Drugs Affecting Blood and Blood Formation — MCQs

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

Question 231: Which of the following is the mechanism of action of Pentasaccharide?

A. Factor Xa inhibition and Thrombin inhibition
B. Factor Xa inhibition (Correct Answer)
C. Antithrombin inhibitor
D. Thrombin inhibition

Explanation: **Explanation:** **Pentasaccharide (Fondaparinux)** is a synthetic anticoagulant that represents the minimum sequence of heparin required to bind to Antithrombin III. 1. **Mechanism of Action (Why B is correct):** Fondaparinux binds selectively and reversibly to **Antithrombin III (AT-III)**. This binding induces a conformational change in AT-III, which significantly increases its affinity for **Factor Xa**. Once bound, AT-III neutralizes Factor Xa, thereby inhibiting the conversion of prothrombin to thrombin and halting the coagulation cascade. Unlike Heparin, the pentasaccharide chain is too short to bridge AT-III to Thrombin (Factor IIa); therefore, it has **zero activity against Thrombin.** 2. **Analysis of Incorrect Options:** * **Option A & D:** These describe the action of **Unfractionated Heparin (UFH)**. UFH has a long polysaccharide chain (>18 units) that allows it to inhibit both Factor Xa and Thrombin (IIa) in a 1:1 ratio. * **Option C:** This is factually incorrect. Pentasaccharide is an **Antithrombin activator/agonist**, not an inhibitor. It utilizes Antithrombin to achieve its effect. **High-Yield Clinical Pearls for NEET-PG:** * **HIT Safety:** Fondaparinux does not bind to Platelet Factor 4 (PF4); therefore, it carries a negligible risk of **Heparin-Induced Thrombocytopenia (HIT)**. * **Monitoring:** Unlike UFH, it does not require routine aPTT monitoring due to its predictable pharmacokinetics. * **Elimination:** It is excreted unchanged by the kidneys; thus, it is **contraindicated in severe renal failure** (CrCl <30 mL/min). * **Antidote:** There is no specific reversal agent (Protamine sulfate does not work for Fondaparinux).

Question 232: Which of the following is a low molecular weight heparin?

A. Hirudin
B. Enoxaparin (Correct Answer)
C. Tranexamic acid
D. Lepirudin

Explanation: **Explanation:** **Correct Answer: B. Enoxaparin** Low Molecular Weight Heparins (LMWHs) are derived from Unfractionated Heparin (UFH) through enzymatic or chemical depolymerization. **Enoxaparin** is the most commonly used LMWH. Unlike UFH, which inhibits both Factor Xa and Thrombin (IIa) equally (1:1 ratio), LMWHs have a higher selectivity for **Factor Xa** (ratio 3:1). They offer several clinical advantages, including better bioavailability, a longer half-life, and a predictable dose-response that eliminates the need for routine aPTT monitoring. **Analysis of Incorrect Options:** * **A & D. Hirudin and Lepirudin:** These are **Direct Thrombin Inhibitors (DTIs)**. Hirudin is a natural anticoagulant derived from leech saliva, while Lepirudin is its recombinant analog. They act independently of Antithrombin III, making them the drugs of choice for patients with Heparin-Induced Thrombocytopenia (HIT). * **C. Tranexamic acid:** This is an **Antifibrinolytic** agent. It works by competitively inhibiting the activation of plasminogen to plasmin, thereby preventing the breakdown of fibrin clots. It is used to control excessive bleeding, not as an anticoagulant. **High-Yield NEET-PG Pearls:** * **Examples of LMWHs:** Enoxaparin, Dalteparin, Reviparin, Nadroparin, and Tinzaparin. * **Monitoring:** While routine monitoring isn't required, **Factor Xa assay** is used if monitoring is necessary (e.g., in renal failure or pregnancy). * **Antidote:** Protamine sulfate partially neutralizes LMWHs (only about 60-75% effective compared to 100% for UFH). * **Elimination:** LMWHs are primarily excreted **renally**; thus, they are contraindicated in severe renal failure (CrCl <30 ml/min), where UFH remains the preferred choice.

Question 233: Which of the following is NOT an advantage of low molecular weight heparin over unfractionated heparin?

A. Higher efficacy in arterial thrombosis (Correct Answer)
B. Less frequent dosing
C. Higher and more consistent subcutaneous bioavailability
D. Laboratory monitoring of response not required

Explanation: **Explanation:** The correct answer is **A. Higher efficacy in arterial thrombosis.** Low Molecular Weight Heparins (LMWHs) like Enoxaparin and Dalteparin are derived from Unfractionated Heparin (UFH) but have different pharmacokinetic and pharmacodynamic profiles [1]. Crucially, **both UFH and LMWH have similar efficacy** in treating and preventing thromboembolic disorders [5]. Neither is superior to the other specifically for arterial thrombosis; in fact, UFH is often preferred in acute coronary syndromes requiring percutaneous intervention due to its shorter half-life and easy reversibility [3]. **Analysis of Incorrect Options:** * **B. Less frequent dosing:** LMWH has a longer half-life (4–6 hours) compared to UFH (1–2 hours). This allows for once or twice-daily subcutaneous dosing, whereas UFH often requires continuous infusion or frequent injections [3]. * **C. Higher and more consistent bioavailability:** LMWH binds less to plasma proteins and endothelial cells [1]. This results in superior subcutaneous bioavailability (~90% for LMWH vs. ~20-30% for UFH) and a more predictable dose-response. * **D. Laboratory monitoring not required:** Due to the predictable response, routine monitoring of aPTT is not required for LMWH [4]. Monitoring (Anti-Xa levels) is only reserved for special populations like obese patients, pregnant women, or those with renal failure [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** UFH inhibits both Factor Xa and IIa (Thrombin) in a 1:1 ratio. LMWH primarily inhibits Factor Xa (ratio of Xa:IIa is 3:1) [2]. * **HIT Risk:** LMWH has a significantly lower risk of Heparin-Induced Thrombocytopenia (HIT) compared to UFH. * **Reversibility:** Protamine sulfate completely neutralizes UFH but only partially neutralizes LMWH. * **Elimination:** LMWH is excreted **renally**; therefore, it is contraindicated in chronic kidney disease (where UFH is the drug of choice) [4].

Question 234: Filgrastim is used for the treatment of which condition?

A. Neutropenia (Correct Answer)
B. Anemia
C. Polycythemia
D. Neutrophilia

Explanation: **Explanation:** **Filgrastim** is a recombinant human **Granulocyte Colony-Stimulating Factor (G-CSF)**. It acts by binding to specific receptors on myeloid progenitor cells in the bone marrow, stimulating the proliferation, differentiation, and activation of **neutrophils**. * **Why Option A is Correct:** Filgrastim is primarily used to treat **Neutropenia** (low neutrophil count). It is the drug of choice for reducing the duration and severity of neutropenia in patients receiving myelosuppressive chemotherapy, those undergoing bone marrow transplantation, or patients with severe chronic neutropenia. By increasing the Absolute Neutrophil Count (ANC), it significantly reduces the risk of life-threatening infections. * **Why Other Options are Incorrect:** * **B. Anemia:** This is a deficiency of red blood cells (RBCs). It is treated with Erythropoiesis-Stimulating Agents (ESAs) like **Erythropoietin** or Darbepoetin, not G-CSF. * **C. Polycythemia:** This is an abnormal increase in RBCs. Treatment usually involves phlebotomy or myelosuppressive agents (e.g., Hydroxyurea); Filgrastim would worsen a high cell count. * **D. Neutrophilia:** This refers to an abnormally high neutrophil count. Filgrastim *causes* neutrophilia as a pharmacological effect; it is never used to treat it. **High-Yield Clinical Pearls for NEET-PG:** 1. **Side Effects:** The most common side effect of Filgrastim is **medullary bone pain** (due to marrow expansion). 2. **Sargramostim:** Unlike Filgrastim (G-CSF), Sargramostim is a **GM-CSF** (Granulocyte-Macrophage CSF) which stimulates neutrophils, monocytes, and eosinophils. 3. **Pegfilgrastim:** A pegylated form of Filgrastim with a much longer half-life, allowing for once-per-chemotherapy cycle dosing. 4. **Stem Cell Harvest:** Filgrastim is also used to mobilize hematopoietic stem cells into the peripheral blood for collection prior to autologous transplantation.

Question 235: Peginesatide is

A. An IL-11 analogue
B. An erythropoietin receptor agonist (Correct Answer)
C. A G-CSF analogue
D. A GM-CSF analogue

Explanation: **Peginesatide** is a synthetic, PEGylated peptide-based **erythropoietin receptor agonist** [1, 2]. Unlike recombinant erythropoietin (Epoetin alfa), it does not share structural homology with endogenous erythropoietin. It works by binding to and activating the erythropoietin receptor on erythroid progenitor cells in the bone marrow, thereby stimulating erythropoiesis [2, 3]. It was primarily developed for the treatment of anemia associated with chronic kidney disease (CKD) in adult patients on dialysis. **Analysis of Incorrect Options:** * **Option A (IL-11 analogue):** **Oprelvekin** is the recombinant form of Interleukin-11. It is used to stimulate megakaryocytopoiesis to prevent severe thrombocytopenia following chemotherapy. * **Option C (G-CSF analogue):** **Filgrastim** and **Pegfilgrastim** are Granulocyte Colony-Stimulating Factor analogues used to treat neutropenia by stimulating the production of neutrophils [2]. * **Option D (GM-CSF analogue):** **Sargramostim** is a Granulocyte-Macrophage Colony-Stimulating Factor analogue that stimulates the production of neutrophils, eosinophils, and monocytes/macrophages. **High-Yield Clinical Pearls for NEET-PG:** * **Unique Structure:** Because Peginesatide has a different amino acid sequence than erythropoietin, it does not cross-react with anti-erythropoietin antibodies. This made it a potential candidate for treating **Pure Red Cell Aplasia (PRCA)** caused by such antibodies. * **FDA Status:** Although effective, Peginesatide was voluntarily withdrawn from the market shortly after its approval due to reports of severe, life-threatening **anaphylactic reactions** during the first dose. * **Dosing Advantage:** Due to PEGylation, it has a long half-life, allowing for once-monthly administration [2].

Question 236: Which one of the following preferentially activates plasminogen bound to fibrin and avoids the systemic lytic state?

A. Streptokinase
B. Aminocaproic acid
C. Tranexamic acid
D. Alteplase (Correct Answer)

Explanation: **Explanation** The correct answer is **Alteplase (Option D)**. **1. Why Alteplase is Correct:** Alteplase is a recombinant **Tissue Plasminogen Activator (tPA)**. The fundamental pharmacological property that distinguishes it from older thrombolytics is its **"fibrin specificity."** Alteplase has a high affinity for plasminogen that is already bound to a fibrin clot. It converts this clot-bound plasminogen into active plasmin, leading to localized thrombolysis. Because it has low affinity for free-circulating plasminogen, it minimizes the systemic conversion of plasminogen to plasmin, thereby reducing the "systemic lytic state" and the associated risk of generalized bleeding. **2. Why Other Options are Incorrect:** * **Streptokinase (A):** This is a non-fibrin-specific thrombolytic derived from Beta-hemolytic Streptococci. It binds to both circulating and clot-bound plasminogen equally, leading to massive systemic depletion of fibrinogen and a high risk of systemic hemorrhage. * **Aminocaproic acid (B) & Tranexamic acid (C):** These are **antifibrinolytics**. They inhibit plasminogen activation and are used to *treat* excessive bleeding (e.g., in overdose of thrombolytics), not to induce clot lysis. **3. NEET-PG High-Yield Pearls:** * **Fibrin-Specific Agents:** Alteplase, Reteplase, and Tenecteplase (Tenecteplase is the most fibrin-specific and has the longest half-life, allowing bolus dosing). * **Non-Specific Agents:** Streptokinase and Urokinase. * **Antidote for Thrombolytics:** If life-threatening bleeding occurs, use Epsilon-aminocaproic acid (EACA) or Tranexamic acid. * **Clinical Note:** Despite fibrin specificity, all thrombolytics still carry a risk of intracranial hemorrhage.

Question 237: Which of the following is true regarding clopidogrel when compared to ticlopidine?

A. Clopidogrel is more likely to cause formation of antiplatelet antibodies.
B. Clopidogrel is less likely to cause neutropenia. (Correct Answer)
C. Clopidogrel is more likely to cause severe bleeding.
D. Clopidogrel has a greater antiplatelet effect.

Explanation: **Explanation:** Both Clopidogrel and Ticlopidine are **P2Y12 receptor antagonists** (thienopyridines) that inhibit ADP-induced platelet aggregation. While they share the same mechanism of action, their side effect profiles differ significantly. **1. Why Option B is Correct:** Ticlopidine is associated with severe hematological toxicities, most notably **life-threatening neutropenia** (occurring in ~1% of patients) and agranulocytosis. It requires frequent monitoring of complete blood counts (CBC) during the first three months of therapy. **Clopidogrel**, a second-generation thienopyridine, was developed specifically to improve safety; it has a much lower incidence of bone marrow suppression and neutropenia, making it the preferred clinical choice. **2. Why the Other Options are Incorrect:** * **Option A:** Neither drug is typically associated with the formation of antiplatelet antibodies. This mechanism is more characteristic of Heparin-Induced Thrombocytopenia (HIT). * **Option C:** Clopidogrel does not inherently cause more severe bleeding than ticlopidine; both carry a similar risk of hemorrhage as a consequence of their antiplatelet action. * **Option D:** At standard clinical doses, both drugs provide comparable levels of maximal platelet inhibition. The primary advantage of clopidogrel is its **safety profile**, not superior efficacy. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Both are **irreversible** inhibitors of the P2Y12 ADP receptor. * **Metabolism:** Clopidogrel is a **prodrug** activated by the hepatic enzyme **CYP2C19**. Genetic polymorphisms in CYP2C19 or concurrent use of **Omeprazole** (a CYP2C19 inhibitor) can reduce its clinical efficacy. * **Ticlopidine Side Effects:** Neutropenia, TTP (Thrombotic Thrombocytopenic Purpura), and severe GI upset. * **Prasugrel/Ticagrelor:** Newer agents that are more potent and have a faster onset of action than clopidogrel.

Question 238: True about iron administration?

A. Iron-sorbitol-citric acid is given intravenously.
B. Iron-dextran binds to transferrin.
C. Iron-dextran is not excreted. (Correct Answer)
D. Iron-dextran has a low molecular weight.

Explanation: ### Explanation **Correct Option: C. Iron-dextran is not excreted.** Iron is a unique mineral because the human body lacks a physiological mechanism for its active excretion. Once iron (in any form, including iron-dextran) is absorbed or injected, it is stored in the body as ferritin or hemosiderin. Loss occurs only through the shedding of intestinal mucosal cells, skin cells, or blood loss (menstruation/hemorrhage). Therefore, iron-dextran is not excreted by the kidneys or the gut. **Analysis of Incorrect Options:** * **A. Iron-sorbitol-citric acid is given intravenously:** This is incorrect. Iron-sorbitol-citric acid has a low molecular weight and is rapidly excreted in the urine if given IV, which can cause systemic toxicity. It is strictly administered via the **Intramuscular (IM)** route. * **B. Iron-dextran binds to transferrin:** This is incorrect. Iron-dextran is a large complex that is first taken up by the **reticuloendothelial system (macrophages)**. The iron is then slowly released from the dextran shell and *subsequently* binds to transferrin. It does not bind to transferrin directly as a complex. * **D. Iron-dextran has a low molecular weight:** This is incorrect. Iron-dextran is a **high molecular weight** complex. This property prevents it from being excreted by the kidneys and necessitates its uptake by macrophages. **High-Yield Clinical Pearls for NEET-PG:** * **Z-track technique:** Always use this method for IM iron injections to prevent skin staining and "tattooing." * **Anaphylaxis:** Iron-dextran carries the highest risk of type I hypersensitivity reactions. A **test dose** is mandatory before the full infusion. * **Oral vs. Parenteral:** Parenteral iron does not raise hemoglobin faster than oral iron; it only replenishes iron stores more rapidly. * **Indications for Parenteral Iron:** Oral intolerance, malabsorption (Celiac disease), chronic kidney disease (on EPO), or severe blood loss where oral iron cannot keep up.

Question 239: Clopidogrel is an antiplatelet agent that acts by which of the following mechanisms?

A. Reducing myocardial oxygen requirements during exertion and stress
B. Reducing myocardial oxygen requirements and by inducing coronary artery vasodilatation
C. Inhibiting ADP-induced platelet aggregation (Correct Answer)
D. None of the above

Explanation: Clopidogrel is a thienopyridine derivative and a potent antiplatelet agent. It acts as a **prodrug** that requires hepatic activation via the **CYP2C19** enzyme [2]. Its active metabolite **irreversibly** binds to the **P2Y12 receptor** (a subtype of ADP receptors) on the platelet surface [2]. By blocking this receptor, Clopidogrel inhibits the activation of the GP IIb/IIIa receptor complex, thereby preventing fibrinogen binding and subsequent **ADP-induced platelet aggregation** [1]. **Analysis of Incorrect Options:** * **Options A and B:** These descriptions refer to the mechanism of **Anti-anginal drugs** (such as Nitrates, Beta-blockers, or Calcium Channel Blockers). While Clopidogrel is frequently used in patients with Ischemic Heart Disease to prevent thrombotic events (like MI), it does not directly alter myocardial oxygen demand or cause significant coronary vasodilation. **High-Yield Clinical Pearls for NEET-PG:** * **Irreversibility:** Because the binding is irreversible, the antiplatelet effect lasts for the lifespan of the platelet (approx. 7–10 days). * **Pharmacogenomics:** Patients with a genetic deficiency of the **CYP2C19** enzyme are "poor metabolizers" and may show resistance to Clopidogrel, increasing the risk of cardiovascular events [2]. * **Drug Interaction:** **Omeprazole** (a PPI) inhibits CYP2C19 and can reduce the clinical efficacy of Clopidogrel; hence, Rabeprazole or Pantoprazole are preferred if a PPI is necessary [2]. * **Other P2Y12 Inhibitors:** Prasugrel (irreversible) and Ticagrelor (reversible) [2].

Question 240: Which of the following statements about oral anticoagulants is FALSE?

A. They interfere with an early step in the synthesis of clotting factors. (Correct Answer)
B. Irrespective of the dose administered, their anticoagulant effect has a latency of onset of 1-3 days.
C. Their dose is adjusted by repeated measurement of prothrombin time.
D. They are contraindicated during pregnancy.

Explanation: ### Explanation **1. Why Option A is the Correct Answer (The False Statement):** Oral anticoagulants like Warfarin do not interfere with an "early step" of clotting factor synthesis. Instead, they inhibit the **final step** of synthesis: the **$\gamma$-carboxylation** of glutamic acid residues on Factors II, VII, IX, and X. This process requires the reduced form of Vitamin K. Warfarin inhibits the enzyme **Vitamin K Epoxide Reductase (VKOR)**, preventing the regeneration of active Vitamin K. Consequently, the liver produces "PIVKA" (Proteins Induced by Vitamin K Absence), which are biologically inactive precursors. **2. Analysis of Other Options:** * **Option B (Latency of onset):** This is **true**. Even with high loading doses, the effect is delayed (1–3 days) because oral anticoagulants only inhibit the *synthesis* of new factors; they have no effect on factors already circulating in the blood. The effect appears only after the pre-existing factors are degraded (Factor VII has the shortest half-life). * **Option C (Prothrombin Time):** This is **true**. PT/INR (International Normalized Ratio) is the standard monitoring tool. It primarily reflects the extrinsic pathway and is sensitive to changes in Factor VII. * **Option D (Pregnancy):** This is **true**. Warfarin is **teratogenic** (causing Fetal Warfarin Syndrome: hypoplastic nasal bridge, chondrodysplasia punctata) and can cause fetal hemorrhage. Heparin is preferred in pregnancy as it does not cross the placenta. **3. NEET-PG High-Yield Pearls:** * **Antidote:** For immediate reversal of Warfarin, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergency reversal, use **Vitamin K1 (Phytonadione)**. * **Skin Necrosis:** Occurs due to a rapid decline in **Protein C** (a natural anticoagulant with a short half-life), leading to a transient hypercoagulable state. This is why "Heparin bridging" is required. * **Drug Interactions:** Enzyme inhibitors (e.g., Cimetidine, Erythromycin) increase Warfarin's effect, while enzyme inducers (e.g., Rifampicin, Phenytoin) decrease it.

Practice by Chapter

Hematopoietic Growth Factors

Practice Questions

Iron Preparations and Management of Iron Deficiency

Practice Questions

Vitamin B12 and Folic Acid

Practice Questions

Anticoagulants: Heparins and Direct Inhibitors

Practice Questions

Oral Anticoagulants

Practice Questions

Antiplatelet Drugs

Practice Questions

Thrombolytic Agents

Practice Questions

Hemostatic Drugs

Practice Questions

Plasma Expanders

Practice Questions

Blood Transfusion and Alternatives

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free