Drugs Affecting Blood and Blood Formation Practice Questions

Q: Which one of the following is a direct thrombin inhibitor?

Argatroban. ### Explanation **Correct Answer: D. Argatroban** **Mechanism of Action:** Argatroban is a **Direct Thrombin Inhibitor (DTI)**. Unlike indirect anticoagulants (like heparin), DTIs bind directly to the active site of thrombin (Factor IIa) and inhibit its enzymatic activity. They do not require the cofactor Antithrombin III to exert their effect. Argatroban is a small molecule, univalent DTI derived from L-arginine. **Analysis of Incorrect Options:** * **A & B (Enoxaparin and Dalteparin):** These are **Low Molecular Weight Heparins (LMWHs)**. They act indirectly by binding to Antithrombin III, which then inactivates Factor Xa and, to a lesser extent, Factor IIa (Thrombin). * **C (Fondaparinux):** This is a synthetic pentasaccharide that acts as a **selective Factor Xa inhibitor**. It binds to Antithrombin III to specifically neutralize Factor Xa, with no activity against Thrombin (IIa). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Argatroban is the preferred anticoagulant in patients with **Heparin-Induced Thrombocytopenia (HIT)**. * **Elimination:** Argatroban is primarily metabolized by the **liver**. Therefore, it is safe to use in patients with renal failure but requires dose adjustment in hepatic impairment. (Contrast this with Bivalirudin/Lepirudin, which are renally cleared). * **Monitoring:** The anticoagulant effect of Argatroban is monitored using the **aPTT** (activated Partial Thromboplastin Time). * **Other DTIs to remember:** Dabigatran (Oral), Bivalirudin, and Desirudin (Parenteral).

Q: Which chelating agent is used in chronic thalassemia major for iron overload?

Deferiprone. **Explanation:** In patients with Thalassemia Major, chronic blood transfusions lead to secondary iron overload (hemosiderosis). Since the human body lacks an active mechanism to excrete excess iron, chelation therapy is mandatory once ferritin levels exceed 1000 ng/ml or after 10–20 transfusions. **Why Deferiprone is correct:** **Deferiprone** is an **oral** iron chelator. It is highly effective and particularly noted for its ability to remove iron from the myocardium, making it superior in preventing iron-induced heart failure. In the context of the options provided, it is a standard agent used for chronic management. **Analysis of Incorrect Options:** * **A. Oral Desferroxamine:** This is incorrect because **Desferroxamine (DFO) is not orally active.** It has poor gastrointestinal absorption and must be administered parenterally. * **B. EDTA:** Ethylene Diamine Tetra-acetic Acid is primarily used for **lead poisoning**, not for chronic iron overload in thalassemia. * **D. Intravenous Deferoxamine:** While Deferoxamine is used for iron overload, it is typically administered via **slow subcutaneous infusion** (over 8–12 hours) rather than bolus intravenous injection for chronic management. Furthermore, oral agents like Deferiprone or Deferasirox are often preferred for better patient compliance in chronic settings. **High-Yield Clinical Pearls for NEET-PG:** * **Deferoxamine:** Side effects include ototoxicity (high-frequency hearing loss) and retinal toxicity. * **Deferiprone:** The most serious side effect is **agranulocytosis/neutropenia**; regular monitoring of Absolute Neutrophil Count (ANC) is required. * **Deferasirox:** A once-daily oral chelator; currently the most commonly used agent due to its long half-life and ease of administration. * **Drug of Choice for Acute Iron Poisoning:** Intravenous Deferoxamine.

Q: Which of the following is a recently approved monoclonal antibody for the treatment of Hemophilia A?

Emicizumab. Emicizumab is a breakthrough humanized bispecific monoclonal antibody used for the prophylaxis of Hemophilia A. Its mechanism of action is high-yield: it mimics the function of activated Factor VIII. It bridges activated Factor IX and Factor X, bringing them into close proximity to facilitate the activation of Factor X, which is the essential step in the coagulation cascade that is deficient in Hemophilia A. Notably, it is effective in patients both with and without Factor VIII inhibitors. Analysis of Incorrect Options: * Sarilumab: An interleukin-6 (IL-6) receptor antagonist primarily used in the treatment of moderate-to-severe Rheumatoid Arthritis. * Abaloparatide: A synthetic analog of parathyroid hormone-related protein (PTHrP) used as an anabolic agent for the treatment of postmenopausal osteoporosis. * Durvalumab: An immune checkpoint inhibitor (anti-PD-L1 monoclonal antibody) used in the treatment of various malignancies, such as non-small cell lung cancer and urothelial carcinoma. Clinical Pearls for NEET-PG: * Route of Administration: Unlike Factor VIII concentrates which require IV infusion, Emicizumab is administered subcutaneously, significantly improving patient compliance. * Half-life: It has a long half-life (approx. 4 weeks), allowing for weekly or even monthly dosing. * Monitoring: Standard aPTT tests cannot be used to monitor coagulation in patients on Emicizumab as it will show a falsely shortened (normal) result. * Other New Drugs: Keep an eye on Fitusiran (siRNA targeting Antithrombin) and Concizumab (anti-TFPI), which are also emerging in hemophilia management.

Q: Aspirin prolongs bleeding by inhibiting the synthesis of which of the following?

Thromboxane A2. ### Explanation **Correct Option: D. Thromboxane A2** Aspirin (Acetylsalicylic acid) is an irreversible inhibitor of the enzyme **Cyclooxygenase-1 (COX-1)**. In platelets, COX-1 is responsible for converting arachidonic acid into **Thromboxane A2 (TXA2)**. TXA2 is a potent vasoconstrictor and a key mediator of platelet aggregation. Because platelets are anucleated, they cannot synthesize new enzymes. Aspirin’s irreversible acetylation of COX-1 lasts for the entire lifespan of the platelet (approx. 7–10 days). By inhibiting TXA2 synthesis, aspirin prevents platelet plug formation, thereby prolonging bleeding time. --- ### Why the other options are incorrect: * **A. Adenosine receptors:** These are involved in coronary vasodilation and cardiac conduction (targeted by drugs like Adenosine or Caffeine), not the primary mechanism of aspirin. * **B. Cyclic AMP:** Increased levels of cAMP in platelets actually *inhibit* aggregation (the mechanism of drugs like Cilostazol or Dipyridamole). Aspirin does not work by decreasing cAMP. * **C. Prostacyclin (PGI2):** Produced by vascular endothelial cells, PGI2 *inhibits* platelet aggregation. While aspirin can inhibit PGI2 at high doses, its anti-platelet effect is specifically due to the suppression of TXA2. Endothelial cells can also resynthesize COX, unlike platelets. --- ### NEET-PG High-Yield Pearls: 1. **Low-dose Aspirin (75–150 mg):** Selectively inhibits TXA2, making it ideal for cardio-protection. 2. **Bleeding Time vs. Clotting Time:** Aspirin increases **Bleeding Time (BT)** but has no effect on Clotting Time (CT) or PT/APTT. 3. **Surgery Protocol:** Aspirin should ideally be stopped **7 days prior** to elective surgery to allow for the generation of new, functional platelets. 4. **Reye’s Syndrome:** Avoid aspirin in children with viral infections (Varicella/Influenza) due to the risk of fulminant hepatic failure and encephalopathy.

Q: Which of the following is a direct-acting thrombin inhibitor?

Hirudin. ### Explanation **Direct Thrombin Inhibitors (DTIs)** are anticoagulants that bind directly to thrombin (Factor IIa) and inhibit its activity without requiring a cofactor like Antithrombin III. **Why Hirudin is Correct:** Hirudin is a naturally occurring polypeptide originally found in the salivary glands of medicinal leeches (*Hirudo medicinalis*). It is a potent, irreversible, and **direct-acting thrombin inhibitor**. Unlike indirect inhibitors, it can neutralize both free-circulating thrombin and fibrin-bound thrombin within a clot. Synthetic analogs include Lepirudin, Desirudin, and Bivalirudin (parenteral), as well as Dabigatran (oral). **Why Other Options are Incorrect:** * **Heparin:** This is an **indirect thrombin inhibitor**. It requires the presence of a plasma cofactor, **Antithrombin III (AT-III)**, to exert its effect. Heparin binds to AT-III, causing a conformational change that accelerates the inactivation of Factor Xa and Thrombin. * **Warfarin:** This is an **oral anticoagulant** that acts as a Vitamin K antagonist. It inhibits the enzyme **VKORC1**, thereby preventing the γ-carboxylation of Vitamin K-dependent clotting factors (II, VII, IX, and X). It has no direct effect on thrombin itself. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** DTIs (like Argatroban or Bivalirudin) are the drugs of choice for patients who develop **Heparin-Induced Thrombocytopenia (HIT)**. * **Monitoring:** The effect of parenteral DTIs is monitored using **aPTT**. * **Oral DTI:** **Dabigatran** is the only oral DTI; its specific reversal agent is **Idarucizumab**. * **Bivalirudin** is a synthetic analog of Hirudin used primarily during Percutaneous Coronary Intervention (PCI).

Q: An elderly patient on warfarin therapy for deep vein thrombosis presents with a nosebleed. Her INR is found to be 7.0. In addition to discontinuing warfarin, what is the most appropriate next step to manage the hemorrhagic risk?

Vitamin K1. **Explanation:** The patient is experiencing **Warfarin toxicity**, characterized by an elevated International Normalized Ratio (INR) and active bleeding. Warfarin acts as a Vitamin K antagonist by inhibiting the enzyme **Vitamin K Epoxide Reductase (VKOR)**, which prevents the gamma-carboxylation (activation) of clotting factors II, VII, IX, and X. **Why Vitamin K1 is correct:** Vitamin K1 (Phytonadione) is the specific antidote for warfarin. It bypasses the inhibited VKOR enzyme to provide a source for the synthesis of functional clotting factors. According to clinical guidelines, for an INR > 10 or INR > 4.5 with bleeding, Vitamin K is indicated. In cases of life-threatening hemorrhage, Vitamin K is supplemented with Prothrombin Complex Concentrate (PCC) or Fresh Frozen Plasma (FFP) for immediate effect. **Why other options are incorrect:** * **Desmopressin (dDAVP):** Used to increase levels of Factor VIII and von Willebrand factor; it is the treatment for von Willebrand disease and mild Hemophilia A, not warfarin reversal. * **Factor VIII:** Specifically used for Hemophilia A. Warfarin affects multiple factors (II, VII, IX, X), so replacing only Factor VIII is ineffective. * **Protamine sulfate:** This is the specific antidote for **Heparin** overdose, acting via chemical neutralization. **NEET-PG High-Yield Pearls:** * **Monitoring:** Warfarin is monitored by **PT/INR** (Extrinsic pathway), while Heparin is monitored by **aPTT** (Intrinsic pathway). * **Half-life:** Factor VII has the shortest half-life (6 hours), making it the first to decline and the first to be reflected in an increased INR. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes Fetal Warfarin Syndrome/Chondrodysplasia punctata); Heparin is the preferred anticoagulant for pregnant women.

Q: Which clotting parameter is most likely to be increased in Vitamin K deficiency?

Prothrombin Time (PT). **Explanation:** Vitamin K is an essential cofactor for the enzyme **gamma-glutamyl carboxylase**, which is responsible for the post-translational modification (gamma-carboxylation) of clotting **factors II, VII, IX, and X**, as well as proteins C and S. **Why PT is the correct answer:** Among these factors, **Factor VII** has the shortest half-life (approximately 4–6 hours). Because Factor VII is a key component of the **extrinsic pathway**, its rapid decline in Vitamin K deficiency leads to an early and significant prolongation of the **Prothrombin Time (PT)**. While the intrinsic pathway (measured by PTT) is eventually affected due to declines in factors IX, X, and II, the PT is the most sensitive and earliest indicator of Vitamin K deficiency. **Analysis of Incorrect Options:** * **A. Partial Thromboplastin Time (PTT):** This measures the intrinsic and common pathways. While PTT can increase in severe Vitamin K deficiency (due to low factors IX, X, and II), it is less sensitive than PT because the involved factors have longer half-lives than Factor VII. * **C. Platelet count:** Vitamin K deficiency affects soluble clotting factors, not the production or consumption of platelets. * **D. Fibrinogen time (Thrombin Time):** This measures the conversion of fibrinogen to fibrin. It is affected by heparin or hypofibrinogenemia, not by Vitamin K status. **High-Yield NEET-PG Pearls:** * **Warfarin** mechanism: Inhibits Vitamin K Epoxide Reductase (VKOR), mimicking Vitamin K deficiency. * **Newborns** are routinely given Vitamin K prophylaxis because they have sterile guts (no Vitamin K-producing bacteria) and poor placental transfer. * **PIVKA** (Proteins Induced by Vitamin K Absence) are non-functional precursors that circulate in deficiency states.

Q: Which of the following GPIIb/IIIa antagonists is safe in renal failure?

Abciximab. **Explanation:** **Glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors** are potent antiplatelet agents that block the final common pathway of platelet aggregation by preventing the binding of fibrinogen to its receptor. **1. Why Abciximab is the correct answer:** Abciximab is a chimeric monoclonal antibody fragment. Unlike other drugs in this class, it is **not primarily cleared by the kidneys**. It is eliminated via the reticuloendothelial system and through binding to platelets (where it remains for the life of the platelet). Because its clearance is independent of renal function, **no dose adjustment is required in renal failure**, making it the safest choice for patients with significant renal impairment. **2. Why the other options are incorrect:** * **Eptifibatide (Option B):** This is a synthetic cyclic peptide. It is primarily excreted by the kidneys. In patients with renal impairment (CrCl < 50 mL/min), the dose must be reduced, and it is contraindicated in patients on dialysis. * **Tirofiban (Option C):** This is a non-peptide small molecule. Like eptifibatide, it is predominantly cleared renally. Dose reduction is mandatory if CrCl is < 60 mL/min. * **Option D:** Since both Eptifibatide and Tirofiban require renal dose adjustment, this option is incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Blocks the binding of fibrinogen and von Willebrand factor to GPIIb/IIIa receptors. * **Reversibility:** Abciximab has a long biological half-life (platelet function recovers in 24–48 hours), whereas Eptifibatide and Tirofiban are short-acting (recovery in 4–8 hours). * **Side Effects:** The most common side effect for all GPIIb/IIIa inhibitors is **bleeding** and **thrombocytopenia**. * **Monitoring:** Always monitor platelet counts within 2–4 hours of starting these drugs.

Q: Which of the following is an example of low molecular weight heparin?

Enoxaparin. **Explanation:** **Correct Option: C. Enoxaparin** Low Molecular Weight Heparins (LMWHs) are derived from unfractionated heparin (UFH) through chemical or enzymatic depolymerization. **Enoxaparin** is the most commonly used LMWH. These drugs act primarily by inhibiting **Factor Xa** via antithrombin III, with minimal effect on Thrombin (Factor IIa). Other examples include Dalteparin, Nadroparin, and Tinzaparin (remember the suffix **"-parin"**). **Analysis of Incorrect Options:** * **A. Alteplase:** This is a **Thrombolytic** (Fibrinolytic) agent. It is a recombinant tissue plasminogen activator (rt-PA) that converts plasminogen to plasmin, which then degrades fibrin clots. * **B & D. Lepirudin and Hirudin:** These are **Direct Thrombin Inhibitors (DTIs)**. Hirudin is a natural anticoagulant derived from leech saliva, and Lepirudin is its recombinant derivative. They bind directly to thrombin without requiring antithrombin III as a cofactor. **High-Yield Clinical Pearls for NEET-PG:** * **Monitoring:** Unlike UFH, LMWHs do not require routine aPTT monitoring due to their predictable bioavailability and pharmacokinetics. * **Renal Clearance:** LMWHs are primarily excreted by the kidneys; therefore, they are **contraindicated in renal failure** (CrCl <30 ml/min). UFH is the drug of choice in such patients. * **Antidote:** Protamine sulfate can completely neutralize UFH, but it only **partially neutralizes** LMWH. * **HIT:** LMWHs have a lower risk of causing Heparin-Induced Thrombocytopenia (HIT) compared to UFH.

Q: All of the following statements about unfractionated heparin are true except?

It is a powerful anticoagulant only in vivo. **Explanation:** The correct answer is **A**, as the statement "It is a powerful anticoagulant only in vivo" is false. **1. Why Option A is the correct answer (False statement):** Unfractionated Heparin (UFH) acts by binding to **Antithrombin III (AT-III)**, which is a naturally occurring plasma protein. Because AT-III is present both in circulating blood and in collected blood samples, heparin is effective **both in vivo (inside the body) and in vitro (outside the body)**. This is why heparinized tubes are used in laboratories to prevent blood from clotting after collection. In contrast, oral anticoagulants like Warfarin work only *in vivo* because they interfere with the hepatic synthesis of clotting factors. **2. Analysis of Incorrect Options (True statements):** * **Option B:** Protamine sulfate is a strongly basic protein that ionically binds to acidic heparin to form a stable, inactive complex. It is the specific chemical antagonist used to reverse heparin overdose. * **Option C:** Heparin should **never be given intramuscularly (IM)** because it can cause large, painful hematomas due to the high vascularity of muscle tissue and the drug's potent anticoagulant effect. * **Option D:** The heparin-AT-III complex inactivates several clotting factors, most significantly **Thrombin (IIa) and Factor Xa** (in a 1:1 ratio). **Clinical Pearls for NEET-PG:** * **Monitoring:** UFH is monitored using **aPTT** (Target: 1.5–2.5 times the control). * **Side Effects:** The most common side effect is bleeding; the most unique is **Heparin-Induced Thrombocytopenia (HIT)**. * **LMWH vs. UFH:** Low Molecular Weight Heparins (e.g., Enoxaparin) mainly inhibit Factor Xa and do not require routine aPTT monitoring. * **Pregnancy:** Heparin is the **anticoagulant of choice during pregnancy** as it does not cross the placenta.

Question 1

Which one of the following is a direct thrombin inhibitor?

Accepted Answer

Argatroban

Answer

Enoxaparin

Answer

Dalteparin

Answer

Fondaparinux

Question 2

Which chelating agent is used in chronic thalassemia major for iron overload?

Accepted Answer

Deferiprone

Answer

Oral desferroxamine

Answer

EDTA

Answer

Intravenous Deferoxamine

Question 3

Which of the following is a recently approved monoclonal antibody for the treatment of Hemophilia A?

Accepted Answer

Emicizumab

Answer

Sarilumab

Answer

Abaloparatide

Answer

Durvalumab

Question 4

Aspirin prolongs bleeding by inhibiting the synthesis of which of the following?

Accepted Answer

Thromboxane A2

Answer

Adenosine receptors

Answer

Cyclic AMP

Answer

Prostacyclin

Question 5

Which of the following is a direct-acting thrombin inhibitor?

Accepted Answer

Hirudin

Answer

Heparin

Answer

Warfarin

Answer

All of the above

Question 6

An elderly patient on warfarin therapy for deep vein thrombosis presents with a nosebleed. Her INR is found to be 7.0. In addition to discontinuing warfarin, what is the most appropriate next step to manage the hemorrhagic risk?

Accepted Answer

Vitamin K1

Answer

Desmopressin

Answer

Factor VIII

Answer

Protamine sulfate

Question 7

Which clotting parameter is most likely to be increased in Vitamin K deficiency?

Accepted Answer

Prothrombin Time (PT)

Answer

Partial Thromboplastin Time (PTT)

Answer

Platelet count

Answer

Fibrinogen time

Question 8

Which of the following GPIIb/IIIa antagonists is safe in renal failure?

Accepted Answer

Abciximab

Answer

Eptifibatide

Answer

Tirofiban

Answer

Eptifibatide and Tirofiban

Question 9

Which of the following is an example of low molecular weight heparin?

Accepted Answer

Enoxaparin

Answer

Alteplase

Answer

Lepirudin

Answer

Hirudin

Question 10

All of the following statements about unfractionated heparin are true except?

Accepted Answer

It is a powerful anticoagulant only in vivo

Answer

Protamine sulfate is the antidote

Answer

It should not be given by intramuscular route

Answer

It acts by inhibiting factor IIa and Xa

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

On this page

Practice by Chapter

Want unlimited practice?