Hematology and Oncology Flashcards
Heparin mechanism of action
Activates antithrombin 3 to inactivate thrombin and factor Xa. Negatively charged molecule. Follow using PTT. Safe during pregnancy because it doesn’t cross placenta.
Used for immediate anticoagulation following PE, MI, DVT, ACS.
Heparin Toxicity
Causes bleeding, can also cause HIT where IgG form to heparin and PF4 complex and cause thrombosis/thrombocytopenia.
Heparin Antidote?
Protamine Sulfate (binds negatively charged molecule)
Argatroban and bivalrudin mechanism
Derivatives of Hirudin, directly block thrombin. Safe to use in patients with HIT.
Warfarin
Small lipid-soluble molecule that blocks epoxide reductase. No vitamin k dependent gamma carboxylation of factors II VII IX X C and S. Long half life and long time to start working because factors aren’t destroyed. Used for DVT prophylaxis, prevention of ACS and MI. Not used in pregnant women (can cross placenta). Does not cause anticoagulation in vitro. Follow PT/INR
Warfarin toxicity
Bleeding, warfarin skin necrosis (due to loss of C and S first and prothrombotic state), terratogenicity. Metabolized by CYP450 system.
Warfarin antidote?
Vitamin K IV or fresh frozen plasma (to replenish factors)
Apixaban, rivaroxaban
Direct factor X inhibitors taken orally for prevention of stroke from afib, and DVT/PE. Don’t require monitoring.
Adverse effects include bleeding with no reversal agent available.
Alteplase, reteplase, tenecteplase
TPA used to bust clots. Activates tissue plasminogen to plasmin to lyse clots. Used in early stroke, MI, DVT. Increases PTT and PT both.
Alteplase, reteplase, tenecteplase toxicity and antidote?
Bleeding. Give aminocaproic acid with overdose to block fibrinolysis. Can also give fresh frozen plasma and cryoprecipitate.
Aspirin
Irreversibly acetylate platelet COX 1 and 2. No TXA2 so platelets cannot be activated to aggregate. Lasts until new platelets are produced, so increases bleeding time.
Aspirin adverse effects?
Gastric ulceration, tinnitus, acute renal failure, upper GI bleeding. Reye syndrome of fever and encephalitis with children with viral illness.
Clopidogrel, ticagrelor, prasugrel, ticopidine
ADP receptor inhibitors. Block activation of platelets so can’t elaborate GP2B3A and bind fibrinogen. Increases bleeding time. Used for ACS, stenting, decrease stroke
Toxicity of ticlopidine and other ADP receptor blockers?
Neutropenia for ticlop. TTP/HUS for others
Cilostazol, dipyridamole
PDE3 inhibitors so increase platelet cAMP and prevent aggregation. Used for claudication, coronary vasodilation, prevention of stroke.
Cilostazol, dipyridamole adverse effects
Flushing, abdominal pain, nausea, headache.
Abciximab, eptifibatide, tirofiban
GP2B3A inhibitors. Fibrinogen can’t cross link platelets, no aggregation. Used for unstable angina. Can cause bleeding and thrombocytopenia.
Methotrexate
Inhibitor of dihydrofolate reductase, blocks creation of dTMP from dUMP. Thus preventing DNA and protein synthesis. Used in leukemia, lymphoma, choriocarcinoma, sarcoma, abortion, ectopic pregnancy, RA, psoriasis, IBD
MTX toxicity
Myelosuppression that is reversible with leukovorin (folinic acid). Macrovesicular fatty change in liver, mucositis, teratogenic.
5FU
Pyrimidine analog that inhibits thymidylate synthase. Less dTMP, less DNA and protein synthesis. Used for colon cancer, pancreatic cancer, and basal cell carcinoma.
5FU toxicity
Myelosuppression that isn’t reversible with leukovorin. Rescue with uridine. Causes photosensitivity
Cytarabine
Pyrimidine analog that blocks DNA polymerase. Used for leukemia and lymphoma.
Cytarabine toxicity
Cytarabine causes pancytopenia and a megaloblastic anemia.