Sketchy Pharma 2 Flashcards
-Gi and Endo drugs -Antimetabolites -Neuropsych drugs
Mechanism of
(a) Fondaparinox
(b) Bivalirudin
(c) Rivaraoxaban
(d) Enoxaparin
Mechanism
(a) Fondaparinox = indirect thrombin inhibitor, acts like LMWH to bind ATIIII (which inactivates Xa)
(b) Bivalirudin = direct thrombin inhibitor
(c) Rivaraoxaban = direct Xa inhibitor (‘Xaban’)
(d) Enoxaparin = LMWH = Lovenox, binds ATIII
Mechanism of
(a) LMWH
(b) Dabigatran
(c) Apixaban
Mechanism
(a) LMWH = Enoxaparin = binds ATIIII (which inactivates Xa)
(b) Dabigatran = direct thrombin inhibitor
(c) Apixaban = direct Xa inhibitor ‘Xaban’
Mechanism of
(a) Argatroban
(b) Rivaroxaban
(c) Heparin
(d) Fondaparinox
Mechanism
(a) Argatroban = direct thrombin inhibitor
(b) Rivaroxaban = direct Xa inhibitor ‘Xaban’
(c) Heparin = binds ATIII to irreversibly inhibit thrombin and Xa
(d) Fondaparinox = indirect thrombin inhibitor that binds and inactivates ATIII
Name the 3 indirect thrombin inhibitors
3 indirect thrombin inhibitors: bind ATIII
Heparin (unfractionated)
LMWH (Enoxaparin)
Fondaparinux
Unfractionated heparin vs. LMWH
(a) Activity
(b) Monitoring
(c) When need to use unfractionated
(a) Unfractionated heparin binds ATIII w/ higher affinity so inhibits both thrombin and Xa, while LMHW binds ATIII to inhibit Xa w/ less effect on thrombin
(b) LMWH doesn’t require monitoring, much more predictable response => just give a weight-based dose
(c) LMWH renally excreted, so need to use unfractionated in renal insufficiency
AC in pregnancy
Heparin (and esp. LMWH) are very safe in pregnancy
“keep the baby heppy w/ heparin”
While coumadin is teratogenic: can cause hemorrhage and abnormal bone formation in utero
Name 3 main clinical indications for indirect thrombin inhibitors
Indirect thrombin inhibitors (heparin, LMWH, fondaparinux)
- Acute tx of DVT and PE
- Ppx of DVT and PE
- Acute tx of MI
Name an electrolyte abnormality seen as an AE to long term heparin therapy
Long term heparin therapy can result in hyperkalemia 2/2 hypoaldosteronism (reduced aldo release from adrenal cortex)
Differentiate the effect of protamine sulfate on indirect thrombin inhibitors
Protamine sulfate = heparin reversal agent
-less effective against LMWH and does not at all reverse fondaparinux
Why does warfarin have so many drug interactions?
B/c it’s metabolized by cyt p450
=> any drug that activates p450 (ex: rifampin, isoniazid) can decrease circulating levels
=> any drug that inhibits p450 can increase risk of warfarin toxicity
Differentiate the risk of HIT w/ the different indirect thrombin inhibitors
HIT risk highest w/ unfractionated heparin
- intermediate risk w/ LMWH (enoxaparin)
- low to no risk w/ fondaparinux
Fondaparinox vs. Enoxaparin
(a) Mechanism of action
(b) Risk of AE
Fondaparinox (binds ATIII so indirect thrombin inhibitor) vs. Enoxaparin (LMWH also binds ATIII)
(a) Both are indirect thrombin inhibitors, but fondaparinox binds ATIII w/ different affinity so inhibits Xa stronger w/ less effect on thrombin
(b) Fondaparinox has lowest risk (almost no risk) of HIT
Main shared indication of Bivalirudin and Argatroban
Bilvalirudin and Argatroban (and Dabigatran) are direct thrombin inhibitors that are used for anticoagulation in HIT
Name the 2 direct Xa inhibitors
Direct Xa inhibitors have ban Xa in their name!!!
Apixaban
Rivaroxaban ‘Xa-ban’
Mechanism of warfarin
Warfarin inhibits VKOR (vitamin K epoxide reductase) enzyme in the liver that activates vit K
-so vit K is inactive and can’t gamma carboxylate protein C/S, factors 1972
What test is best for monitoring warfarin therapy and why?
Warfarin therapy best monitored by PT/INR (INR is just an internationally standardized PT) b/c PT measured extrinsic pathway and common pathway
Extrinsic pathway involves just factor VII and X, and factor VII has the shortest half life of the vitamin-K dependent clotting factors so best to monitor for warfarin effect
What to do when you get symptomatic bleeding on warfarin therapy
- Stop warfarin therapy
- Give factors
- need to immediately replace factors, b/c stopping warfarin and giving vitamin K only allows for synthesis of new factors, still takes time for these factors to be made, so need to treat immediately by giving factors - Give vitamin K
Why does warfarin have so many drug interactions?
B/c it’s metabolized by cyt p450
=> any drug that activates p450 (ex: rifampin, isoniazid) can decrease circulating levels
=> any drug that inhibits p450 can increase risk of warfarin toxicity
Mechanism of
(a) Fondaparinox
(b) Clopidogrel
(c) Rivaraoxaban
(d) Abcximab
Mechanism of
(a) Fondaparinux = indirect thrombin inhibitor by binding ATIII (antithrombin III)
(b) Clopidogrel = ADP-receptor antagonist
- ADP receptor (P2-Y12) on plts is what allows ADP to bind and activate plts to aggregate
(c) Rivaraoxaban = direct Xa inhibitor
(d) Abcximab = monoclonal ab against plt receptor Gp2b3a
TXA2 released by plt degranulation
(a) Where and how produced
(b) Function
TXA2 (thromboxane A2)
(a) Produced by COX enzyme in plts- so this is inhibited by plts (mechanism by which plts inhibit plts)
(b) Function to activate plts to degranulate and aggregate
Mechanism by which aspirin inhibits platelets
ASA inhibits COX1 and COX2 (irreversibly via covalent acetylation) => decreased production of TXA2 which stimulates plt degranulation and aggregation
What is dual plt therapy?
Dual therapy = both
- Aspirin (inhibits TXA2 production by inhibiting COX)
- ADP receptor (P2-Y12) inhibitor that prevents ADP’s activation of plts to cause aggregation
Describe aspirin pseudo-allergy
(a) Clinical symptoms
(b) Why ‘pseudo’
(c) Seen in what pts?
ASA pseudo allergy
(a) Hives, itching, SOB shortly after ASA administration
(b) Pseudo b/c not due to IgE cross-linking, instead is due to increased leukotriene synthesis (AA shunted down LOX since COX is inhibited)
(c) More common in pts w/ h/o asthma, atopy
Why is aspirin held for a few days and not just one dose before surgery?
Aspirin irreversibly inhibits COX enzyme by covalently acetylating COX
-so can’t make any more TXA (no more active COX) until gene transcription upregulated and new COX enzyme is produced
Key is that aspirin irreversibly covalently acetylates COX
Name some indications for anti-platelet therapy
Antiplatelet: often use ASA first line, ADP-inhibitor (Clopidogrel) if ASA pseudo-allergy
- reduce CV events in pts w/ PAD
- prevent coronary stent thrombosis
- prevent stroke in pts w/ atherosclerosis
Why is clopidogrel first line before ticlopidine
Both clopidogrel and ticlopidine are ADP receptor inhibitors (prevent ADP from binding to and therefore activating plts)
But ticlopidine carries risk of agranulocytosis => clopidogrel used as first line
Drugs that inhibit
(a) Platelet adhesion
(b) Plt aggregation
Drugs that inhibit
(a) Plt adhesion requires vWF, Gp1b,
(b) Plt aggregation requires TXA2 (production inhibited by aspirin), ADP (receptors blocked by clopidogrel), and Gp2b3a (receptors blocked by abcximab)
Abcximiab
(a) Mechanism
(b) Side effect
Abcximab
(a) Monoclonal IgG to Gp2b3a = plt receptor required for aggregation
- fibrinogen molecules bind to multiple Gp2b3a on plts to aggregate plts
(b) Side effect = drug-induced thrombocytopenia
- so need to monitor plts in pts on abcximab
Mechanism by which phosphodiestrase inhibitors inhibit platelets
Phosphodiesterase inhibitors increase cAMP in plts which activates PKA and decreases plt activity
Differentiate indication of dipyridamole and cilostazol
Both dipyridamole and cilostazol are phosphodiesterase inhibitors. PDE breaks down cAMP => PDE inhibitors cause increased cAMP in plts which activates PKA and interferes w/ plt function
Dipyridamole = anti-plt agent often combined w/ ASA to prevent stroke
Cilostazole = anti-plt also w/ vasodilatory properties => used in tx of claudication
Which anti-platelet agent is indicated in coronary steal phenomenon?
Dipyridamole implicated in coronary steal (circulation shunted away from stenosed vessel)
Dipyridamole = phosphodiesterase inhibitor that causes vasodilation and plt inhibition
Narrowed coronaries are already maximally dilated, so adding vasodilator shunts blood away from coronary vessels => worsens ischemia
First clotting factor to disappear when pt is put on warfarin therapy
Well first protein C and S (which are anti-coagulants) have the shortest half life = explains the transient hypercoagulable state when first starting warfarin therapy
Then factor VII (7) has the shortest t1/2 of the clotting factors (about 6 hrs), full clinical effect of warfarin can take 3 days
Risk of warfarin therapy in pts w/ protein C/S deficiency
Warfarin doesn’t acutely stop coagulation (that’s what heparin is for), instead it prevents formation of new clots by inhibiting VKOR enzyme needed to activate vitamin K
So doesn’t touch existing factors, just prevents formation of new ones, so effect only starts when existing factors die off
Protein C/S have the shortest half life => die off before clotting factors 1972 do = transient hypercoagulable state when first start coumadin therapy (why pts are kept on heparin bridge)
Pts w/ protein C/S deficiency are hit harder by this initial hypercoagulable state and therefore at higher risk of warfarin-induced necrosis
Risk of warfarin therapy in pts w/ protein C/S deficiency
Warfarin doesn’t acutely stop coagulation (that’s what heparin is for), instead it prevents formation of new clots by inhibiting VKOR enzyme needed to activate vitamin K
So doesn’t touch existing factors, just prevents formation of new ones, so effect only starts when existing factors die off
Protein C/S have the shortest half life => die off before clotting factors 1972 do = transient hypercoagulable state when first start coumadin therapy (why pts are kept on heparin bridge)
Pts w/ protein C/S deficiency are hit harder by this initial hypercoagulable state and therefore at higher risk of warfarin-induced necrosis
Risk of warfarin therapy in pts w/ protein C/S deficiency
Warfarin doesn’t acutely stop coagulation (that’s what heparin is for), instead it prevents formation of new clots by inhibiting VKOR enzyme needed to activate vitamin K
So doesn’t touch existing factors, just prevents formation of new ones, so effect only starts when existing factors die off
Protein C/S have the shortest half life => die off before clotting factors 1972 do = transient hypercoagulable state when first start coumadin therapy (why pts are kept on heparin bridge)
Pts w/ protein C/S deficiency are hit harder by this initial hypercoagulable state and therefore at higher risk of warfarin-induced necrosis
Effect of streptokinase on PT and PTT
Streptokinase (endogenously produced by streptococcus bacteria) lyses clots by activating plasminogen to plasmin (same mechanism as recombinant tPA agents Alteplase and reteplase)
Prolongs both PT and PTT (b/c inhibits end of both coagulation cascade pathways)
Name some contraindications to thrombolytic therapy
Contraindications to tPA (alteplase/reteplase) and streptokinase
- any e/o internal bleeding: esp need to r/o intracerebral hemorrhage
- recent head trauma or major surgery
- severe HTN
Risk of streptokinase over alteplase
Streptokinase carries small risk of allergic rxn, can even be as severe as anaphylaxis
Name 2 reversal agents of thrombolytics
- aminocaproic acid (lysine derivative that inhibits plasmin)
- tranexamic acid
Name 2 reversal agents of thrombolytics
- aminocaproic acid (lysine derivative that inhibits plasmin)
- tranexamic acid
Differentiate VLDL and LDL
VLDL = mostly (60%) TG, VLDL directly excreted from liver then –> IDL –> LDL as lose TG to peripheral tissue
LDL = high proportion of cholesterol (less TG than VLDL), delivers cholesterol to peripheral tissue
Main transporter of the following to peripheral tissue
(a) TG
(b) Cholesterol
Main transporters
(a) TG given to peripheral tissues by both chylomicrons (intestines to liver) and VLDL (excreted from liver)
(b) Cholesterol bought to tissues by LDL, then removed from peripheral tissues to be returned to liver by HDL
Which apolipoprotein marks the ‘bad’ cholesterol
‘Bad’ cholesterol = VLDL and LDL, b/c when these are in serum in excess they deposit in BV walls
ApoB100 = major apoprotein on VLDL and HDL
2 mechanisms by which statins lower lipids
Statins- reduce LDL by 30-60% (first line agent)
- Inhibit HMG-CoA reductase = rate limiting step in endogenous cholesterol synthesis
- Increase LDL-R expression to remove more LDL from serum
Indications for statins
They have a mortality benefit!!! Basically give to errybody…
- secondary prevention for pts w/ diabetes, PAD, h/o stroke or TIA
- first line LDL-lowering agent
- reduce risk of cardiac complications after ACS
MC complication of statin therapy
Myopathy! Usually presents as proximal symmetric muscle weakness/soreness
2 lab abnormalities seen 2/2 statin therapy
- CK elevation 2/2 myopathy
- LFT elevations
- reversible
2 lab abnormalities seen 2/2 statin therapy
- CK elevation 2/2 myopathy
- LFT elevations
- reversible
Mechanism of
(a) Cholestyramine
(b) Ezetimibe
(c) Gemfibrazil
(a) Cholestyramine = bile acid resins, bind bile acids in intestinal lumen to make sure they go to ‘cholon’ (aka excreted instead of reabsorbed and recycled to liver)
(b) Ezetimibe = binds intestinal cholesterol, preventing absorption into enterocyte
(c) Gemfibrazil = fibrate, activates PPARgamma to upregulate LPL activity
Mechanism of PCSK-9 inhibitors
PCSK-9 degrade LDL receptors => when inhibited there are more LDLR on hepatocytes available to remove LDL from serum
Reduction in LDL 2/2
(a) Cholestryamine
(b) Ezetimibe
(c) Gemfibrazil
None of these are first line (ummm statins still run the show), so use in conjunction w/ statins for hyperlipidemia
(a) Cholestyramine (bile acid resin) reduces LDL by about 20%
(b) Ezetimibe (chol reabsorption inhibitor) reduces LDL by about 25%
(c) Gemfibrazil (fibrate) reduces LDL very minimally, really work to reduce VLDL 35-50%
Result in liver of decreased bile acid recycling
Decreased bile acids recycled to liver => liver revs up bile acid production, also means stimulation of HMG CoA reductase and upregulation of LDL-R
-so are slightly increasing exogenous cholesterol production, but removing more LDL from the circulation => overall reduce serum LDL
Limitation of bile-acid resins
(a) Can’t use w/ what other concomitant lipid abnormality
(b) Risk
Bile acid resins (Cholestyramine)
(a) Can increase TG => don’t use if pt has concomitant hypertriglycerides (can only really use in isolated LDL elevation)
(b) Increased risk of cholesterol gallstones
Which other lipid lowering agent needs to be spread out from statin therapy (aka not taken at the same time)
Bile acid resins (cholestyramine) reduces statin absorption => suggested to take them 4 hrs apart
Differentiate risk of cholestyramine from Ezetimibe
Cholestyramine carries increased risk of cholesterol gallstones (b/c decreases bile acid recycling) and increased TG
While Ezetimibe (reduces chol absorption) can cause elevated LFTs and diarrhea
Mechanism of fibrate therapy
Fibrates (Gemfibrazil, Fenofibrate) activate PPARalpha to upregulate extrahepatic LPL => accelerate VLDL and chylomicron hydrolysis
-so reduce VLDL
Also reduces VLDL secretion from the liver
Dangerous of TG over 1,000
RIsk of acute pancreatitis
MC side effect of
(a) Fibrates
(b) Niacin
(a) Fibrates => muscle toxicity, especially if taken w/ statin
(b) Niacin => cutaneous flushing and warmth shortly after taking agent or increasing dose, 2/2 prostaglandin release
- effect blunted by taking ppx NSAID before niacin dose
Most effective HDL-raising agent
HDL raising agent = Niacin (vit B3)