Antitumor Antibiotics — MCQs
Which of the following aminoglycosides is most cochleotoxic:-
Bleomycin toxicity affects which type of cells?
Which of the following drugs is not associated with significant cardiotoxicity?
Many drugs are used as rescue therapy for preventing the adverse effects of anticancer drugs. Folinic acid is used in:-
What is the mechanism of action of quinolones?
Bleomycin toxicity affects which organ predominantly?
Which is the most cardiotoxic anti-cancer drug among the following?
What is the mechanism of action of Methotrexate?
Match List-I with List-II and select the correct answer using the code given below the Lists:
A patient with a malignancy is undergoing chemotherapy. The platelet counts were reduced after the previous cycle of chemotherapy. Which of the following drugs can be used to treat this patient?
Antitumor Antibiotics Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following aminoglycosides is most cochleotoxic:-
- A. Streptomycin
- B. Amikacin
- C. Gentamycin (Correct Answer)
- D. Minocycline
Explanation: ***Gentamycin*** - **Gentamycin** is known to be the most **cochleotoxic** aminoglycoside, causing irreversible damage to the hair cells in the cochlea [1]. - This toxicity can lead to **permanent hearing loss** and **tinnitus** due to its selective accumulation in inner ear fluids [2]. *Streptomycin* - While streptomycin can cause ototoxicity, its primary adverse effect is vestibulo-toxicity, affecting **balance** more than hearing [2]. - It mainly targets the hair cells of the semicircular canals and otolithic organs, leading to **vertigo** and ataxia [3]. *Amikacin* - Amikacin is also an ototoxic aminoglycoside but is generally considered **less cochleotoxic** than gentamycin. - Its ototoxic effects are comparable to gentamicin, but it is often reserved for infections resistant to other aminoglycosides. *Minocycline* - Minocycline is a **tetracycline antibiotic**, not an aminoglycoside, and is not associated with significant ototoxicity. - Its side effects typically include photosensitivity, gastrointestinal upset, and **vestibular dysfunction** (dizziness, vertigo) in some patients, distinct from cochlear damage.
Question 2: Bleomycin toxicity affects which type of cells?
- A. Type I pneumocytes
- B. Type II pneumocytes (Correct Answer)
- C. Endothelial cells
- D. Pulmonary macrophages
Explanation: ***Type II pneumocytes*** - **Bleomycin** primarily causes lung toxicity by damaging **Type II pneumocytes**, leading to fibrosis. - These cells are more vulnerable due to their **lower concentrations of bleomycin hydrolase**, an enzyme that inactivates the drug. *Type I pneumocytes* - While **Type I pneumocytes** line most of the alveolar surface, they are less directly affected by bleomycin in the initial stages of toxicity compared to Type II cells. - Damage to Type I pneumocytes usually follows more severe and widespread lung injury. *Endothelial cells* - **Endothelial cells** play a role in vascular permeability and inflammation but are not the primary target of bleomycin toxicity in the lung. - Bleomycin's direct toxic effect is on the **alveolar epithelial cells**. *Pulmonary macrophages* - **Pulmonary macrophages** are immune cells involved in clearing debris and pathogens, and while they participate in the inflammatory response to bleomycin-induced lung injury, they are not the direct cellular target of the drug. - Their role is largely secondary to initial damage to **Type II pneumocytes**.
Question 3: Which of the following drugs is not associated with significant cardiotoxicity?
- A. 5-Fluorouracil
- B. Cyclophosphamide
- C. Doxorubicin
- D. Cisplatin (Correct Answer)
Explanation: ***Cisplatin*** - While cisplatin is associated with various toxicities, including **nephrotoxicity** and **neurotoxicity**, significant **cardiotoxicity** (like cardiomyopathy or severe arrhythmias) is much less common compared to the other listed agents. - Its primary cardiac effects are often indirect, such as electrolyte disturbances, or less severe, making it the least cardiotoxic among the options. *5-Fluorouracil* - This drug is known to cause **coronary vasospasm**, leading to **angina** or **myocardial infarction** in some patients. - The cardiotoxicity can manifest as **ischemic events** and **arrhythmias**, particularly during or shortly after infusion. *Cyclophosphamide* - High doses of cyclophosphamide can induce **hemorrhagic myocarditis** and **congestive heart failure**, particularly in the setting of bone marrow transplantation. - It causes direct myocardial damage and can lead to rapid-onset cardiac dysfunction. *Doxorubicin* - Doxorubicin is a well-known cause of **dose-dependent cardiomyopathy**, which can lead to **irreversible heart failure**. - Its cardiotoxicity can be acute (arrhythmias, pericarditis-myocarditis syndrome) or chronic (dilated cardiomyopathy).
Question 4: Many drugs are used as rescue therapy for preventing the adverse effects of anticancer drugs. Folinic acid is used in:-
- A. Cyclophosphamide toxicity
- B. Doxorubicin toxicity
- C. Methotrexate toxicity (Correct Answer)
- D. Cisplatin toxicity
Explanation: ***Methotrexate toxicity*** - **Folinic acid (leucovorin)** is a reduced folate that bypasses the metabolic block caused by **methotrexate** on dihydrofolate reductase. - It replenishes the body's **folate stores** and protects healthy cells from methotrexate's cytotoxic effects, particularly in the bone marrow and gastrointestinal tract. *Cyclophosphamide toxicity* - **Cyclophosphamide** toxicity, primarily hemorrhagic cystitis, is prevented by **mesna** (2-mercaptoethane sulfonate). - Mesna inactivates the urotoxic metabolite **acrolein** in the urine, preventing bladder damage. *Doxorubicin toxicity* - **Doxorubicin** causes cardiotoxicity, which can be mitigated by the iron-chelating agent **dexrazoxane**. - Dexrazoxane reduces the formation of **free radicals** that contribute to doxorubicin-induced myocardial damage. *Cisplatin toxicity* - **Cisplatin** toxicity, especially nephrotoxicity, is largely prevented by **aggressive hydration** and administration of **diuretics**. - **Amifostine** is another agent that can reduce cisplatin-induced nephrotoxicity, neurotoxicity, and ototoxicity by acting as a cytoprotectant.
Question 5: What is the mechanism of action of quinolones?
- A. Inhibit tetrahydrofolate reductase
- B. Inhibit DNA gyrase (Correct Answer)
- C. Bind to 30S ribosomal subunit
- D. Bind to bacterial cell membrane
Explanation: ***Inhibit DNA gyrase*** - Quinolones, particularly **fluoroquinolones**, exert their bactericidal effect by targeting **bacterial DNA gyrase (topoisomerase II)** and **topoisomerase IV**. - This inhibition prevents the uncoiling and replication of bacterial DNA, leading to cell death. *Bind to 30S ribosomal subunit* - This mechanism is characteristic of **aminoglycosides** and **tetracyclines**, which disrupt bacterial protein synthesis. - Quinolones do not interfere with ribosomal function but rather with **DNA replication**. *Bind to bacterial cell membrane* - This is the mechanism of action for **polymyxins** and **daptomycin**, which disrupt the integrity of the bacterial cell membrane. - Quinolones specifically target **intracellular enzymes** involved in DNA handling. *Inhibit tetrahydrofolate reductase* - This enzyme name in the option is technically imprecise; **trimethoprim** actually inhibits **dihydrofolate reductase**, which is part of the **sulfonamide-trimethoprim (Bactrim)** combination. - This pathway is involved in **folic acid synthesis**, crucial for bacterial DNA and RNA production, a mechanism distinct from quinolones.
Question 6: Bleomycin toxicity affects which organ predominantly?
- A. Bone marrow
- B. Lungs (Correct Answer)
- C. Liver
- D. RBC
Explanation: ***Lungs*** - **Bleomycin** is well-known for causing **pulmonary fibrosis**, an irreversible scarring of the lungs, as its most significant and dose-limiting toxicity. - This toxicity is thought to be due to an inability of the lungs to adequately inactivate bleomycin, leading to oxidative damage. *Bone marrow* - While many chemotherapeutic agents cause **bone marrow suppression**, bleomycin is notable for causing **minimal myelosuppression** compared to other cytotoxic drugs. - Therefore, bone marrow is not the predominantly affected organ for toxicity with bleomycin. *Liver* - **Hepatotoxicity** (liver damage) can occur with some chemotherapy agents, but it is **not a primary or prominent toxicity associated with bleomycin**. - Other drugs are much more frequently associated with liver damage. *RBC* - Bleomycin does not directly target **red blood cells (RBCs)** for toxicity. - While severe bone marrow suppression from other drugs can lead to anemia, bleomycin's effect on RBCs is indirect and not its predominant toxicity profile.
Question 7: Which is the most cardiotoxic anti-cancer drug among the following?
- A. Cyclophosphamide
- B. Tamoxifen
- C. Imatinib
- D. Anthracyclines (Correct Answer)
Explanation: ***Anthracyclines*** - **Anthracyclines** (e.g., doxorubicin, daunorubicin) are notorious for causing **dose-dependent cardiotoxicity**, leading to **irreversible dilated cardiomyopathy** and **heart failure**. - Their cardiotoxic effect is primarily due to the generation of **reactive oxygen species** and interference with cardiac topoisomerase IIβ. *Cyclophosphamide* - Cyclophosphamide can cause cardiotoxicity, particularly at **high doses**, manifesting as **hemorrhagic myocardial necrosis** or **pericarditis**. - However, its cardiotoxicity is generally considered **less frequent and severe** than that of anthracyclines. *Tamoxifen* - Tamoxifen is primarily associated with an **increased risk of thromboembolic events** and **endometrial cancer**. - While some cardiac effects like **QT prolongation** can occur, it is not considered a primary cardiotoxic agent leading to cardiomyopathy. *Imatinib* - Imatinib, a **tyrosine kinase inhibitor**, has been linked to **cardiac dysfunction** including heart failure in some patients. - However, the incidence and severity of cardiotoxicity with imatinib are **lower** compared to anthracyclines, which are broadly cardiotoxic.
Question 8: What is the mechanism of action of Methotrexate?
- A. Inhibition of Dihydrofolate reductase (Correct Answer)
- B. Inhibits pyrimidine synthesis
- C. Inhibits cell replication by acting on G phase of cell cycle
- D. Inhibits Thymidylate synthase
- E. Inhibits RNA polymerase
Explanation: ***Inhibition of Dihydrofolate reductase*** - **Methotrexate** is a **folate analog** that competitively inhibits **dihydrofolate reductase (DHFR)**, an enzyme essential for converting **dihydrofolate** to **tetrahydrofolate**. - This inhibition blocks the synthesis of **purines** and **pyrimidines**, thereby preventing DNA and RNA synthesis and ultimately inhibiting cell proliferation. *Inhibits pyrimidine synthesis* - While methotrexate ultimately inhibits pyrimidine synthesis by depleting tetrahydrofolate, its direct mechanism is not the inhibition of the pyrimidine synthesis pathway enzymes themselves. - Its primary action is upstream, by inhibiting DHFR. *Inhibits cell replication by acting on G phase of cell cycle* - Methotrexate primarily inhibits cells in the **S-phase** of the cell cycle, as it interferes with DNA synthesis. - It does not specifically target the G phase; rather, it affects cells that are actively attempting to replicate their DNA. *Inhibits Thymidylate synthase* - **Thymidylate synthase** is inhibited by drugs like **5-fluorouracil**, which directly blocks the conversion of **deoxyuridine monophosphate (dUMP)** to **deoxythymidine monophosphate (dTMP)**. - Methotrexate's effect on thymidylate synthesis is indirect, mediated by the depletion of the cofactor **N5,N10-methylene-tetrahydrofolate** due to DHFR inhibition. *Inhibits RNA polymerase* - **RNA polymerase** inhibition is the mechanism of drugs like **rifampin** (bacterial RNA polymerase) and **α-amanitin** (eukaryotic RNA polymerase). - Methotrexate does not directly inhibit RNA polymerase; its effects on RNA synthesis are secondary to depletion of nucleotide precursors through DHFR inhibition.
Question 9: Match List-I with List-II and select the correct answer using the code given below the Lists:
- A. A→3 B→4 C→2 D→1
- B. A→4 B→3 C→2 D→1
- C. A→4 B→3 C→1 D→2
- D. A→3 B→4 C→1 D→2 (Correct Answer)
Explanation: ***A→3 B→4 C→1 D→2*** - This option correctly matches each anticancer drug to its characteristic adverse effect: **Cisplatinum (A)** with **tubular necrosis (3)**, **Adriamycin (B)** with **cardiomyopathy (4)**, **Bleomycin (C)** with **pulmonary fibrosis (1)**, and **Cyclophosphamide (D)** with **haemorrhagic cystitis (2)**. - These drug-toxicity associations are clinically important for monitoring and managing patients on chemotherapy. *A→3 B→4 C→2 D→1* - This option incorrectly matches Bleomycin with haemorrhagic cystitis (should be pulmonary fibrosis) and Cyclophosphamide with pulmonary fibrosis (should be haemorrhagic cystitis). - While Cisplatinum and Adriamycin are correctly paired, the last two associations are reversed. *A→4 B→3 C→2 D→1* - This option incorrectly matches Cisplatinum with cardiomyopathy (should be tubular necrosis) and Adriamycin with tubular necrosis (should be cardiomyopathy). - Additionally, Bleomycin and Cyclophosphamide complications are also incorrectly paired. *A→4 B→3 C→1 D→2* - This option incorrectly swaps the complications for Cisplatinum and Adriamycin: Cisplatinum is matched with cardiomyopathy (should be tubular necrosis) and Adriamycin with tubular necrosis (should be cardiomyopathy). - While Bleomycin and Cyclophosphamide are correctly paired with their respective complications, the first two associations are incorrect.
Question 10: A patient with a malignancy is undergoing chemotherapy. The platelet counts were reduced after the previous cycle of chemotherapy. Which of the following drugs can be used to treat this patient?
- A. Oprelvekin (IL-11) - stimulates platelet production (Correct Answer)
- B. Filgrastim - stimulates white blood cell production
- C. Amifostine - protects against chemotherapy toxicity
- D. Erythropoietin - stimulates red blood cell production
Explanation: ***Oprelvekin (IL-11) - stimulates platelet production*** - **Oprelvekin** is a recombinant interleukin-11 (IL-11) that directly stimulates the proliferation and maturation of **megakaryocytes**, leading to increased platelet production. - It is specifically indicated for the prevention of **severe thrombocytopenia** and the reduction of the need for platelet transfusions following myelosuppressive chemotherapy. *Filgrastim - stimulates white blood cell production* - **Filgrastim** is a **granulocyte colony-stimulating factor (G-CSF)** that primarily acts on neutrophil precursors, promoting their proliferation and maturation. - It is used to prevent and treat **neutropenia** and reduce the incidence of febrile neutropenia, but it does not significantly affect platelet counts. *Amifostine - protects against chemotherapy toxicity* - **Amifostine** is a **cytoprotective agent** that reduces toxicities associated with chemotherapy and radiation by preferentially protecting non-malignant cells. - It does not directly stimulate blood cell production but rather acts as a **free radical scavenger** to mitigate damage from cytotoxic treatments. *Erythropoietin - stimulates red blood cell production* - **Erythropoietin** is a **hematopoietic growth factor** that specifically stimulates the production of **red blood cells** by promoting the proliferation and differentiation of erythroid progenitor cells. - It is used to treat **anemia**, particularly in patients with chronic kidney disease or those undergoing chemotherapy, but it has no role in managing thrombocytopenia.
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