Drugs Affecting Blood and Blood Formation Practice Questions

Q: An elderly woman who suffered a stroke was treated with alteplase and improved considerably. To prevent stroke recurrence, what medication is she most likely to be treated with indefinitely?

Aspirin. **Explanation:** **1. Why Aspirin is Correct:** The patient has suffered an **ischemic stroke** (implied by the use of alteplase). For long-term secondary prevention of non-cardioembolic ischemic strokes, **antiplatelet therapy** is the standard of care. Aspirin (low dose, 75–150 mg) irreversibly inhibits the enzyme **Cyclooxygenase-1 (COX-1)**, preventing the synthesis of Thromboxane A2. This inhibits platelet aggregation and reduces the risk of recurrent arterial thrombosis indefinitely. **2. Why the Other Options are Incorrect:** * **Warfarin (Option B):** This is an oral anticoagulant. It is indicated for stroke prevention only if the stroke was **cardioembolic** (e.g., due to Atrial Fibrillation). In a standard non-cardioembolic stroke, antiplatelets are preferred over anticoagulants due to a lower risk of major bleeding. * **Urokinase (Option C):** This is a thrombolytic agent (fibrinolytic). Like alteplase, it is used for the **acute** management of a stroke to dissolve an existing clot. It is never used for long-term prophylaxis. * **Enoxaparin (Option D):** This is a Low Molecular Weight Heparin (LMWH) administered parenterally. It is used for DVT prophylaxis or acute anticoagulation, not for the indefinite secondary prevention of ischemic stroke. **3. NEET-PG Clinical Pearls:** * **Golden Hour:** Alteplase (rt-PA) must be administered within **3 to 4.5 hours** of the onset of ischemic stroke symptoms. * **Dual Antiplatelet Therapy (DAPT):** In high-risk TIA or minor stroke, a combination of Aspirin and Clopidogrel is often used for the first 21–90 days, followed by long-term monotherapy. * **Primary Side Effect:** The most common side effect of long-term Aspirin is **gastrointestinal mucosal damage** and bleeding.

Q: Streptokinase and urokinase are contraindicated in which of the following conditions?

Intracranial malignancy. **Explanation:** Streptokinase and urokinase are **fibrinolytic (thrombolytic) agents** that convert plasminogen to plasmin, which subsequently degrades fibrin clots. Because these drugs induce a systemic lytic state, they carry a significant risk of severe hemorrhage. **Why Intracranial Malignancy is the Correct Answer:** Intracranial malignancy is an **absolute contraindication** for thrombolytic therapy. Tumors within the brain are often highly vascular or can cause structural compromise of the blood-brain barrier. Administering a fibrinolytic agent in this setting poses an extremely high risk of **fatal intracranial hemorrhage (ICH)**. Other absolute contraindications include a history of prior ischemic stroke (within 3 months), active internal bleeding, or recent intracranial/intraspinal surgery. **Analysis of Incorrect Options:** * **B. Pulmonary Embolism:** This is actually a primary **indication** for thrombolytics, especially in "massive" PE associated with hemodynamic instability (hypotension). * **C. AV Fistula:** The presence of an arteriovenous fistula (commonly used for hemodialysis) is not a contraindication for streptokinase or urokinase. * **D. Thrombophlebitis:** While usually treated with NSAIDs or anticoagulants, superficial thrombophlebitis is not a contraindication for using thrombolytics if they are needed for a more serious concurrent condition (like an MI). **NEET-PG High-Yield Pearls:** * **Mechanism:** Streptokinase is non-fibrin specific (acts on both circulating and clot-bound plasminogen), whereas Alteplase (tPA) is fibrin-specific. * **Antidote:** In case of overdose or excessive bleeding, use **Epsilon-aminocaproic acid** or **Tranexamic acid**. * **Side Effect:** Streptokinase is antigenic; it can cause hypersensitivity reactions and should not be repeated within 6–12 months due to neutralizing antibodies.

Q: All of the following are antiplatelet agents EXCEPT:

Tranexamic acid. **Explanation:** The correct answer is **D. Tranexamic acid**. **1. Why Tranexamic Acid is the Correct Answer:** Tranexamic acid is an **antifibrinolytic agent**, not an antiplatelet drug [1]. It works by competitively inhibiting the activation of plasminogen to plasmin [3]. By preventing plasmin from binding to and degrading fibrin, it stabilizes clots and reduces bleeding [2]. It is clinically used in conditions like menorrhagia, trauma, and post-prostatectomy bleeding [1]. **2. Why the Other Options are Incorrect:** * **A. Aspirin:** A classic antiplatelet agent that causes irreversible inhibition of the **COX-1 enzyme**, thereby suppressing the synthesis of Thromboxane A2 (TXA2), a potent platelet aggregator [4]. * **B. Clopidogrel:** A P2Y12 receptor antagonist [4]. It prevents platelet aggregation by blocking the binding of **ADP** to its specific receptors on the platelet surface. * **C. Abciximab:** A Glycoprotein **IIb/IIIa receptor antagonist** [4]. It blocks the "final common pathway" of platelet aggregation by preventing the binding of fibrinogen to platelets. **3. NEET-PG High-Yield Pearls:** * **Aspirin:** Low doses (75–150 mg) are selective for COX-1; higher doses inhibit COX-2 and prostacyclin (PGI2). * **P2Y12 Inhibitors:** Clopidogrel is a prodrug (requires CYP2C19 activation), whereas **Ticagrelor** is a direct-acting, reversible inhibitor [4]. * **GP IIb/IIIa Inhibitors:** Includes Abciximab (monoclonal antibody), Eptifibatide, and Tirofiban [4]. * **Antifibrinolytics:** Besides Tranexamic acid, **Epsilon-aminocaproic acid (EACA)** is another key agent in this class [3].

Q: As compared to unfractionated heparin, low molecular weight heparin:

Is absorbed more uniformly when given subcutaneously. **Explanation:** Low Molecular Weight Heparins (LMWHs), such as Enoxaparin and Dalteparin, are derived from Unfractionated Heparin (UFH) by depolymerization. They offer several pharmacokinetic advantages over UFH. **1. Why Option A is Correct:** LMWHs have **higher bioavailability** (>90%) and a more **predictable dose-response** when administered subcutaneously. This is because LMWHs bind less extensively to plasma proteins, macrophages, and endothelial cells compared to UFH. This reduced non-specific binding leads to uniform and consistent absorption, allowing for fixed dosing without the need for routine monitoring. **2. Why the Other Options are Incorrect:** * **Option B:** LMWHs have a predictable anticoagulant effect; therefore, **routine lab monitoring (aPTT) is NOT required**. Monitoring (anti-Factor Xa levels) is only reserved for special cases like renal failure, pregnancy, or extreme obesity. * **Option C:** LMWHs show high **cross-reactivity** with UFH antibodies. Therefore, they are strictly **contraindicated** in patients with Heparin-Induced Thrombocytopenia (HIT). Alternatives like Fondaparinux or Argatroban should be used instead. * **Option D:** LMWHs have a **lower risk of osteopenia** and osteoporosis compared to UFH because they have a lower affinity for osteoblasts. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** LMWH mainly inhibits **Factor Xa** (Ratio of Xa:IIa inhibition is 3:1), whereas UFH inhibits both Xa and IIa (Thrombin) equally (1:1). * **Antidote:** Protamine sulfate completely neutralizes UFH but only **partially neutralizes** LMWH. * **Elimination:** LMWHs are primarily excreted **renally**; thus, they are contraindicated in chronic kidney disease (UFH is preferred in renal failure). * **Pregnancy:** LMWH is the drug of choice for anticoagulation during pregnancy as it does not cross the placenta.

Q: Which of the following is the mechanism of action of Fondaparinux?

Factor Xa inhibition. **Explanation:** **Fondaparinux** is a synthetic pentasaccharide that acts as a **selective Factor Xa inhibitor**. Its mechanism is mediated through **Antithrombin III (AT-III)**. When Fondaparinux binds to AT-III, it induces a conformational change that increases the neutralization of Factor Xa by 300-fold. Unlike Heparin, the pentasaccharide chain of Fondaparinux is too short to bridge AT-III to Thrombin; therefore, it has **no activity against Thrombin (Factor IIa).** **Analysis of Options:** * **Option B (Correct):** Fondaparinux selectively accelerates the neutralization of Factor Xa. * **Option A & D (Incorrect):** These describe the action of Unfractionated Heparin (UFH). UFH inhibits both Xa and IIa (ratio 1:1). Low Molecular Weight Heparins (LMWH) also inhibit both, but with a higher selectivity for Xa (ratio 2:1 to 4:1). Fondaparinux is unique in its pure Xa selectivity. * **Option C (Incorrect):** Fondaparinux is an Antithrombin **activator/cofactor**, not an inhibitor. **High-Yield Clinical Pearls for NEET-PG:** 1. **HIT Safety:** Fondaparinux does not bind to Platelet Factor 4 (PF4); thus, it carries virtually **no risk of Heparin-Induced Thrombocytopenia (HIT)**. 2. **Pharmacokinetics:** It has a long half-life (~17 hours), allowing for once-daily subcutaneous dosing. 3. **Excretion:** It is primarily excreted unchanged by the kidneys; it is **contraindicated** in patients with severe renal impairment (CrCl <30 mL/min). 4. **Monitoring:** Unlike Warfarin (PT/INR) or UFH (aPTT), Fondaparinux does not require routine laboratory monitoring.

Q: Which of the following drugs is used for the treatment of sickle cell anemia?

Hydroxyurea. **Explanation:** **Hydroxyurea** is the mainstay of pharmacological management for sickle cell anemia (SCA). Its primary mechanism of action involves the **inhibition of the enzyme ribonucleotide reductase**, but in the context of SCA, it works by **increasing the production of fetal hemoglobin (HbF)**. HbF interferes with the polymerization of hemoglobin S (HbS), thereby preventing the sickling of red blood cells, reducing vaso-occlusive crises, and decreasing the need for blood transfusions. Additionally, it has anti-inflammatory effects by lowering the white blood cell count and improving RBC hydration. **Analysis of Incorrect Options:** * **Cisplatin & Carboplatin (Options B & D):** These are platinum-based alkylating agents used as chemotherapy for solid tumors (e.g., lung, ovarian, and testicular cancers). They work by causing DNA cross-linking, leading to apoptosis, and have no role in treating hemoglobinopathies. * **Paclitaxel (Option C):** This is a taxane derivative that acts as a microtubule stabilizer. It is used in the treatment of breast, ovarian, and lung cancers but does not affect hemoglobin synthesis. **High-Yield Clinical Pearls for NEET-PG:** * **Dose-limiting toxicity:** The most common side effect of Hydroxyurea is **myelosuppression** (neutropenia and thrombocytopenia). * **Teratogenicity:** It is contraindicated in pregnancy (Category D). * **Other Indications:** Hydroxyurea is also used in chronic myeloid leukemia (CML) and polycythemia vera to reduce cell counts. * **Newer Drugs for SCA:** Keep an eye on **Voxelotor** (HbS polymerization inhibitor) and **Crizanlizumab** (P-selectin inhibitor), which are also FDA-approved for SCA.

Q: Which of the following iron preparations is used for parenteral iron therapy?

Iron dextran. **Explanation:** **1. Why Iron Dextran is Correct:** Parenteral iron therapy is indicated when oral iron is not tolerated, ineffective (malabsorption), or when rapid replenishment of iron stores is required (e.g., chronic kidney disease or severe anemia in late pregnancy). **Iron dextran** is a complex of ferric hydroxide and dextran. It can be administered via deep intramuscular (IM) injection or slow intravenous (IV) infusion. It is a high-molecular-weight compound that allows for the delivery of large doses of iron in a single session (Total Dose Infusion). **2. Why the Other Options are Incorrect:** * **Ferrous sulfate, Ferrous fumarate, and Ferrous gluconate** are all **oral iron salts**. * These are the preferred first-line treatments for iron deficiency anemia due to their safety, low cost, and effectiveness. * Among these, Ferrous sulfate is the most commonly prescribed, while Ferrous fumarate contains the highest percentage of elemental iron (~33%). **3. High-Yield Clinical Pearls for NEET-PG:** * **Adverse Effects:** The most significant risk with Iron dextran is **anaphylaxis** (Type I hypersensitivity). A **test dose** is mandatory before the full therapeutic dose is administered. * **Z-track Technique:** When giving iron dextran intramuscularly, the Z-track technique must be used to prevent skin staining and local irritation. * **Newer Parenteral Agents:** Modern alternatives like **Iron Sucrose** and **Ferric Carboxymaltose** are often preferred over iron dextran because they carry a significantly lower risk of anaphylaxis and do not require a test dose. * **Calculation:** The dose of parenteral iron is calculated using the **Ganzoni Equation**: * *Iron deficit (mg) = Body weight (kg) × (Target Hb - Actual Hb) × 2.4 + Iron stores (500 mg).*

Q: Effect of Heparin is reversed by which of the following agents?

Protamine. **Explanation:** **1. Why Protamine is the Correct Answer:** Protamine sulfate is the specific pharmacological antagonist for Heparin. [1] The mechanism is based on a **chemical neutralization** (acid-base reaction). Heparin is a highly acidic, negatively charged molecule, while Protamine is a strongly basic, positively charged protein (derived from salmon sperm). When administered intravenously, they combine to form a stable, inactive salt complex, thereby rapidly reversing the anticoagulant effect of Unfractionated Heparin (UFH). [1] **2. Analysis of Incorrect Options:** * **Vitamin K:** This is the specific antidote for **Warfarin** (Coumarin) toxicity. [2] It acts by promoting the hepatic synthesis of clotting factors II, VII, IX, and X, which takes several hours to manifest. [2] * **Hirudin:** This is a **Direct Thrombin Inhibitor (DTI)** derived from leech saliva. It is an anticoagulant itself, not an antidote. It is often used in patients with Heparin-Induced Thrombocytopenia (HIT). * **Tranexamic acid:** This is an **Antifibrinolytic** agent. It works by inhibiting the activation of plasminogen to plasmin. It is used to control bleeding in trauma or surgery but does not neutralize heparin. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dosage:** 1 mg of Protamine neutralizes approximately 100 units of Heparin. [1] * **LMWH Reversal:** Protamine only **partially** reverses Low Molecular Weight Heparin (Enoxaparin) and has **no effect** on Fondaparinux. * **Adverse Effect:** Rapid injection of Protamine can cause "Protamine Reaction," characterized by hypotension, bradycardia, and anaphylaxis due to histamine release. [1] * **Monitoring:** The effect of Heparin is monitored by **aPTT** (activated Partial Thromboplastin Time).

Question 1

An elderly woman who suffered a stroke was treated with alteplase and improved considerably. To prevent stroke recurrence, what medication is she most likely to be treated with indefinitely?

Accepted Answer

Aspirin

Answer

Warfarin

Answer

Urokinase

Answer

Enoxaparin

Question 2

Streptokinase and urokinase are contraindicated in which of the following conditions?

Accepted Answer

Intracranial malignancy

Answer

Pulmonary embolism

Answer

AV fistula

Answer

Thrombophlebitis

Question 3

All of the following are antiplatelet agents EXCEPT:

Accepted Answer

Tranexamic acid

Answer

Aspirin

Answer

Clopidogrel

Answer

Abciximab

Question 4

As compared to unfractionated heparin, low molecular weight heparin:

Accepted Answer

Is absorbed more uniformly when given subcutaneously

Answer

Requires more frequent lab monitoring

Answer

Can be given to patients with heparin-induced thrombocytopenia

Answer

Has a higher risk of osteopenia

Question 5

Which of the following is the mechanism of action of Fondaparinux?

Accepted Answer

Factor Xa inhibition

Answer

Factor Xa inhibition and Thrombin inhibition

Answer

Antithrombin inhibitor

Answer

Thrombin inhibition

Question 6

Folate deficiency can occur due to which of the following medications?

Accepted Answer

All of the above

Answer

Phenytoin

Answer

Phenobarbitone

Answer

Primidone

Question 7

All of the following are target-specific oral anticoagulants except?

Accepted Answer

Betrixaban

Answer

Apixaban

Answer

Dabigatran

Answer

Rivaroxaban

Question 8

Which of the following drugs is used for the treatment of sickle cell anemia?

Accepted Answer

Hydroxyurea

Answer

Cisplatin

Answer

Paclitaxel

Answer

Carboplatin

Question 9

Which of the following iron preparations is used for parenteral iron therapy?

Accepted Answer

Iron dextran

Answer

Ferrous sulfate

Answer

Ferrous fumarate

Answer

Ferrous gluconate

Question 10

Effect of Heparin is reversed by which of the following agents?

Accepted Answer

Protamine

Answer

Vitamin K

Answer

Hirudin

Answer

Tranexamic acid

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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