Drugs Affecting Blood and Blood Formation Practice Questions

Q: Which of the following drugs does NOT inhibit platelet aggregation?

Celecoxib. **Explanation:** The correct answer is **Celecoxib**. The underlying medical concept involves the differential expression of Cyclooxygenase (COX) enzymes in platelets versus vascular endothelium. 1. **Why Celecoxib is correct:** Celecoxib is a **selective COX-2 inhibitor**. Platelets only express **COX-1**, which is responsible for synthesizing **Thromboxane A2 (TXA2)**—a potent platelet aggregator and vasoconstrictor. Because Celecoxib does not inhibit COX-1 at therapeutic doses, it does not affect TXA2 production or platelet aggregation. In fact, by inhibiting COX-2 in the endothelium (which produces PGI2, an anti-aggregatory prostaglandin), selective COX-2 inhibitors can shift the balance toward a pro-thrombotic state, increasing cardiovascular risk. 2. **Why other options are incorrect:** * **Aspirin:** Irreversibly inhibits COX-1, leading to a lifelong (for the platelet) suppression of TXA2. It is the gold standard antiplatelet NSAID. * **Ibuprofen:** A non-selective COX inhibitor that reversibly inhibits COX-1, thereby temporarily inhibiting platelet aggregation. * **Clopidogrel:** A P2Y12 receptor antagonist that inhibits ADP-induced platelet aggregation. It is a potent antiplatelet agent used in ACS and post-stenting. **High-Yield Clinical Pearls for NEET-PG:** * **The "Aspirin-Ibuprofen Interaction":** If taken together, Ibuprofen can block Aspirin’s access to the COX-1 active site, reducing its cardioprotective effect. Always advise taking Aspirin at least 30 minutes before or 8 hours after Ibuprofen. * **COX-2 Selectivity & Sulfa Allergy:** Celecoxib contains a sulfonamide moiety; use caution in patients with sulfa allergies. * **Platelet Lifespan:** Because Aspirin is an irreversible inhibitor, its effects last for the life of the platelet (**7–10 days**).

Q: In contrast to heparin, what is a characteristic difference of enoxaparin?

Can be used without monitoring the patient's aPTT. **Explanation:** The fundamental difference between Unfractionated Heparin (UFH) and Low Molecular Weight Heparins (LMWH) like **Enoxaparin** lies in their molecular weight and pharmacological predictability. **1. Why Option A is Correct:** Enoxaparin has a smaller molecular chain, which results in a more predictable pharmacokinetic profile and better bioavailability after subcutaneous injection. Unlike UFH, which binds non-specifically to plasma proteins and requires frequent monitoring of **activated Partial Thromboplastin Time (aPTT)**, Enoxaparin has a minimal effect on aPTT. Monitoring is generally unnecessary except in specific populations (e.g., renal failure, pregnancy, or extreme obesity), where **Factor Xa levels** are measured instead. **2. Why the other options are incorrect:** * **Option B:** Neither UFH nor Enoxaparin crosses the placenta; both are considered safe in pregnancy and are **not teratogenic**. * **Option C:** Enoxaparin is primarily administered **subcutaneously**. UFH can be given both intravenously (for rapid anticoagulation) and subcutaneously. * **Option D:** Enoxaparin has a **lower risk** of causing Heparin-Induced Thrombocytopenia (HIT) and thrombosis compared to UFH because it has less affinity for Platelet Factor 4 (PF4). **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** UFH inhibits both Thrombin (IIa) and Factor Xa (1:1 ratio). LMWH (Enoxaparin) predominantly inhibits **Factor Xa** (ratio of Xa:IIa is 3:1). * **Antidote:** **Protamine sulfate** completely neutralizes UFH but only partially neutralizes LMWH. * **Elimination:** Enoxaparin is **renally excreted**; therefore, it is contraindicated or requires dose adjustment in patients with a Creatinine Clearance <30 ml/min. UFH is preferred in severe renal failure.

Q: In low doses, aspirin primarily acts on which enzyme?

Cyclooxygenase. **Explanation:** **Aspirin (Acetylsalicylic Acid)** is a non-steroidal anti-inflammatory drug (NSAID) that acts by **irreversibly inhibiting the enzyme Cyclooxygenase (COX-1 and COX-2)**. It achieves this by acetylating a serine residue at the active site of the enzyme. **Why Option A is correct:** At **low doses (75–150 mg/day)**, aspirin is highly selective for **COX-1** found in platelets. Because platelets are anuclear, they cannot synthesize new enzymes. This leads to a permanent inhibition of COX-1 for the entire lifespan of the platelet (7–10 days), effectively preventing the formation of Thromboxane A2 (TXA2), a potent platelet aggregator. **Why other options are incorrect:** * **B. Thromboxane A2 synthase:** Aspirin inhibits the *precursor* enzyme (COX) that produces cyclic endoperoxides (PGG2/PGH2). It does not directly inhibit the specific TXA2 synthase enzyme. * **C. PGI2 synthase:** While high doses of aspirin can inhibit COX in endothelial cells (reducing Prostacyclin/PGI2), low-dose aspirin spares endothelial COX because these nucleated cells can regenerate the enzyme. * **D. Lipoxygenase:** This enzyme is part of the leukotriene pathway. Aspirin does not inhibit lipoxygenase; in fact, by blocking the COX pathway, it may "shunt" arachidonic acid toward the lipoxygenase pathway, potentially triggering "aspirin-exacerbated respiratory disease" (AERD). **High-Yield Clinical Pearls for NEET-PG:** * **Antiplatelet effect:** Occurs at low doses (75–325 mg). * **Analgesic/Antipyretic effect:** Occurs at intermediate doses (0.3–2 g). * **Anti-inflammatory effect:** Occurs at high doses (3–5 g). * **Zero-order kinetics:** Aspirin shifts from first-order to zero-order kinetics at therapeutic/toxic doses. * **Reye’s Syndrome:** Avoid aspirin in children with viral infections (except in Kawasaki disease).

Q: Which one of the following statements is FALSE about Ticlopidine?

Stimulates platelet aggregation and clot retraction.. ### Explanation **Ticlopidine** is a first-generation **P2Y12 receptor antagonist** (Thienopyridine class). It works by irreversibly inhibiting the binding of Adenosine Diphosphate (ADP) to its receptors on platelets. **1. Why Option B is the Correct (False) Statement:** Ticlopidine is an **antiplatelet drug**. Its primary therapeutic goal is to **inhibit** platelet aggregation and prevent thrombus formation. It does not stimulate aggregation; rather, it prevents the activation of the GP IIb/IIIa complex, which is essential for fibrinogen binding and subsequent clot retraction. Therefore, saying it "stimulates" these processes is physiologically incorrect. **2. Analysis of Other Options:** * **Option A:** By blocking ADP receptors, Ticlopidine prevents the conformational change in the GP IIb/IIIa receptor. This mimics **Glanzmann’s Thrombasthenia** (a genetic deficiency of GP IIb/IIIa), effectively inducing a "thrombasthenia-like state." * **Option C:** Since it inhibits the primary step of platelet plug formation, it significantly **prolongs bleeding time**. * **Option D:** While its primary target is the P2Y12 receptor, the downstream effect is a direct interference with the activation and function of the **GP IIb/IIIa receptor** membrane complex. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Irreversible P2Y12 inhibition (Prodrug). * **Adverse Effects:** The most serious side effect is **Severe Neutropenia/Agranulocytosis** (requires frequent CBC monitoring in the first 3 months). It can also cause **Thrombotic Thrombocytopenic Purpura (TTP)**. * **Current Status:** Largely replaced by **Clopidogrel** (better safety profile) and **Prasugrel/Ticagrelor** (faster onset/more potent). * **Clinical Use:** Prevention of stroke in patients intolerant to Aspirin and prevention of stent thrombosis.

Q: What is the mechanism of action of apixaban?

Inhibition of factor Xa. **Explanation:** **Mechanism of Action (Correct Answer: A)** Apixaban is a **Direct Oral Anticoagulant (DOAC)** that acts as a potent, reversible, and highly selective **direct inhibitor of Factor Xa**. Factor Xa is the pivotal point where the intrinsic and extrinsic coagulation pathways converge to form the "common pathway." By binding directly to the active site of both free and clot-bound Factor Xa, apixaban prevents the conversion of prothrombin (Factor II) to thrombin (Factor IIa), thereby inhibiting fibrin clot formation. **Analysis of Incorrect Options:** * **B. Inhibition of thrombin:** This is the mechanism of **Direct Thrombin Inhibitors (DTIs)** like **Dabigatran** (oral) or Argatroban and Bivalirudin (parenteral). * **C. Stimulation of antithrombin:** This describes the mechanism of **Heparin** and **Low Molecular Weight Heparins (LMWH)**. They act indirectly by accelerating the activity of Antithrombin III, which then inactivates Factor Xa and Thrombin. * **D. Vitamin K antagonism:** This is the mechanism of **Warfarin**. It inhibits the enzyme Vitamin K Epoxide Reductase (VKOR), preventing the γ-carboxylation of Factors II, VII, IX, and X. **High-Yield NEET-PG Pearls:** * **The "Xabans":** Remember that drugs ending in "-xaban" (Apixaban, Rivaroxaban, Edoxaban) target Factor **Xa** (the "Xa" is in the name). * **Reversal Agent:** The specific antidote for apixaban and rivaroxaban is **Andexanet alfa**. * **Clinical Advantage:** Unlike Warfarin, apixaban does not require routine INR monitoring and has fewer drug-food interactions. * **Excretion:** Apixaban has significant fecal excretion, making it a preferred DOAC in patients with mild-to-moderate renal impairment compared to dabigatran.

Q: What is the difference between iron sorbitol-citric acid and iron dextran?

Iron sorbitol-citric acid cannot be injected intravenously.. ### Explanation The primary difference between **Iron Sorbitol-Citric Acid (Jectofer)** and **Iron Dextran** lies in their molecular weight and route of administration. **1. Why Option A is Correct:** Iron sorbitol-citric acid is a low-molecular-weight complex. Due to its small molecular size, it is rapidly absorbed into the systemic circulation directly from the injection site. If given intravenously, it would saturate transferrin too quickly, leading to high levels of free iron in the blood, which is highly toxic. Therefore, it is strictly administered via **deep intramuscular (IM)** injection using the Z-track technique. In contrast, Iron Dextran is a high-molecular-weight complex that can be given both IM and IV. **2. Analysis of Incorrect Options:** * **Option B:** Both forms eventually bind to transferrin in the plasma to be transported to the bone marrow for erythropoiesis. * **Option C:** Unlike Iron Dextran (which is too large to be filtered), roughly **30% of Iron Sorbitol-Citric Acid is excreted in the urine** because of its small molecular weight. This can cause the urine to turn dark on standing, a benign but notable side effect. * **Option D:** Iron sorbitol-citric acid does not necessarily produce fewer side effects; in fact, it is often associated with more systemic symptoms like a metallic taste, palpitations, and local pain compared to modern IV iron preparations. **3. NEET-PG High-Yield Pearls:** * **Z-track Technique:** Essential for IM iron to prevent skin staining. * **Iron Dextran Warning:** Carries the highest risk of **Type I Hypersensitivity (Anaphylaxis)**; a test dose is mandatory. * **Iron Sucrose/Ferric Carboxymaltose:** Preferred modern IV agents as they do not require a test dose and have lower anaphylaxis risk. * **Contraindication:** Never give oral and parenteral iron simultaneously, as it increases toxicity and does not speed up the response.

Q: Which of the following plasma expanders, similar to albumin with a molecular weight of 30,000, causes fewer hypersensitivity reactions but should be used with caution?

Polygeline. **Explanation:** **Polygeline** (commercially known as Haemaccel) is a synthetic colloid derived from degraded bovine gelatin. It has an average molecular weight of approximately **30,000 Daltons**, which is similar to the effective oncotic pressure exerted by albumin. It is widely used as a plasma expander because it is iso-oncotic and does not interfere with cross-matching. While it is generally safer than older colloids, it must be used with caution because it can trigger **histamine release**, leading to flushing, urticaria, or hypotension (though true anaphylaxis is rarer than with Dextrans). **Analysis of Other Options:** * **Hydroxyethyl Starch (HES):** These are larger molecules (MW 130,000–450,000). While effective for volume expansion, they are associated with significant risks of **nephrotoxicity** and coagulopathy. * **Dextran:** These are glucose polymers. Dextran 70 and Dextran 40 are notorious for causing **severe anaphylactoid reactions** (due to pre-formed antibodies) and interfering with blood grouping/cross-matching. * **Polypyrrolidone (PVP):** Historically used as a plasma expander, it is now obsolete due to its tendency to be stored in the reticuloendothelial system for long periods, causing potential organ damage. **High-Yield Clinical Pearls for NEET-PG:** * **Gelatins (Polygeline):** Unique because they contain **Calcium (6.25 mmol/L)**; therefore, they should not be infused through the same line as citrated blood to avoid clotting. * **Maximum Dose:** Unlike HES, there is no strict maximum dose for gelatins, but they have a short duration of action (2–4 hours). * **Renal Safety:** Gelatins are generally considered safer for the kidneys compared to HES in critically ill patients.

Q: Iron tablets should never be given along with which of the following?

Milk. **Explanation:** The correct answer is **Milk**. The absorption of oral iron is highly sensitive to the pH of the stomach and the presence of specific dietary ligands. **1. Why Milk is the Correct Answer:** Milk and dairy products are rich in **calcium** and **phosphates**. Calcium competes with iron for absorption in the duodenum, while phosphates (and phytates) form insoluble complexes with iron, significantly reducing its bioavailability. Additionally, milk has a slight neutralizing effect on gastric acid; since iron (ferrous form) requires an acidic environment for optimal absorption, milk further hinders this process. **2. Why Other Options are Incorrect:** * **Water:** This is the ideal vehicle for taking iron tablets as it does not interfere with the chemical state or absorption of the drug. * **Lemon Water:** This is actually **beneficial**. Lemon water contains **Vitamin C (Ascorbic acid)**, which acts as a reducing agent. It maintains iron in the **Ferrous (Fe²⁺)** state, which is more soluble and more easily absorbed than the Ferric (Fe³⁺) state. **NEET-PG High-Yield Pearls:** * **The "Acid" Rule:** Iron absorption is enhanced by acidic environments (Vitamin C, Gastric acid) and inhibited by alkaline environments (Antacids, H2 blockers, PPIs). * **Food Interference:** Apart from milk, iron should not be taken with **tea or coffee** because they contain **tannins**, which bind iron and prevent absorption. * **Best Practice:** For maximum absorption, iron should be taken on an **empty stomach**. However, if gastric irritation occurs (a common side effect), it may be taken with a small amount of food, avoiding dairy and caffeine.

Q: Which of the following agents is used for the treatment of thrombocytopenia secondary to myelosuppressive cancer chemotherapy?

Oprelvekin. **Explanation:** The correct answer is **Oprelvekin (C)**. **1. Why Oprelvekin is Correct:** Oprelvekin is a recombinant form of **Interleukin-11 (IL-11)**. It acts by stimulating the proliferation of hematopoietic stem cells and megakaryocyte progenitor cells, leading to increased platelet production. It is specifically FDA-approved for the prevention of severe **thrombocytopenia** in patients receiving myelosuppressive chemotherapy for non-myeloid malignancies. **2. Why Other Options are Incorrect:** * **Filgrastim (A):** This is a recombinant **Granulocyte Colony-Stimulating Factor (G-CSF)**. It specifically stimulates the production of neutrophils and is used to treat chemotherapy-induced **neutropenia**, not thrombocytopenia. * **Sargramostim (B):** This is a recombinant **Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF)**. It stimulates the production of neutrophils, eosinophils, and monocytes. While it has a broader spectrum than Filgrastim, its primary clinical use is to accelerate myeloid recovery after bone marrow transplantation. * **Erythropoietin (D):** This hormone stimulates the proliferation and differentiation of red blood cell precursors. It is used to treat **anemia** associated with chronic kidney disease or chemotherapy. **3. NEET-PG High-Yield Pearls:** * **Oprelvekin Side Effects:** The most characteristic side effect is **fluid retention** (edema, dyspnea, and pleural effusion) due to sodium and water retention. It can also cause transient atrial arrhythmias. * **Alternative Agents:** **Romiplostim** (a thrombopoietin mimetic peptide) and **Eltrombopag** (an oral TPO receptor agonist) are also used for thrombocytopenia, but primarily in Chronic Immune Thrombocytopenic Purpura (ITP). * **Mnemonic:** Oprelvekin = **11** letters = **IL-11**.

Q: All of the following cause macrocytic anemia, except?

Primaquine. **Explanation:** The correct answer is **Primaquine**. To answer this question, one must distinguish between drugs that interfere with DNA synthesis (causing megaloblastic/macrocytic anemia) and those that cause oxidative stress. **1. Why Primaquine is the correct answer:** Primaquine is an antimalarial drug that induces oxidative stress. In individuals with **G6PD deficiency**, this leads to the oxidation of hemoglobin, formation of Heinz bodies, and subsequent **acute hemolytic anemia** (normocytic). It does not interfere with folate metabolism or DNA synthesis, and therefore does not cause macrocytosis. **2. Why the other options are incorrect:** * **Methotrexate:** A potent **dihydrofolate reductase (DHFR) inhibitor**. It prevents the conversion of dihydrofolate to tetrahydrofolate, halting DNA synthesis and leading to megaloblastic macrocytic anemia. * **Trimethoprim:** Also a **DHFR inhibitor** (though with higher affinity for bacterial enzymes). Prolonged high-dose use or use in predisposed patients can cause folate deficiency and macrocytic anemia. * **Azathioprine:** A purine synthesis inhibitor (antimetabolite). By interfering with the synthesis of adenine and guanine, it disrupts DNA replication in the bone marrow, commonly resulting in macrocytosis. **High-Yield Clinical Pearls for NEET-PG:** * **Megaloblastic Anemia (Macrocytic):** Caused by "DNA-inhibitors" like Hydroxyurea, Zidovudine (AZT), 5-Fluorouracil, and Phenytoin (interferes with folate absorption). * **Non-megaloblastic Macrocytosis:** Commonly seen in Alcoholism, Hypothyroidism, and Liver disease. * **Primaquine Contraindication:** Always screen for G6PD deficiency before administration to avoid life-threatening hemolysis. It is also contraindicated in pregnancy due to the risk of fetal hemolysis.

Question 1

Which of the following drugs does NOT inhibit platelet aggregation?

Accepted Answer

Celecoxib

Answer

Aspirin

Answer

Ibuprofen

Answer

Clopidogrel

Question 2

In contrast to heparin, what is a characteristic difference of enoxaparin?

Accepted Answer

Can be used without monitoring the patient's aPTT

Answer

Is less likely to have a teratogenic effect

Answer

Is more likely to be given intravenously

Answer

Is more likely to cause thrombosis and thrombocytopenia

Question 3

In low doses, aspirin primarily acts on which enzyme?

Accepted Answer

Cyclooxygenase

Answer

Thromboxane A2 synthase

Answer

PGI2 synthase

Answer

Lipoxygenase

Question 4

Which one of the following statements is FALSE about Ticlopidine?

Accepted Answer

Stimulates platelet aggregation and clot retraction.

Answer

Inhibits platelet function by inducing a thrombasthenia-like state.

Answer

Prolongs the bleeding time.

Answer

Directly interacts with platelet membrane glycoprotein IIb/IIIa receptors.

Question 5

What is the mechanism of action of apixaban?

Accepted Answer

Inhibition of factor Xa

Answer

Inhibition of thrombin

Answer

Stimulation of antithrombin

Answer

Vitamin K antagonism

Question 6

What is the difference between iron sorbitol-citric acid and iron dextran?

Accepted Answer

Iron sorbitol-citric acid cannot be injected intravenously.

Answer

Iron sorbitol-citric acid is not bound to transferrin in plasma.

Answer

Iron sorbitol-citric acid is not excreted in urine.

Answer

Iron sorbitol-citric acid produces fewer side effects.

Question 7

Which of the following plasma expanders, similar to albumin with a molecular weight of 30,000, causes fewer hypersensitivity reactions but should be used with caution?

Accepted Answer

Polygeline

Answer

Hydroxy ethyl starch (HES)

Answer

Dextran

Answer

Polypyrrolidone

Question 8

Iron tablets should never be given along with which of the following?

Accepted Answer

Milk

Answer

Water

Answer

Lemon water

Answer

All of the above

Question 9

Which of the following agents is used for the treatment of thrombocytopenia secondary to myelosuppressive cancer chemotherapy?

Accepted Answer

Oprelvekin

Answer

Filgrastim

Answer

Sargramostim

Answer

Erythropoetin

Question 10

All of the following cause macrocytic anemia, except?

Accepted Answer

Primaquine

Answer

Methotrexate

Answer

Trimethoprim

Answer

Azathioprine

Drugs Affecting Blood and Blood Formation — MCQs

Drugs Affecting Blood and Blood Formation — MCQs

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