Drugs Affecting Blood and Blood Formation Practice Questions

Q: Neutropenia develops in a patient undergoing cancer chemotherapy. Administration of which one of the following agents would accelerate recovery of neutrophil counts?

Filgrastim. ### Explanation **Correct Option: B. Filgrastim** Filgrastim is a recombinant human **Granulocyte Colony-Stimulating Factor (G-CSF)**. It acts on the bone marrow to stimulate the proliferation and differentiation of progenitor cells into mature neutrophils. In patients undergoing chemotherapy, it is specifically used to reduce the duration and severity of **neutropenia**, thereby decreasing the risk of life-threatening infections (febrile neutropenia). **Why the other options are incorrect:** * **A. Leucovorin (Folinic Acid):** This is a reduced form of folic acid used as a "rescue" therapy following high-dose **Methotrexate** to protect healthy cells from toxicity. It does not directly stimulate neutrophil production. * **C. Prednisone:** While glucocorticoids can cause "pseudoneutrophilia" (by decreasing the margination of neutrophils from blood vessel walls into tissues), they are not used to treat chemotherapy-induced bone marrow suppression. In fact, long-term use can increase infection risk. * **D. Vitamin B12:** This is used to treat megaloblastic anemia caused by B12 deficiency. It has no role in recovering neutrophil counts depleted by cytotoxic chemotherapy. **High-Yield Clinical Pearls for NEET-PG:** * **Sargramostim:** A recombinant **GM-CSF** (Granulocyte-Macrophage CSF) that stimulates both neutrophils and macrophages. * **Oprelvekin (IL-11):** Used to treat chemotherapy-induced **thrombocytopenia** (stimulates platelet production). * **Epoetin Alfa:** A recombinant Erythropoietin used to treat chemotherapy-induced **anemia**. * **Timing:** G-CSF is typically administered 24–72 hours after the completion of chemotherapy; it should not be given simultaneously with cytotoxic drugs as it may worsen myelosuppression. * **Common Side Effect:** The most frequent side effect of Filgrastim is **medullary bone pain**.

Q: Which of the following drugs may cause thrombocytopenia?

Ticlopidine. **Explanation:** **Ticlopidine** is the correct answer because it is notorious for causing severe hematological adverse effects. It is a first-generation P2Y12 receptor antagonist that inhibits ADP-induced platelet aggregation. Its clinical use has been largely superseded by newer agents due to its association with **neutropenia, agranulocytosis, and thrombocytopenia**. Most critically, it can cause **Thrombotic Thrombocytopenic Purpura (TTP)**, necessitating frequent blood count monitoring (CBC) during the first three months of therapy. **Analysis of Incorrect Options:** * **Clopidogrel:** While also a P2Y12 inhibitor, it is a second-generation drug designed to be safer than Ticlopidine. Although rare cases of TTP have been reported, it does not typically cause the significant bone marrow suppression or routine thrombocytopenia seen with Ticlopidine. * **Abciximab:** This is a Glycoprotein IIb/IIIa inhibitor. While it can cause *acute* immune-mediated thrombocytopenia in a small percentage of patients, it is not the classic "textbook" association for drug-induced hematological toxicity in the same category as Ticlopidine for NEET-PG purposes. * **Aspirin:** Aspirin inhibits COX-1, leading to decreased Thromboxane A2. It affects platelet *function* (irreversible inhibition) rather than platelet *count*. It does not cause thrombocytopenia. **High-Yield NEET-PG Pearls:** * **Ticlopidine Side Effects:** Neutropenia (most common), TTP, and Diarrhea. * **Monitoring:** Patients on Ticlopidine require a CBC every 2 weeks for the first 3 months. * **Prasugrel/Ticagrelor:** Newer P2Y12 inhibitors; Prasugrel is contraindicated in patients with a history of stroke/TIA, and Ticagrelor can cause transient dyspnea and hyperuricemia.

Q: What is the anticoagulant of choice for prophylaxis of pulmonary thromboembolism?

Low molecular weight heparin. **Explanation:** The correct answer is **Low Molecular Weight Heparin (LMWH)**. **1. Why LMWH is the Correct Choice:** For the prophylaxis of pulmonary thromboembolism (PTE) and Deep Vein Thrombosis (DVT), LMWHs (e.g., Enoxaparin, Dalteparin) are preferred over Unfractionated Heparin (UFH). This is due to their **superior pharmacokinetic profile**: * **Higher Bioavailability:** Better absorption after subcutaneous injection. * **Longer Half-life:** Allows for once or twice-daily dosing. * **Predictable Response:** Eliminates the need for routine laboratory monitoring (aPTT). * **Safety:** Lower risk of Heparin-Induced Thrombocytopenia (HIT) and osteoporosis compared to UFH. **2. Analysis of Incorrect Options:** * **A. Heparan Sulfate:** This is a naturally occurring glycosaminoglycan found on the cell surface and extracellular matrix. While it has minor anticoagulant properties, it is not used clinically as a drug for prophylaxis. * **B. Protamine Sulfate:** This is the **antidote** (chemical antagonist) used to reverse the effects of Heparin in cases of overdose. It is not an anticoagulant. * **D. Warfarin:** While used for long-term maintenance, it is not the first choice for acute prophylaxis because it has a **slow onset of action** (requires 3-5 days to achieve therapeutic effect) and carries a risk of initial skin necrosis. **High-Yield NEET-PG Pearls:** * **Mechanism:** LMWH mainly inhibits **Factor Xa** (Ratio of Xa:IIa activity is 3:1), whereas UFH inhibits both Xa and IIa (1:1). * **Monitoring:** If monitoring is required (e.g., in renal failure or pregnancy), **Anti-Factor Xa levels** are measured, not aPTT. * **Excretion:** LMWHs are primarily excreted by the **kidneys**; therefore, they must be used with caution or dose-adjusted in patients with renal impairment.

Q: A 60-year-old man with unstable angina is treated with an intravenously administered glycoprotein IIb-IIIa inhibitor. What is the mechanism of action of this agent?

Inhibit platelet aggregation.. ### Explanation **Mechanism of Action: Inhibition of Platelet Aggregation** Glycoprotein (GP) IIb/IIIa inhibitors (e.g., **Abciximab, Eptifibatide, and Tirofiban**) act on the "final common pathway" of platelet activation. The GP IIb/IIIa receptor is a surface integrin that, when activated, binds to **fibrinogen** and von Willebrand factor. Fibrinogen acts as a bridge, linking multiple platelets together to form a stable plug. By blocking this receptor, these drugs prevent fibrinogen binding, thereby directly inhibiting **platelet aggregation**. **Analysis of Incorrect Options:** * **A. Dilate coronary arteries:** This is the mechanism of Nitrates or Calcium Channel Blockers, not antiplatelets. * **B. Inhibit atherogenesis:** Atherogenesis is a chronic inflammatory process involving LDL oxidation and foam cell formation. While Statins may slow this, GP IIb/IIIa inhibitors are acute-phase antithrombotics. * **C. Inhibit platelet adhesion:** Adhesion is the initial step where platelets bind to the subendothelial matrix (via GP Ib-IX-V and vWF). GP IIb/IIIa inhibitors act later in the process during the aggregation phase. **High-Yield Clinical Pearls for NEET-PG:** * **The "Final Common Pathway":** GP IIb/IIIa inhibitors are more potent than Aspirin or Clopidogrel because they block the final step of aggregation regardless of the initial stimulus (ADP, Thrombin, or TXA2). * **Abciximab:** A monoclonal antibody; it is non-competitive and has the longest biological half-life (irreversible binding). * **Eptifibatide & Tirofiban:** Small molecules; they are competitive, reversible inhibitors with shorter durations of action. * **Major Side Effect:** Bleeding and **thrombocytopenia** (especially with Abciximab). * **Clinical Use:** Primarily used in Acute Coronary Syndrome (ACS) undergoing Percutaneous Coronary Intervention (PCI).

Q: Clopidogrel inhibits platelet aggregation by:

Inhibiting ADP-mediated signaling. **Explanation:** **Clopidogrel** is a thienopyridine derivative that acts as an antiplatelet agent. Its mechanism of action involves the **irreversible inhibition of the P2Y12 receptor**, which is a subtype of the purinergic **ADP (Adenosine Diphosphate) receptor** on the platelet surface. Under normal physiological conditions, ADP binds to this receptor to activate the Gp IIb/IIIa complex, leading to platelet cross-linking via fibrinogen. By blocking ADP-mediated signaling, Clopidogrel prevents platelet activation and subsequent aggregation for the remainder of the platelet's lifespan (7–10 days). **Analysis of Incorrect Options:** * **Option A (Gp IIb/IIIa inhibitors):** These include drugs like **Abciximab, Eptifibatide, and Tirofiban**. They block the "final common pathway" of platelet aggregation. * **Option B (Phosphodiesterase inhibitors):** Drugs like **Dipyridamole and Cilostazol** work by inhibiting PDE, leading to increased intracellular cAMP, which inhibits aggregation and promotes vasodilation. * **Option D (Cyclooxygenase inhibitors):** This is the mechanism of **Aspirin**, which irreversibly inhibits COX-1, thereby preventing the synthesis of Thromboxane A2 (TXA2). **High-Yield Clinical Pearls for NEET-PG:** * **Prodrug Status:** Clopidogrel is a **prodrug** that requires activation by the hepatic cytochrome P450 enzyme, specifically **CYP2C19**. * **Drug Interaction:** Avoid concomitant use with **Omeprazole** (a PPI), as it inhibits CYP2C19, reducing the antiplatelet efficacy of Clopidogrel. * **Other P2Y12 Inhibitors:** Prasugrel (irreversible) and Ticagrelor (reversible). Ticagrelor is notable for not being a thienopyridine and not requiring metabolic activation. * **Clinical Use:** Primarily used in Dual Antiplatelet Therapy (DAPT) following Coronary Stent implantation and for secondary prevention of Stroke/MI.

Q: What is the dose of streptokinase to be used in myocardial infarction (MI)?

1.5 Million units. **Explanation:** **1. Understanding the Correct Answer (B):** Streptokinase is a first-generation fibrinolytic agent derived from Beta-hemolytic Streptococci. In the management of ST-elevation myocardial infarction (STEMI), the standard therapeutic dose is **1.5 Million Units (MU)**. This dose is administered via intravenous infusion over 30 to 60 minutes. The goal is to activate plasminogen into plasmin, which degrades the fibrin mesh of the coronary thrombus, thereby restoring myocardial perfusion. **2. Analysis of Incorrect Options:** * **Option A (0.15 MU):** This dose is sub-therapeutic for systemic thrombolysis in MI. While lower doses may be used for catheter-directed thrombolysis in peripheral arterial occlusion, it is insufficient for coronary reperfusion. * **Options C & D (15 MU and 150 MU):** These doses are excessively high and would lead to catastrophic, life-threatening systemic hemorrhage. The therapeutic window for fibrinolytics is narrow, making precise dosing critical. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** It is a non-specific fibrinolytic (acts on both clot-bound and circulating plasminogen), leading to a "systemic lytic state." * **Antigenicity:** Because it is derived from bacteria, it is antigenic. It can cause **Type I hypersensitivity (anaphylaxis)**. * **Repeat Dosing:** It should **not** be repeated within 6 months to 1 year (or ever, ideally) due to the presence of neutralizing antibodies which render it ineffective and increase allergy risk. * **Side Effect:** Hypotension is a common side effect during infusion; if it occurs, the infusion rate should be slowed. * **Contraindication:** Previous streptococcal infection or prior streptokinase use within the last year.

Q: Which one of the following drugs is a parenteral direct thrombin inhibitor?

Argatroban. **Explanation:** The correct answer is **Argatroban**. **1. Why Argatroban is correct:** Direct Thrombin Inhibitors (DTIs) bind directly to thrombin (Factor IIa) and inhibit its enzymatic activity without requiring the cofactor antithrombin III. Argatroban is a synthetic L-arginine derivative that acts as a **parenteral** DTI. It is primarily used as an anticoagulant in patients with **Heparin-Induced Thrombocytopenia (HIT)** because it does not cross-react with heparin-induced antibodies. **2. Why the other options are incorrect:** * **Enoxaparin (Option A):** This is a Low Molecular Weight Heparin (LMWH). It acts **indirectly** by accelerating the activity of Antithrombin III, primarily inhibiting Factor Xa and, to a lesser extent, Factor IIa. * **Apixaban (Option B):** This is a Direct Factor Xa inhibitor (part of the DOAC class). It is administered **orally**, not parenterally. * **Dabigatran (Option C):** While Dabigatran is a Direct Thrombin Inhibitor, it is administered **orally** (it is the only oral DTI currently available). The question specifically asks for a parenteral agent. **3. NEET-PG High-Yield Pearls:** * **Parenteral DTIs:** Lepirudin, Desirudin, Bivalirudin (derived from leech saliva/hirudin), and Argatroban. * **Metabolism:** Argatroban is metabolized by the **liver** (safe in renal failure), whereas Bivalirudin and Lepirudin are cleared by the kidneys. * **Monitoring:** The effect of parenteral DTIs is monitored using **aPTT**. * **Reversal:** Idarucizumab is the specific reversal agent for Dabigatran, but there is no specific reversal agent for Argatroban.

Q: A 40-year-old male presented to the ER with bleeding diathesis and was diagnosed with Glanzmann thrombasthenia. This disorder is believed to be due to the absence of a particular platelet receptor protein. Which of the following drugs acts as an anti-platelet agent by inhibiting the same platelet receptor protein?

Tirofiban. **Explanation:** The core of this question lies in understanding the pathophysiology of **Glanzmann thrombasthenia** and matching it with the mechanism of action of anti-platelet drugs. **1. Why Tirofiban is Correct:** Glanzmann thrombasthenia is a rare autosomal recessive bleeding disorder characterized by a deficiency or dysfunction of the **Glycoprotein IIb/IIIa (GPIIb/IIIa)** receptor on the platelet surface. This receptor is essential for platelet aggregation as it binds to fibrinogen, forming "bridges" between platelets. **Tirofiban** (along with Abciximab and Eptifibatide) is a specific **GPIIb/IIIa receptor antagonist**. By inhibiting this receptor, it prevents the final common pathway of platelet aggregation, mimicking the defect seen in Glanzmann thrombasthenia. **2. Why the Other Options are Incorrect:** * **Ticlopidine:** This is a P2Y12 receptor antagonist (Thienopyridine). It prevents platelet activation by inhibiting the ADP pathway, not the GPIIb/IIIa receptor. * **Cilostazol:** This is a Phosphodiesterase-3 (PDE3) inhibitor. It increases cAMP levels in platelets and blood vessels, leading to vasodilation and inhibition of aggregation. It is primarily used in intermittent claudication. * **Dipyridamole:** This acts by inhibiting phosphodiesterase and adenosine uptake. It is often used in combination with Aspirin for stroke prevention. **Clinical Pearls for NEET-PG:** * **Bernard-Soulier Syndrome:** Characterized by a deficiency of **GPIb-IX-V** (the receptor for von Willebrand factor), leading to defective platelet **adhesion**. * **Final Common Pathway:** GPIIb/IIIa inhibitors are the most potent anti-platelet agents because they block the final step of aggregation regardless of the initial stimulus (ADP, Thromboxane A2, or Collagen). * **Abciximab:** A monoclonal antibody against GPIIb/IIIa; unlike Tirofiban, its binding is non-competitive and irreversible.

Q: A 54-year-old bed-bound woman in a nursing home developed swelling of her left leg. Doppler ultrasound confirmed deep vein thrombosis. Which chemical should be administered to prevent the clot from enlarging?

Heparin. **Explanation:** The clinical presentation of a bed-bound patient with unilateral leg swelling and a positive Doppler ultrasound is diagnostic of **Deep Vein Thrombosis (DVT)**. The primary goal in managing acute DVT is to prevent the extension of the thrombus and the occurrence of pulmonary embolism. **Why Heparin is correct:** Heparin is a rapid-acting parenteral anticoagulant. It works by binding to **Antithrombin III (AT-III)**, inducing a conformational change that accelerates the inactivation of thrombin (Factor IIa) and Factor Xa. By inhibiting these key proteases in the coagulation cascade, heparin prevents the conversion of fibrinogen to fibrin, thereby stopping the clot from enlarging. It is the drug of choice for the immediate anticoagulation of DVT. **Why the other options are incorrect:** * **Digitalis & Ouabain:** These are cardiac glycosides used to treat heart failure and certain arrhythmias (like atrial fibrillation). They inhibit the Na+/K+-ATPase pump and have no effect on the coagulation cascade. * **Heparan sulfate:** While structurally related to heparin, heparan sulfate is a glycosaminoglycan found naturally on the surface of endothelial cells and in the extracellular matrix. It has much weaker anticoagulant activity compared to pharmacological heparin and is not used as a therapeutic agent for DVT. **High-Yield NEET-PG Pearls:** * **Antidote:** The specific antagonist for heparin overdose is **Protamine sulfate** (1 mg neutralizes ~100 units of heparin). * **Monitoring:** Unfractionated Heparin (UFH) is monitored using **aPTT** (activated Partial Thromboplastin Time). * **Side Effect:** Watch for **Heparin-Induced Thrombocytopenia (HIT)**, caused by antibodies against the Heparin-Platelet Factor 4 complex. * **LMWH:** Low Molecular Weight Heparins (e.g., Enoxaparin) primarily inhibit Factor Xa and do not require routine lab monitoring.

Q: What is the recommended dose of streptokinase for fibrinolysis in myocardial infarction?

1.5 million units. **Explanation:** **Streptokinase** is a first-generation fibrinolytic agent derived from Beta-hemolytic Streptococci. In the management of ST-elevation myocardial infarction (STEMI), the standard recommended dose is **1.5 million units (MU)**. **Why 1.5 million units is correct:** This dose is administered via **intravenous infusion** over **30 to 60 minutes**. Clinical trials (such as GISSI-1 and ISIS-2) established that 1.5 MU provides the optimal balance between achieving coronary artery patency (reperfusion) and minimizing the risk of major systemic bleeding. It works by forming a complex with plasminogen, which then converts free plasminogen into active plasmin to degrade fibrin clots. **Why other options are incorrect:** * **0.5 and 1.0 million units:** These doses are sub-therapeutic for systemic fibrinolysis in MI and are associated with lower rates of successful reperfusion. * **2.0 million units:** Higher doses do not significantly increase the efficacy of clot lysis but drastically increase the risk of life-threatening hemorrhagic complications, such as intracranial hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** It is a **non-fibrin-specific** agent, meaning it causes systemic depletion of fibrinogen (unlike Alteplase). * **Antigenicity:** Because it is a bacterial protein, it is highly antigenic. It can cause **Type I hypersensitivity (anaphylaxis)**. * **Repeat Dosing:** It should **not** be repeated within 6 months to 1 year (or ever, ideally) due to the presence of neutralizing antibodies which render it ineffective and increase allergy risk. * **Side Effect:** Hypotension is a common side effect during infusion.

Question 1

Neutropenia develops in a patient undergoing cancer chemotherapy. Administration of which one of the following agents would accelerate recovery of neutrophil counts?

Accepted Answer

Filgrastim

Answer

Leucovorin

Answer

Prednisone

Answer

Vitamin B12

Question 2

Which of the following drugs may cause thrombocytopenia?

Accepted Answer

Ticlopidine

Answer

Clopidogrel

Answer

Abciximab

Answer

Aspirin

Question 3

What is the anticoagulant of choice for prophylaxis of pulmonary thromboembolism?

Accepted Answer

Low molecular weight heparin

Answer

Heparan sulfate

Answer

Protamine sulfate

Answer

Warfarin

Question 4

A 60-year-old man with unstable angina is treated with an intravenously administered glycoprotein IIb-IIIa inhibitor. What is the mechanism of action of this agent?

Accepted Answer

Inhibit platelet aggregation.

Answer

Dilate coronary arteries.

Answer

Inhibit atherogenesis.

Answer

Inhibit platelet adhesion.

Question 5

Clopidogrel inhibits platelet aggregation by:

Accepted Answer

Inhibiting ADP-mediated signaling

Answer

Inhibiting the gp IIb/IIIa receptor

Answer

Inhibiting phosphodiesterase

Answer

Inhibiting cyclooxygenase

Question 6

What is the dose of streptokinase to be used in myocardial infarction (MI)?

Accepted Answer

1.5 Million units

Answer

0.15 Million units

Answer

15 Million units

Answer

150 Million units

Question 7

Which one of the following drugs is a parenteral direct thrombin inhibitor?

Accepted Answer

Argatroban

Answer

Enoxaparin

Answer

Apixaban

Answer

Dabigatran

Question 8

A 40-year-old male presented to the ER with bleeding diathesis and was diagnosed with Glanzmann thrombasthenia. This disorder is believed to be due to the absence of a particular platelet receptor protein. Which of the following drugs acts as an anti-platelet agent by inhibiting the same platelet receptor protein?

Accepted Answer

Tirofiban

Answer

Ticlopidine

Answer

Cilostazol

Answer

Dipyridamole

Question 9

A 54-year-old bed-bound woman in a nursing home developed swelling of her left leg. Doppler ultrasound confirmed deep vein thrombosis. Which chemical should be administered to prevent the clot from enlarging?

Accepted Answer

Heparin

Answer

Digitalis

Answer

Ouabain

Answer

Heparan sulfate

Question 10

What is the recommended dose of streptokinase for fibrinolysis in myocardial infarction?

Accepted Answer

1.5 million units

Answer

0.5 million units

Answer

1.0 million units

Answer

2.0 million units

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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