Drugs Affecting Blood and Blood Formation — MCQs

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

Question 311: Which of the following is given to treat thrombocytopenia secondary to anticancer therapy and is known to stimulate progenitor megakaryocytes?

A. Filgrastim
B. Oprelvekin (Correct Answer)
C. Erythropoietin
D. Anagrelide

Explanation: ***Oprelvekin*** - **Oprelvekin** is a recombinant form of **interleukin-11 (IL-11)**, which is a **thrombopoietic growth factor**. - It stimulates the proliferation and maturation of **megakaryocyte progenitors**, leading to an increase in platelet production. *Filgrastim* - **Filgrastim** is a **granulocyte colony-stimulating factor (G-CSF)**, primarily used to stimulate the production of **neutrophils** to counteract **neutropenia**. - It does not directly affect **megakaryocyte** or **platelet production**. *Erythropoietin* - **Erythropoietin** is a **hematopoietic growth factor** that specifically stimulates the production of **red blood cells (erythropoiesis)**. - It is used to treat **anemia**, particularly in patients with **chronic kidney disease** or those undergoing **chemotherapy**. *Anagrelide* - **Anagrelide** is an **antiplatelet agent** that works by reducing platelet production, often used to treat **thrombocythemia**. - Its action is the opposite of what is required to treat **thrombocytopenia**.

Question 312: The following factors are inhibited by heparin except?

A. IIa
B. VIIa (Correct Answer)
C. IXa
D. Xa

Explanation: ***VIIa*** - Heparin, through its activation of **antithrombin III**, primarily inhibits factors **IIa (thrombin)**, **Xa**, **IXa**, **XIa**, and **XIIa**. - **Factor VIIa** is part of the extrinsic pathway and is not directly inhibited by the heparin-antithrombin III complex. *IIa* - **Factor IIa (thrombin)** is a direct target for inhibition by the **heparin-antithrombin III complex**. - Its inhibition is crucial for heparin's anticoagulant effect, as thrombin plays a central role in amplifying coagulation and converting fibrinogen to fibrin. *IXa* - **Factor IXa** is part of the intrinsic pathway and is effectively inhibited by the **heparin-antithrombin III complex**. - Inhibition of IXa prevents the activation of factor X, thereby disrupting the coagulation cascade. *Xa* - **Factor Xa** is a key component in the common pathway of coagulation and is potently inhibited by the **heparin-antithrombin III complex**. - Its inhibition is a primary mechanism by which both unfractionated heparin and low molecular weight heparins exert their anticoagulant effects.

Question 313: Which of the following statements accurately compares low molecular weight heparin to high molecular weight heparin?

A. Low molecular weight heparin is less likely to be filtered at the glomerulus compared to high molecular weight heparin.
B. Low molecular weight heparin interacts with plasma proteins similarly to high molecular weight heparin.
C. Monitoring is generally not required for low molecular weight heparin compared to high molecular weight heparin. (Correct Answer)
D. Low molecular weight heparin requires twice daily subcutaneous administration, unlike high molecular weight heparin which is given once daily.

Explanation: ***Monitoring is generally not required for low molecular weight heparin compared to high molecular weight heparin.*** - **Low molecular weight heparins (LMWH)** have a more predictable anticoagulant response due to their smaller size and reduced non-specific binding, eliminating the routine need for monitoring unless specific patient conditions (e.g., renal impairment, extreme weight) warrant it. - **High molecular weight heparin (HMWH)**, also known as unfractionated heparin, has a variable anticoagulant response and requires frequent monitoring of the **activated partial thromboplastin time (aPTT)** to ensure therapeutic levels and prevent bleeding. *Low molecular weight heparin is less likely to be filtered at the glomerulus compared to high molecular weight heparin.* - This statement is **incorrect and backwards**. LMWH is actually **MORE likely** to undergo glomerular filtration compared to HMWH due to its smaller molecular size (4,000-6,000 Da). - LMWH is primarily eliminated by the **kidneys via glomerular filtration**, which is why it accumulates in patients with renal impairment and dose adjustment is required. - HMWH (unfractionated heparin), being a **larger molecule** (12,000-15,000 Da), is cleared primarily by **reticuloendothelial cells** and hepatic mechanisms, making it less dependent on renal function for elimination. *Low molecular weight heparin interacts with plasma proteins similarly to high molecular weight heparin.* - LMWH has **less non-specific binding to plasma proteins** and endothelial cells compared to HMWH, which contributes to its more predictable pharmacokinetics and anticoagulant effect. - HMWH's extensive binding to plasma proteins, endothelial cells, and macrophages leads to its highly **variable bioavailability** and makes its anticoagulant response unpredictable. *Low molecular weight heparin requires twice daily subcutaneous administration, unlike high molecular weight heparin which is given once daily.* - This is incorrect. LMWH typically has a **longer half-life** and can often be administered **once or twice daily subcutaneously** depending on the indication. - HMWH usually requires **intravenous (IV) administration** as a continuous infusion or multiple times daily for therapeutic anticoagulation due to its shorter half-life, not once daily administration.

Question 314: Which agent is used for the treatment of heparin-induced thrombocytopenia?

A. Abciximab
B. Warfarin
C. Alteplase
D. Argatroban (Correct Answer)

Explanation: ***Argatroban*** - **Argatroban** is a **direct thrombin inhibitor** and is a primary agent used for the treatment of **heparin-induced thrombocytopenia (HIT)**. - Its short half-life and independent metabolism from renal function make it suitable for patients with **renal impairment**. *Abciximab* - **Abciximab** is a **glycoprotein IIb/IIIa inhibitor** used to prevent platelet aggregation in conditions like percutaneous coronary intervention. - It is not indicated for HIT and can further exacerbate **thrombocytopenia** in certain situations. *Warfarin* - **Warfarin** is a **vitamin K antagonist** used for long-term anticoagulation, but it is **contraindicated in acute HIT**. - Initiating warfarin in acute HIT can worsen **thrombosis** due to initial protein C and S depletion, leading to a prothrombotic state. *Alteplase* - **Alteplase** is a **thrombolytic agent** (tissue plasaminogen activator) used to dissolve existing clots in conditions like acute ischemic stroke or pulmonary embolism. - It is not an anticoagulant for HIT and could increase the risk of **bleeding** without addressing the underlying prothrombotic state of HIT.

Question 315: What is the effect of nicotinic acid on cholesterol levels?

A. Increases HDL (Correct Answer)
B. Increased triglyceride synthesis
C. Type II hyperlipoproteinemia
D. Decreased hydrolysis of VLDL

Explanation: ***Increases HDL*** - **Nicotinic acid**, or niacin, effectively **raises high-density lipoprotein (HDL)** cholesterol levels, which is beneficial for cardiovascular health. - It achieves this by decreasing the **hepatic uptake of HDL-apoA-I**, thus prolonging the half-life of HDL particles. *Increased triglyceride synthesis* - Nicotinic acid actually **reduces triglyceride synthesis** and secretion by the liver. - It **inhibits diacylglycerol acyltransferase 2 (DGAT2)**, a key enzyme in triglyceride synthesis. *Type II hyperlipoproteinemia* - **Type II hyperlipoproteinemia** is characterized by elevated **LDL cholesterol**. - While nicotinic acid can lower LDL, its primary effect and a key distinguishing feature is its ability to significantly **raise HDL**, not cause hyperlipoproteinemia. *Decreased hydrolysis of VLDL* - Nicotinic acid **enhances the clearance of VLDL** (very-low-density lipoprotein) and IDL (intermediate-density lipoprotein) from plasma. - It **decreases VLDL synthesis and secretion** rather than decreasing its hydrolysis.

Question 316: Which of the following is true about iron dextran except?

A. It can be given either IV or IM
B. It binds to transferrin (Correct Answer)
C. It is a parenteral iron preparation
D. It is not excreted

Explanation: ***It binds to transferrin*** - This statement is **false** because **iron dextran** is a stable complex designed to release iron slowly and does **not directly bind to transferrin** in its dextran-bound form. - The iron from iron dextran is taken up by the **reticuloendothelial system**, processed, and then released into the plasma to bind with transferrin. *It is a parenteral iron preparation* - **Iron dextran** is indeed administered parenterally, typically via **intravenous (IV)** or **intramuscular (IM)** injection, bypassing the gastrointestinal tract. - This route is preferred for patients who cannot tolerate oral iron or have severe iron deficiency. *It can be given either IV or IM* - **Iron dextran** can be administered both **intravenously (IV)** and **intramuscularly (IM)**, offering flexibility based on patient needs and clinical situations. - The IV route is often preferred due to better absorption and fewer local reactions compared to IM injections. *It is not excreted* - The iron component of **iron dextran** is primarily **recycled** within the body and is not readily excreted, reflecting iron's crucial role in various metabolic processes. - While trace amounts may be lost, significant excretion does not occur, and the iron is stored or utilized for erythropoiesis.

Question 317: Which of the following is a univalent direct thrombin inhibitor?

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

Explanation: ***Argatroban*** - **Argatroban** is a **synthetic L-arginine derivative** that acts as a **direct thrombin inhibitor** and binds only to the catalytic site of thrombin, making it univalent. - It is used particularly in patients with **heparin-induced thrombocytopenia (HIT)** due to its independent mechanism from heparin [2]. *Hirudin* - **Hirudin** is a **bivalent direct thrombin inhibitor** originally isolated from leech saliva. - It binds to both the **catalytic site** and the **exosite 1 (fibrinogen-binding site)** of thrombin, preventing its enzymatic activity. *Bivalirudin* - **Bivalirudin** is a **synthetic peptide** that acts as a **bivalent direct thrombin inhibitor** [1]. - It binds reversibly to both the **catalytic site** and the **exosite 1** of thrombin [1]. *Lepirudin* - **Lepirudin** is a **recombinant hirudin derivative**, making it a **bivalent direct thrombin inhibitor** [2]. - Like hirudin, it binds to both the **catalytic site** and **exosite 1** of thrombin.

Question 318: A patient with a malignancy is undergoing chemotherapy. The platelet counts were reduced after the previous cycle of chemotherapy. Which of the following drugs can be used to treat this patient?

A. Oprelvekin (IL-11) - stimulates platelet production (Correct Answer)
B. Filgrastim - stimulates white blood cell production
C. Amifostine - protects against chemotherapy toxicity
D. Erythropoietin - stimulates red blood cell production

Explanation: ***Oprelvekin (IL-11) - stimulates platelet production*** - **Oprelvekin** is a recombinant interleukin-11 (IL-11) that directly stimulates the proliferation and maturation of **megakaryocytes**, leading to increased platelet production. - It is specifically indicated for the prevention of **severe thrombocytopenia** and the reduction of the need for platelet transfusions following myelosuppressive chemotherapy. *Filgrastim - stimulates white blood cell production* - **Filgrastim** is a **granulocyte colony-stimulating factor (G-CSF)** that primarily acts on neutrophil precursors, promoting their proliferation and maturation. - It is used to prevent and treat **neutropenia** and reduce the incidence of febrile neutropenia, but it does not significantly affect platelet counts. *Amifostine - protects against chemotherapy toxicity* - **Amifostine** is a **cytoprotective agent** that reduces toxicities associated with chemotherapy and radiation by preferentially protecting non-malignant cells. - It does not directly stimulate blood cell production but rather acts as a **free radical scavenger** to mitigate damage from cytotoxic treatments. *Erythropoietin - stimulates red blood cell production* - **Erythropoietin** is a **hematopoietic growth factor** that specifically stimulates the production of **red blood cells** by promoting the proliferation and differentiation of erythroid progenitor cells. - It is used to treat **anemia**, particularly in patients with chronic kidney disease or those undergoing chemotherapy, but it has no role in managing thrombocytopenia.

Question 319: Which of the following clotting factors in a patient on Warfarin therapy would show the earliest decrease in functional activity?

A. Factor VII (Correct Answer)
B. Factor IX
C. Factor X
D. Prothrombin (Factor 2)

Explanation: ***Factor VII*** - Factor VII has the **shortest half-life** (approximately 6 hours) among the vitamin K-dependent clotting factors, meaning its functional activity decreases **most rapidly** after starting warfarin therapy. - Warfarin inhibits vitamin K epoxide reductase, preventing gamma-carboxylation of **all vitamin K-dependent factors** (II, VII, IX, X). However, Factor VII's short half-life means pre-existing functional Factor VII is depleted first. - This is why **PT/INR** (which measures the extrinsic pathway dependent on Factor VII) rises before aPTT in warfarin therapy. - Reduced gamma-carboxylation impairs Factor VII's ability to bind calcium and phospholipids, essential for its activation in the extrinsic coagulation pathway. *Factor IX* - Factor IX is a **vitamin K-dependent factor** affected by warfarin, but its longer half-life (approximately 24 hours) means functional activity decreases more slowly than Factor VII. - It plays a key role in the **intrinsic coagulation pathway**. *Factor X* - Factor X is a **vitamin K-dependent clotting factor** whose gamma-carboxylation is inhibited by warfarin. - Its half-life (approximately 40 hours) is longer than Factor VII, resulting in a **slower decline in functional activity**. *Prothrombin (Factor II)* - Prothrombin (Factor II) is a **vitamin K-dependent factor** affected by warfarin. - It has the **longest half-life** (60-72 hours) among vitamin K-dependent factors, meaning its functional levels decrease most slowly after initiating warfarin therapy.

Question 320: Which drug requires continuous monitoring of prothrombin time?

A. Coumadin (Correct Answer)
B. Digoxin
C. Aspirin
D. Lepirudin

Explanation: ***Coumadin*** - **Coumadin (warfarin)** is an oral anticoagulant that inhibits vitamin K epoxide reductase, thereby reducing the synthesis of **vitamin K-dependent clotting factors** (II, VII, IX, X). - Its narrow therapeutic index and significant variability in dosage requirements necessitate continuous monitoring of the **prothrombin time (PT)**, reported as the **International Normalized Ratio (INR)**, to ensure efficacy and prevent bleeding complications. *Aspirin* - **Aspirin** is an antiplatelet agent that irreversibly inhibits cyclooxygenase-1 (COX-1), preventing the synthesis of thromboxane A2, which is crucial for platelet aggregation. - It does not directly affect the coagulation cascade or prothrombin time; its antiplatelet effects are typically monitored by patient response and bleeding time, though routine monitoring is not usually required for standard antiplatelet therapy. *Digoxin* - **Digoxin** is a cardiac glycoside used to treat heart failure and atrial fibrillation by increasing myocardial contractility and slowing AV nodal conduction. - Its therapeutic effects and potential toxicity are monitored through serum digoxin levels, electrolyte balance (especially potassium), and electrocardiograms for signs of dysrhythmias, not by prothrombin time. *Lepirudin* - **Lepirudin** is a direct thrombin inhibitor (DTI) used in patients with heparin-induced thrombocytopenia (HIT). - Its anticoagulant effect is typically monitored using the **activated partial thromboplastin time (aPTT)**, not prothrombin time.

Practice by Chapter

Hematopoietic Growth Factors

Practice Questions

Iron Preparations and Management of Iron Deficiency

Practice Questions

Vitamin B12 and Folic Acid

Practice Questions

Anticoagulants: Heparins and Direct Inhibitors

Practice Questions

Oral Anticoagulants

Practice Questions

Antiplatelet Drugs

Practice Questions

Thrombolytic Agents

Practice Questions

Hemostatic Drugs

Practice Questions

Plasma Expanders

Practice Questions

Blood Transfusion and Alternatives

Practice Questions

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