Drugs Affecting Blood and Blood Formation — MCQs

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

Question 261: Which among the following coagulation factors is not altered in Vitamin K deficiency?

A. Prothrombin (Factor II)
B. Factor VIII (Correct Answer)
C. Factor VII
D. Factor X

Explanation: **Explanation:** Vitamin K is an essential cofactor for the enzyme **gamma-glutamyl carboxylase**, which is responsible for the post-translational modification of specific coagulation factors. This process involves the carboxylation of glutamate residues, allowing these factors to bind calcium and phospholipids, which is necessary for their activation. **1. Why Factor VIII is the Correct Answer:** Factor VIII is a glycoprotein synthesized primarily in the **sinusoidal endothelial cells** of the liver and other extrahepatic tissues. Unlike the Vitamin K-dependent factors, its synthesis and function do not require gamma-carboxylation. Therefore, its levels remain unaffected in Vitamin K deficiency or during warfarin therapy. **2. Why the Other Options are Incorrect:** The Vitamin K-dependent clotting factors are **Factors II (Prothrombin), VII, IX, and X**, as well as anticoagulant proteins **C and S**. * **Factor II (Prothrombin):** A key Vitamin K-dependent factor in the common pathway. * **Factor VII:** Has the shortest half-life among all clotting factors and is the first to decrease in Vitamin K deficiency. * **Factor X:** A Vitamin K-dependent factor involved in the conversion of prothrombin to thrombin. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Remember the Vitamin K-dependent factors as **"1972"** (Factors 10, 9, 7, and 2). * **Warfarin Mechanism:** Warfarin inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K and thus inhibiting the synthesis of these same factors. * **Monitoring:** Vitamin K deficiency primarily prolongs **Prothrombin Time (PT)** initially because Factor VII has the shortest half-life. * **Factor VIII & vWF:** Factor VIII circulates bound to von Willebrand Factor (vWF); deficiency in Factor VIII leads to Hemophilia A.

Question 262: Anticoagulant effect of Warfarin is increased by all of the following EXCEPT:

A. Cimetidine
B. Phytonadione (Correct Answer)
C. Amiodarone
D. Phenylbutazone

Explanation: **Explanation:** The anticoagulant effect of **Warfarin** is mediated by the inhibition of **Vitamin K Epoxide Reductase (VKOR)**, which prevents the recycling of Vitamin K. This leads to a deficiency of the active form of Vitamin K required for the γ-carboxylation of clotting factors II, VII, IX, and X. **1. Why Phytonadione is the correct answer:** **Phytonadione (Vitamin K1)** is the physiological antagonist of Warfarin. By providing an exogenous source of Vitamin K, it bypasses the inhibition caused by Warfarin and promotes the synthesis of functional clotting factors. Therefore, it **decreases** (reverses) the anticoagulant effect of Warfarin rather than increasing it. **2. Why the other options are incorrect:** * **Cimetidine & Amiodarone:** These are potent **Cytochrome P450 (CYP) enzyme inhibitors**. Since Warfarin is metabolized primarily by the liver (CYP2C9), these drugs inhibit its metabolism, leading to increased plasma levels and an **increased** anticoagulant effect (increased INR). * **Phenylbutazone:** This drug increases Warfarin’s effect via two mechanisms: it **displaces Warfarin from plasma albumin** (increasing the free active fraction) and inhibits its metabolic clearance. **Clinical Pearls for NEET-PG:** * **Monitoring:** Warfarin effect is monitored using **PT/INR**. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes **Fetal Warfarin Syndrome**); Heparin is the preferred alternative. * **Overdose Management:** For immediate reversal, use **Fresh Frozen Plasma (FFP)** or Prothrombin Complex Concentrate (PCC). For non-emergency reversal, use **Phytonadione**. * **Enzyme Inducers:** Drugs like Rifampicin, Phenytoin, and Carbamazepine **decrease** Warfarin's effect by increasing its metabolism.

Question 263: Warm antibody hemolytic anemia is seen in all of the following drugs except?

A. Stibophen (Correct Answer)
B. Methyldopa
C. Penicillin
D. Quinidine

Explanation: Drug-induced immune hemolytic anemia (DIIHA) occurs via three primary mechanisms. Understanding these is crucial for NEET-PG. **Explanation of the Correct Answer:** **Option A (Stibophen):** This drug causes hemolysis via the **"Innocent Bystander" (Immune Complex) mechanism**. In this type, the drug binds to a plasma protein to form a complex; antibodies (usually IgM) then bind to this complex and activate the complement system on the red blood cell (RBC) surface. Because it involves complement activation rather than direct warm-antibody (IgG) coating of the RBC, it is categorized separately from classic warm antibody hemolytic anemia. **Explanation of Incorrect Options:** * **Option B (Methyldopa):** This is the classic example of the **True Autoimmune mechanism**. It induces the formation of warm IgG antibodies (anti-Rh) that react directly with RBC antigens even in the absence of the drug. * **Option C (Penicillin):** This follows the **Hapten/Drug Adsorption mechanism**. Penicillin binds to the RBC membrane; IgG antibodies then target the drug-membrane complex. These are warm antibodies (IgG) that cause extravascular hemolysis. * **Option D (Quinidine):** While Quinidine is traditionally associated with the immune complex mechanism (like Stibophen), it is frequently grouped under drugs causing warm-antibody mediated destruction in clinical classification, making Stibophen the "most correct" exception in this specific MCQ context. **High-Yield Clinical Pearls for NEET-PG:** * **Methyldopa:** Causes a **Positive Direct Coombs Test** in 15% of patients, but only 1% develop actual hemolysis. * **Warm Antibodies:** Usually **IgG**; cause extravascular hemolysis (spleen). * **Cold Antibodies:** Usually **IgM**; cause intravascular hemolysis (complement-mediated). * **Drug of choice for Warm AIHA:** Corticosteroids.

Question 264: Epsilon aminocaproic acid (EACA) can be used in the treatment of adverse effects caused by which of the following agents?

A. Streptokinase (Correct Answer)
B. Heparin
C. Warfarin
D. Any of the above

Explanation: ### Explanation **1. Why Streptokinase is Correct:** Streptokinase is a **thrombolytic (fibrinolytic)** agent that works by converting plasminogen to plasmin. Plasmin is the enzyme responsible for degrading fibrin clots. Excessive plasmin activity can lead to systemic fibrinolysis and life-threatening hemorrhage. **Epsilon aminocaproic acid (EACA)** is an **antifibrinolytic** drug. It acts as a lysine analogue that competitively inhibits plasminogen activation and prevents plasmin from binding to fibrin. Therefore, EACA (along with Tranexamic acid) is the specific antidote used to reverse bleeding caused by thrombolytics like Streptokinase, Alteplase, or Urokinase. **2. Why Other Options are Incorrect:** * **Heparin (Option B):** Heparin is an anticoagulant that enhances the activity of Antithrombin III. Its specific pharmacological antagonist is **Protamine sulfate**. * **Warfarin (Option C):** Warfarin inhibits Vitamin K Epoxide Reductase (VKOR). Its effects are reversed using **Vitamin K1 (Phytonadione)** for slow reversal, or **Fresh Frozen Plasma (FFP)** and **Prothrombin Complex Concentrate (PCC)** for immediate reversal. * **Any of the above (Option D):** This is incorrect because EACA has a specific mechanism targeting the fibrinolytic pathway, not the coagulation cascade inhibited by Heparin or Warfarin. **3. High-Yield Clinical Pearls for NEET-PG:** * **Tranexamic Acid (TXA):** It is 7–10 times more potent than EACA and is more commonly used in clinical practice for trauma, menorrhagia, and postpartum hemorrhage. * **Mechanism Tip:** Remember that EACA/TXA block the **"Lysine Binding Sites"** on plasminogen. * **Contraindication:** EACA should be avoided in cases of upper urinary tract bleeding (e.g., hematuria) as it can cause unlysed clots leading to ureteral obstruction and acute renal failure. * **Aprotinin:** Another antifibrinolytic that acts by directly inhibiting plasmin (direct enzyme inhibitor).

Question 265: Eltrombopag is a

A. Erythropoietin analogue
B. Erythropoietin receptor agonist
C. Thrombopoietin analogue (Correct Answer)
D. GMCSF analogue

Explanation: **Explanation:** **Eltrombopag** is a small-molecule, orally active **thrombopoietin (TPO) receptor agonist**. It functions as a TPO analogue by binding to the transmembrane domain of the erythropoietin/thrombopoietin (c-mpl) receptor. This interaction initiates signaling pathways (JAK/STAT and MAPK) that lead to the proliferation and differentiation of megakaryocytes, ultimately increasing platelet production. **Analysis of Options:** * **Option A & B (Erythropoietin analogue/receptor agonist):** These drugs (e.g., Epoetin alfa, Darbepoetin alfa) stimulate the production of red blood cells. They are used in anemias related to chronic kidney disease or chemotherapy, not for platelet disorders. * **Option C (Correct):** Eltrombopag mimics the action of endogenous thrombopoietin, making it a functional analogue used to treat thrombocytopenia. * **Option D (GMCSF analogue):** Granulocyte-Macrophage Colony-Stimulating Factor analogues (e.g., Sargramostim) primarily stimulate the production of neutrophils and monocytes. **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** Chronic immune thrombocytopenia (ITP) refractory to steroids, thrombocytopenia in Hepatitis C patients (to allow interferon therapy), and severe aplastic anemia. * **Route of Administration:** Eltrombopag is **oral**, whereas **Romiplostim** (another TPO agonist) is administered **subcutaneously**. * **Key Side Effect:** Hepatotoxicity (monitor LFTs) and potential for marrow fibrosis. * **Drug Interaction:** It chelates with polyvalent cations (calcium, iron, antacids); it must be taken on an empty stomach (1 hour before or 2 hours after meals).

Question 266: Which of the following is a longer-acting erythropoietin derivative?

A. Sargramostim
B. Darbepoetin alfa (Correct Answer)
C. Dornase alfa
D. Oprelvekin

Explanation: **Explanation:** **Darbepoetin alfa** is the correct answer because it is a synthetic glycosylated form of erythropoietin. The primary medical concept here is **hyperglycosylation**. While recombinant human erythropoietin (Epoetin alfa) has three N-linked carbohydrate chains, Darbepoetin alfa contains **five**. These additional chains significantly increase its molecular weight and decrease its affinity for the erythropoietin receptor, which paradoxically results in a much **longer half-life** (approximately 24–26 hours compared to 4–8 hours for Epoetin). This allows for less frequent dosing (once weekly or every two weeks) in patients with chronic kidney disease or chemotherapy-induced anemia. **Analysis of Incorrect Options:** * **A. Sargramostim:** This is a recombinant **GM-CSF** (Granulocyte-Macrophage Colony-Stimulating Factor) used to stimulate the production of neutrophils and monocytes, not red blood cells. * **C. Dornase alfa:** This is a recombinant **DNase enzyme** used via inhalation in Cystic Fibrosis to decrease the viscosity of mucus by breaking down extracellular DNA. * **D. Oprelvekin:** This is a recombinant **Interleukin-11 (IL-11)** used to stimulate megakaryocytopoiesis and prevent severe thrombocytopenia. **High-Yield Clinical Pearls for NEET-PG:** * **Methoxy polyethylene glycol-epoetin beta:** This is the longest-acting erythropoietin (Continuous Erythropoietin Receptor Activator - CERA), administered once a month. * **Adverse Effect:** The most common side effect of erythropoiesis-stimulating agents (ESAs) is **hypertension** and an increased risk of thromboembolism. * **Black Box Warning:** ESAs can increase the risk of tumor progression or recurrence in certain cancers.

Question 267: A 40-year-old man presents with megaloblastic anemia and early neurological abnormalities. Which drug is most likely required?

A. Folic acid
B. Iron sulfate
C. Erythropoietin
D. Vitamin B12 (Correct Answer)

Explanation: The clinical presentation of **megaloblastic anemia** combined with **neurological abnormalities** is the classic hallmark of **Vitamin B12 (Cobalamin) deficiency**. **Why Vitamin B12 is correct:** Vitamin B12 is essential for two critical enzymatic reactions: 1. **DNA Synthesis:** It acts as a cofactor for methionine synthase, which converts homocysteine to methionine [1]. This process recycles folate; without B12, folate is "trapped" (the **Folate Trap**), leading to impaired DNA synthesis and megaloblastic changes [1]. 2. **Myelin Integrity:** B12 is a cofactor for methylmalonyl-CoA mutase. Deficiency leads to an accumulation of **methylmalonic acid (MMA)**, which results in the synthesis of abnormal fatty acids that incorporate into neuronal lipids. This causes **Subacute Combined Degeneration (SCD)** of the spinal cord, manifesting as paresthesia, loss of vibration/proprioception, and ataxia [2]. **Why other options are incorrect:** * **Folic acid:** While it can correct the megaloblastic anemia (by bypassing the folate trap), it **cannot** correct the neurological deficits [3]. In fact, giving folic acid alone in B12 deficiency can worsen neurological damage. * **Iron sulfate:** Used for microcytic hypochromic anemia, not megaloblastic anemia. * **Erythropoietin:** Used for anemia of chronic kidney disease; it does not address vitamin deficiencies. **High-Yield NEET-PG Pearls:** * **Diagnostic Marker:** Elevated levels of **Methylmalonic Acid (MMA)** are specific for B12 deficiency, whereas **Homocysteine** is elevated in both B12 and Folate deficiency [1]. * **Schilling Test:** Historically used to determine the cause of B12 malabsorption (e.g., Pernicious Anemia). * **Neurological involvement:** Always rule out B12 deficiency before starting Folate to prevent irreversible cord damage [2].

Question 268: Which drug does not cause hemolysis in G6PD deficiency?

A. Primaquine
B. Dapsone
C. Corticosteroids (Correct Answer)
D. Methylene Blue

Explanation: **Explanation:** Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is an X-linked recessive disorder where erythrocytes lack the ability to generate sufficient NADPH. NADPH is essential for maintaining a pool of reduced glutathione, which protects red blood cells from oxidative stress. When exposed to oxidizing agents, hemoglobin denatures into **Heinz bodies**, leading to hemolysis. **Why Corticosteroids are the Correct Answer:** Corticosteroids (Option C) are anti-inflammatory and immunosuppressive agents. They do not possess oxidative properties and do not interfere with the glutathione pathway. Therefore, they do not trigger hemolytic crises in G6PD-deficient individuals. **Analysis of Incorrect Options:** * **Primaquine (Option A):** A classic "high-yield" trigger. It is an antimalarial that generates reactive oxygen species (ROS), causing severe hemolysis in G6PD deficiency. * **Dapsone (Option B):** Used for leprosy and dermatitis herpetiformis, it is a potent oxidizing agent known to cause both hemolysis and methemoglobinemia. * **Methylene Blue (Option D):** While used to treat methemoglobinemia, it requires NADPH to be converted to leukomethylene blue. In G6PD deficiency, the lack of NADPH makes it ineffective and potentially oxidative, worsening hemolysis. **NEET-PG High-Yield Pearls:** * **Other common triggers:** Nitrofurantoin, Sulfonamides, Quinolones, and Fava beans (Favism). * **Diagnosis:** Look for "Bite cells" (degmacytes) and "Heinz bodies" on a peripheral smear. * **Timing:** Hemolysis typically occurs 2–3 days after drug exposure. * **Safe Alternatives:** For analgesia, Paracetamol is generally safe in therapeutic doses; for malaria, Chloroquine is safe.

Question 269: Which drug is used in mild hemophilia?

A. Corticosteroids
B. DDAVP (Correct Answer)
C. Vitamin K
D. Tranexamic acid

Explanation: **Explanation:** **Correct Option: B (DDAVP / Desmopressin)** DDAVP is a synthetic analogue of vasopressin (ADH) [3]. In patients with **mild Hemophilia A** and **Type 1 von Willebrand Disease (vWD)**, DDAVP acts on V2 receptors to trigger the release of stored **Factor VIII** and **von Willebrand Factor (vWF)** from the Weibel-Palade bodies of endothelial cells. This transiently increases plasma levels of these factors (usually 3–5 fold), making it the treatment of choice for minor surgical procedures or spontaneous bleeding in mild cases. It is ineffective in severe Hemophilia A (where factor stores are absent) or Hemophilia B (Factor IX deficiency). **Incorrect Options:** * **A. Corticosteroids:** These are used to manage immune-mediated complications (like inhibitors) or joint inflammation (hemophilic arthropathy) but do not increase clotting factor levels. * **C. Vitamin K:** This is essential for the synthesis of Factors II, VII, IX, and X [2]. It is used for warfarin reversal or Vitamin K deficiency but has no role in treating Hemophilia A. * **D. Tranexamic acid:** This is an antifibrinolytic agent. While often used as an **adjunct** in hemophilia (especially for mucosal bleeds) to prevent clot breakdown, it is not the primary drug used to elevate factor levels. **High-Yield Pearls for NEET-PG:** * **Route:** DDAVP can be administered IV, SC, or via a high-concentration nasal spray (Stimate). * **Side Effects:** Hyponatremia and water intoxication (due to antidiuretic effect) and facial flushing [1]. * **Tachyphylaxis:** Repeated doses lead to diminished effect as endothelial stores become exhausted. * **Contraindication:** Avoid in Type 2B vWD (may cause paradoxical thrombocytopenia).

Question 270: A patient is diagnosed to be having iron deficiency anemia. What agent can be used to improve the absorption of iron?

A. Antacids
B. Tetracyclines
C. Phosphates
D. Ascorbic acid (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Ascorbic acid** **Mechanism of Action:** Iron is primarily absorbed in the duodenum and proximal jejunum. Dietary iron exists in two forms: Heme and Non-heme (ferric, $Fe^{3+}$). However, the human body can only absorb iron in its **ferrous ($Fe^{2+}$) state** via the divalent metal transporter 1 (DMT1). **Ascorbic acid (Vitamin C)** enhances iron absorption through two mechanisms: 1. It acts as a reducing agent, converting ferric iron ($Fe^{3+}$) to the more soluble ferrous iron ($Fe^{2+}$). 2. It forms a soluble iron-ascorbate complex that prevents the precipitation of iron in the alkaline environment of the small intestine. **Analysis of Incorrect Options:** * **A. Antacids:** These increase gastric pH. An acidic environment is essential for the ionization and solubilization of iron; therefore, antacids significantly **decrease** iron absorption. * **B. Tetracyclines:** These drugs form insoluble **chelates** with divalent and trivalent cations like iron, preventing the absorption of both the drug and the mineral. * **C. Phosphates:** Found in foods like eggs and cereals, phosphates (along with phytates and oxalates) form **insoluble complexes** with iron in the gut, hindering its uptake. **NEET-PG High-Yield Pearls:** * **Oral Iron:** Ferrous salts (Sulfate, Fumarate, Gluconate) are preferred over ferric salts due to better bioavailability. * **Hepcidin:** This liver-derived peptide is the **master regulator** of iron homeostasis; it inhibits iron absorption by degrading ferroportin. * **Drug Interactions:** Iron should be taken on an empty stomach for maximal absorption, but if GI distress occurs, it is taken with food (though this reduces absorption by 40-50%). * **Toxicity:** Acute iron poisoning is treated with **Desferrioxamine** (IV) or **Deferiprone/Deferasirox** (Oral).

Practice by Chapter

Hematopoietic Growth Factors

Practice Questions

Iron Preparations and Management of Iron Deficiency

Practice Questions

Vitamin B12 and Folic Acid

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Anticoagulants: Heparins and Direct Inhibitors

Practice Questions

Oral Anticoagulants

Practice Questions

Antiplatelet Drugs

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Thrombolytic Agents

Practice Questions

Hemostatic Drugs

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Plasma Expanders

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Blood Transfusion and Alternatives

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