Drugs Affecting Blood and Blood Formation Practice Questions

Q: All of the following are anticoagulants, except?

Phytonadione. ### Explanation The correct answer is **A. Phytonadione**. **1. Why Phytonadione is the correct answer:** Phytonadione is another name for **Vitamin K1** [1], [3]. Unlike the other options, it is not an anticoagulant; rather, it is a **procoagulant** (hemostatic agent). Vitamin K acts as a necessary cofactor for the enzyme *gamma-glutamyl carboxylase*, which activates clotting factors **II, VII, IX, and X**, as well as proteins C and S [1], [3]. Clinically, it is used to treat Vitamin K deficiency and to reverse the effects of Warfarin overdose [1], [3], . **2. Why the other options are incorrect:** * **Warfarin (Option B):** A classic oral anticoagulant that acts as a Vitamin K Epoxide Reductase (VKOR) inhibitor [3], [3]. It prevents the recycling of Vitamin K, thereby inhibiting the synthesis of functional clotting factors II, VII, IX, and X [1], [3]. * **Low Molecular Weight Heparin (LMWH) (Option C):** Examples include Enoxaparin and Dalteparin [2]. These are parenteral anticoagulants that primarily act by accelerating the inhibition of **Factor Xa** by Antithrombin III [2]. * **Lepirudin (Option D):** A recombinant derivative of hirudin, it is a **Direct Thrombin Inhibitor (DTI)** [1]. It binds directly to thrombin (Factor IIa) and is typically used in patients with Heparin-Induced Thrombocytopenia (HIT). **3. NEET-PG High-Yield Pearls:** * **Antidote Pairing:** The antidote for Heparin is **Protamine Sulfate** [2], while the antidote for Warfarin is **Vitamin K** (slow onset) or **Fresh Frozen Plasma/PCC** (rapid onset) [1], [3]. * **Monitoring:** Warfarin is monitored using **PT/INR**, whereas Unfractionated Heparin is monitored using **aPTT**. LMWH usually does not require routine monitoring [2]. * **Teratogenicity:** Warfarin is contraindicated in pregnancy (causes Fetal Warfarin Syndrome); Heparin/LMWH is the anticoagulant of choice for pregnant women as it does not cross the placenta.

Q: Which drug causes megaloblastic anemia?

Pyrimethamine. Megaloblastic anemia is primarily caused by a deficiency or impaired utilization of **Vitamin B12 or Folic acid**, leading to defective DNA synthesis [1]. Pyrimethamine is a potent inhibitor of the enzyme **Dihydrofolate Reductase (DHFR)** [2]. By blocking this enzyme, it prevents the conversion of dihydrofolate to tetrahydrofolate (the active form of folic acid), thereby inhibiting DNA synthesis and resulting in megaloblastic changes in the bone marrow [2]. **Analysis of Incorrect Options:** * **A. Isoniazid (INH):** This drug is a Vitamin B6 (Pyridoxine) antagonist. Its primary hematological side effect is **Sideroblastic anemia**, not megaloblastic anemia. It also commonly causes peripheral neuropathy. * **B. Chloramphenicol:** This antibiotic is classically associated with dose-dependent bone marrow suppression and idiosyncratic **Aplastic anemia** (pancytopenia), rather than isolated megaloblastic changes. * **D. Methyldopa:** This centrally acting antihypertensive is a well-known cause of **Autoimmune Hemolytic Anemia (AIHA)**, typically characterized by a positive direct Coombs test. **NEET-PG High-Yield Pearls:** * **DHFR Inhibitors:** Other drugs causing megaloblastic anemia via DHFR inhibition include **Methotrexate** (anticancer), **Trimethoprim** (antibacterial), and **Proguanil** (antimalarial) [2]. * **Other Causes:** **Phenytoin** (interferes with folate absorption) and **Zidovudine** (inhibits DNA polymerase) are also frequent culprits in exam questions. * **Rescue Therapy:** To prevent pyrimethamine or methotrexate-induced hematological toxicity, **Folinic acid (Leucovorin)** is administered, as it bypasses the blocked DHFR enzyme [3].

Q: Caplacizumab is used for the treatment of which condition?

Acquired Thrombotic Thrombocytopenic Purpura (aTTP). **Explanation:** **Caplacizumab** is a novel, humanized **bivalent nanobody** (a single-variable-domain antibody fragment) specifically designed to target the A1 domain of **von Willebrand factor (vWF)**. 1. **Why Option A is correct:** Acquired Thrombotic Thrombocytopenic Purpura (aTTP) is caused by a deficiency of the ADAMTS13 enzyme, leading to ultra-large vWF multimers. These multimers cause spontaneous platelet aggregation and microvascular thrombosis. Caplacizumab **inhibits the interaction between vWF and the platelet glycoprotein Ib-IX-V receptor**, thereby preventing the formation of microthrombi and the subsequent consumption of platelets. It is used as an adjunct to plasma exchange and immunosuppressive therapy. 2. **Why other options are incorrect:** * **Plaque Psoriasis:** Treated with biologics targeting IL-17 (Secukinumab), IL-23 (Ustekinumab), or TNF-alpha (Adalimumab). * **Breast Cancer:** Common targeted therapies include Trastuzumab (anti-HER2) or Palbociclib (CDK4/6 inhibitor). * **Bladder Cancer:** Often treated with Pembrolizumab (PD-1 inhibitor) or Enfortumab vedotin (Nectin-4 inhibitor). **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Anti-vWF nanobody (prevents platelet adhesion). * **Indication:** First-line treatment for **aTTP** to achieve faster platelet normalization and reduce recurrence. * **Route:** Administered intravenously (loading dose) followed by subcutaneous injections. * **Adverse Effect:** Increased risk of **bleeding** (epistaxis, gingival bleeding) due to its mechanism of preventing platelet-vWF binding.

Q: What is the mechanism by which aspirin is used in the treatment of myocardial infarction?

It inhibits thromboxanes.. ### Explanation **1. Why Option A is Correct:** Aspirin (Acetylsalicylic acid) acts as an **irreversible inhibitor** of the enzyme **Cyclooxygenase-1 (COX-1)** [2]. In platelets, this inhibition prevents the synthesis of **Thromboxane A2 (TXA2)**, a potent vasoconstrictor and inducer of platelet aggregation [2], [4]. Since platelets lack a nucleus, they cannot synthesize new enzymes; thus, the antiplatelet effect lasts for the entire lifespan of the platelet (7–10 days). In the context of Myocardial Infarction (MI), aspirin prevents the enlargement of the coronary thrombus, maintaining some degree of blood flow and reducing mortality [1], [3]. **2. Why Other Options are Incorrect:** * **Option B:** Aspirin does not stimulate prostacyclins (PGI2). In fact, at high doses, it inhibits PGI2 synthesis in vascular endothelium. However, at low doses, its effect is selective for platelet TXA2 [2]. * **Option C:** Aspirin is not a vasodilator. While some NSAIDs affect renal blood flow, aspirin’s primary benefit in MI is antithrombotic, not hemodynamic [1], [2]. * **Option D:** While aspirin has anti-inflammatory properties at high doses, its immediate life-saving benefit in acute MI is due to its **anti-aggregatory** effect on platelets, not the reduction of inflammatory aggregates [4]. **3. NEET-PG High-Yield Pearls:** * **Loading Dose:** In acute MI, a loading dose of **162–325 mg** is given. It should be **chewed** (not swallowed whole) to ensure rapid buccal absorption and faster onset of action. * **Selectivity:** Low-dose aspirin (75–150 mg) is more selective for COX-1 than COX-2 [2]. * **Primary vs. Secondary Prevention:** Aspirin is a cornerstone for secondary prevention of MI and stroke [3]. * **Aspirin Resistance:** Some patients may not respond to aspirin due to genetic polymorphisms or drug interactions (e.g., Ibuprofen can block the aspirin binding site on COX-1).

Q: What is the formula for parenteral iron therapy?

4.4 x body weight (kg) x Hb deficit (g/dL). The correct formula for calculating the total dose of parenteral iron is based on the **Ganzoni Equation**. This formula ensures that the patient receives enough iron to restore hemoglobin to normal levels and replenish depleted iron stores. ### **Explanation of the Correct Answer** **Option A (4.4 x body weight x Hb deficit)** is the correct simplified version of the Ganzoni Equation. * **The Logic:** To raise hemoglobin (Hb) by 1 g/dL, approximately 150 mg of iron is needed in an average adult. When factored by body weight (kg) and the deficit (Target Hb - Actual Hb), the constant **2.4** is typically used if Hb is in g/dL. However, when accounting for **iron stores** (usually 500 mg for adults), the simplified clinical multiplier often cited in standard pharmacology textbooks (like KD Tripathi) for total replacement is **4.4**. * **Formula:** Total Iron Dose (mg) = 4.4 × Body weight (kg) × Hb deficit (g/dL). ### **Why Other Options are Incorrect** * **Options B, C, and D** (3.3, 2.2, 1.1) are mathematically incorrect. These multipliers would result in significant under-dosing, failing to provide enough elemental iron to both reach the target hemoglobin level and provide the necessary 500 mg buffer for storage (ferritin). ### **NEET-PG High-Yield Pearls** 1. **Indications for Parenteral Iron:** Oral iron intolerance (most common), malabsorption (Celiac disease), chronic kidney disease (CKD) on erythropoietin, or the need for rapid replenishment (e.g., late pregnancy). 2. **Iron Sucrose vs. Ferric Carboxymaltose:** Iron sucrose is given in divided doses, whereas Ferric Carboxymaltose can be given as a large single-dose infusion. 3. **Adverse Effects:** Anaphylaxis is a risk (highest with older High Molecular Weight Iron Dextran). Always monitor the patient for at least 30 minutes post-infusion. 4. **Target Hb:** Usually taken as 14 g/dL or 15 g/dL for calculation purposes.

Q: An 18-year-old previously healthy man is placed on intravenous heparin after having a pulmonary embolism (PE) after exploratory laparotomy for a small-bowel injury following a motor vehicle collision. Five days later, his platelet count is 90,000/mL and continues to fall over the next several days. The patient's serum is positive for antibodies to the heparin-platelet factor complexes. Which of the following is the most appropriate next management step?

Cessation of heparin and institution of lepirudin. ### Explanation **Concept: Heparin-Induced Thrombocytopenia (HIT) Type II** The patient presents with a classic case of **HIT Type II**, an immune-mediated reaction caused by IgG antibodies against the **Heparin-Platelet Factor 4 (PF4) complex**. This typically occurs 5–10 days after starting heparin, leading to platelet activation, consumption (thrombocytopenia), and a paradoxical high risk of arterial and venous thrombosis. **Why Option D is Correct:** The management of HIT requires the **immediate cessation of all heparin products** (including LMWH) and the initiation of a non-heparin anticoagulant. **Lepirudin** (a recombinant Hirudin) is a **Direct Thrombin Inhibitor (DTI)** that does not cross-react with HIT antibodies, making it a safe and effective alternative for systemic anticoagulation in these patients. **Why Other Options are Wrong:** * **Option A:** Stopping all anticoagulation is dangerous. HIT is a pro-thrombotic state; without alternative anticoagulation, the patient is at high risk for new or worsening PE/thrombosis. * **Option B:** Warfarin should **never** be used as monotherapy in acute HIT. It can cause a rapid drop in Protein C levels, leading to a hypercoagulable state and **venous limb gangrene**. Warfarin is only started after the platelet count has recovered to >150,000/mL. * **Option C:** LMWH (e.g., Enoxaparin) is contraindicated because it has high cross-reactivity (nearly 100%) with HIT antibodies and will worsen the condition. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Serotonin Release Assay (SRA). * **Screening Test:** ELISA for anti-PF4 antibodies (high sensitivity, low specificity). * **Alternative DTIs:** Argatroban (safe in renal failure) and Bivalirudin. * **Lepirudin Note:** It is renally excreted; monitor APTT closely. * **HIT Type I:** A non-immunologic, transient drop in platelets occurring within 48 hours; heparin can be continued.

Q: Apixaban is:

Direct Xa inhibitor. **Explanation:** **Apixaban** belongs to the class of drugs known as **Direct Oral Anticoagulants (DOACs)**. Its mechanism of action involves the direct, reversible, and highly selective inhibition of **Factor Xa** (both free and clot-bound). Factor Xa is a critical component of the "common pathway" in the coagulation cascade; by inhibiting it, Apixaban prevents the conversion of prothrombin to thrombin, thereby stopping fibrin clot formation. **Analysis of Options:** * **Option A (Antithrombin inhibitor):** This is incorrect. Drugs like Heparin actually work by *activating* Antithrombin III. Apixaban acts independently of antithrombin. * **Option C (Platelet activator):** This is incorrect. Apixaban is an anticoagulant, not a pro-coagulant. Furthermore, it affects the coagulation cascade, not platelet activation (which is the target of antiplatelet drugs like Aspirin or Clopidogrel). * **Option D (Clotting Factor XII):** This is incorrect. Factor XII (Hageman factor) is involved in the intrinsic pathway. There are currently no major clinical anticoagulants targeting Factor XII used in standard practice. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Remember the **"xa"** in the name: Api**xa**ban, Rivaro**xa**ban, and Edo**xa**ban are all direct **Xa** inhibitors. * **Monitoring:** Unlike Warfarin, DOACs do not require routine PT/INR monitoring. * **Reversal Agent:** The specific antidote for Apixaban and Rivaroxaban is **Andexanet alfa**. * **Clinical Use:** Primarily used for stroke prevention in non-valvular atrial fibrillation and the treatment/prophylaxis of DVT and pulmonary embolism.

Question 1

What is given in case of pernicious anaemia?

Accepted Answer

Methyl cobalamin

Answer

Folic acid

Answer

Folinic acid

Answer

Erythropoietin

Question 2

All of the following are anticoagulants, except?

Accepted Answer

Phytonadione

Answer

Warfarin

Answer

Low molecular weight heparin

Answer

Lepirudin

Question 3

Which drug causes megaloblastic anemia?

Accepted Answer

Pyrimethamine

Answer

Isoniazid (INH)

Answer

Chloramphenicol

Answer

Methyldopa

Question 4

Caplacizumab is used for the treatment of which condition?

Accepted Answer

Acquired Thrombotic Thrombocytopenic Purpura (aTTP)

Answer

Plaque Psoriasis

Answer

Breast cancer

Answer

Bladder cancer

Question 5

What is the mechanism by which aspirin is used in the treatment of myocardial infarction?

Accepted Answer

It inhibits thromboxanes.

Answer

It stimulates prostacyclins.

Answer

It is a vasodilator.

Answer

It helps in reducing inflammatory aggregates.

Question 6

What is the formula for parenteral iron therapy?

Accepted Answer

4.4 x body weight (kg) x Hb deficit (g/dL)

Answer

3.3 x body weight (kg) x Hb deficit (g/dL)

Answer

2.2 x body weight (kg) x Hb deficit (g/dL)

Answer

1.1 x body weight (kg) x Hb deficit (g/dL)

Question 7

Which of the following is most useful in the treatment of Kostmann's Syndrome?

Accepted Answer

Filgrastim

Answer

Sargramostim

Answer

Aldesleukin

Answer

Oprelvekin

Question 8

An 18-year-old previously healthy man is placed on intravenous heparin after having a pulmonary embolism (PE) after exploratory laparotomy for a small-bowel injury following a motor vehicle collision. Five days later, his platelet count is 90,000/mL and continues to fall over the next several days. The patient's serum is positive for antibodies to the heparin-platelet factor complexes. Which of the following is the most appropriate next management step?

Accepted Answer

Cessation of heparin and institution of lepirudin

Answer

Cessation of all anticoagulation therapy

Answer

Cessation of heparin and immediate institution of high-dose warfarin therapy

Answer

Cessation of heparin and institution of low-molecular-weight heparin

Question 9

Which anticoagulant is only effective in vivo?

Accepted Answer

Coumarin

Answer

Heparin

Answer

EDTA

Answer

Sodium citrate

Question 10

Apixaban is:

Accepted Answer

Direct Xa inhibitor

Answer

Antithrombin inhibitor

Answer

Platelet activator

Answer

Clotting Factor XII

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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