Drugs Affecting Blood and Blood Formation Practice Questions

Q: Low doses of aspirin prolong bleeding time by selectively inhibiting synthesis of the following mediator in the platelets?

Thromboxane A2. ### Explanation **Correct Option: A. Thromboxane A2 (TXA2)** Aspirin (Acetylsalicylic acid) acts by **irreversibly inhibiting the enzyme Cyclooxygenase-1 (COX-1)** via acetylation of a serine residue. In platelets, COX-1 is responsible for converting arachidonic acid into **Thromboxane A2 (TXA2)**, a potent vasoconstrictor and platelet aggregator. * **Mechanism of Selectivity:** Platelets are anuclear and cannot synthesize new enzymes. Therefore, a low dose of aspirin (75–150 mg) permanently disables COX-1 for the entire lifespan of the platelet (8–11 days), leading to a prolonged bleeding time. **Incorrect Options:** * **B. 5-Hydroxytryptamine (Serotonin):** While released from platelet dense granules during activation to promote aggregation, its synthesis is not the primary target of aspirin. * **C. Platelet Activating Factor (PAF):** This is a phospholipid mediator of inflammation and aggregation; its pathway is independent of the COX-1 enzyme inhibited by aspirin. * **D. Prostacyclin (PGI2):** PGI2 is a vasodilator and anti-aggregatory mediator produced by **vascular endothelial cells**. Unlike platelets, endothelial cells have nuclei and can regenerate COX enzymes. Low-dose aspirin spares PGI2 production while inhibiting TXA2, maintaining a favorable antithrombotic balance. **High-Yield Clinical Pearls for NEET-PG:** * **Irreversibility:** Aspirin is the only NSAID that binds irreversibly to COX. * **Bleeding Time (BT) vs. Clotting Time (CT):** Aspirin increases BT (platelet function) but has no effect on CT (coagulation cascade). * **Primary Prevention:** Low-dose aspirin is used for prophylaxis in Ischemic Heart Disease (IHD) and Stroke. * **Aspirin Resistance:** Can occur in patients with high platelet turnover.

Q: Abciximab is:

An antibody against Ilb/Illa receptors. **Explanation:** **Abciximab** is a potent antiplatelet agent classified as a **Glycoprotein (GP) IIb/IIIa receptor antagonist**. It is a chimeric monoclonal antibody (Fab fragment) that binds irreversibly to the GP IIb/IIIa receptors on the surface of activated platelets. Since these receptors are the "final common pathway" for platelet aggregation—serving as the binding site for fibrinogen and von Willebrand factor to cross-link platelets—blocking them effectively prevents thrombus formation regardless of the initial stimulus (ADP, Thromboxane A2, or Collagen). **Analysis of Options:** * **Option A (Correct):** Abciximab is a monoclonal antibody specifically targeting the GP IIb/IIIa receptor. * **Option B (Incorrect):** GP Ib/IX is the receptor for von Willebrand factor involved in platelet *adhesion* to the subendothelium, not the target of Abciximab. * **Option C (Incorrect):** Topoisomerase inhibitors (e.g., Etoposide, Irinotecan) are cytotoxic chemotherapy agents used in cancer treatment, not antiplatelets. * **Option D (Incorrect):** Adenosine inhibitors are not a standard class for this context; however, Dipyridamole is an adenosine *reuptake* inhibitor used as an antiplatelet. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Administered only via **Intravenous (IV)** route. * **Clinical Use:** Primarily used in patients undergoing **Percutaneous Coronary Intervention (PCI)** to prevent ischemic complications. * **Other GP IIb/IIIa Inhibitors:** **Eptifibatide** (a cyclic peptide) and **Tirofiban** (a non-peptide small molecule). Unlike Abciximab, these are reversible inhibitors. * **Side Effects:** The most significant risk is **bleeding** and **thrombocytopenia**. * **Monitoring:** Platelet counts should be monitored closely after administration.

Q: Ferrous sulfate is a hydrated salt containing what percentage of Iron?

20%. **Explanation:** The correct answer is **20% (Option A)**. In pharmacology, it is crucial to distinguish between the total weight of an iron salt and its **elemental iron** content, as the latter determines the therapeutic efficacy and potential toxicity. **1. Why 20% is correct:** Ferrous sulfate is commonly administered as the hydrated salt ($FeSO_4 \cdot 7H_2O$) or the dried salt. The standard hydrated form contains approximately **20% elemental iron** by weight. For example, a standard 300 mg tablet of ferrous sulfate provides roughly 60 mg of elemental iron ($300 \times 0.20 = 60$). This is the "gold standard" for oral iron therapy due to its high bioavailability and low cost. **2. Why other options are incorrect:** * **Options B, C, and D:** These percentages do not correspond to Ferrous sulfate. However, they may be confused with other iron salts. For instance, **Ferrous fumarate** contains about **33%** elemental iron (closest to Option C/D), while **Ferrous gluconate** contains only **12%**. **High-Yield Clinical Pearls for NEET-PG:** * **Elemental Iron Content:** Remember the "Rule of Iron Salts": * Ferrous Gluconate: 12% * Ferrous Sulfate: 20% * Ferrous Fumarate: 33% (Highest among common oral salts). * **Absorption:** Oral iron is best absorbed in the **ferrous ($Fe^{2+}$)** state and in an **acidic medium**. Vitamin C (Ascorbic acid) enhances absorption, while antacids, tea, and tetracyclines inhibit it. * **Side Effects:** Epigastric pain, constipation, and black stools (must be differentiated from melena). * **Treatment Duration:** In Iron Deficiency Anemia, treatment should continue for **3–6 months** after hemoglobin normalizes to replenish depleted iron stores (ferritin).

Q: Which of the following drugs is not used for thromboprophylaxis?

Antithrombin III. **Explanation:** The core concept in this question is distinguishing between **antithrombotic agents** (used for prophylaxis) and **replacement therapies** (used for deficiency states). **Why Antithrombin III is the correct answer:** Antithrombin III (ATIII) is a natural endogenous anticoagulant that inactivates thrombin and Factor Xa. While it is used as a **replacement therapy** in patients with hereditary ATIII deficiency (especially during surgery or childbirth) to prevent clots, it is **not** used as a standard pharmacological agent for routine thromboprophylaxis in the general population. Its clinical use is highly specific and restricted to correcting a deficiency rather than actively inhibiting the coagulation cascade in a normal individual. **Analysis of Incorrect Options:** * **Heparin (Unfractionated & LMWH):** The gold standard for parenteral thromboprophylaxis. It acts by accelerating the activity of ATIII, primarily inhibiting Factor Xa and Thrombin. * **Warfarin:** The most common oral anticoagulant used for long-term thromboprophylaxis, especially in patients with atrial fibrillation or prosthetic heart valves. It inhibits Vitamin K Epoxide Reductase (VKOR). * **Aspirin:** An antiplatelet drug used for arterial thromboprophylaxis to prevent myocardial infarction and stroke by irreversibly inhibiting COX-1. **NEET-PG High-Yield Pearls:** * **Heparin Resistance:** If a patient does not respond to heparin (activated partial thromboplastin time - aPTT does not prolong), suspect **Antithrombin III deficiency**. * **LMWH vs. Heparin:** LMWH (e.g., Enoxaparin) is preferred for prophylaxis due to a longer half-life, more predictable response, and lower risk of Heparin-Induced Thrombocytopenia (HIT). * **Bridge Therapy:** Warfarin requires "bridging" with Heparin initially because it induces a transient prothrombotic state by depleting Protein C and S before affecting clotting factors.

Q: What is the mode of action of warfarin?

Vitamin K antagonist. **Explanation:** **Mechanism of Action:** Warfarin is a **Vitamin K Antagonist (VKA)**. It acts by inhibiting the enzyme **Vitamin K Epoxide Reductase (VKORC1)**. This enzyme is responsible for converting inactive vitamin K epoxide back into its active form (hydroquinone). Active vitamin K is a necessary cofactor for the **gamma-carboxylation** of glutamate residues on certain clotting factors. Without this post-translational modification, **Factors II, VII, IX, and X**, as well as **Proteins C and S**, remain inactive (PIVKA—Proteins Induced by Vitamin K Absence). **Analysis of Incorrect Options:** * **Option A (Factor Xa inhibitor):** This describes the mechanism of Direct Oral Anticoagulants (DOACs) like **Rivaroxaban** and **Apixaban**, or indirect inhibitors like Fondaparinux. * **Option C (Activates antithrombin III):** This is the mechanism of **Heparin** and Low Molecular Weight Heparins (LMWH). They bind to antithrombin III, accelerating its inactivation of Thrombin (IIa) and Factor Xa. * **Option D (Activates factor IX):** This is incorrect; anticoagulants aim to inhibit, not activate, clotting factors. **NEET-PG High-Yield Pearls:** * **Monitoring:** Warfarin therapy is monitored using **PT/INR** (Prothrombin Time/International Normalized Ratio). * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes **Fetal Warfarin Syndrome**—chondrodysplasia punctata); LMWH is the drug of choice. * **Skin Necrosis:** Occurs due to the rapid depletion of Protein C (short half-life) causing a transient hypercoagulable state. This is why "Heparin bridging" is required. * **Antidote:** For immediate reversal, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergency reversal, use **Vitamin K1 (Phytonadione)**.

Q: Ticlopidine is which of the following types of drugs?

Antiplatelet drug. **Explanation:** **Ticlopidine** is a first-generation **P2Y12 receptor antagonist**, belonging to the thienopyridine class of **antiplatelet drugs**. Its primary mechanism involves the irreversible inhibition of the P2Y12 subtype of ADP receptors on the platelet surface. This prevents the activation of the GPIIb/IIIa receptor complex, thereby inhibiting platelet aggregation and thrombus formation. **Analysis of Options:** * **Option A (Correct):** Ticlopidine inhibits ADP-induced platelet aggregation, making it a classic antiplatelet agent used to prevent thromboembolic events like stroke or MI. * **Option B (Incorrect):** Antiarrhythmic drugs (e.g., Amiodarone, Lidocaine) act on ion channels (Na+, K+, Ca2+) of the myocardium to treat rhythm disorders; they do not affect platelet function. * **Option C (Incorrect):** Anticoagulants (e.g., Heparin, Warfarin) interfere with the coagulation cascade and fibrin formation. While both prevent clots, antiplatelets specifically target platelet activation. * **Option D (Incorrect):** Antifibrinolytics (e.g., Tranexamic acid) inhibit the breakdown of fibrin to promote clotting; Ticlopidine does the opposite by preventing clot initiation. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Irreversible P2Y12 inhibition (similar to Clopidogrel and Prasugrel). * **Adverse Effects:** Ticlopidine is notorious for causing **severe neutropenia/agranulocytosis** and **Thrombotic Thrombocytopenic Purpura (TTP)**. Due to these hematological toxicities, it has largely been replaced by Clopidogrel in clinical practice. * **Monitoring:** If used, frequent CBC monitoring is mandatory during the first 3 months of therapy. * **Prodrug Status:** Like Clopidogrel, Ticlopidine is a prodrug requiring hepatic activation.

Q: Low molecular weight heparin therapy is associated with all of the following except:

High biological interaction to plasma proteins. ### Explanation The correct answer is **D. High biological interaction to plasma proteins.** Low Molecular Weight Heparins (LMWHs), such as Enoxaparin and Dalteparin, are derived from Unfractionated Heparin (UFH) through depolymerization. This process significantly alters their pharmacokinetic profile. **1. Why Option D is the correct (incorrect statement):** Unlike UFH, LMWHs have **low affinity for plasma proteins**, vascular endothelial cells, and macrophages. This lack of protein binding results in a highly **predictable dose-response relationship**, eliminating the need for routine laboratory monitoring (like aPTT). UFH, conversely, binds extensively to plasma proteins, leading to variable bioavailability. **2. Analysis of Incorrect Options:** * **A. Less chances of bleeding:** LMWHs have a higher ratio of Anti-Xa to Anti-IIa activity. They do not inhibit thrombin as strongly as UFH and have less effect on platelet function and vascular permeability, leading to a lower risk of major bleeding and Heparin-Induced Thrombocytopenia (HIT). * **B. Single dose per day:** LMWHs have a longer half-life (3–6 hours) compared to UFH (1–2 hours) and better subcutaneous bioavailability. This allows for convenient once or twice-daily dosing. * **C. Easy filterability by glomerular capillaries:** Due to their smaller molecular size (~5000 Da), LMWHs are primarily excreted by the kidneys. This makes them "easily filterable" but also necessitates dose adjustment or avoidance in patients with renal failure (CrCl <30 ml/min). **Clinical Pearls for NEET-PG:** * **Monitoring:** While UFH is monitored by **aPTT**, LMWH monitoring (if required, e.g., in pregnancy or obesity) is done via **Factor Xa assay**. * **Antidote:** Protamine sulfate completely neutralizes UFH but only **partially** neutralizes LMWH. * **Drug of Choice:** LMWH is the preferred anticoagulant in **pregnancy** as it does not cross the placenta.

Q: What is the target International Normalized Ratio (INR) for a patient receiving warfarin therapy?

2.5. **Explanation:** Warfarin is an oral anticoagulant that acts as a Vitamin K epoxide reductase (VKOR) inhibitor, preventing the synthesis of clotting factors II, VII, IX, and X. The intensity of warfarin therapy is monitored using the **International Normalized Ratio (INR)**, which standardizes Prothrombin Time (PT) results across different laboratories. **1. Why Option B is Correct:** For most clinical indications—including the treatment and prevention of Deep Vein Thrombosis (DVT), Pulmonary Embolism (PE), and prevention of systemic embolism in patients with Atrial Fibrillation—the recommended **therapeutic target INR is 2.5** (with a typical range of **2.0 to 3.0**). This range provides an optimal balance between preventing thromboembolic events and minimizing the risk of spontaneous hemorrhage. **2. Why Other Options are Incorrect:** * **Option A (1.5):** This is sub-therapeutic. An INR below 2.0 significantly increases the risk of clot formation and stroke. * **Option C (3.5):** While a higher target (range 2.5–3.5) is used for high-risk patients, such as those with **mechanical prosthetic heart valves**, it is not the standard target for general warfarin therapy. * **Option D (4.5):** This is supra-therapeutic. An INR above 4.0 exponentially increases the risk of major bleeding, including intracranial hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Inhibits $\gamma$-carboxylation of glutamate residues on clotting factors. * **Antidote:** For immediate reversal, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergency reversal, use **Vitamin K1 (Phytonadione)**. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes Fetal Warfarin Syndrome); **Heparin** is the anticoagulant of choice for pregnant women. * **Skin Necrosis:** Occurs due to a rapid decline in Protein C levels; prevented by "bridging" with Heparin.

Q: Which of the following statements about erythropoietin is FALSE?

It results in a decrease in reticulocyte count. ### Explanation **Why Option B is the Correct (False) Statement:** Erythropoietin (EPO) is a glycoprotein hormone that stimulates the proliferation and differentiation of red blood cell precursors in the bone marrow. When administered, it triggers the release of immature red blood cells, known as **reticulocytes**, into the bloodstream. Therefore, a successful response to EPO therapy is characterized by an **increase in reticulocyte count** (usually within 7–10 days), not a decrease. A rising reticulocyte count is the earliest indicator of the drug's efficacy. **Analysis of Incorrect Options:** * **Option A:** Chronic Renal Failure (CRF) leads to a deficiency of endogenous erythropoietin because the peritubular interstitial cells of the kidney are damaged. Recombinant human erythropoietin (Epoetin alfa) is the **standard of care** for anemia in CRF. * **Option C:** By stimulating the body’s own production of RBCs, EPO increases hemoglobin levels, thereby significantly **reducing the need for repeated blood transfusions** and minimizing risks like iron overload or transfusion-transmitted infections. * **Option D:** **Hypertension** is the most common and serious side effect of EPO therapy. It is thought to occur due to a rapid increase in red cell mass and peripheral vascular resistance. **NEET-PG High-Yield Pearls:** * **Target Hemoglobin:** In CRF patients, EPO should be titrated to maintain Hb between **10–12 g/dL**. Exceeding 12 g/dL increases the risk of stroke and cardiovascular events. * **Iron Stores:** EPO therapy is ineffective if iron stores are low. Always check **ferritin levels** before starting treatment. * **Darbepoetin alfa:** A long-acting glycosylated form of EPO with a half-life 3 times longer than Epoetin alfa. * **Other Uses:** Anemia due to Zidovudine (in HIV), chemotherapy-induced anemia, and preoperative autologous blood donation.

Question 1

Low doses of aspirin prolong bleeding time by selectively inhibiting synthesis of the following mediator in the platelets?

Accepted Answer

Thromboxane A2

Answer

5-Hydroxytryptamine

Answer

Platelet activating factor

Answer

Prostacyclin

Question 2

Abciximab is:

Accepted Answer

An antibody against Ilb/Illa receptors

Answer

An antibody against Ib/IX receptors

Answer

A topoisomerase inhibitor

Answer

An adenosine inhibitor

Question 3

Ferrous sulfate is a hydrated salt containing what percentage of Iron?

Accepted Answer

20%

Answer

25%

Answer

30%

Answer

35%

Question 4

Which of the following drugs is not used for thromboprophylaxis?

Accepted Answer

Antithrombin III

Answer

Heparin

Answer

Warfarin

Answer

Aspirin

Question 5

What is the mode of action of warfarin?

Accepted Answer

Vitamin K antagonist

Answer

Factor Xa inhibitor

Answer

Activates antithrombin III

Answer

Activates factor IX

Question 6

Arrange the following drugs in decreasing order of their antiplatelet potency: Clopidogrel, Prasugrel, Aspirin, Abciximab?

Accepted Answer

Abciximab > Prasugrel > Clopidogrel > Aspirin

Answer

Prasugrel > Abciximab > Aspirin > Clopidogrel

Answer

Aspirin > Abciximab > Clopidogrel > Prasugrel

Answer

Clopidogrel > Abciximab > Aspirin > Prasugrel

Question 7

Ticlopidine is which of the following types of drugs?

Accepted Answer

Antiplatelet drug

Answer

Antiarrhythmic drug

Answer

Anticoagulant drug

Answer

Antifibrinolytic drug

Question 8

Low molecular weight heparin therapy is associated with all of the following except:

Accepted Answer

High biological interaction to plasma proteins

Answer

Less chances of bleeding

Answer

Single dose per day

Answer

Easy filterability by glomerular capillaries

Question 9

What is the target International Normalized Ratio (INR) for a patient receiving warfarin therapy?

Accepted Answer

2.5

Answer

1.5

Answer

3.5

Answer

4.5

Question 10

Which of the following statements about erythropoietin is FALSE?

Accepted Answer

It results in a decrease in reticulocyte count

Answer

It is used for the treatment of anemia due to chronic renal failure

Answer

It decreases the requirement for blood transfusions

Answer

It can cause hypertension

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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