Hematology and Antineoplastics SketchyPharm Flashcards
What is the mechanism of heparin interfering with potassium balance?
Heparin is directly toxic to adrenal cells of the zona glomerulosa -> leads to Type IV RTA (hyperkalemic hypoaldosteronism)
What are the three primary indications for heparin and its reversal agent?
- Acute PE
- DVT
- Acute MI
Reversal via protamine sulfate -> does not work as well on LMWH (i.e. enoxaparin, dalteparin)
How are the pharmacokinetics of LMWH different from UFH?
LMWH is more bioavailable, longer half life, and eliminated renally (tapering flag sticking into kidney from LMWH daughter)
-> UFH safer in renal insufficiency (metabolized via liver)
What monitoring is required for UFH and LMWH?
UFH - aPTT, much more sensitive to changes in factor II levels
LMWH - blood monitoring not required, but this also makes it harder to work with in the acute setting (anti-Xa only assays are only readily available)
What drugs should be immediately thought of for the treatment of HIT after discontinuing the offending agent? What can be used for reversal of these agents if anticoagulation is too much?
Direct thrombin inhibitors, i.e. bivalirudin, argatroban, dabigatran
Dabigatran has a reversal agent monoclonal antibody, but the other two you must stop the bleeding somehow:
- Anti-tPA’s / antifibrinolytics: tranexamic acid, aminocaproic acid
- Prothrombin complex concentrate
What is the main indication for factor Xa inhibitors and what are they?
ApiXaban, rivaroXaban
- > used as direct oral anticoagulants (DOACs) for longterm DVT and PE prophylaxis, as well as stroke prevention in AFib
- > the only direct thrombin inhibitor which is a DOAC is the one with a reversal agent: Dabigatran.
What factor which procoagulant warfarin inhibits has the shortest halflife? Why is this clinically relevant?
Factor 7 - think of the 7 deadly sins soldier on the ground
Relevant because factor 7 is part of the extrinsic pathway
- > reason why we measure to PT to monitor warfarin activity
- > rest of factors are part of common pathway (or factor 9).
What drugs notoriously increase and decrease INR with Warfarin? What’s the target INR?
Target INR: 2-3
Increase:
TMP-SMX (displaces warfarin from albumin)
All CYP inhibitors, i.e. amiodarone, azithromycin, fluconazole
Decrease: CYP inducers - carbamazepine, phenobarbital, rifampin
What are the fetal abnormalities which result from warfarin use in pregnancy?
- Bone abnormalities - interferes with gamma-carboxylation needed for calcium-using proteins
- Bleeding abnormalities and retinal hemorrhage.
What are the indications for warfarin?
Longterm anticoagulation in AFib, or PE / DVT prophylaxis in those at high risk or following the event
- > think of the ship going down the iliofemoral river
- > warfarin is generally first line over the expensive Xa inhibitors
What is the mechanism of action of ticagrelor and prasugrel?
Same as clopidogrel - block P2Y12 receptor to prevent ADP binding, which prevents upregulation of Gp2b/3a receptors
-> remember that ADP functions to aggregate da platelets
What is dual antiplatelet therapy and what are three indications?
Aspirin (anti-TXA2) and ADP receptor blocker (i.e. clopidogrel)
- Acute coronary syndromes - broken heart strings
- Prevention of coronary stent thrombosis - think of Sammy Sosa corked bats
- Ischemic stroke - think of black paint on painter’s head, also seen in statins sketchy
What is the mechanism of action of ticlodipine and the adverse effect of worry?
Think Ty Cobb next to the grill
ADP receptor blocker, associated with neutropenia / granulocytopenia (think of the hourglass)
Give three Gp2b/3a inhibitors and their major unique side effect? Indication?
Abciximab - monoclonal antibody
Eptifibatide - Tied
Tirofiban - Tied
Side effect - think of broken plates all around -> thrombocytopenia
Main indication - patients about to undergo percutaneous coronary intervention (PCI)
What are the two phosphodiesterase inhibitors used to impair platelet activation and their mechanism of action?
Dipyridamole - Two pyramids on tent
Cilostazole - He lost the ball!
increased cAMP will impair platelet aggregation (i.e. TXA2 is meant to decrease cAMP synthesis), also causes vasodilation
What is the main indication for dipyridamole?
Sometimes used in combination with aspirin for the prevention of stroke (dual therapy)
What is cilastazol used for?
- Coronary steal testing -> causes general coronary vasodilation
- Can be used for intermittent claudication -> prevents pain from peripheral artery disease by direct arterial vasodilation
When but thrombolytics be administered for ischemic stroke? When should it be administered for MI? Also give a list of these drugs in your answer.
Streptokinase, alteplase, reteplase, or tenecteplase must be administered within 3-4.5 hours of stroke onset
Administer for MI if patient cannot have percutaneous coronary intervention within two hours (think of the guy in the background holding up two fingers)
What are some contraindications of fibrinolytic therapy?
- Recent head trauma
- Recent neurosurgery
- Active bleeding
What can be used for reversal of thrombolytic therapy?
Competitive inhibitors of plasminogen - tranexamic acid (exam) or aminocaproic acid (capping paint)
FFP - fighter plane
Crypoprecipitate - the cap that the kid is wearing
What are the gynecologic uses of methotrexate?
Think of the uterus backpack with shit falling out
- Abortion - in combination with misoprostol
- Molar pregnancy / choriocarcinoma - think of the mole falling out of the bag
- Unruptured ectopic pregnancy - think of the baby hanging from the straps
What are the uses of methotrexate in treatment of chronic inflammatory conditions?
Psoriasis - think of the scaly pads
Rheumatoid arthritis - think of the lanterns
IBD, SLE, vasculitis, dermatomyositis (after steroids) - other inflammatory conditions
What are the main side effects of MTX? Are any of these acutely reversible?
Myelosuppression - reversible by leucovorin / folinic acid
Pulmonary fibrosis - progressive, think bonzai tree
Hepatotoxicity - sweat spot on Chef - monitor LFTs
Oral mucositis - poking your mouth
Alopecia
When 5-fluorouracil is given, what is the product which actually interferes with thymidine synthesis? Why is this relevant?
5-FU is made into 5-fluorodeoxyuridinemonophosphate (5-FdUMP) sits in the active site of thymidylate synthetase along with reduced folate.
If MTX is given along with 5-FU, it can actually inhibit 5-FU’s action by limiting reduced folate’s availability
-> effects are actually enhanced by leucovorin
What is FU used to treat? Why?
Treats solid tumors with long-term low dosages, since leukemias often lack the salvage pathways required to activate it (not useful for these)
Especially good for colorectal cancer, pancreatic cancer, and basal cell carcinoma.
What does high vs low-dose FU do in terms of toxicity?
High dose: myelosuppresion
Low dose: dose used for solid tumors - simply pain and swelling of palms and soles of feet “hand foot syndrome”, also called “erythrodysthesia”
What is the function of ribonucleotide reductase? What inhibits them?
Converts ribonucleotides to deoxyribonucleotides
Inhibited by hydroxyurea
What is the mechanism of action of 6-MP and what is the name of its prodrug? What must activate it?
Azathioprine - 6-mercaptopurine
Activated by HGPRT (think of HiGh PRiesT)
Inhibits formation of IMP (think of azameralda kicking over the IMP imp) -> stops de novo purine synthesis
What is the drug interaction of note with azathioprine?
Inhibitors of xanthine oxidase (i.e. febuxostat, allopurinol) will slow the degradation of 6-MP
- > more 6-MP will go through the HGPRT pathway
- > toxic accumulation and bone marrow suppresion
What are the side effects of 6-MP?
Myelosuppression (nun holding birdseed marrow)
Liver toxicity (liver apron)
Pancreatitis (pancreas sponge)