Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation Indian Medical PG Practice Questions and MCQs

Question 31: Which of the following medications is primarily used for long-term stroke prevention?

A. Streptokinase
B. Streptase
C. Warfarin (Correct Answer)
D. Tissue plasminogen activator

Explanation: **Explanation:** The primary goal of long-term stroke prevention, particularly in patients with atrial fibrillation or prosthetic heart valves, is chronic anticoagulation to prevent the formation of systemic emboli. **Why Warfarin is Correct:** Warfarin is an oral anticoagulant that acts as a **Vitamin K Epoxide Reductase (VKOR) inhibitor**. By interfering with the cyclic interconversion of Vitamin K, it inhibits the synthesis of Vitamin K-dependent clotting factors (**II, VII, IX, and X**) and anticoagulant proteins C and S. Because of its oral bioavailability and long half-life, it is the classic choice for long-term prophylaxis against thromboembolic events like stroke. **Why the Other Options are Incorrect:** * **Streptokinase & Streptase (Option A & B):** These are the same drug (Streptase is a brand name for Streptokinase). They are **thrombolytic (fibrinolytic) agents** used for the acute management of ST-elevation myocardial infarction (STEMI) or massive pulmonary embolism. They are administered intravenously for immediate clot lysis, not for long-term prevention. * **Tissue Plasminogen Activator (tPA) (Option D):** tPA (e.g., Alteplase) is a fibrinolytic used in the **acute/emergency** management of ischemic stroke (within a 3–4.5 hour window) to dissolve an existing thrombus. It is never used for long-term prevention due to its short half-life and high risk of hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Monitoring:** Warfarin therapy is monitored using **PT/INR** (Target: 2.0–3.0). * **Initial Paradox:** Warfarin can cause a transient prothrombotic state (due to rapid depletion of Protein C); thus, it is often "bridged" with Heparin. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (**Fetal Warfarin Syndrome**); LMWH is the preferred alternative. * **Antidote:** For immediate reversal of Warfarin, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergency reversal, use Vitamin K1.

Question 32: Which of the following agents is used for the treatment of thrombocytopenia secondary to myelosuppressive cancer chemotherapy?

A. Filgrastim
B. Sargramostim
C. Oprelvekin (Correct Answer)
D. Erythropoetin

Explanation: **Explanation:** The correct answer is **Oprelvekin (C)**. **1. Why Oprelvekin is Correct:** Oprelvekin is a recombinant form of **Interleukin-11 (IL-11)**. It acts by stimulating the proliferation of hematopoietic stem cells and megakaryocyte progenitor cells, leading to increased platelet production. It is specifically FDA-approved for the prevention of severe **thrombocytopenia** in patients receiving myelosuppressive chemotherapy for non-myeloid malignancies. **2. Why Other Options are Incorrect:** * **Filgrastim (A):** This is a recombinant **Granulocyte Colony-Stimulating Factor (G-CSF)**. It specifically stimulates the production of neutrophils and is used to treat chemotherapy-induced **neutropenia**, not thrombocytopenia. * **Sargramostim (B):** This is a recombinant **Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF)**. It stimulates the production of neutrophils, eosinophils, and monocytes. While it has a broader spectrum than Filgrastim, its primary clinical use is to accelerate myeloid recovery after bone marrow transplantation. * **Erythropoietin (D):** This hormone stimulates the proliferation and differentiation of red blood cell precursors. It is used to treat **anemia** associated with chronic kidney disease or chemotherapy. **3. NEET-PG High-Yield Pearls:** * **Oprelvekin Side Effects:** The most characteristic side effect is **fluid retention** (edema, dyspnea, and pleural effusion) due to sodium and water retention. It can also cause transient atrial arrhythmias. * **Alternative Agents:** **Romiplostim** (a thrombopoietin mimetic peptide) and **Eltrombopag** (an oral TPO receptor agonist) are also used for thrombocytopenia, but primarily in Chronic Immune Thrombocytopenic Purpura (ITP). * **Mnemonic:** Oprelvekin = **11** letters = **IL-11**.

Question 33: All of the following cause macrocytic anemia, except?

A. Primaquine (Correct Answer)
B. Methotrexate
C. Trimethoprim
D. Azathioprine

Explanation: **Explanation:** The correct answer is **Primaquine**. To answer this question, one must distinguish between drugs that interfere with DNA synthesis (causing megaloblastic/macrocytic anemia) and those that cause oxidative stress. **1. Why Primaquine is the correct answer:** Primaquine is an antimalarial drug that induces oxidative stress. In individuals with **G6PD deficiency**, this leads to the oxidation of hemoglobin, formation of Heinz bodies, and subsequent **acute hemolytic anemia** (normocytic). It does not interfere with folate metabolism or DNA synthesis, and therefore does not cause macrocytosis. **2. Why the other options are incorrect:** * **Methotrexate:** A potent **dihydrofolate reductase (DHFR) inhibitor**. It prevents the conversion of dihydrofolate to tetrahydrofolate, halting DNA synthesis and leading to megaloblastic macrocytic anemia. * **Trimethoprim:** Also a **DHFR inhibitor** (though with higher affinity for bacterial enzymes). Prolonged high-dose use or use in predisposed patients can cause folate deficiency and macrocytic anemia. * **Azathioprine:** A purine synthesis inhibitor (antimetabolite). By interfering with the synthesis of adenine and guanine, it disrupts DNA replication in the bone marrow, commonly resulting in macrocytosis. **High-Yield Clinical Pearls for NEET-PG:** * **Megaloblastic Anemia (Macrocytic):** Caused by "DNA-inhibitors" like Hydroxyurea, Zidovudine (AZT), 5-Fluorouracil, and Phenytoin (interferes with folate absorption). * **Non-megaloblastic Macrocytosis:** Commonly seen in Alcoholism, Hypothyroidism, and Liver disease. * **Primaquine Contraindication:** Always screen for G6PD deficiency before administration to avoid life-threatening hemolysis. It is also contraindicated in pregnancy due to the risk of fetal hemolysis.

Question 34: Which antibiotic decreases the absorption of iron?

A. Sulfonamide
B. Tetracyclines (Correct Answer)
C. Erythromycin
D. Ciprofloxacin

Explanation: **Explanation:** The correct answer is **Tetracyclines**. **Mechanism of Interaction:** The primary mechanism behind this interaction is **chelation**. Tetracyclines are metal chelators; when taken orally with multivalent cations like iron ($Fe^{2+}$), calcium ($Ca^{2+}$), magnesium ($Mg^{2+}$), or aluminum ($Al^{3+}$), they form insoluble, non-absorbable complexes in the gastrointestinal tract. This process significantly reduces the bioavailability of both the antibiotic and the iron supplement, leading to therapeutic failure. **Analysis of Incorrect Options:** * **Sulfonamides:** These drugs primarily interfere with folic acid synthesis in bacteria. They do not have significant chelating properties with iron. * **Erythromycin:** A macrolide that inhibits protein synthesis. While it is a potent CYP3A4 inhibitor (causing many drug-drug interactions), it does not interfere with iron absorption. * **Ciprofloxacin:** While Fluoroquinolones (like Ciprofloxacin) *also* undergo chelation with iron, the question asks for the most classic example. In pharmacological literature and standard textbooks (like K.D. Tripathi), the interaction between Tetracyclines and iron is the prototypical example taught for absorption-related drug interactions. **NEET-PG High-Yield Pearls:** * **The "2-Hour Rule":** To avoid this interaction, patients should be advised to take iron supplements at least 2 hours before or 2 hours after tetracycline administration. * **Other Chelators:** Fluoroquinolones (Ciprofloxacin, Levofloxacin) and Bisphosphonates also exhibit decreased absorption when co-administered with iron. * **Vitamin C Connection:** While tetracyclines *decrease* iron absorption, **Vitamin C (Ascorbic acid)** *increases* it by maintaining iron in the more soluble ferrous ($Fe^{2+}$) state. * **Contraindication:** Tetracyclines are contraindicated in pregnancy and children under 8 years due to chelation with calcium, leading to permanent tooth discoloration and bone growth retardation.

Question 35: Which of the following laboratory tests is monitored in a patient receiving coumarin (warfarin) therapy?

A. Partial thromboplastin time (PTT)
B. Prothrombin time (PT) (Correct Answer)
C. Bleeding time (BT)
D. Capillary fragility test (CFT)

Explanation: **Explanation:** **Warfarin (Coumarin)** is an oral anticoagulant that acts as a Vitamin K antagonist. It inhibits the enzyme **Vitamin K Epoxide Reductase (VKOR)**, preventing the γ-carboxylation of Vitamin K-dependent clotting factors: **II, VII, IX, and X**, as well as proteins C and S. **Why Prothrombin Time (PT) is the correct answer:** The PT measures the integrity of the **Extrinsic and Common pathways**. Factor VII has the shortest half-life (~6 hours) among the clotting factors, making it the first to decline during warfarin therapy. Therefore, PT is highly sensitive to warfarin’s effects. In clinical practice, PT is standardized as the **International Normalized Ratio (INR)** to ensure consistent monitoring across laboratories. **Why other options are incorrect:** * **A. Partial Thromboplastin Time (PTT/aPTT):** This test monitors the **Intrinsic pathway** and is primarily used to monitor **Unfractionated Heparin** therapy. * **B. Bleeding Time (BT):** This measures **platelet function** and vascular integrity, not the coagulation cascade. It is prolonged in conditions like von Willebrand disease or aspirin use. * **C. Capillary Fragility Test (CFT):** Also known as the Hess test, it assesses capillary resistance and is used to evaluate platelet deficiency or vascular disorders (e.g., Dengue). **High-Yield Clinical Pearls for NEET-PG:** * **Target INR:** Usually **2.0–3.0** for most conditions (e.g., Atrial Fibrillation, DVT). * **Warfarin-Induced Skin Necrosis:** Caused by a rapid decline in Protein C (short half-life), leading to a transient hypercoagulable state. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes **Fetal Warfarin Syndrome**); Heparin is the drug of choice. * **Antidote:** For immediate reversal, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC); for non-emergency reversal, use **Vitamin K1**.

Question 36: What is the longest-acting erythropoietin analogue?

A. Epoietin α
B. Epoietin β
C. Darbepoetin (Correct Answer)
D. Romiplostim

Explanation: **Explanation:** **Darbepoetin alfa** is the correct answer because it is a genetically engineered erythropoiesis-stimulating agent (ESA) designed for a significantly longer half-life compared to recombinant human erythropoietin (e.g., Epoetin α). The underlying medical concept is **glycosylation**. While Epoetin α has 3 N-linked carbohydrate chains, Darbepoetin has **5 N-linked chains**. This increased carbohydrate content decreases its affinity for the erythropoietin receptor but significantly reduces its clearance. Consequently, Darbepoetin has a half-life of approximately **24–26 hours** (about 3 times longer than Epoetin α), allowing for weekly or bi-weekly dosing instead of thrice-weekly. **Analysis of Incorrect Options:** * **A & B (Epoetin α and β):** These are recombinant human erythropoietins with identical amino acid sequences to endogenous erythropoietin. They have a short half-life (4–8 hours) and require frequent administration (usually 3 times a week). * **D (Romiplostim):** This is a **thrombopoietin receptor agonist** (TPO mimetic) used to treat immune thrombocytopenic purpura (ITP). It stimulates platelet production, not red blood cells. **NEET-PG High-Yield Pearls:** * **Methoxy polyethylene glycol-epoetin beta (CERA):** If mentioned, this is a "Continuous Erythropoietin Receptor Activator" with an even longer half-life (~130 hours), allowing for once-monthly dosing. * **Side Effects:** The most common side effect of ESAs is **hypertension** and increased risk of **thrombotic events** (stroke/MI). * **Indication:** Primarily used in anemia due to Chronic Kidney Disease (CKD) and chemotherapy-induced anemia. Target hemoglobin should not exceed 11–12 g/dL to avoid toxicity.

Question 37: Which of the following statements about Dabigatran is true?

A. Dabigatran is a Factor Xa inhibitor.
B. Dabigatran is primarily excreted by the liver.
C. Idarucizumab is a reversal agent for dabigatran. (Correct Answer)
D. Dabigatran is an inexpensive anticoagulant.

Explanation: **Explanation:** **Dabigatran** is a Direct Thrombin Inhibitor (DTI) that binds directly to the active site of both free and clot-bound thrombin (Factor IIa) [1, 2]. 1. **Why Option C is Correct:** **Idarucizumab** is a humanized monoclonal antibody fragment designed specifically to reverse the anticoagulant effects of dabigatran. It binds to dabigatran with an affinity 350 times higher than that of thrombin, neutralizing it immediately. This is a high-yield fact for emergencies like life-threatening bleeding or urgent surgery. 2. **Why Other Options are Incorrect:** * **Option A:** Dabigatran is a **Direct Thrombin (Factor IIa) inhibitor**, not a Factor Xa inhibitor [1]. Drugs like Rivaroxaban and Apixaban are Factor Xa inhibitors. * **Option B:** Dabigatran is unique among NOACs because it is **primarily excreted by the kidneys (~80%)**. Therefore, it is contraindicated in patients with severe renal impairment (CrCl <30 mL/min) [1]. * **Option D:** Dabigatran, like most New Oral Anticoagulants (NOACs), is significantly **more expensive** than traditional anticoagulants like Warfarin. **Clinical Pearls for NEET-PG:** * **Mechanism:** Direct Thrombin Inhibitor (DTI) [1, 2]. * **Prodrug:** Dabigatran etexilate is a prodrug converted by esterases in the gut and liver [1, 2]. * **Monitoring:** Routine monitoring (like PT/INR) is not required [2]; however, **aPTT** or Ecarin Clotting Time (ECT) can be used to assess its effect if necessary. * **Storage:** It is highly sensitive to moisture and must be kept in its original blister packaging. * **Other DTIs:** Lepirudin, Desirudin, Bivalirudin (Parenteral); Argatroban (used in HIT).

Question 38: Decreased effect of warfarin is seen in which of the following conditions?

A. Nephrotic syndrome (Correct Answer)
B. Acute intake of alcohol
C. Concurrent treatment with phenylbutazone
D. Congestive heart failure

Explanation: ### Explanation **Correct Option: A. Nephrotic Syndrome** Warfarin is a highly protein-bound drug (approximately 99% bound to plasma albumin) [1, 2]. In **Nephrotic Syndrome**, significant hypoalbuminemia occurs due to massive proteinuria. This leads to a decrease in the available binding sites for warfarin [3]. While this initially increases the free (active) fraction of the drug, it also significantly accelerates its **metabolic clearance** by the liver. Furthermore, the loss of transport proteins in the urine can lead to an overall lower steady-state concentration of the drug, ultimately resulting in a **decreased anticoagulant effect**. **Analysis of Incorrect Options:** * **B. Acute intake of alcohol:** Acute alcohol consumption inhibits the hepatic microsomal enzymes (CYP450), leading to decreased metabolism of warfarin and an **increased** anticoagulant effect (increased risk of bleeding). * **C. Concurrent treatment with phenylbutazone:** Phenylbutazone is a potent inhibitor of warfarin metabolism and also displaces warfarin from albumin binding sites without increasing clearance as rapidly as in disease states. This leads to a dangerous **increase** in warfarin's effect [1]. * **D. Congestive heart failure (CHF):** In CHF, hepatic congestion occurs, which impairs the liver's ability to metabolize warfarin and synthesize clotting factors. This results in an **enhanced** response to warfarin [3, 4]. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Inducers (Decrease Warfarin effect):** Rifampicin, Phenytoin, Barbiturates, Carbamazepine, and St. John’s Wort. * **Enzyme Inhibitors (Increase Warfarin effect):** Erythromycin, Ketoconazole, Cimetidine, and Amiodarone [1]. * **Vitamin K:** High dietary intake (green leafy vegetables) antagonizes warfarin. * **Monitoring:** Warfarin is monitored using **PT/INR** (Extrinsic pathway), whereas Heparin is monitored via **aPTT** (Intrinsic pathway). * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes Fetal Warfarin Syndrome); Heparin is the anticoagulant of choice.

Question 39: Ticlopidine acts by which mechanism?

A. Decreasing ADP mediated cAMP activation (Correct Answer)
B. Decreasing COX enzyme irreversibly
C. Gp IIb/IIIa antagonist
D. None of the above

Explanation: **Explanation:** **Mechanism of Action (Why A is correct):** Ticlopidine is a first-generation **Thienopyridine** antiplatelet agent. It acts as an irreversible antagonist of the **P2Y12 receptor**, which is a G-protein coupled receptor for ADP on the platelet surface. Normally, ADP binding to P2Y12 inhibits adenylyl cyclase, leading to a decrease in intracellular cAMP. By blocking this receptor, Ticlopidine prevents the ADP-mediated suppression of cAMP. Consequently, **cAMP levels remain elevated**, which inhibits platelet activation and the subsequent expression of GP IIb/IIIa receptors, preventing fibrinogen binding and platelet aggregation. **Analysis of Incorrect Options:** * **Option B:** This describes the mechanism of **Aspirin**, which causes irreversible inhibition of the Cyclooxygenase-1 (COX-1) enzyme, thereby blocking Thromboxane A2 (TXA2) synthesis. * **Option C:** This refers to drugs like **Abciximab, Eptifibatide, and Tirofiban**, which directly block the Glycoprotein IIb/IIIa receptor, the "final common pathway" for platelet aggregation. **NEET-PG High-Yield Pearls:** 1. **The Thienopyridine Family:** Includes Ticlopidine, Clopidogrel, and Prasugrel. All are **prodrugs** and act irreversibly on P2Y12. (Note: Ticagrelor is a non-thienopyridine and acts reversibly). 2. **Adverse Effects:** Ticlopidine is rarely used today due to severe hematological toxicities, specifically **Neutropenia/Agranulocytosis** and **Thrombotic Thrombocytopenic Purpura (TTP)**. 3. **Monitoring:** Frequent CBC monitoring is required during the first 3 months of Ticlopidine therapy. Clopidogrel is preferred clinically due to a better safety profile.

Question 40: What is the antidote for heparin overdose?

A. Protamine sulfate (Correct Answer)
B. Phylloquinone
C. Ticlopidine
D. Clopidogrel

Explanation: **Explanation:** **1. Why Protamine Sulfate is Correct:** Protamine sulfate is the specific pharmacological antagonist for heparin. It is a highly basic, low-molecular-weight protein (derived from salmon sperm) that carries a strong positive charge. Heparin, conversely, is a highly acidic molecule with a strong negative charge. When administered, protamine reacts with heparin to form a stable, inactive **ion-pair complex** (salt), effectively neutralizing its anticoagulant effect. This is a classic example of **chemical antagonism**. It is most effective against Unfractionated Heparin (UFH) and only partially neutralizes Low Molecular Weight Heparin (LMWH). **2. Why Other Options are Incorrect:** * **Phylloquinone (Vitamin K1):** This is the antidote for **Warfarin** overdose. It acts by promoting the hepatic synthesis of clotting factors II, VII, IX, and X. It has no effect on heparin. * **Ticlopidine & Clopidogrel:** These are **P2Y12 receptor inhibitors** (antiplatelet drugs). They inhibit platelet aggregation and have no role in reversing anticoagulation; in fact, they would increase the risk of bleeding if given during an overdose. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dosing Rule:** 1 mg of protamine sulfate neutralizes approximately 100 units of heparin. * **The "Protamine Paradox":** In high doses, protamine itself has weak anticoagulant properties (it inhibits platelets and fibrinogen), so it must be dosed carefully. * **Adverse Effects:** Rapid IV injection can cause **histamine release**, leading to hypotension, bradycardia, and anaphylaxis. * **LMWH Reversal:** Protamine only neutralizes about 60-75% of the anti-Xa activity of LMWH (e.g., Enoxaparin). It has **no effect** on Fondaparinux.

Practice by Chapter

Hematopoietic Growth Factors

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Iron Preparations and Management of Iron Deficiency

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Vitamin B12 and Folic Acid

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Anticoagulants: Heparins and Direct Inhibitors

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Oral Anticoagulants

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Antiplatelet Drugs

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Thrombolytic Agents

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Hemostatic Drugs

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Plasma Expanders

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Blood Transfusion and Alternatives

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