continuous infusion- short T1/2 (25-75 mins), monitor aPTT to adjust dose
