Hematology and Oncology Flashcards
What is the mechanism of Heparin?
Cofactor for the activation of antithrombin, ↓ thrombin, and ↓ factor Xa. Short half-life.
What is the clinical use of Heparin?
Immediate anticoagulation for PE, acute coronary syndrome, MI, DVT. Used during pregnancy (does not cross placenta). Follow PTT.
What is the toxicity of Heparin?
Bleeding, thrombocytopenia (HIT), osteoporosis, drug-drug interactions. For rapid reversal (antidote), use protamine sulfate (positively charged molecule that binds negatively charged heparin).
What are some additional key facts about Heparin?
Low-molecular-weight heparins (e.g., enoxaparin, dalteparin) act more on factor Xa, have better bioavailability and 2–4 times longer half-life. Can be administered subcutaneously and without laboratory monitoring. Not easily reversible.
Describe Heparin-induced thrombocytopenia (HIT).
Development of IgG antibodies against heparin bound to platelet factor 4 (PF4). Antibody-heparin-PF4 complex activates platelets → thrombosis and thrombocytopenia.
What are the key features of Argatroban and bivalirudin?
Derivatives of hirudin, the anticoagulant used by leeches; inhibit thrombin directly. Used instead
of heparin for anticoagulating patients with HIT.
What is the mechanism of Warfarin (Coumadin)?
Interferes with normal synthesis and γ-carboxylation of vitamin K–dependent clotting factors II, VII, IX, and X and proteins C and S. Metabolized by the cytochrome P-450 pathway. In laboratory assay, has effect on Extrinsic pathway and ↑ PT. Long half-life.
What is the clinical use of Warfarin (Coumadin)?
Chronic anticoagulation (after STEMI, venous thromboembolism prophylaxis, and prevention of stroke in atrial fibrillation). Not used in pregnant women (because warfarin, unlike heparin, can cross the placenta). Follow PT/INR values.
What are the toxicities of Warfarin (Coumadin)?
Bleeding, teratogenic, skin/tissue necrosis A, drug-drug interactions.
For reversal of warfarin overdose, give vitamin K. For rapid reversal of severe warfarin overdose, give fresh frozen plasma.
What are the direct factor Xa inhibitors?
Apixaban and rivaroxaban
What is the mechanism of direct factor Xa inhibitors?
Bind and directly inhibit the activity of factor Xa.
What is the clinical use of direct factor Xa inhibitors?
Treatment and prophylaxis of DVT and PE (rivaroxaban), stroke prophylaxis in patients with atrial fibrillation.
Oral agents do not usually require coagulation monitoring.
What is the toxicity of direct factor Xa inhibitors?
Bleeding (no specific reversal agent available)
Compare the structure of Heparin to Warfarin.
Heparin - Large anionic, acidic polymer
Warfarin - Small lipid-soluble molecule
Compare the route of administration of Heparin to Warfarin.
Heparin - Parenteral (IV, SC)
Warfarin - Oral
Compare the site of action of Heparin to Warfarin.
Heparin - Blood
Warfarin - Liver
Compare onset of the of Heparin to Warfarin.
Heparin - Rapid (seconds)
Warfarin - Slow, limited by half-lives of normal clotting factors
Compare the mechanism of action of Heparin to Warfarin.
Heparin - Activates antithrombin, which ↓ the action of IIa (thrombin) and factor Xa
Warfarin - Impairs the synthesis of vitamin K–dependent clotting factors II, VII, IX, and X (vitamin K antagonist)
Compare the duration of action of Heparin to Warfarin.
Heparin - Acute (hours)
Warfarin - Chronic (days)
Do Heparin and Warfarin inhibit coagulation in vitro?
Heparin - Yes
Warfarin - No
Compare the treatment of acute overdose of Heparin to Warfarin.
Heparin - Protamine sulfate
Warfarin - IV vitamin K and fresh frozen plasma
Compare how Heparin and Warfarin are monitored.
Heparin - PTT (intrinsic pathway)
Warfarin - PT/INR (extrinsic pathway)
Do Heparin and Warfarin cross the placenta?
Heparin - No
Warfarin - Yes (teratogenic)
What are the Thrombolytics?
Alteplase (tPA), reteplase (rPA), tenecteplase (TNK-tPA)
What is the mechanism of the thrombolytics?
Directly or indirectly aid conversion of plasminogen to plasmin, which cleaves thrombin and fibrin clots. ↑ PT, ↑ PTT, no change in platelet count.
What is the clinical use of thrombolytics?
Early MI, early ischemic stroke, direct thrombolysis of severe PE.
What is the toxicity of thrombolytics?
Bleeding. Contraindicated in patients with active bleeding, history of intracranial bleeding, recent surgery, known bleeding diatheses, or severe hypertension. Treat toxicity with aminocaproic acid, an inhibitor of fibrinolysis. Fresh frozen plasma and cryoprecipitate can also be used to correct factor deficiencies.
What is the mechanism of Aspirin (ASA)?
Irreversibly inhibits cyclooxygenase (both COX-1 and COX-2) enzyme by covalent acetylation. Platelets cannot synthesize new enzyme, so effect lasts until new platelets are produced: ↑ bleeding time, ↓ TXA2 and prostaglandins. No effect on PT or PTT.
What is the clinical use of Aspirin (ASA)?
Antipyretic, analgesic, anti-inflammatory, antiplatelet (↓ aggregation).
What is the toxicity of Aspirin (ASA)?
Gastric ulceration, tinnitus (CN VIII). Chronic use can lead to acute renal failure, interstitial nephritis, and upper GI bleeding. Reye syndrome in children with viral infection. Overdose causes respiratory alkalosis initially, which is then superimposed by metabolic acidosis.
What are the ADP receptor inhibitors?
Clopidogrel, ticlopidine, prasugrel, ticagrelor
What is the mechanism of ADP receptor inhibitors?
Inhibit platelet aggregation by irreversibly blocking ADP receptors. Inhibit fibrinogen binding by preventing glycoprotein IIb/IIIa from binding to fibrinogen.
What is the clinical use of ADP receptor inhibitors?
Acute coronary syndrome; coronary stenting. ↓ incidence or recurrence of thrombotic stroke.
What is the toxicity of ADP receptor inhibitors?
Neutropenia (ticlopidine). TTP/HUS may be seen.
What is the mechanism of Cilostazol and Dipyridamole?
Phosphodiesterase III inhibitor; ↑ cAMP in platelets, thus inhibiting platelet aggregation; vasodilators
What is the clinical use of Cilostazol and Dipyridamole?
Intermittent claudication, coronary vasodilation, prevention of stroke or TIAs (combined with aspirin), angina prophylaxis.
What is the toxicity of Cilostazol and Dipyridamole?
Nausea, headache, facial flushing, hypotension, abdominal pain
What are the GP IIb/IIIa inhibitors?
Abciximab, eptifibatide, tirofiban
What is the mechanism of GP IIb/IIIa inhibitors?
Bind to the glycoprotein receptor IIb/IIIa on activated platelets, preventing aggregation. Abciximab is made from monoclonal antibody Fab fragments.
What is the clinical use of GP IIb/IIIa inhibitors?
Unstable angina, percutaneous transluminal coronary angioplasty.
What is the toxicity of GP IIb/IIIa inhibitors?
Bleeding, thrombocytopenia
Cancer drugs (cell cycle) - What part of the cell cycle does Bleomycin block?
G2 (synthesis of components needed for mitosis)
Cancer drugs (cell cycle) - What part of the cell cycle do Vinca alkaloids and taxols block?
M
Cancer drugs (cell cycle) - What part of the cell cycle do Antimetabolites block?
S (DNA synthesis)
Cancer drugs (cell cycle) - What parts of the cell cycle does Etoposide block?
G2 (synthesis of components needed for mitosis) and S (DNA synthesis)
Cancer drugs (cell cycle) - What drug blocks G1 (synthesis of components needed for DNA synthesis?
None
Antineoplastics - What drugs inhibit Nucleotide synthesis?
MTX, 5-FU: ↓ thymidine synthesis
6-MP: ↓ purine synthesis
Antineoplastics - What drugs block DNA?
Alkylating agents, cisplatin: cross-link DNA
Dactinomycin, doxorubicin: DNA intercalators
Etoposide: inhibits topoisomerase II
Antineoplastics - What drugs inhibit cell division?
Vinca alkaloids: inhibit microtubule formation
Paclitaxel: inhibits microtubule disassembly
Antimetabolites - What is the mechanism of Methotrexate (MTX)?
Folic acid analog that inhibits dihydrofolate reductase → ↓ dTMP → ↓ DNA and ↓ protein synthesis.
All anti-metabolites are S-phase specific.
Antimetabolites - What is the clinical use of Methotrexate (MTX)?
Cancers: leukemias, lymphomas, choriocarcinoma, sarcomas.
Non-neoplastic: abortion, ectopic pregnancy, rheumatoid arthritis, psoriasis, IBD.
Antimetabolites - What are the toxicities of Methotrexate (MTX)?
Myelosuppression, which is reversible with leucovorin (folinic acid) “rescue.”
Macrovesicular fatty change in liver.
Mucositis.
Teratogenic.
Antimetabolites - What is the mechanism of 5-fluorouracil (5-FU)?
Pyrimidine analog bioactivated to 5F-dUMP, which covalently complexes folic acid.
This complex inhibits thymidylate synthase → ↓ dTMP → ↓ DNA and ↓ protein synthesis.
All anti-metabolites are S-phase specific.
Antimetabolites - What is the clinical use of 5-fluorouracil (5-FU)?
Colon cancer, pancreatic cancer, basal cell carcinoma (topical).
Antimetabolites - What are the toxicities of 5-fluorouracil (5-FU)?
Myelosuppression, which is not reversible with leucovorin. Overdose: “rescue” with uridine.
Photosensitivity.
Antimetabolites - What is the mechanism of Cytarabine (arabinofuranosyl cytidine)?
Pyrimidine analog → inhibition of DNA polymerase.
Antimetabolites - What is the clinical use of Cytarabine (arabinofuranosyl cytidine)?
Leukemias, lymphomas
Antimetabolites - What are the toxicities of Cytarabine (arabinofuranosyl cytidine)?
Leukopenia, thrombocytopenia, megaloblastic anemia. Cytarabine causes pancytopenia.