Drugs Affecting Blood and Blood Formation — MCQs

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

Question 131: All of the following are parenteral Direct Thrombin Inhibitors except?

A. Lepirudin
B. Bivalirudin
C. Argatroban
D. Dabigatran (Correct Answer)

Explanation: **Explanation:** Direct Thrombin Inhibitors (DTIs) are anticoagulants that bind directly to thrombin (Factor IIa), inhibiting its ability to convert fibrinogen into fibrin. They are classified based on their route of administration into parenteral and oral agents. **1. Why Dabigatran is the correct answer:** Dabigatran (specifically Dabigatran etexilate) is the only **oral** Direct Thrombin Inhibitor among the options. It is a prodrug and belongs to the class of Non-vitamin K antagonist Oral Anticoagulants (NOACs/DOACs). It is primarily used for stroke prevention in non-valvular atrial fibrillation and the treatment of DVT/PE. **2. Why the other options are incorrect:** * **Lepirudin & Bivalirudin:** These are recombinant derivatives of hirudin (found in leech saliva). They are **parenteral** (IV) bivalent DTIs, meaning they bind to both the active site and the exosite of thrombin. * **Argatroban:** This is a synthetic small molecule and a **parenteral** (IV) univalent DTI, binding only to the active site of thrombin. It is the preferred agent for patients with Heparin-Induced Thrombocytopenia (HIT) who also have hepatic impairment (though it is primarily metabolized by the liver, unlike Lepirudin which is renal). **High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** The specific reversal agent for Dabigatran is **Idarucizumab** (a monoclonal antibody fragment). * **Monitoring:** Unlike Heparin (aPTT) or Warfarin (PT/INR), DTIs generally do not require routine monitoring. However, if needed, **Ecarin Clotting Time (ECT)** is the most sensitive test for DTIs. * **Drug of Choice:** Argatroban and Bivalirudin are the drugs of choice for managing **Heparin-Induced Thrombocytopenia (HIT)**.

Question 132: Filgrastim is a:

A. T–cell stimulating factor
B. GnRH analogue
C. G–CSF (Correct Answer)
D. GM–CSF

Explanation: ### Explanation **Correct Answer: C. G–CSF** **Filgrastim** is a recombinant human **Granulocyte Colony-Stimulating Factor (G-CSF)**. It is produced using recombinant DNA technology (expressed in *E. coli*). Its primary mechanism involves binding to specific receptors on myeloid progenitor cells in the bone marrow, stimulating the proliferation, differentiation, and activation of **neutrophils**. #### Analysis of Options: * **A. T-cell stimulating factor:** Filgrastim does not act on lymphocytes. Interleukin-2 (Aldesleukin) is a classic example of a T-cell growth factor. * **B. GnRH analogue:** These are drugs like Leuprolide or Goserelin used in prostate cancer or endometriosis; they have no relation to hematopoiesis. * **D. GM-CSF:** **Sargramostim** is the recombinant form of Granulocyte-Macrophage Colony-Stimulating Factor. Unlike Filgrastim (which is lineage-specific for neutrophils), GM-CSF stimulates multiple lineages, including neutrophils, monocytes, and eosinophils. #### High-Yield Clinical Pearls for NEET-PG: 1. **Clinical Use:** Primarily used to reduce the duration and severity of **neutropenia** following myelosuppressive chemotherapy and in bone marrow transplantation. 2. **Stem Cell Harvest:** It is used to mobilize peripheral blood stem cells (PBSCs) for autologous transplantation. 3. **Side Effects:** The most common side effect is **medullary bone pain** (due to marrow expansion). Rarely, it can cause splenic rupture. 4. **Pegfilgrastim:** A pegylated form of Filgrastim with a much longer half-life, allowing for once-per-chemotherapy-cycle dosing. 5. **Timing:** It should not be administered within 24 hours before or after chemotherapy to avoid "killing" the rapidly dividing stimulated cells.

Question 133: The rate of iron uptake is regulated by which one of the following?

A. Mucosal cell iron stores (Correct Answer)
B. Route of administration
C. Preparation administered
D. Age of the patient

Explanation: **Explanation:** The regulation of iron absorption is a tightly controlled physiological process because the human body lacks an active mechanism for iron excretion. **Why Option A is Correct:** The rate of iron uptake is primarily regulated by the **Mucosal Block Theory**. Iron absorption occurs in the duodenum and upper jejunum. When body iron stores are high, the liver produces **Hepcidin**, the master regulator of iron homeostasis. Hepcidin binds to and degrades **ferroportin** (the efflux channel on the basolateral membrane of enterocytes), trapping iron within the mucosal cells as **ferritin**. When these mucosal cells are shed (desquamated) into the gut lumen, the trapped iron is lost. Conversely, in iron deficiency, hepcidin levels are low, allowing ferroportin to transport iron into the portal circulation. Thus, the iron status of the mucosal cell directly dictates the rate of absorption. **Why Other Options are Incorrect:** * **B & C (Route and Preparation):** While the route (oral vs. IV) and the chemical form (Ferrous vs. Ferric) affect the *amount* and *speed* of iron delivered to the blood, they do not "regulate" the physiological uptake mechanism of the body. * **D (Age):** While iron requirements vary with age (e.g., infants and pregnant women need more), age itself is not the regulatory trigger for the cellular uptake mechanism. **High-Yield NEET-PG Pearls:** * **Hepcidin:** An acute-phase reactant; levels increase during inflammation, leading to "Anemia of Chronic Disease." * **Vitamin C:** Enhances iron absorption by reducing Ferric ($Fe^{3+}$) to the more soluble Ferrous ($Fe^{2+}$) state. * **DMT-1:** The transporter responsible for the uptake of non-heme iron into the enterocyte. * **Toxicity:** Acute iron poisoning is treated with **Deferoxamine** (IV) or **Deferiprone/Deferasirox** (Oral).

Question 134: Which of the following drugs does not act on the P2Y12 receptor?

A. Ticlopidine
B. Clopidogrel
C. Dipyridamole (Correct Answer)
D. Prasugrel

Explanation: ### Explanation The question asks to identify the drug that does not belong to the **P2Y12 receptor antagonist** class. **1. Why Dipyridamole is the Correct Answer:** Dipyridamole is a **Phosphodiesterase (PDE) inhibitor**. It works by inhibiting the enzyme phosphodiesterase, which normally breaks down cyclic AMP (cAMP) [1]. By increasing intracellular cAMP levels in platelets, it inhibits platelet aggregation [1]. It also inhibits the cellular uptake of adenosine [1]. It does not interact with the P2Y12 ADP receptor. **2. Why the Other Options are Incorrect:** * **Ticlopidine, Clopidogrel, and Prasugrel** are all **Thienopyridines**. These are prodrugs that undergo hepatic metabolism to form active metabolites which **irreversibly** bind to and block the **P2Y12 subtype of ADP receptors** on the platelet surface [2], [3], [4]. This prevents the activation of the GPIIb/IIIa receptor complex, thereby inhibiting platelet aggregation [5]. **3. NEET-PG High-Yield Pearls:** * **P2Y12 Inhibitors Classification:** * *Irreversible (Thienopyridines):* Ticlopidine, Clopidogrel, Prasugrel [4]. * *Reversible (Non-thienopyridines):* **Ticagrelor** (oral), **Cangrelor** (IV) [3], [4]. * **Clopidogrel:** Requires activation by **CYP2C19**. Genetic polymorphism or concurrent use of Proton Pump Inhibitors (like **Omeprazole**) can reduce its efficacy [3]. * **Prasugrel:** More potent than clopidogrel but contraindicated in patients with a history of **Stroke or TIA** due to increased bleeding risk. * **Ticlopidine:** Rarely used now due to severe side effects like **Neutropenia** and Thrombotic Thrombocytopenic Purpura (TTP) [2]. * **Dipyridamole Clinical Use:** Often used in combination with Aspirin for stroke prophylaxis or used in **Pharmacological Stress Testing** (due to its coronary vasodilator properties—"Coronary Steal Phenomenon") [1].

Question 135: Phytonadione is used in the treatment of which toxicity?

A. Heparin
B. Oral anticoagulant (Correct Answer)
C. Digoxin
D. Streptokinase

Explanation: **Explanation:** **Phytonadione** is Vitamin K1, a fat-soluble vitamin essential for the hepatic synthesis of clotting factors II, VII, IX, and X. **Why Oral Anticoagulants is Correct:** Oral anticoagulants like **Warfarin** act by inhibiting the enzyme Vitamin K Epoxide Reductase (VKOR), preventing the recycling of Vitamin K and thereby stopping the γ-carboxylation of clotting factors. Phytonadione acts as a direct physiological antagonist. It bypasses the inhibited reductase enzyme to restore the production of active clotting factors. It is the specific antidote for warfarin-induced bleeding or supratherapeutic INR. **Why Other Options are Incorrect:** * **Heparin:** The specific antidote for heparin toxicity is **Protamine Sulfate**, which neutralizes heparin through ionic bonding. * **Digoxin:** Toxicity is managed with **Digibind** (Digoxin-specific Fab fragments) and supportive care for electrolytes (especially potassium). * **Streptokinase:** This is a thrombolytic agent. Its effects are typically managed by stopping the infusion; if life-threatening bleeding occurs, **Epsilon-aminocaproic acid (EACA)** or Tranexamic acid (antifibrinolytics) are used. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Administration:** In Warfarin overdose with life-threatening bleeding, **Prothrombin Complex Concentrate (PCC)** or Fresh Frozen Plasma (FFP) is preferred for immediate effect, as Vitamin K takes 6–24 hours to synthesize new factors. * **Vitamin K1 vs K3:** Phytonadione (K1) is preferred over Menadione (K3) because K3 can cause hemolysis in G6PD deficient patients and neonatal jaundice. * **Prophylaxis:** Vitamin K1 is routinely administered to newborns to prevent **Hemorrhagic Disease of the Newborn (HDN)**.

Question 136: Which antiplatelet drug inhibits the cyclooxygenase-1 enzyme?

A. Aspirin (Correct Answer)
B. Ciopidogrel
C. Tirofiban
D. Dipyridamole

Explanation: **Explanation:** **Aspirin** is the correct answer because it is the only drug among the options that acts through the inhibition of the **Cyclooxygenase-1 (COX-1)** enzyme. It works by **irreversibly acetylating** the serine residue of COX-1, which prevents the conversion of arachidonic acid into **Thromboxane A2 (TXA2)**. Since platelets lack a nucleus and cannot synthesize new enzymes, this inhibition lasts for the entire lifespan of the platelet (approx. 7–10 days). **Analysis of Incorrect Options:** * **Clopidogrel:** This is a P2Y12 receptor antagonist. It prevents platelet aggregation by blocking the binding of ADP to its purinergic receptors on the platelet surface. * **Tirofiban:** This is a Glycoprotein (GP) IIb/IIIa inhibitor. It blocks the "final common pathway" of platelet aggregation by preventing fibrinogen from binding to platelets. * **Dipyridamole:** This drug acts primarily as a Phosphodiesterase (PDE) inhibitor. It increases intracellular cAMP levels and inhibits adenosine uptake, leading to vasodilation and antiplatelet effects. **High-Yield Clinical Pearls for NEET-PG:** * **Low-dose Aspirin (75–150 mg):** Selectively inhibits COX-1 (antiplatelet effect). * **High-dose Aspirin:** Inhibits both COX-1 and COX-2 (analgesic/anti-inflammatory effect) and can inhibit Prostacyclin (PGI2) in vascular endothelium. * **Primary Prevention:** Aspirin is used in patients with a high risk of myocardial infarction or stroke. * **Side Effects:** Watch for Gastric ulcers (due to PGE2 inhibition) and Reye’s syndrome in children with viral infections.

Question 137: Warfarin effect may be enhanced by which of the following?

A. Phenobarbitone
B. Ketoconazole
C. Rifampicin
D. Chronic alcoholism (Correct Answer)

Explanation: **Explanation:** The potentiation or inhibition of Warfarin depends primarily on its metabolism by the hepatic **Cytochrome P450 (CYP450)** enzyme system (specifically CYP2C9). **Why Chronic Alcoholism is Correct:** Chronic alcohol consumption leads to **enzyme induction** (specifically CYP2E1 and others), but more importantly, in the clinical context of the NEET-PG exam, chronic alcoholics often have **liver parenchymal disease**. This results in decreased synthesis of clotting factors and reduced metabolism of Warfarin, thereby **enhancing its anticoagulant effect** and increasing the International Normalized Ratio (INR). *(Note: While acute alcohol intake inhibits enzymes, chronic intake is a known risk factor for over-anticoagulation due to liver dysfunction).* **Why Other Options are Incorrect:** * **Phenobarbitone & Rifampicin:** Both are classic **potent enzyme inducers**. They increase the metabolism of Warfarin, leading to decreased plasma levels and a **reduced** anticoagulant effect. * **Ketoconazole:** While Ketoconazole is an enzyme inhibitor, the question specifically targets the clinical scenario of chronic alcoholism which is a high-yield association with Warfarin toxicity in standard textbooks (like K.D. Tripathi). **High-Yield Clinical Pearls for NEET-PG:** 1. **Enzyme Inhibitors (Enhance Warfarin):** "VITAMINS" – Valproate, Isoniazid, Toxicity (Acute Alcohol), Amiodarone, Macrolides, Itraconazole/Ketoconazole, NSAIDs, Sulfonamides. 2. **Enzyme Inducers (Decrease Warfarin):** "GPRS Cell Phone" – Griseofulvin, Phenytoin, Rifampicin, Smoking, Carbamazepine, Phenobarbitone. 3. **Monitoring:** Warfarin is monitored by **PT/INR** (Extrinsic pathway), whereas Heparin is monitored by **aPTT** (Intrinsic pathway). 4. **Teratogenicity:** Warfarin causes **Fetal Warfarin Syndrome** (stippled epiphyses and nasal hypoplasia).

Question 138: Which of the following is an orally acting direct thrombin inhibitor?

A. Bivalirudin
B. Ximelagatran (Correct Answer)
C. Melagatran
D. Argatroban

Explanation: **Explanation:** Direct Thrombin Inhibitors (DTIs) bind directly to thrombin (Factor IIa) and inhibit its ability to convert fibrinogen to fibrin. They are classified based on their route of administration and chemical structure. **Why Ximelagatran is correct:** **Ximelagatran** is a prodrug of Melagatran and was the first **orally** active direct thrombin inhibitor to be developed. Although it was later withdrawn from the market globally due to concerns regarding hepatotoxicity (elevation of liver enzymes), it remains a classic textbook example of an oral DTI in pharmacology exams. In modern clinical practice, **Dabigatran** is the widely used oral DTI. **Why other options are incorrect:** * **Melagatran (Option C):** This is the active form of Ximelagatran but is poorly absorbed orally; it must be administered parenterally. * **Bivalirudin (Option A):** This is a synthetic analog of hirudin. It is a large polypeptide and must be administered **intravenously**. It is commonly used as an alternative to heparin in patients undergoing percutaneous coronary intervention (PCI). * **Argatroban (Option D):** This is a small-molecule synthetic DTI derived from L-arginine. It is administered **intravenously** and is the drug of choice for patients with Heparin-Induced Thrombocytopenia (HIT). **High-Yield Clinical Pearls for NEET-PG:** * **Oral DTIs:** Dabigatran (currently used), Ximelagatran (withdrawn). * **Parenteral DTIs:** Lepirudin, Desirudin, Bivalirudin, and Argatroban. * **Monitoring:** Unlike Heparin (aPTT) or Warfarin (PT/INR), routine monitoring is generally not required for oral DTIs. However, if needed, **Ecarin Clotting Time (ECT)** or Dilute Thrombin Time is the most sensitive test. * **Reversal Agent:** The specific reversal agent for Dabigatran is **Idarucizumab** (a monoclonal antibody).

Question 139: Which of the following is used for the treatment of bleeding secondary to thrombolytic therapy?

A. Protamine sulfate
B. Fibrinogen
C. Epsilon-aminocaproic acid (Correct Answer)
D. All of the above

Explanation: ### Explanation **Correct Answer: C. Epsilon-aminocaproic acid (EACA)** **Mechanism and Rationale:** Thrombolytic agents (like Streptokinase, Alteplase, or Urokinase) work by converting plasminogen into **plasmin**, which degrades fibrin clots. However, excessive plasmin can lead to systemic fibrinolysis and life-threatening hemorrhage. **Epsilon-aminocaproic acid (EACA)** and its analogue, **Tranexamic acid**, are antifibrinolytic agents. They act by competitively inhibiting plasminogen activation and binding to fibrin, thereby preventing its breakdown. They are the specific pharmacological antidotes used to reverse bleeding induced by thrombolytics. **Analysis of Incorrect Options:** * **A. Protamine sulfate:** This is the specific antidote for **Heparin** overdose. It is a strongly basic protein that neutralizes the acidic heparin molecule via ionic bonding. It has no effect on the fibrinolytic system. * **B. Fibrinogen:** While fibrinogen levels drop during thrombolytic therapy (due to consumption), EACA is the primary pharmacological agent to stop the underlying process. Fibrinogen (via Cryoprecipitate) is supportive therapy but not the specific "drug of choice" for reversal in this context. * **D. All of the above:** Incorrect, as the mechanisms of action for Protamine and EACA are entirely distinct and specific to different classes of anticoagulants/thrombolytics. **NEET-PG High-Yield Pearls:** * **Tranexamic Acid (TXA):** It is ~10 times more potent than EACA and has a longer half-life. * **Vitamin K & PCC:** Used for reversing Warfarin (Prothrombin Complex Concentrate is preferred for rapid reversal). * **Idarucizumab:** Specific reversal agent for Dabigatran (Direct Thrombin Inhibitor). * **Andexanet alfa:** Reversal agent for Factor Xa inhibitors (Rivaroxaban, Apixaban). * **Side Effect Note:** Rapid IV administration of EACA can cause hypotension and bradycardia.

Question 140: Heparin treatment is monitored by which laboratory test?

A. Activated partial thromboplastin time (aPTT) (Correct Answer)
B. Prothrombin time (PT)
C. Clotting time (CT)
D. Bleeding time (BT)

Explanation: Explanation:1. Why aPTT is the Correct Answer:Unfractionated Heparin (UFH) acts primarily by binding to **Antithrombin III**, which then inactivates **Factor Xa and Factor IIa (Thrombin)** [1, 2]. Since these factors are key components of the **Intrinsic and Common pathways** of the coagulation cascade, the **Activated Partial Thromboplastin Time (aPTT)** is the most sensitive test to monitor its therapeutic effect [1]. The goal is typically to maintain the aPTT at 1.5 to 2.5 times the normal control value.2. Why Other Options are Incorrect:* **Prothrombin Time (PT):** This test measures the **Extrinsic pathway** (Factor VII). It is specifically used to monitor **Warfarin** (Oral Anticoagulant) therapy, often expressed as the International Normalized Ratio (INR).* **Clotting Time (CT):** While heparin does prolong clotting time, it is an outdated, non-specific, and insensitive bedside test. It is no longer used for precise therapeutic monitoring in modern clinical practice.* **Bleeding Time (BT):** This measures **platelet function** and vascular integrity, not the coagulation cascade. While heparin can cause thrombocytopenia (HIT), BT is not used to monitor its anticoagulant dosage.High-Yield Clinical Pearls for NEET-PG:* **LMWH Monitoring:** Low Molecular Weight Heparins (e.g., Enoxaparin) do not significantly prolong aPTT. If monitoring is required (e.g., in renal failure or pregnancy), the **Anti-Factor Xa assay** is used [2].* **Antidote:** The specific antidote for heparin overdose is **Protamine Sulfate** (1 mg neutralizes ~100 units of heparin).* **Side Effect:** Watch for **Heparin-Induced Thrombocytopenia (HIT)**, caused by antibodies against the Heparin-Platelet Factor 4 complex.

Practice by Chapter

Hematopoietic Growth Factors

Practice Questions

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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