Drugs Affecting Blood and Blood Formation — MCQs

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

Question 161: Which of the following drugs is used in sickle cell anemia?

A. Hydroxyzine
B. Hydroxyurea (Correct Answer)
C. Hydralazine
D. Hydroxychloroquine

Explanation: **Explanation:** **Hydroxyurea** is the standard of care for the management of sickle cell anemia (SCA). Its primary mechanism of action involves the **induction of Fetal Hemoglobin (HbF)** synthesis. HbF inhibits the polymerization of deoxygenated Hemoglobin S (HbS), which prevents the sickling of red blood cells, reduces vaso-occlusive crises, and decreases the need for blood transfusions. Additionally, it reduces the expression of neutrophil adhesion molecules, further improving microvascular flow. **Analysis of Incorrect Options:** * **A. Hydroxyzine:** An H1-receptor antagonist (antihistamine) with sedative properties, used primarily for pruritus and anxiety. It has no role in hemoglobin modulation. * **C. Hydralazine:** A direct-acting arterial vasodilator used in the management of hypertension and heart failure. It does not affect red blood cell morphology. * **D. Hydroxychloroquine:** A Disease-Modifying Antirheumatic Drug (DMARD) and antimalarial used in SLE and Rheumatoid Arthritis. It does not treat sickle cell disease. **High-Yield NEET-PG Pearls:** * **Mechanism:** Hydroxyurea acts as a **Ribonucleotide Reductase inhibitor**, which is also why it is used as a chemotherapeutic agent in myeloproliferative disorders (e.g., Polycythemia Vera). * **Adverse Effects:** The dose-limiting toxicity is **myelosuppression** (neutropenia, thrombocytopenia). It is also potentially teratogenic. * **Other Drugs for SCA:** Newer FDA-approved agents include **Crizanlizumab** (P-selectin inhibitor), **Voxelotor** (HbS polymerization inhibitor), and **L-glutamine**. * **Clinical Benefit:** Hydroxyurea is proven to reduce the frequency of **Acute Chest Syndrome** and painful crises in SCA patients.

Question 162: Which of the following is advocated in dicumarol overdose?

A. Warfarin
B. Heparin
C. LMWH
D. Vitamin K (Correct Answer)

Explanation: **Explanation:** **Dicumarol** is a coumarin derivative and an oral anticoagulant that acts as a **Vitamin K antagonist**. It functions by inhibiting the enzyme Vitamin K Epoxide Reductase (VKOR), which prevents the regeneration of active Vitamin K. This leads to a deficiency in the gamma-carboxylation of Vitamin K-dependent clotting factors (**II, VII, IX, and X**), resulting in an anticoagulant effect. **Why Vitamin K is the correct answer:** In cases of overdose, the physiological antidote is **Vitamin K1 (Phytonadione)**. It bypasses the inhibited reductase enzyme to restore the synthesis of functional clotting factors. For immediate reversal in life-threatening bleeds, Fresh Frozen Plasma (FFP) or Prothrombin Complex Concentrate (PCC) is preferred, followed by Vitamin K. **Why other options are incorrect:** * **Warfarin (Option A):** Like dicumarol, warfarin is a Vitamin K antagonist. Administering it would worsen the toxicity and bleeding risk. * **Heparin (Option B) & LMWH (Option C):** These are parenteral anticoagulants that activate Antithrombin III. They do not reverse the effects of coumarins; instead, they would further increase the patient’s bleeding diathesis. **NEET-PG High-Yield Pearls:** * **Antidote for Heparin:** Protamine Sulfate (a basic protein that neutralizes acidic heparin). * **Monitoring:** Dicumarol/Warfarin therapy is monitored using **PT/INR** (Extrinsic pathway), while Heparin is monitored using **aPTT** (Intrinsic pathway). * **Teratogenicity:** Coumarins are teratogenic (Fetal Warfarin Syndrome), whereas Heparin is the anticoagulant of choice during pregnancy as it does not cross the placenta. * **Skin Necrosis:** A rare side effect of coumarins due to a rapid decline in Protein C levels.

Question 163: All of the following features are common for both cangrelor and ticagrelor except?

A. They are antiplatelet drugs.
B. They reversibly inhibit ADP.
C. Both drugs can be given orally. (Correct Answer)
D. Both drugs have short half-lives.

Explanation: ### Explanation The correct answer is **C: Both drugs can be given orally.** #### 1. Why Option C is Correct (The Key Difference) While both drugs belong to the same pharmacological class (P2Y12 receptor antagonists), they differ significantly in their **route of administration**. * **Ticagrelor** is an **oral** drug. * **Cangrelor** is an **intravenous (IV)** drug. It is the only P2Y12 inhibitor available for parenteral use, characterized by an ultra-rapid onset and offset of action, making it ideal for patients undergoing Percutaneous Coronary Intervention (PCI) who have not been pre-treated with oral antiplatelet agents. #### 2. Analysis of Incorrect Options * **Option A (Antiplatelet drugs):** Both are P2Y12 receptor antagonists that prevent ADP-induced platelet aggregation. * **Option B (Reversible inhibition):** Unlike Clopidogrel and Prasugrel (which are irreversible thienopyridines), both Cangrelor and Ticagrelor are **reversible** inhibitors. They do not require hepatic activation (they are not prodrugs) and bind directly to the receptor. * **Option D (Short half-lives):** Both drugs have relatively short half-lives compared to irreversible agents. Cangrelor has an extremely short half-life (approx. 3–6 minutes), while Ticagrelor’s half-life is about 7–12 hours (requiring twice-daily dosing). #### 3. High-Yield Clinical Pearls for NEET-PG * **Non-Prodrugs:** Ticagrelor and Cangrelor are **direct-acting**; they do not require conversion by CYP450 enzymes (unlike Clopidogrel). * **Ticagrelor Side Effects:** Watch for **Dyspnea** (due to adenosine level elevation) and **Bradycardia/Ventricular pauses**. * **Cangrelor Utility:** Used in the cath lab for immediate platelet inhibition; platelet function returns to normal within 1 hour of stopping the infusion. * **Classification Tip:** Remember **"CP"** (Clopidogrel, Prasugrel) are **Irreversible Prodrugs**, while **"TC"** (Ticagrelor, Cangrelor) are **Reversible Direct-acting** agents.

Question 164: Which of the following drugs inhibits thromboxane A2 synthase?

A. Dazoxiben (Correct Answer)
B. Daltroban
C. Sultroban
D. Lamifiban

Explanation: ### Explanation **Correct Option: A. Dazoxiben** The synthesis of Thromboxane A2 (TXA2) from arachidonic acid involves the enzyme **Thromboxane Synthase**. **Dazoxiben** is a selective inhibitor of this enzyme. By blocking this step, it prevents the conversion of cyclic endoperoxides (PGH2) into TXA2, which is a potent platelet aggregator and vasoconstrictor. Interestingly, inhibiting this enzyme can "shunt" endoperoxides toward the production of Prostacyclin (PGI2) in vascular endothelium, which has anti-aggregatory effects. **Analysis of Incorrect Options:** * **B & C (Daltroban and Sultroban):** These drugs are **Thromboxane Receptor Antagonists**. Unlike Dazoxiben, they do not stop the production of TXA2; instead, they block the TP receptors on the surface of platelets and smooth muscle cells, preventing TXA2 from exerting its action. * **D (Lamifiban):** This is a **Glycoprotein IIb/IIIa (GP IIb/IIIa) receptor antagonist**. It acts on the "final common pathway" of platelet aggregation by preventing the binding of fibrinogen to platelets. Other drugs in this class include Abciximab, Eptifibatide, and Tirofiban. **High-Yield NEET-PG Pearls:** * **Aspirin vs. Dazoxiben:** Aspirin inhibits *Cyclooxygenase (COX-1)*, preventing the formation of the precursor PGH2. Dazoxiben acts further downstream on *TXA2 Synthase*. * **Ridogrel:** A unique agent that acts as both a TXA2 synthase inhibitor and a TXA2 receptor antagonist. * **Clinical Note:** While TXA2 synthase inhibitors are pharmacologically significant, they have shown limited clinical superiority over Aspirin in trials for stroke or MI prevention.

Question 165: Sargramostim is a:

A. GM-CSF (Correct Answer)
B. G-CSF
C. IL-11 analogue
D. Erythropoietin analogue

Explanation: **Explanation:** **Sargramostim** is a recombinant human **Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF)**. It is produced using recombinant DNA technology in yeast [1]. It works by binding to specific receptors on hematopoietic progenitor cells, stimulating the proliferation and differentiation of neutrophils, monocytes/macrophages, and eosinophils [2]. **Analysis of Options:** * **A. GM-CSF (Correct):** Sargramostim is the pharmacological analog of GM-CSF [1]. It is primarily used to accelerate myeloid recovery in patients undergoing bone marrow transplantation or intensive chemotherapy [3]. * **B. G-CSF:** **Filgrastim** and **Pegfilgrastim** are the recombinant forms of Granulocyte Colony-Stimulating Factor (G-CSF). Unlike GM-CSF, G-CSF acts more selectively on the neutrophil lineage [2]. * **C. IL-11 analogue:** **Oprelvekin** is the recombinant Interleukin-11 used to treat chemotherapy-induced thrombocytopenia by stimulating megakaryocyte maturation. * **D. Erythropoietin analogue:** **Epoetin alfa** and **Darbepoetin alfa** are erythropoiesis-stimulating agents used to treat anemia associated with chronic kidney disease or chemotherapy. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Use:** Sargramostim is used to reduce the duration of neutropenia and the incidence of life-threatening infections following autologous bone marrow transplantation [1]. * **Side Effects:** A unique side effect of Sargramostim (GM-CSF) not typically seen with Filgrastim (G-CSF) is the **"First-dose reaction,"** characterized by hypotension, flushing, and tachycardia. It can also cause capillary leak syndrome (edema, pleural/pericardial effusions) at high doses. * **Mnemonic:** Sar**gram**ostim = **Granulocyte-Macrophage** (GM). Fil**g**rastim = **G**-CSF.

Question 166: Which of the following is not used for thromboprophylaxis?

A. Heparin
B. Warfarin
C. Antithrombin III (Correct Answer)
D. Aspirin

Explanation: **Explanation:** The goal of **thromboprophylaxis** is to prevent the formation of a thrombus in high-risk patients (e.g., post-surgery or prolonged immobilization). **Why Antithrombin III is the correct answer:** Antithrombin III (ATIII) is a naturally occurring endogenous anticoagulant. While ATIII concentrates are used as **replacement therapy** in patients with hereditary ATIII deficiency (to prevent or treat thromboembolism) or during heparin resistance, it is **not** used as a standard pharmacological agent for routine thromboprophylaxis in the general population. Its use is highly specific and restricted to replacement in deficient states. **Analysis of Incorrect Options:** * **Heparin (Option A):** Low-dose Unfractionated Heparin (UFH) or Low Molecular Weight Heparins (LMWH like Enoxaparin) are the "gold standard" for VTE prophylaxis in surgical and medical patients. * **Warfarin (Option B):** An oral vitamin K antagonist used for long-term thromboprophylaxis, particularly in patients with prosthetic heart valves or chronic atrial fibrillation. * **Aspirin (Option C):** An antiplatelet drug used for "arterial" thromboprophylaxis to prevent myocardial infarction and stroke in high-risk cardiovascular patients. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Heparin:** Heparin does not have intrinsic anticoagulant activity; it works by accelerating the action of **Antithrombin III** by 1000-fold. * **Heparin Resistance:** If a patient does not respond to heparin (monitored via aPTT), suspect **Antithrombin III deficiency**. * **Virchow’s Triad:** Remember the three factors predisposing to thrombus: Endothelial injury, Stasis, and Hypercoagulability. Prophylaxis targets these pathways. * **DOC for Pregnancy:** Heparin (LMWH) is the drug of choice for thromboprophylaxis in pregnancy as it does not cross the placenta, unlike Warfarin (which is teratogenic).

Question 167: Which of the following drugs commonly used in dentistry affects platelet function?

A. Gentamicin
B. Diclofenac
C. Aspirin
D. All of the above (Correct Answer)

Explanation: This question tests the understanding of drug-induced platelet dysfunction, a critical consideration in dental procedures where hemostasis is vital. While Aspirin is the most well-known agent, several other classes of drugs used in dentistry also impair platelet activity. [2] ### **Explanation of the Correct Answer** The correct answer is **D (All of the above)** because each of these drugs interferes with platelet function through different mechanisms: 1. **Aspirin (NSAID):** It causes **irreversible inhibition** of the enzyme Cyclooxygenase-1 (COX-1) [3]. This prevents the synthesis of **Thromboxane A2 (TXA2)**, a potent platelet aggregator and vasoconstrictor [3]. Since platelets lack a nucleus, they cannot synthesize new enzymes, and the effect lasts for the entire lifespan of the platelet (7–10 days). 2. **Diclofenac (NSAID):** Like other non-selective NSAIDs (e.g., Ibuprofen), it causes **reversible inhibition** of COX-1 [2]. Platelet function typically returns to normal once the drug is cleared from the plasma (usually within 24–48 hours) [2]. 3. **Gentamicin (Aminoglycoside):** Though primarily an antibiotic, high doses of aminoglycosides can interfere with platelet aggregation by antagonizing **calcium ions** at the platelet membrane or interfering with membrane phospholipids, thereby inhibiting the release of platelet granules. ### **High-Yield Clinical Pearls for NEET-PG** * **Aspirin Timing:** Aspirin should ideally be stopped **5–7 days** before major surgery to allow for the generation of new, functional platelets. * **NSAID vs. Aspirin:** Unlike Aspirin, the antiplatelet effect of Diclofenac is transient and correlates with its half-life [2]. * **Other Drugs Affecting Platelets:** Apart from those listed, high-dose **Penicillins** (e.g., Carbenicillin, Ticarcillin) are notorious for inhibiting platelet aggregation by binding to the platelet surface. * **Dental Implication:** For routine dental extractions, stopping low-dose aspirin is often not required, but local hemostatic measures (e.g., tranexamic acid mouthwash) should be available [1].

Question 168: Which anticoagulant is not used in vitro?

A. Heparin
B. Warfarin (Correct Answer)
C. Oxalate
D. Citrate

Explanation: **Explanation:** The fundamental distinction in this question lies in the **mechanism of action** of anticoagulants. **Warfarin (Option B)** is a Vitamin K antagonist that acts exclusively **in vivo** (inside a living body). It works by inhibiting the enzyme *Vitamin K Epoxide Reductase (VKOR)* in the liver, thereby preventing the ̳-carboxylation of clotting factors II, VII, IX, and X [1]. Since this process requires a functioning liver and protein synthesis, adding Warfarin directly to a test tube (in vitro) will have no effect on the clotting factors already present in the blood sample. **Analysis of Incorrect Options:** * **Heparin (Option A):** Acts by activating Antithrombin III, which directly neutralizes thrombin and factor Xa [2]. This interaction occurs immediately upon contact, making it effective both **in vivo and in vitro** (e.g., in blood gas syringes). * **Oxalate (Option C) and Citrate (Option D):** These are **calcium chelators** [2]. They prevent coagulation by binding to ionized calcium (Factor IV), a necessary cofactor in the clotting cascade. They are used strictly **in vitro** for laboratory samples and blood banking (Citrate). **High-Yield Clinical Pearls for NEET-PG:** * **Rapid Anticoagulation:** Heparin is the drug of choice for immediate effect (in vivo) [3]. * **Monitoring:** Warfarin is monitored by **PT/INR** (Extrinsic pathway), while Heparin is monitored by **aPTT** (Intrinsic pathway). * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes Fetal Warfarin Syndrome); Heparin is the preferred anticoagulant as it does not cross the placenta. * **Antidotes:** Vitamin K/FFP for Warfarin; Protamine Sulfate for Heparin.

Question 169: Danaparoid is absent of which of the following?

A. Chondroitin sulfate
B. Chitin (Correct Answer)
C. Dermatan sulphate
D. Heparan sulphate

Explanation: **Danaparoid** is a low-molecular-weight heparinoid used primarily as an anticoagulant in patients who develop Heparin-Induced Thrombocytopenia (HIT). It is derived from porcine intestinal mucosa and consists of a specific mixture of glycosaminoglycans [1].**Why Chitin is the correct answer:**Chitin is a long-chain polymer of N-acetylglucosamine found in the exoskeletons of arthropods and cell walls of fungi. It is **not** a component of human or porcine connective tissue and is entirely absent from the formulation of Danaparoid.**Analysis of incorrect options:**Danaparoid is composed of a mixture of three specific glycosaminoglycans (GAGs):* **Heparan sulfate (~84%):** The major component responsible for most of its anti-Xa activity.* **Dermatan sulfate (~12%):** Contributes to the antithrombotic effect by catalyzing thrombin inhibition via Heparin Cofactor II [2].* **Chondroitin sulfate (~4%):** A minor constituent of the natural GAG mixture [2].**Clinical Pearls for NEET-PG:** * **Mechanism of Action:** It acts predominantly by inhibiting **Factor Xa** (Anti-Xa to Anti-IIa ratio is >20:1, much higher than LMWH). * **Drug of Choice:** It is a gold-standard alternative for anticoagulation in **Heparin-Induced Thrombocytopenia (HIT)** because it shows minimal cross-reactivity with heparin antibodies (<10%). * **Monitoring:** Routine monitoring is usually not required, but if necessary, **Anti-Xa levels** are measured (PT and aPTT are not reliable). * **Elimination:** It is primarily cleared by the kidneys; dose adjustment is required in renal failure.

Question 170: Which parameter should be tested before starting heparin therapy?

A. Serum bleeding time
B. Serum clotting time
C. Prothrombin time
D. Activated partial thromboplastin time (Correct Answer)

Explanation: **Explanation:** **Why Option D is correct:** Unfractionated Heparin (UFH) acts primarily by accelerating the activity of **Antithrombin III**, which inhibits Thrombin (Factor IIa) and Factor Xa. It also affects the intrinsic and common pathways of the coagulation cascade. The **Activated Partial Thromboplastin Time (aPTT)** is the standard test used to monitor the intrinsic pathway. Establishing a baseline aPTT is essential before starting therapy to ensure the patient does not have a pre-existing coagulopathy and to calculate the therapeutic range (usually 1.5 to 2.5 times the control). **Why other options are incorrect:** * **A. Bleeding Time:** This measures platelet function and vascular integrity, not the coagulation cascade. It is typically normal in patients on heparin unless there is associated thrombocytopenia. * **B. Clotting Time:** While heparin does prolong clotting time, this test is non-specific, insensitive, and no longer used in modern clinical practice for monitoring anticoagulation. * **C. Prothrombin Time (PT/INR):** This test monitors the extrinsic pathway and is the gold standard for monitoring **Warfarin** (Vitamin K antagonists), not heparin. **High-Yield Clinical Pearls for NEET-PG:** * **Monitoring:** UFH is monitored by **aPTT**, whereas Low Molecular Weight Heparin (LMWH) generally does not require monitoring (if needed, **Anti-Factor Xa levels** are used). * **Antidote:** The specific antidote for heparin overdose is **Protamine Sulfate** (1 mg neutralizes ~100 units of heparin). * **Side Effect:** Watch for **Heparin-Induced Thrombocytopenia (HIT)**; if it occurs, stop heparin immediately and switch to a direct thrombin inhibitor like **Argatroban** or **Lepirudin**. * **Safe in Pregnancy:** Heparin does not cross the placenta, making it the anticoagulant of choice during pregnancy.

Practice by Chapter

Hematopoietic Growth Factors

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Iron Preparations and Management of Iron Deficiency

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Vitamin B12 and Folic Acid

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Anticoagulants: Heparins and Direct Inhibitors

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Oral Anticoagulants

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Antiplatelet Drugs

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Thrombolytic Agents

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Hemostatic Drugs

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Plasma Expanders

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Blood Transfusion and Alternatives

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