Drugs Affecting Blood and Blood Formation — MCQs
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Which of the following is a parenteral direct thrombin inhibitor?
Which of the following drugs inhibits the activation of plasminogen?
What is the mechanism of action of Warfarin?
Mechanism of action of tranexamic acid is
What is Hydroxyethyl starch?
The best agent for increasing HDL cholesterol is?
Which drug is used as a treatment for sickle cell anemia by promoting fetal hemoglobin production?
Low molecular weight heparin mainly inhibits which factor?
Which of the following antibiotics is known to cause bleeding due to its effect on blood clotting?
Romiplostim mimics which of the following receptors?
Drugs Affecting Blood and Blood Formation Indian Medical PG Practice Questions and MCQs
Question 331: Which of the following is a parenteral direct thrombin inhibitor?
- A. Ximelagatran
- B. Dabigatran
- C. Argatroban (Correct Answer)
- D. Heparin
Explanation: ***Argatroban*** - **Argatroban** is a **synthetic direct thrombin inhibitor** administered exclusively via **intravenous infusion**, making it a parenteral drug. - It does not require antithrombin for its action and is primarily used in patients with **heparin-induced thrombocytopenia (HIT)**. *Ximelagatran* - **Ximelagatran** was an **oral direct thrombin inhibitor** but was withdrawn from the market due to concerns about severe **liver toxicity**. - As an oral drug, it is not a parenteral medication. *Dabigatran* - **Dabigatran** is a **direct thrombin inhibitor** that is administered **orally** in capsule form (as dabigatran etexilate, a prodrug). - Therefore, it is not a parenteral medication. *Heparin* - **Heparin** is an **indirect thrombin inhibitor** because it requires binding to **antithrombin** to exert its anticoagulant effect. - Although administered parenterally, its mechanism of action is indirect.
Question 332: Which of the following drugs inhibits the activation of plasminogen?
- A. Streptokinase
- B. Aminocaproic acid (Correct Answer)
- C. Reteplase
- D. Clopidogrel
Explanation: ***Correct Option: Aminocaproic acid*** - **Aminocaproic acid** is an antifibrinolytic drug that acts by competitively inhibiting the activation of **plasminogen** to plasmin. - By preventing the formation of plasmin, it stabilizes blood clots and is used to treat excessive bleeding. *Incorrect Option: Streptokinase* - **Streptokinase** is a **thrombolytic agent** that forms a complex with plasminogen, converting uncomplexed plasminogen into plasmin. - This action promotes the degradation of fibrin clots, making it a **fibrinolytic drug**, not an inhibitor of plasminogen activation. *Incorrect Option: Reteplase* - **Reteplase** is a **recombinant tissue plasminogen activator (tPA)** that directly converts plasminogen to plasmin. - This drug actively promotes **fibrinolysis** and clot breakdown, making it a thrombolytic agent. *Incorrect Option: Clopidogrel* - **Clopidogrel** is an **antiplatelet drug** that inhibits platelet aggregation by irreversibly blocking the P2Y12 adenosine diphosphate (ADP) receptor on platelets. - Its mechanism of action is focused on **platelet function**, not on the plasminogen-plasmin system.
Question 333: What is the mechanism of action of Warfarin?
- A. Inhibition of Vitamin K epoxide reductase (Correct Answer)
- B. Inhibition of gamma glutamyl carboxylase
- C. Activation of Vitamin K epoxide reductase
- D. Activation of gamma glutamyl carboxylase
Explanation: ***Inhibition of Vitamin K epoxide reductase*** - Warfarin blocks **Vitamin K epoxide reductase (VKORC1)** [1, 2, 3], an enzyme essential for recycling oxidized vitamin K into its active reduced form [1, 3]. - This reduction prevents the activation of **vitamin K-dependent clotting factors** (II, VII, IX, X), leading to anticoagulation [1, 3]. *Inhibition of gamma glutamyl carboxylase* - **Gamma-glutamyl carboxylase** uses reduced vitamin K as a cofactor to carboxylate specific glutamic acid residues on clotting factors [1, 3]. - While essential for clotting factor activation, this enzyme itself is **not directly inhibited by warfarin** [1, 3]. *Activation of Vitamin K epoxide reductase* - Activating **VKORC1** would increase the production of reduced vitamin K, thereby **promoting coagulation** rather than inhibiting it [1, 2]. - This is the opposite of warfarin's intended therapeutic effect. *Activation of gamma glutamyl carboxylase* - Activating **gamma-glutamyl carboxylase** would enhance the carboxylation and activation of **clotting factors**, leading to procoagulant effects [1, 3]. - This mechanism contradicts warfarin's role as an **anticoagulant**.
Question 334: Mechanism of action of tranexamic acid is
- A. Decrease vascular permeability
- B. Smooth muscle contraction
- C. Activates Plasmin formation
- D. Prevents fibrinolysis (Correct Answer)
Explanation: ***Correct: Prevents fibrinolysis*** - Tranexamic acid is an **antifibrinolytic agent** that works by inhibiting the activation of plasminogen to plasmin. - By preventing the formation of plasmin, it stabilizes **fibrin clots** and reduces bleeding. *Incorrect: Decrease vascular permeability* - This is primarily the mechanism of action of drugs like antihistamines or corticosteroids, which work on **inflammation** and **allergic reactions**. - Tranexamic acid does not directly target vascular permeability; its primary role is in **hemostasis**. *Incorrect: Smooth muscle contraction* - This describes the action of drugs like **vasoconstrictors** (e.g., epinephrine) or agents that promote uterine contractions (e.g., oxytocin). - Tranexamic acid has no direct effect on **smooth muscle contraction**. *Incorrect: Activates Plasmin formation* - This is the opposite of tranexamic acid's action; drugs that activate plasmin, such as **tissue plasminogen activators (tPAs)**, are used to break down clots. - Tranexamic acid specifically **inhibits plasminogen activation**, thereby preventing plasmin formation.
Question 335: What is Hydroxyethyl starch?
- A. Vasodilator
- B. Inotrope
- C. Plasma expander (Correct Answer)
- D. Diuretic
Explanation: ***Plasma expander*** - **Hydroxyethyl starch** is a **colloid solution** used intravenously to increase plasma volume and maintain oncotic pressure. - It is often used in situations of **hypovolemia** or shock to support circulation. *Vasodilator* - A **vasodilator** is a medication that widens blood vessels, typically used to lower blood pressure or improve blood flow. - Hydroxyethyl starch does not directly cause **vasodilation** as its primary mechanism of action. *Inotrope* - An **inotrope** is an agent that alters the force or energy of muscular contractions, mainly affecting the heart's contractility. - Hydroxyethyl starch has no direct effect on **myocardial contractility**. *Diuretic* - A **diuretic** is a substance that promotes increased production of urine, thereby increasing the excretion of water from the body. - While fluid administration can temporarily increase urine output, hydroxyethyl starch is not classified as a **diuretic agent** itself.
Question 336: The best agent for increasing HDL cholesterol is?
- A. Statin
- B. Nicotinic acid (Correct Answer)
- C. Gugulipids
- D. Fibrates
Explanation: ***Nicotinic acid*** - **Nicotinic acid** (niacin) is known to significantly increase **high-density lipoprotein (HDL) cholesterol** levels by reducing its catabolism. - It also has beneficial effects on other lipid parameters, such as lowering **triglycerides** and **LDL cholesterol**. *Statin* - **Statins** (HMG-CoA reductase inhibitors) are highly effective at lowering **LDL cholesterol** and moderately lowering triglycerides. - While they can cause a modest increase in HDL cholesterol, their primary role is not HDL elevation. *Gugulipids* - **Gugulipids**, derived from the gum resin of the _Commiphora mukul_ tree, have been used in traditional medicine to lower cholesterol. - Evidence for their efficacy in significantly increasing HDL cholesterol is weak and not clinically recommended. *Fibrates* - **Fibrates** primarily work to lower **triglyceride levels** and can modestly increase HDL cholesterol. - Their effect on HDL is generally less pronounced compared to nicotinic acid.
Question 337: Which drug is used as a treatment for sickle cell anemia by promoting fetal hemoglobin production?
- A. Trypsin
- B. Hydroxyurea (Correct Answer)
- C. L-glutamine
- D. Glucose 6-phosphate dehydrogenase
Explanation: ***Hydroxyurea*** - **Hydroxyurea** is the primary drug used to treat sickle cell anemia by promoting **fetal hemoglobin (HbF)** production - It is a **ribonucleotide reductase inhibitor** that increases HbF levels, which reduces sickling of red blood cells - Clinical benefits include reduced frequency of **vaso-occlusive crises**, decreased need for transfusions, and improved survival - Mechanism: Increases **HbF** production, which dilutes the abnormal **HbS** and prevents polymerization *Trypsin* - **Trypsin** is a **proteolytic enzyme** involved in protein digestion in the gastrointestinal tract - It has no role in the treatment of **sickle cell anemia** or in promoting **fetal hemoglobin** production *L-glutamine* - **L-glutamine** is an **amino acid** (not a drug that promotes HbF) approved for sickle cell disease - Its mechanism involves reducing **oxidative stress** by increasing NAD+ levels and improving red blood cell energy metabolism - It reduces complications but does not primarily work by increasing **fetal hemoglobin** production *Glucose 6-phosphate dehydrogenase* - **G6PD** is an **enzyme** in the **pentose phosphate pathway**, not a therapeutic agent - **G6PD deficiency** causes hemolytic anemia but is unrelated to sickle cell disease treatment or fetal hemoglobin production
Question 338: Low molecular weight heparin mainly inhibits which factor?
- A. Factor VIIIa
- B. Factor Xa (Correct Answer)
- C. Factor XIIa
- D. Factor IIa
Explanation: ***Factor Xa*** - Low molecular weight heparin (LMWH) primarily exerts its anticoagulant effect by binding to **antithrombin III** and increasing its inhibitory activity against **Factor Xa**. - This selective inhibition of Factor Xa, rather than Factor IIa (thrombin), accounts for its more predictable anticoagulant response and lower risk of bleeding compared to unfractionated heparin. *Factor VIIIa* - **Factor VIIIa** is a cofactor in the intrinsic pathway, crucial for activating Factor X, but it is not directly inhibited by LMWH. - Its inhibition is more characteristic of **activated protein C**, not LMWH. *Factor XIIa* - **Factor XIIa** is involved in the initiation of the intrinsic coagulation pathway and the kallikrein-kinin system. - LMWH has no significant inhibitory effect on Factor XIIa. *Factor IIa* - While unfractionated heparin inhibits **Factor IIa (thrombin)** relatively equally to Factor Xa, LMWH has a much weaker inhibitory effect on Factor IIa due to its shorter chain length. - The anti-Factor IIa activity of LMWH is generally considered to be negligible compared to its **anti-Factor Xa activity**.
Question 339: Which of the following antibiotics is known to cause bleeding due to its effect on blood clotting?
- A. Moxalactam (Correct Answer)
- B. Cefaloridine
- C. Cefazolin
- D. Ceftazidime
Explanation: Moxalactam - Moxalactam is a **third-generation cephalosporin** known to cause **hypoprothrombinemia** and platelet dysfunction, leading to an increased risk of bleeding. - This effect is due to its **N-methylthiotetrazole (NMTT) side chain**, which inhibits vitamin K-dependent clotting factor synthesis. Cefaloridine - This is a **first-generation cephalosporin** that does not have the NMTT side chain and is not commonly associated with significant bleeding risks. - Its primary adverse effect of concern is **nephrotoxicity** at high doses, rather than coagulopathy. Ceftazidime - Ceftazidime is a **third-generation cephalosporin** primarily used for *Pseudomonas aeruginosa* infections but does **not contain the NMTT side chain** responsible for bleeding complications. - While broad-spectrum, it generally has a favorable safety profile concerning coagulation. *Cefazolin* - Cefazolin is a **first-generation cephalosporin** [1] widely used for surgical prophylaxis and skin infections [1], and it does **not interfere with coagulation** pathways. - Its main side effects are typical for penicillin-related antibiotics, such as hypersensitivity reactions [1],[2].
Question 340: Romiplostim mimics which of the following receptors?
- A. IL 6
- B. IL 8
- C. PGE 1
- D. Thrombopoietin (Correct Answer)
Explanation: ***Thrombopoietin*** - **Romiplostim** is a **thrombopoietin receptor agonist**, meaning it binds to and activates the **thrombopoietin receptor** [1]. - This activation mimics the effect of endogenous thrombopoietin, stimulating the production of **platelets** in the bone marrow [2].*IL 6* - **Interleukin-6 (IL-6)** is a cytokine involved in inflammation, immune response, and hematopoiesis, but it is not the primary target of romiplostim. - While IL-6 can influence platelet production indirectly, romiplostim directly targets the thrombopoietin pathway.*IL 8* - **Interleukin-8 (IL-8)** is a chemokine primarily involved in neutrophil chemotaxis and inflammation. - It plays no direct role in the mechanism of action of romiplostim.*PGE 1* - **Prostaglandin E1 (PGE1)** is a lipid compound with various effects, including vasodilation and inhibition of platelet aggregation. - Romiplostim's mechanism of action is distinct from that of prostaglandins, as it specifically targets platelet production rather than platelet function or vascular tone.
Practice by Chapter
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Oral Anticoagulants
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Thrombolytic Agents
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Hemostatic Drugs
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