Drugs Affecting Blood and Blood Formation — MCQs

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

Question 51: Which of the following drugs does not cause thrombocytopenia?

A. Methotrexate
B. Aspirin (Correct Answer)
C. Ticlopidine
D. Heparin

Explanation: **Explanation:** The correct answer is **Aspirin (Option B)**. The core concept here is the distinction between **platelet dysfunction** and **thrombocytopenia** (a decrease in the absolute number of platelets). 1. **Why Aspirin is correct:** Aspirin is an irreversible inhibitor of the enzyme Cyclooxygenase-1 (COX-1). This action prevents the synthesis of Thromboxane A2 (TXA2), which is essential for platelet aggregation. While Aspirin significantly impairs **platelet function** (increasing bleeding time), it does **not** reduce the actual platelet count. Therefore, it does not cause thrombocytopenia. 2. **Why the other options are incorrect:** * **Methotrexate (Option A):** As a cytotoxic antimetabolite (folic acid antagonist), it causes generalized **bone marrow suppression**. This leads to a decrease in all cell lines, including megakaryocytes, resulting in thrombocytopenia. * **Ticlopidine (Option C):** This P2Y12 receptor blocker is notorious for hematological toxicities, including **neutropenia** and **Thrombotic Thrombocytopenic Purpura (TTP)**, which presents with severe thrombocytopenia. * **Heparin (Option D):** Heparin can cause **Heparin-Induced Thrombocytopenia (HIT)**. This is an immune-mediated reaction where antibodies form against the Heparin-Platelet Factor 4 (PF4) complex, leading to platelet activation and subsequent consumption (low count). **High-Yield Clinical Pearls for NEET-PG:** * **Aspirin:** Affects *quality*, not *quantity* of platelets. * **HIT Type II:** Is an IgG-mediated "white clot syndrome" that paradoxically increases the risk of thrombosis despite low platelet counts. * **Clopidogrel vs. Ticlopidine:** Clopidogrel is preferred over Ticlopidine because it has a much lower risk of causing TTP and neutropenia.

Question 52: Which fibrinolytic agent is antigenic?

A. Streptokinase (Correct Answer)
B. Urokinase
C. Alteplase
D. Tenecteplase

Explanation: **Explanation:** The antigenicity of a fibrinolytic agent depends on its biological source. **1. Why Streptokinase is the correct answer:** Streptokinase is a protein produced by **Group C β-hemolytic streptococci**. Because it is derived from a bacterial source rather than human tissue, the human immune system recognizes it as a foreign antigen. This leads to the production of antistreptococcal antibodies. * **Clinical Implication:** These antibodies can cause hypersensitivity reactions (ranging from rashes to anaphylaxis) and can neutralize the drug, making it less effective if administered again. Therefore, it is generally recommended **not to repeat streptokinase treatment within 6 months to 1 year** of the first dose. **2. Why the other options are incorrect:** * **Urokinase:** It is an enzyme naturally found in human urine and synthesized by kidney cells. Being a human-derived protein, it is **non-antigenic**. * **Alteplase (rt-PA):** This is a recombinant form of human tissue-type plasminogen activator. Since it is structurally identical to endogenous human t-PA, it is **non-antigenic**. * **Tenecteplase:** This is a genetically engineered mutant of alteplase with a longer half-life and higher fibrin specificity. Like alteplase, it is human-based and **non-antigenic**. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Streptokinase is a *non-specific* plasminogen activator (acts on both bound and free plasminogen), leading to a "systemic lytic state" and higher bleeding risk compared to fibrin-specific agents like Tenecteplase. * **Side Effect:** Hypotension is a common side effect of Streptokinase infusion. * **DOC:** Tenecteplase is currently the preferred agent for ST-elevation MI (STEMI) due to its bolus administration and high fibrin specificity.

Question 53: Which of the following drugs is administered orally?

A. Dalteparin
B. Rivaroxaban (Correct Answer)
C. Lepirudin
D. None of the above

Explanation: **Explanation:** The correct answer is **Rivaroxaban**. This question tests your knowledge of the routes of administration for various anticoagulants, a high-yield topic for NEET-PG. **1. Why Rivaroxaban is correct:** Rivaroxaban belongs to the class of **Direct Oral Anticoagulants (DOACs)**. It is a potent, competitive, and highly selective **Direct Factor Xa inhibitor**. Unlike traditional anticoagulants like Heparin, it has high oral bioavailability, a rapid onset of action, and does not require routine laboratory monitoring (like PT/INR), making it a preferred choice for long-term outpatient management of DVT and Atrial Fibrillation. **2. Why the other options are incorrect:** * **Dalteparin:** This is a **Low Molecular Weight Heparin (LMWH)**. Due to its large molecular size and polar nature, it is not absorbed through the gastrointestinal tract and must be administered **subcutaneously**. * **Lepirudin:** This is a recombinant hirudin derivative that acts as a **Direct Thrombin Inhibitor (DTI)**. It is administered **intravenously**, primarily used in patients with Heparin-Induced Thrombocytopenia (HIT). **Clinical Pearls for NEET-PG:** * **Mnemonic for Factor Xa Inhibitors:** Drugs with **"xa"** in their name (Rivaroxaban, Apixaban, Edoxaban) inhibit Factor **Xa**. * **Antidote:** The specific reversal agent for Rivaroxaban and Apixaban is **Andexanet alfa**. * **Direct Thrombin Inhibitors (DTIs):** While Lepirudin and Argatroban are parenteral, **Dabigatran** is the only commonly used **oral** DTI. * **Monitoring:** While DOACs don't require routine monitoring, if necessary, Rivaroxaban effect is measured by anti-Xa assays.

Question 54: When heparin is given during pregnancy, it should be supplemented with which of the following?

A. Zinc
B. Calcium (Correct Answer)
C. Folic acid
D. Ferrous sulphate

Explanation: **Explanation:** **1. Why Calcium is the Correct Answer:** Heparin, when used for prolonged periods (typically >6 months), is associated with **Heparin-Induced Osteoporosis**. The underlying mechanism involves heparin increasing osteoclast activity and decreasing osteoblast function, leading to a reduction in bone mineral density. During pregnancy, the demand for calcium is already high to support fetal skeletal development. Therefore, to mitigate the risk of bone loss and fractures in the mother, **Calcium and Vitamin D supplementation** is mandatory when heparin is administered long-term. **2. Analysis of Incorrect Options:** * **A. Zinc:** While zinc is an essential trace element for fetal growth, it has no direct interaction with heparin therapy or its side effect profile. * **C. Folic acid:** Folic acid is routinely supplemented in pregnancy to prevent neural tube defects, but its requirement is not specifically linked to heparin administration. * **D. Ferrous sulphate:** Iron is supplemented to prevent gestational anemia. While important, it does not counteract the specific adverse effect of heparin on bone metabolism. **3. Clinical Pearls for NEET-PG:** * **Drug of Choice:** Low Molecular Weight Heparin (LMWH), such as Enoxaparin, is the anticoagulant of choice in pregnancy because it does not cross the placenta (non-teratogenic). * **Warfarin Contraindication:** Warfarin is contraindicated in pregnancy (especially the 1st trimester) as it is teratogenic, causing **Fetal Warfarin Syndrome** (nasal hypoplasia, stippled epiphyses). * **Monitoring:** While Unfractionated Heparin (UFH) requires aPTT monitoring, LMWH generally does not, though Anti-Xa levels may be monitored in high-risk pregnant patients. * **Side Effects:** Apart from osteoporosis, watch for **HIT (Heparin-Induced Thrombocytopenia)**, though the risk is lower with LMWH than with UFH.

Question 55: Which of the following plasminogen activators (fibrinolytics) can be given as a bolus dose in patients with acute myocardial infarction?

A. Urokinase
B. Alteplase
C. Reteplase (Correct Answer)
D. None

Explanation: **Explanation:** The correct answer is **Reteplase**. The primary factor determining whether a fibrinolytic can be administered as a bolus is its **plasma half-life**. **1. Why Reteplase is correct:** Reteplase is a second-generation recombinant tissue plasminogen activator (rt-PA). It is a deletion mutant of alteplase, lacking several amino acid domains. This structural modification results in a **longer half-life** (approx. 15 minutes) and reduced hepatic clearance compared to alteplase. Consequently, it can be administered as **two intravenous bolus injections** (10 units each, 30 minutes apart), making it more convenient in emergency settings like Acute MI. **2. Why other options are incorrect:** * **Alteplase (rt-PA):** It has a very short half-life (approx. 5 minutes) and lacks high fibrin specificity compared to newer agents. Due to its rapid clearance, it must be administered as an **accelerated infusion** (bolus followed by a 90-minute infusion) rather than a simple bolus. * **Urokinase:** It is a non-fibrin-specific activator obtained from human urine or kidney cultures. It has a short half-life and is typically administered via **continuous intravenous infusion**. It is rarely used for MI today, being more common in peripheral arterial occlusion or PE. **3. High-Yield Clinical Pearls for NEET-PG:** * **Tenecteplase (TNK-tPA):** This is the most fibrin-specific agent with the longest half-life. It is administered as a **single weight-based IV bolus**, making it the preferred agent for pre-hospital thrombolysis. * **Fibrin Specificity:** Tenecteplase > Reteplase > Alteplase. * **Antigenicity:** Unlike Streptokinase (which is derived from bacteria), recombinant agents like Alteplase, Reteplase, and Tenecteplase are **non-antigenic** and do not cause allergic reactions. * **Mechanism:** All these agents act by converting plasminogen to plasmin, which then degrades fibrin clots.

Question 56: Alteplase acts by which mechanism?

A. Converting plasminogen to plasmin (Correct Answer)
B. Converting fibrin to fibrin degradation products
C. Converting fibrinogen to fibrin
D. Blocking VEGF receptor

Explanation: **Explanation:** Alteplase is a **recombinant tissue-type plasminogen activator (rt-PA)**. It belongs to the class of **thrombolytic (fibrinolytic) agents**. **1. Why Option A is Correct:** The fundamental mechanism of all thrombolytics is the activation of the endogenous fibrinolytic system. Alteplase binds to fibrin in a thrombus and selectively converts **plasminogen to plasmin**. Plasmin is a serine protease that acts as "molecular scissors," proteolytically digesting the fibrin meshwork of a clot into soluble fragments. **2. Why Incorrect Options are Wrong:** * **Option B:** This describes the *result* of plasmin activity, not the direct mechanism of Alteplase itself. Alteplase is the catalyst that creates the enzyme (plasmin) responsible for this step. * **Option C:** This describes the action of **Thrombin**, which is the final step in the coagulation cascade (clot formation), the exact opposite of what Alteplase achieves. * **Option D:** This describes the mechanism of drugs like **Bevacizumab or Ranibizumab**, used in oncology and ophthalmology (AMD), and has no relation to thrombolysis. **NEET-PG High-Yield Pearls:** * **Fibrin Specificity:** Alteplase, Reteplase, and Tenecteplase are **clot-specific** (fibrin-selective), meaning they preferentially activate plasminogen bound to clots, causing less systemic lytic state compared to Streptokinase. * **Therapeutic Window:** Crucial for "Golden Hour" management. It must be administered within **3–4.5 hours** for Ischemic Stroke and is used for ST-elevation MI (STEMI) if PCI is not available within 90–120 minutes. * **Antidote:** In cases of excessive bleeding due to thrombolytics, **Epsilon-aminocaproic acid or Tranexamic acid** (plasminogen activation inhibitors) can be used.

Question 57: Which of the following is an oral direct Factor Xa inhibitor?

A. Rivaroxaban (Correct Answer)
B. Dabigatran
C. Fondaparinux
D. Lepirudin

Explanation: **Explanation:** The correct answer is **Rivaroxaban**. **1. Why Rivaroxaban is correct:** Rivaroxaban belongs to the class of **Direct Oral Anticoagulants (DOACs)**. It works by binding directly and reversibly to the active site of **Factor Xa**, inhibiting its ability to convert prothrombin to thrombin. A helpful mnemonic to remember this class is that their names contain **"-xa-"** (e.g., Ri-**xa**-roba-**xa**-n, Api-**xa**-ban, Edo-**xa**-ban), signifying their target: Factor **Xa** inhibitor. **2. Why the other options are incorrect:** * **Dabigatran:** While it is an oral anticoagulant, it is a **Direct Thrombin (Factor IIa) Inhibitor**, not a Factor Xa inhibitor. * **Fondaparinux:** This is a synthetic pentasaccharide that inhibits Factor Xa, but it is administered **parenterally** (subcutaneously), not orally. It acts indirectly by binding to Antithrombin III. * **Lepirudin:** This is a parenteral (IV) **Direct Thrombin Inhibitor**, a recombinant derivative of hirudin, primarily used in patients with Heparin-Induced Thrombocytopenia (HIT). **3. High-Yield Clinical Pearls for NEET-PG:** * **Monitoring:** Unlike Warfarin, DOACs like Rivaroxaban do not require routine PT/INR monitoring. * **Reversal Agent:** The specific reversal agent for Factor Xa inhibitors (Rivaroxaban/Apixaban) is **Andexanet alfa**. (For Dabigatran, it is Idarucizumab). * **Advantages:** They have a rapid onset of action, predictable pharmacokinetics, and fewer drug-food interactions compared to Vitamin K antagonists. * **Excretion:** Rivaroxaban is partially cleared by the kidneys; thus, dose adjustment is required in chronic kidney disease (CKD).

Question 58: What is a disadvantage of using dextran as a plasma expander?

A. Interference with blood group matching (Correct Answer)
B. Causes thrombocytopenia
C. Decreases microcirculation
D. Promotes rouleaux formation

Explanation: Dextrans are high-molecular-weight polysaccharides used as colloidal plasma expanders. The correct answer is **Interference with blood group matching** because dextran molecules coat the surface of red blood cells (RBCs). This coating leads to **pseudo-agglutination**, which interferes with cross-matching and blood grouping procedures [1]. Therefore, it is a standard clinical practice to draw blood for grouping and matching *before* administering dextran. **Analysis of Incorrect Options:** * **B. Causes thrombocytopenia:** Dextran does not typically cause a decrease in platelet count (thrombocytopenia). However, it can cause **platelet dysfunction** by reducing platelet adhesiveness and interfering with Factor VIII/vWF complex, leading to an increased bleeding time. * **C. Decreases microcirculation:** This is incorrect. Dextran (especially Dextran-40 or Low Molecular Weight Dextran) actually **improves microcirculation** by reducing blood viscosity and preventing the sludging of RBCs. * **D. Promotes rouleaux formation:** This is the opposite of its clinical effect. Dextran **decreases rouleaux formation** by increasing the electronegativity of RBCs, causing them to repel each other. **High-Yield Clinical Pearls for NEET-PG:** * **Dextran-70 (Clinical Dextran):** Most commonly used for volume expansion; stays in circulation for ~24 hours. * **Dextran-40 (Rheomacrodex):** Used specifically to improve microcirculation in shock or peripheral vascular surgery; however, it carries a higher risk of **acute renal failure** due to tubular obstruction. * **Anaphylaxis:** Dextran is highly immunogenic and can cause severe hypersensitivity reactions [1]. * **Contraindication:** Avoid in patients with severe bleeding disorders, congestive heart failure, or renal failure.

Question 59: Which of the following statements about vitamin K are true?

A. Increases the synthesis of factor II, VII, IX and X
B. Requires exposure to sunlight (Correct Answer)
C. Causes hemolytic anemia in patients with G–6–PD deficiency
D. Half-life is less than 6 hours

Explanation: **Explanation:** **Vitamin K** is a fat-soluble vitamin essential for the coagulation cascade. The correct answer highlights a specific biochemical property of the vitamin. **1. Why "Requires exposure to sunlight" is correct:** Vitamin K exists in several forms (K1 from plants, K2 from bacteria). A crucial step in the synthesis of Vitamin K1 (Phylloquinone) in plants is the **photochemical process** involving sunlight. Furthermore, in clinical practice, Vitamin K is known to be **photosensitive**. It undergoes degradation when exposed to light, which is why Vitamin K ampoules are typically stored in amber-colored vials to prevent loss of potency. **2. Why the other options are incorrect:** * **Option A:** Vitamin K does **not** increase the *synthesis* of factors II, VII, IX, and X. These proteins are already synthesized by the liver. Vitamin K acts as a cofactor for the enzyme **gamma-glutamyl carboxylase**, which performs **post-translational modification** (carboxylation of glutamate residues), making these factors functional. * **Option C:** While high doses of synthetic Vitamin K3 (Menadione) can cause hemolysis, it is not a classic trigger for G6PD deficiency in the same way as Primaquine or Fava beans. More importantly, Vitamin K is actually used to *treat* hemorrhagic tendencies, not typically associated with inducing hemolytic anemia as a primary characteristic. * **Option D:** The biological half-life of Vitamin K is approximately **24 to 48 hours**, not less than 6 hours. Its clinical effect (onset of action) after administration also takes about 6–12 hours because it takes time for newly carboxylated clotting factors to reach therapeutic levels in the blood. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Gamma-carboxylation of factors **2, 7, 9, 10** and proteins **C and S**. * **Warfarin Connection:** Warfarin inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the regeneration of active Vitamin K. * **Newborns:** All newborns receive prophylactic Vitamin K because they have sterile guts (no K2-producing bacteria) and poor placental transfer. * **Antidote:** Vitamin K is the specific antidote for Warfarin overdose (takes time); for immediate reversal, use Fresh Frozen Plasma (FFP) or Prothrombin Complex Concentrate (PCC).

Question 60: Desmopressin nasal spray is most useful in which of the following types of Von Willebrand Disease?

A. Type 1 VWD (Correct Answer)
B. Type 2A VWD
C. Type 3 VWD
D. Type 1 & Type 3 VWD

Explanation: Explanation: Mechanism of Action: Desmopressin (DDAVP) is a synthetic analogue of vasopressin that acts on V2 receptors on endothelial cells [3]. This stimulation triggers the release of pre-stored Von Willebrand Factor (vWF) and Factor VIII from the Weibel-Palade bodies into the plasma. Why Type 1 VWD is the correct answer: Type 1 VWD is characterized by a quantitative deficiency (partial) of vWF, but the protein produced is structurally normal. Because these patients have functional stores of vWF, DDAVP can effectively "squeeze" out these stores to achieve hemostatic levels [4]. It is the treatment of choice for minor surgeries and bleeding episodes in these patients. Analysis of Incorrect Options: * Type 2A VWD: This involves a qualitative defect where vWF is present but lacks high-molecular-weight multimers. While some Type 2 subtypes might show a partial response, it is inconsistent and often inadequate compared to Type 1. (Note: In Type 2B, DDAVP is contraindicated as it can cause transient thrombocytopenia). * Type 3 VWD: This is a total/severe quantitative deficiency of vWF. Since there are virtually no stores of vWF in the endothelial cells, DDAVP has nothing to release and is therefore ineffective. These patients require vWF/Factor VIII concentrate [4]. * Option D: Incorrect because Type 3 is a contraindication/non-responder. High-Yield NEET-PG Pearls: * Route: For VWD, it can be given IV, SC, or as a high-concentration nasal spray (Stimate) [1]. Note that the nasal spray for VWD is 15x more concentrated than the one used for Diabetes Insipidus. * Side Effects: Hyponatremia (due to water retention/antidiuretic effect) [2] and facial flushing. * Tachyphylaxis: Repeated doses lead to diminished response as endothelial stores become exhausted. * Clinical Use: Also used in Mild Hemophilia A (not Hemophilia B) and Enuresis.

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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