Drugs Affecting Blood and Blood Formation Practice Questions

Q: What is the mechanism of action of dipyridamole?

Adenosine reuptake inhibition. **Explanation:** Dipyridamole is a pyrimidine derivative that acts as a coronary vasodilator and an antiplatelet agent. **1. Why Option A is Correct:** The primary mechanism of dipyridamole involves the **inhibition of adenosine uptake** by erythrocytes and vascular endothelial cells. This leads to increased local concentrations of extracellular adenosine, which acts on $A_2$ receptors to stimulate adenylate cyclase, increasing intracellular **cAMP** levels. Elevated cAMP inhibits platelet aggregation and causes vasodilation. Additionally, dipyridamole directly inhibits **phosphodiesterase (PDE3 and PDE5)**, further preventing the breakdown of cAMP and cGMP. **2. Why Other Options are Incorrect:** * **Option B:** Dipyridamole **decreases** (inhibits) phosphodiesterase activity rather than increasing it. Increasing PDE activity would lead to lower cAMP levels and promote platelet aggregation. * **Option C:** Inhibition of cyclooxygenase (COX) is the mechanism of action for **Aspirin** and other NSAIDs, not dipyridamole. **3. Clinical Pearls for NEET-PG:** * **Coronary Steal Phenomenon:** Dipyridamole dilates healthy coronary arteries more than stenosed ones. This can divert blood flow away from ischemic areas, potentially worsening angina. * **Diagnostic Use:** Due to its vasodilatory properties, it is used in **pharmacological stress testing** (Thallium imaging) for patients unable to exercise. * **Therapeutic Use:** It is often combined with low-dose aspirin (Aggrenox) for **secondary stroke prevention** or used with warfarin for prophylaxis of thromboembolism in patients with **prosthetic heart valves**. * **Side Effects:** Headache (most common due to vasodilation) and dizziness.

Q: Which of the following anticoagulants is indicated for atrial fibrillation in a patient with a prior history of stroke, with a reduced risk of hemorrhage?

Apixaban. **Explanation:** **Apixaban** is the correct answer because it belongs to the class of **Direct Oral Anticoagulants (DOACs)**, specifically a direct **Factor Xa inhibitor**. In the landmark ARISTOTLE trial, Apixaban was found to be superior to Warfarin in preventing stroke and systemic embolism in patients with non-valvular atrial fibrillation (AF), while significantly reducing the risk of major bleeding (especially intracranial hemorrhage). This makes it a preferred choice for secondary stroke prevention in AF patients. **Analysis of Incorrect Options:** * **Vitamin K Antagonists (e.g., Warfarin):** While effective for stroke prevention in AF, they have a narrow therapeutic index, require frequent INR monitoring, and carry a higher risk of life-threatening hemorrhagic complications compared to DOACs like Apixaban. * **Clopidogrel & Ticlopidine:** These are **antiplatelet agents** (P2Y12 inhibitors). While they are used in coronary artery disease and certain stroke subtypes, they are significantly less effective than anticoagulants for preventing cardioembolic strokes caused by atrial fibrillation. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Apixaban and Rivaroxaban inhibit Factor Xa; Dabigatran is a direct thrombin (Factor IIa) inhibitor. * **Reversal Agent:** The specific reversal agent for Apixaban and Rivaroxaban is **Andexanet alfa**. For Dabigatran, it is **Idarucizumab**. * **Contraindication:** DOACs are generally avoided in patients with **valvular AF** (moderate-to-severe mitral stenosis or mechanical heart valves); Warfarin remains the drug of choice in these cases. * **Renal Dosing:** Apixaban is the DOAC least dependent on renal clearance, making it safer in mild-to-moderate chronic kidney disease.

Q: Which of the following is an indication for intramuscular iron therapy?

Oral deferiprone. **Explanation:** The question pertains to **Iron Chelating Agents** used in the management of chronic iron overload (e.g., in Thalassemia Major patients receiving multiple blood transfusions). **Why Option B is Correct:** **Deferiprone** is an orally active iron chelator. It is specifically indicated for treating iron overload when current chelation therapy is inadequate. Its primary advantage is its ability to remove iron from the heart, making it highly effective in preventing iron-induced cardiotoxicity. **Analysis of Incorrect Options:** * **A. Oral Desferrioxamine:** Desferrioxamine is **not** orally active. It has poor gastrointestinal absorption and must be administered via slow subcutaneous or intravenous infusion. * **C. Intramuscular EDTA:** Calcium disodium EDTA is primarily used for **Lead poisoning**, not iron toxicity. While it is administered parenterally, it is not the treatment of choice for iron overload. * **D. Oral Succimer:** Succimer (DMSA) is an oral chelating agent used primarily for **Lead, Mercury, and Arsenic** poisoning in children. It does not have a role in iron chelation. **High-Yield NEET-PG Pearls:** * **Deferasirox:** Currently the most commonly used **oral** iron chelator due to its once-daily dosing and better safety profile compared to Deferiprone. * **Adverse Effects:** * *Deferiprone:* Most serious side effect is **Agranulocytosis** (requires weekly CBC monitoring). * *Desferrioxamine:* Can cause ototoxicity and retinal toxicity. * **Acute Iron Poisoning:** The drug of choice is **Intravenous Desferrioxamine**. Oral chelators are used for *chronic* overload.

Q: Platelet aggregation is blocked by aspirin due to its action on which of the following?

Thromboxane A2. **Explanation:** **Mechanism of Action:** Aspirin (Acetylsalicylic acid) acts by **irreversibly inhibiting the enzyme Cyclooxygenase-1 (COX-1)**. In platelets, this inhibition prevents the conversion of arachidonic acid into **Thromboxane A2 (TXA2)**. TXA2 is a potent vasoconstrictor and a key mediator that promotes platelet aggregation and degranulation. Since platelets are anucleated and cannot synthesize new enzymes, the inhibitory effect of aspirin lasts for the entire lifespan of the platelet (approx. 7–10 days). **Analysis of Incorrect Options:** * **Option A (Prostacyclin/PGI2):** Produced by vascular endothelial cells, PGI2 inhibits platelet aggregation. While high-dose aspirin can inhibit PGI2, the low-dose antiplatelet effect specifically targets TXA2 to favor an anti-thrombotic state. * **Option B (Prostaglandin F2 alpha):** This prostaglandin is primarily involved in uterine contraction and bronchoconstriction; it does not play a primary role in platelet aggregation. * **Option D (Phospholipase C):** This is an enzyme involved in the second messenger system (IP3/DAG pathway). Aspirin does not act on this enzyme; it acts downstream on the COX pathway. **NEET-PG High-Yield Pearls:** * **Low-dose Aspirin (75–150 mg):** Exhibits "selective" antiplatelet action by inhibiting TXA2 without significantly suppressing endothelial PGI2. * **Secondary Prevention:** Aspirin is the drug of choice for secondary prophylaxis of Myocardial Infarction (MI) and Ischemic Stroke. * **Platelet Turnover:** Surgery is usually delayed for 7 days after stopping aspirin to allow for the generation of new, functional platelets. * **Other Antiplatelets:** Note that Clopidogrel/Prasugrel act on **P2Y12 (ADP) receptors**, while Abciximab acts on **GP IIb/IIIa receptors**.

Q: All of the following statements about Heparin are true, except:

Causes Hypokalemia. **Explanation:** The correct answer is **D (Causes Hypokalemia)** because Heparin actually causes **Hyperkalemia**, not hypokalemia. **Mechanism of Hyperkalemia:** Heparin inhibits the synthesis of **Aldosterone** in the adrenal cortex (by reducing the number and affinity of angiotensin II receptors in the zona glomerulosa). Since aldosterone is responsible for sodium reabsorption and potassium excretion, its suppression leads to potassium retention, resulting in hyperkalemia. This effect can occur even with low-dose prophylactic heparin. **Analysis of Other Options:** * **A. Causes Alopecia:** True. Transient alopecia (hair loss) is a documented, though less common, side effect of heparin therapy, typically occurring 1–4 months after starting treatment. * **B. Non-Teratogenic:** True. Heparin is a large, polar polysaccharide molecule that **does not cross the placenta**. Therefore, it is the anticoagulant of choice during pregnancy (unlike Warfarin, which is teratogenic). * **C. Releases Lipoprotein Lipase:** True. Heparin clears lipemic plasma by releasing the enzyme lipoprotein lipase from the vascular endothelium into the circulation. This enzyme breaks down triglycerides into free fatty acids. **NEET-PG High-Yield Pearls:** * **Antidote:** Protamine Sulfate (1 mg neutralizes 100 units of heparin). * **Monitoring:** aPTT (Activated Partial Thromboplastin Time). * **Most Common Side Effect:** Bleeding/Hemorrhage. * **Serious Immune Side Effect:** Heparin-Induced Thrombocytopenia (HIT), caused by antibodies against the Heparin-Platelet Factor 4 (PF4) complex. * **Long-term Use:** Can lead to **Osteoporosis**.

Q: Heparin is the commonly used anticoagulant in cardiac surgery. Which of the following statements about heparin is FALSE?

It is the weakest acid found in living things.. ### Explanation **1. Why Option A is the Correct (False) Statement:** Heparin is actually the **strongest organic acid** found in the human body, not the weakest. It is a highly sulfated glycosaminoglycan with a high negative charge density [1]. This strong acidity is fundamental to its pharmacological action, as it allows heparin to bind to various proteins and enzymes [1]. **2. Analysis of Incorrect Options (True Statements):** * **Option B:** Historically, heparin was obtained from beef lungs, but modern commercial preparations primarily utilize **porcine (pig) intestinal mucosa** due to higher yield and lower risk of prion diseases [4]. * **Option C:** Heparin acts as an indirect anticoagulant. It binds to **Antithrombin III (AT-III)**, inducing a conformational change that accelerates the inactivation of Factor Xa and Thrombin (Factor IIa) by 1,000 to 10,000 times [1], [3]. * **Option D:** **Heparin-Induced Thrombocytopenia (HIT)** is a significant side effect [4]. Type II HIT is an immune-mediated reaction where antibodies form against the Heparin-Platelet Factor 4 (PF4) complex, leading to paradoxically increased risk of thrombosis despite low platelet counts. **3. High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** Protamine sulfate (a strong base) neutralizes heparin (a strong acid) via chemical antagonism [2]. * **Monitoring:** The effect of Unfractionated Heparin (UFH) is monitored using **aPTT** (Target: 1.5–2.5 times the control). * **Drug of Choice:** Heparin is the anticoagulant of choice during **pregnancy** (it does not cross the placenta) and in **cardiac bypass surgery** (due to its rapid onset and reversibility) [2]. * **LMWH vs. UFH:** Low Molecular Weight Heparin (e.g., Enoxaparin) mainly inhibits Factor Xa and does not require routine aPTT monitoring [5].

Q: Gp2b3A inhibitors are all except?

Prasugrel. **Explanation:** The Glycoprotein (GP) IIb/IIIa inhibitors are a class of antiplatelet drugs that block the "final common pathway" of platelet aggregation. They prevent the binding of fibrinogen and von Willebrand factor to the GP IIb/IIIa receptor on the platelet surface, thereby inhibiting cross-linking between platelets. **Why Prasugrel is the correct answer:** Prasugrel is **not** a GP IIb/IIIa inhibitor. It belongs to the **P2Y12 receptor antagonists** (Thienopyridines) class. It works by irreversibly inhibiting the ADP receptor on platelets, preventing the subsequent activation of the GP IIb/IIIa complex. Other drugs in this class include Clopidogrel and Ticlopidine. **Analysis of incorrect options:** * **Abciximab:** A chimeric monoclonal antibody that binds irreversibly to the GP IIb/IIIa receptor. It has the longest biological half-life among the three. * **Eptifibatide:** A synthetic cyclic peptide that acts as a reversible antagonist at the GP IIb/IIIa receptor. It is derived from rattlesnake venom. * **Tirofiban:** A non-peptide, small-molecule reversible antagonist of the GP IIb/IIIa receptor. **High-Yield NEET-PG Pearls:** * **Route of Administration:** All GP IIb/IIIa inhibitors (Abciximab, Eptifibatide, Tirofiban) are administered **intravenously**, whereas P2Y12 inhibitors like Prasugrel are administered **orally**. * **Clinical Use:** Primarily used in Acute Coronary Syndrome (ACS) and during Percutaneous Coronary Intervention (PCI). * **Side Effect:** The most significant side effect of GP IIb/IIIa inhibitors is bleeding and **thrombocytopenia**. * **Prasugrel Contraindication:** It is strictly contraindicated in patients with a prior history of **Stroke or TIA** due to a high risk of intracranial hemorrhage.

Q: What is the mechanism of action of dicumarol?

Inhibits vitamin K dependant Clotting factors. Inhibits vitamin K dependant Clotting factors- Dicumarol, a classic anticoagulant, acts as a **vitamin K antagonist** (VKA), preventing the utilization of vitamin K [1].- It inhibits the enzyme **vitamin K epoxide reductase**, which is essential for the activation (**gamma-carboxylation**) of factors II (prothrombin), VII, IX, and X [4]. *Activates antithrombin III.*- This mechanism is characteristic of **unfractionated heparin** and **low molecular weight heparins** (LMWH).- Heparin binds to **antithrombin III** (ATIII), greatly accelerating its ability to neutralize activated clotting factors, particularly Thrombin (IIa) and Factor Xa [2]. *Inhibits tissue plasminogen activator*- Dicumarol affects the synthesis of clotting factors and has no direct influence on the **fibrinolytic system** (clot breakdown).- Inhibition of **tissue plasminogen activator** (tPA) or plasmin is the role of anti-fibrinolytic drugs like **tranexamic acid**. *Inhibitor of factor Xa*- This is the specific mechanism utilized by the direct oral anticoagulants (DOACs), such as **rivaroxaban** and **apixaban** (referred to as 'xabans') [3].- While dicumarol ultimately reduces active **Factor X** levels, it acts indirectly by preventing its synthesis/activation, not by directly binding to and inhibiting the already formed Factor Xa.

Q: A patient on anti-cancer therapy developed an infection. Blood analysis revealed neutropenia. Which of the following drugs is likely to be effective in this patient?

Filgrastim. ***Filgrastim***- It is a recombinant form of **granulocyte colony-stimulating factor (G-CSF)**, which stimulates the proliferation and differentiation of neutrophil precursors in the bone marrow.- It is the standard treatment for **chemotherapy-induced neutropenia** (as seen in patients on anti-cancer therapy) to raise neutrophil counts and reduce infection risk.*Romiplostim*- This drug is a **thrombopoietin (TPO) receptor agonist** used to stimulate platelet production.- It is indicated for conditions like **immune thrombocytopenia** and would not be effective in stimulating neutrophil recovery in neutropenia.*Oprelvekin*- It is a recombinant form of **interleukin-11 (IL-11)**, indicated specifically for the prevention of severe **thrombocytopenia** following myelosuppressive chemotherapy.- While it has some broad hematopoietic effects, its primary clinical use is platelet restoration, making it ineffective for acute **neutropenia** in this context.*Epoetin alfa*- This drug is a recombinant form of **erythropoietin (EPO)**, primarily used to stimulate red blood cell production to treat **anemia**.- It specifically targets the erythroid lineage and has no clinical utility in increasing **neutrophil** counts.

Question 1

What is the mechanism of action of dipyridamole?

Accepted Answer

Adenosine reuptake inhibition

Answer

Increases phosphodiesterase activity

Answer

Inhibits cyclooxygenase

Answer

None of the above

Question 2

Which of the following anticoagulants is indicated for atrial fibrillation in a patient with a prior history of stroke, with a reduced risk of hemorrhage?

Accepted Answer

Apixaban

Answer

Vitamin K antagonists

Answer

Clopidogrel

Answer

Ticlopidine

Question 3

Which of the following is an indication for intramuscular iron therapy?

Accepted Answer

Oral deferiprone

Answer

Oral desferrioxamine

Answer

Intramuscular EDTA

Answer

Oral succimer

Question 4

If a fibrinolytic drug is used for the treatment of acute myocardial infarction, what is the most likely adverse effect to occur?

Accepted Answer

Hemorrhagic stroke

Answer

Acute renal failure

Answer

Development of antiplatelet antibodies

Answer

Encephalitis secondary to liver dysfunction

Question 5

Platelet aggregation is blocked by aspirin due to its action on which of the following?

Accepted Answer

Thromboxane A2

Answer

Prostacyclin

Answer

Prostaglandin F2 alpha

Answer

Phospholipase C

Question 6

All of the following statements about Heparin are true, except:

Accepted Answer

Causes Hypokalemia

Answer

Causes Alopecia

Answer

Non Teratogenic

Answer

Releases Lipoprotein Lipase

Question 7

Heparin is the commonly used anticoagulant in cardiac surgery. Which of the following statements about heparin is FALSE?

Accepted Answer

It is the weakest acid found in living things.

Answer

Most commercial preparations of heparin now utilize pig intestinal mucosa.

Answer

It acts via Antithrombin activation.

Answer

It can produce thrombocytopenia.

Question 8

Gp2b3A inhibitors are all except?

Accepted Answer

Prasugrel

Answer

Abciximab

Answer

Eptifibatide

Answer

Tirofiban

Question 9

What is the mechanism of action of dicumarol?

Accepted Answer

Inhibits vitamin K dependant Clotting factors

Answer

Inhibitor of factor Xa

Answer

Activates antithrombin III.

Answer

Inhibits tissue plasminogen activator

Question 10

A patient on anti-cancer therapy developed an infection. Blood analysis revealed neutropenia. Which of the following drugs is likely to be effective in this patient?

Accepted Answer

Filgrastim

Answer

Epoetin alfa

Answer

Oprelvekin

Answer

Romiplostim

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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