Hematology and Oncology - Pharmacology Flashcards
1
Q
Heparin
- Mechanism
- Clinical use
- Toxicity
- Low-molecular-weight heparins
- Heparin-induced thrombocytopenia (HIT)
A
- Mechanism
- Cofactor for the activation of antithrombin, decrease thrombin, and decrease factor Xa.
- Short half-life.
- Clinical use
- Immediate anticoagulation for PE, acute coronary syndrome, MI, DVT.
- Used during pregnancy (does not cross placenta).
- Follow PTT.
- Toxicity
- Bleeding, thrombocytopenia (HIT), osteoporosis, drug-drug interactions.
- For rapid reversal (antidote), use protamine sulfate (positively charged molecule that binds negatively charged 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.
-
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.
2
Q
Argatroban, bivalirudin
A
- Derivatives of hirudin, the anticoagulant used by leeches
- Inhibit thrombin directly.
- Used instead of heparin for anticoagulating patients with HIT.
3
Q
Warfarin (Coumadin)
- Mechanism
- Clinical use
- Toxicity
A
- Mechanism
- 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 increases PT.
- The EX-PresidenT** went to war(farin).**
- Long half-life.
- Clinical use
- 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.
- Toxicity
- 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.
4
Q
Direct factor Xa inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
A
- Examples
- Apixaban, rivaroxaban.
- Mechanism
- Bind and directly inhibit the activity of factor Xa.
- Clinical use
- Treatment and prophylaxis of DVT and PE (rivaroxaban), stroke prophylaxis in patients with atrial fibrillation.
- Oral agents do not usually require coagulation monitoring.
- Toxicity
- Bleeding (no specific reversal agent available).
5
Q
Heparin vs. warfarin
- Structure
- Route of administration
- Site of action
- Onset of action
- Mechanism of action
- Duration of action
- Inhibits coagulation in vitro?
- Treatment of acute overdose
- Monitoring
- Crosses placenta?
A
- Structure
- H: Large anionic, acidic polymer
- W: Small lipid-soluble molecule
- Route of administration
- H: Parenteral (IV, SC)
- W: Oral
- Site of action
- H: Blood
- W: Liver
- Onset of action
- H: Rapid (seconds)
- W: Slow, limited by half-lives of normal clotting factors
- Mechanism of action
- H: Activates antithrombin, which decreases the action of IIa (thrombin) and factor Xa
- W: Impairs the synthesis of vitamin K–dependent clotting factors II, VII, IX, and X (vitamin K antagonist)
- Duration of action
- H: Acute (hours)
- W: Chronic (days)
- Inhibits coagulation in vitro?
- H: Yes
- W: No
- Treatment of acute overdose
- H: Protamine sulfate
- W: IV vitamin K and fresh frozen plasma
- Monitoring
- H: PTT (intrinsic pathway)
- W: PT/INR (extrinsic pathway)
- Crosses placenta?
- H: No
- W: Yes (teratogenic)
6
Q
Thrombolytics
- Examples
- Mechanism
- Clinical use
- Toxicity
A
- Examples
- Alteplase (tPA), reteplase (rPA), tenecteplase (TNK-tPA).
- Mechanism
- Directly or indirectly aid conversion of plasminogen to plasmin, which cleaves thrombin and fibrin clots.
- Increase PT, increase PTT, no change in platelet count.
- Clinical use
- Early MI, early ischemic stroke, direct thrombolysis of severe PE.
- Toxicity
- 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.
7
Q
Aspirin (ASA)
- Mechanism
- Clinical use
- Toxicity
A
- Mechanism
- 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:
- Increased bleeding time, decreased TXA2 and prostaglandins.
- No effect on PT or PTT.
- Clinical use
- Antipyretic, analgesic, anti-inflammatory, antiplatelet (decreased aggregation).
- Toxicity
- 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.
8
Q
ADP receptor inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
A
- Examples
- Clopidogrel, ticlopidine, prasugrel, ticagrelor.
- Mechanism
- Inhibit platelet aggregation by irreversibly blocking ADP receptors.
- Inhibit fibrinogen binding by preventing glycoprotein IIb/IIIa from binding to fibrinogen.
- Clinical use
- Acute coronary syndrome
- Coronary stenting.
- Decreased incidence or recurrence of thrombotic stroke.
- Toxicity
- Neutropenia (ticlopidine).
- TTP/HUS may be seen.
9
Q
Cilostazol, dipyridamole
- Mechanism
- Clinical use
- Toxicity
A
- Mechanism
- Phosphodiesterase III inhibitor
- Increases cAMP in platelets, thus inhibiting platelet aggregation
- Vasodilators.
- Clinical use
- Intermittent claudication, coronary vasodilation, prevention of stroke or TIAs (combined with aspirin), angina prophylaxis.
- Toxicity
- Nausea, headache, facial flushing, hypotension, abdominal pain.
10
Q
GP IIb/IIIa inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
A
- Examples
- Abciximab, eptifibatide, tirofiban.
- Mechanism
- Bind to the glycoprotein receptor IIb/IIIa on activated platelets, preventing aggregation.
- Abciximab is made from monoclonal antibody Fab fragments.
- Clinical use
- Unstable angina, percutaneous transluminal coronary angioplasty.
- Toxicity
- Bleeding, thrombocytopenia.
11
Q
Cancer drugs—cell cycle
A
12
Q
Antineoplastics (402)
A
- Nucleotide synthesis
- MTX, 5-FU: decreased thymidine synthesis
- 6-MP: decreased purine synthesis
- DNA
- Alkylating agents, cisplatin: cross-link DNA
- Dactinomycin, doxorubicin: DNA intercalators
- Etoposide: inhibits topoisomerase II
- RNA
- Protein
- Cellular division
- Vinca alkaloids: inhibit microtubule formation
- Paclitaxel: inhibits microtubule disassembly
13
Q
Methotrexate (MTX)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
A
- Type of drug
- Antimetabolite
- Mechanism
- S-phase specific
- Folic acid analog that inhibits dihydrofolate reductase –> decreased dTMP –> decreased DNA and decreased protein synthesis.
- Clinical use
- Cancers: leukemias, lymphomas, choriocarcinoma, sarcomas.
- Non-neoplastic: abortion, ectopic pregnancy, rheumatoid arthritis, psoriasis, IBD.
- Toxicity
- Myelosuppression, which is reversible with leucovorin (folinic acid) “rescue.”
- Macrovesicular fatty change in liver.
- Mucositis.
- Teratogenic.
14
Q
5-fluorouracil (5-FU)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
A
- Type of drug
- Antimetabolite
- Mechanism
- S-phase specific
- Pyrimidine analog bioactivated to 5F-dUMP, which covalently complexes folic acid.
- This complex inhibits thymidylate synthase –> decreased dTMP –> decreased DNA and decreased protein synthesis.
- Clinical use
- Colon cancer, pancreatic cancer, basal cell carcinoma (topical).
- Toxicity
- Myelosuppression, which is not reversible with leucovorin.
- Overdose: “rescue” with uridine.
- Photosensitivity.
15
Q
Cytarabine (arabinofuranosyl cytidine)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
A
- Type of drug
- Antimetabolite
- Mechanism
- S-phase specific
- Pyrimidine analog –> inhibition of DNA polymerase.
- Clinical use
- Leukemias, lymphomas.
- Toxicity
- Leukopenia, thrombocytopenia, megaloblastic anemia.
- CYTarabine causes panCYTopenia.