Hematology and Oncology - Pharmacology Flashcards
Heparin
- Mechanism
- Clinical use
- Toxicity
- Low-molecular-weight heparins
- Heparin-induced thrombocytopenia (HIT)
- 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.
Argatroban, bivalirudin
- Derivatives of hirudin, the anticoagulant used by leeches
- Inhibit thrombin directly.
- Used instead of heparin for anticoagulating patients with HIT.
Warfarin (Coumadin)
- Mechanism
- Clinical use
- Toxicity
- 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.
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Direct factor Xa inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
- 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).
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?
- 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)
Thrombolytics
- Examples
- Mechanism
- Clinical use
- Toxicity
- 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.
Aspirin (ASA)
- Mechanism
- Clinical use
- Toxicity
- 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.
ADP receptor inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
- 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.
Cilostazol, dipyridamole
- Mechanism
- Clinical use
- Toxicity
- 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.
GP IIb/IIIa inhibitors
- Examples
- Mechanism
- Clinical use
- Toxicity
- 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.
Cancer drugs—cell cycle
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Antineoplastics (402)
- 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
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Methotrexate (MTX)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- 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.
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5-fluorouracil (5-FU)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- 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.
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Cytarabine (arabinofuranosyl cytidine)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- 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.
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Azathioprine 6-mercaptopurine (6-MP) 6-thioguanine (6-TG)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Antimetabolite
- Mechanism
- S-phase specific
- Purine (thiol) analogs –> decreased de novo purine synthesis.
- Activated by HGPRT.
- Clinical use
- Preventing organ rejection, RA, SLE (azathioprine).
- Leukemia, IBD (6-MP, 6-TG).
- Toxicity
- Bone marrow, GI, liver.
- Azathioprine and 6-MP are metabolized by xanthine oxidase
- Thus both have increased toxicity with allopurinol, which inhibits their metabolism.
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Dactinomycin (actinomycin D)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Antitumor antibiotic
- Mechanism
- Intercalates in DNA.
- Clinical use
- Wilms tumor, Ewing sarcoma, rhabdomyosarcoma.
- Used for childhood tumors
- “Children act out”
- Toxicity
- Myelosuppression.
Doxorubicin (Adriamycin), daunorubicin
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Antitumor antibiotic
- Mechanism
- Generate free radicals.
- Intercalate in DNA –> breaks in DNA –> decreased replication.
- Clinical use
- Solid tumors, leukemias, lymphomas.
- Toxicity
- Cardiotoxicity (dilated cardiomyopathy), myelosuppression, alopecia.
- Toxic to tissues following extravasation.
- Dexrazoxane (iron chelating agent), used to prevent cardiotoxicity.
- Cardiotoxicity (dilated cardiomyopathy), myelosuppression, alopecia.
Bleomycin
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Antitumor antibiotic
- Mechanism
- Induces free radical formation, which causes breaks in DNA strands.
- Clinical use
- Testicular cancer, Hodgkin lymphoma.
- Toxicity
- Pulmonary fibrosis, skin changes, mucositis.
- Minimal myelosuppression.
Cyclophosphamide, ifosfamide
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Alkylating agent
- Mechanism
- Covalently X-link (interstrand) DNA at guanine N-7.
- Require bioactivation by liver.
- Clinical use
- Solid tumors, leukemia, lymphomas, and some brain cancers.
- Toxicity
- Myelosuppression
- Hemorrhagic cystitis, partially prevented with mesna (thiol group of mesna binds toxic metabolites).
Nitrosoureas (carmustine, lomustine, semustine, streptozocin)
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Alkylating agent
- Mechanism
- Require bioactivation.
- Cross blood-brain barrier –> CNS.
- Cross-links DNA.
- Clinical use
- Brain tumors (including glioblastoma multiforme).
- Toxicity
- CNS toxicity (convulsions, dizziness, ataxia).
Busulfan
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Alkylating agent
- Mechanism
- Cross-links DNA.
- Clinical use
- CML.
- Also used to ablate patient’s bone marrow before bone marrow transplantation.
- Toxicity
- Severe myelosuppression (in almost all cases), pulmonary fibrosis, hyperpigmentation.
Vincristine, vinblastine
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Microtubule inhibitors
- Mechanism
- Vinca alkaloids that bind β-tubulin, inhibit its polymerization into microtubules, thereby preventing mitotic spindle formation (M-phase arrest).
- Clinical use
- Solid tumors, leukemias, and lymphomas.
- Toxicity
- Vincristine—neurotoxicity (areflexia, peripheral neuritis), paralytic ileus.
- Vinblastine blasts bone marrow (suppression).
Paclitaxel, other taxols
- Type of drug
- Mechanism
- Clinical use
- Toxicity
- Type of drug
- Microtubule inhibitors
- Mechanism
- Hyperstabilize polymerized microtubules in M phase so that mitotic spindle cannot break down (anaphase cannot occur).
- “It is taxing to stay polymerized.”
- Clinical use
- Ovarian and breast carcinomas.
- Toxicity
- Myelosuppression, alopecia, hypersensitivity.
Cisplatin, carboplatin
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Cross-link DNA.
- Clinical use
- Testicular, bladder, ovary, and lung carcinomas.
- Toxicity
- Nephrotoxicity and acoustic nerve damage.
- Prevent nephrotoxicity with amifostine (free radical scavenger) and chloride diuresis.
Etoposide, teniposide
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Etoposide inhibits topoisomerase II –> increased DNA degradation.
- Clinical use
- Solid tumors (particularly testicular and small cell lung cancer), leukemias, lymphomas.
- Toxicity
- Myelosuppression, GI irritation, alopecia.
Irinotecan, topotecan
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Inhibit topoisomerase I and prevent DNA unwinding and replication.
- Clinical use
- Colon cancer (irinotecan)
- Ovarian and small cell lung cancers (topotecan).
- Toxicity
- Severe myelosuppression, diarrhea.
Hydroxyurea
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Inhibits ribonucleotide reductase –> decreased DNA Synthesis (S-phase specific).
- Clinical use
- Melanoma, CML, sickle cell disease (increased HbF).
- Toxicity
- Bone marrow suppression, GI upset.
Prednisone, prednisolone
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- May trigger apoptosis.
- May even work on nondividing cells.
- Clinical use
- Most commonly used glucocorticoids in cancer chemotherapy.
- Used in CLL, non-Hodgkin lymphomas (part of combination chemotherapy regimen).
- Also used as immunosuppressants (e.g., autoimmune diseases).
- Toxicity
- Cushing-like symptoms
- Weight gain, central obesity, muscle breakdown, cataracts, acne, osteoporosis, hypertension, peptic ulcers, hyperglycemia, psychosis.
Tamoxifen, raloxifene
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Selective estrogen receptor modulators (SERMs)—receptor antagonists in breast and agonists in bone.
- Block the binding of estrogen to ER (+) cells.
- Clinical use
- Breast cancer treatment (tamoxifen only) and prevention.
- Raloxifene also useful to prevent osteoporosis.
- Toxicity
- Tamoxifen—partial agonist in endometrium, which increases the risk of endometrial cancer; “hot flashes.”
- Raloxifene—no increase in endometrial carcinoma because it is an endometrial antagonist.
Trastuzumab (Herceptin)
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Monoclonal antibody against HER-2 (c-erbB2), a tyrosine kinase receptor.
- Helps kill breast cancer cells that overexpress HER-2, through inhibition of HER2-initiated cellular signaling and antibody-dependent cytotoxicity.
- Clinical use
- HER-2 (+) breast cancer and gastric cancer (tras2zumab).
- Toxicity
- Cardiotoxicity.
- “HEARTceptin” damages the HEART
Imatinib (Gleevec)
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Tyrosine kinase inhibitor of bcr-abl (Philadelphia chromosome fusion gene in CML) and c-Kit (common in GI stromal tumors).
- Clinical use
- CML, GI stromal tumors.
- Toxicity
- Fluid retention.
Rituximab
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Monoclonal antibody against CD20, which is found on most B-cell neoplasms.
- Clinical use
- Non-Hodgkin lymphoma, rheumatoid arthritis (with MTX), ITP.
- Toxicity
- Increased risk of progressive multifocal leukoencephalopathy.
Vemurafenib
- Mechanism
- Clinical use
- Mechanism
- Small molecule inhibitor of forms of the B-Raf kinase with the V600E mutation.
- Clinical use
- Metastatic melanoma.
Bevacizumab
- Mechanism
- Clinical use
- Toxicity
- Mechanism
- Monoclonal antibody against VEGF.
- Inhibits angiogenesis.
- Clinical use
- Solid tumors (colorectal cancer, renal cell carcinoma).
- Toxicity
- Hemorrhage and impaired wound healing.
Common chemotoxicities
- Cisplatin/Carboplatin
- Vincristine
- Bleomycin, Busulfan
- Doxorubicin
- Trastuzumab
- Cisplatin/Carboplatin
- Cyclophosphamide
- 5-FU
- 6-MP
- Methotrexate
- Cisplatin/Carboplatin –> acoustic nerve damage (and nephrotoxicity)
- Vincristine –> peripheral neuropathy
- Bleomycin, Busulfan –> pulmonary fibrosis
- Doxorubicin –> cardiotoxicity
- Trastuzumab –> cardiotoxicity
- Cisplatin/Carboplatin–> nephrotoxic (and acoustic nerve damage)
- CYclophosphamide –> hemorrhagic cystitis
- 5-FU –> myelosuppression
- 6-MP –> myelosuppression
- Methotrexate –> myelosuppression
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