Chemotherapy of infections and cancer

40 Gulf Prometric Pharmacist (DHA, DOH, MOH, SCFHS, QCHP) practice questions on Chemotherapy of infections and cancer, part of Pharmacology and Medicinal Chemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   G6PD deficiency is common in the Gulf region. Which antimalarial must not be given before G6PD status is known because it can cause haemolysis?

   1. AChloroquine at standard doses
   2. BAtovaquone
   3. CPrimaquine
   4. DArtemether

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   Answer: C · Primaquine

   Primaquine, used for radical cure of Plasmodium vivax and ovale, generates oxidants that cannot be neutralised by red cells lacking G6PD, so haemolysis follows. G6PD status is therefore tested first, and tafenoquine has the same limitation. The other drugs listed are not associated with significant haemolysis in this setting.

   • A: Standard-dose chloroquine is considered safe in G6PD deficiency.
   • B: Atovaquone is not a typical oxidant haemolysis trigger.
   • D: Artemether does not usually cause haemolysis in G6PD deficiency.

   Remember this

   Test G6PD before primaquine or tafenoquine.

2. Question 2 · Medium

   Paclitaxel kills tumour cells by which mechanism?

   1. AInhibits topoisomerase I
   2. BCross-links DNA strands
   3. CPrevents polymerisation of tubulin into microtubules
   4. DStabilises microtubules and blocks depolymerisation

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   Answer: D · Stabilises microtubules and blocks depolymerisation

   Taxanes bind beta-tubulin and stabilise microtubules, so the mitotic spindle cannot disassemble and cells arrest in the M phase. Vinca alkaloids have the opposite effect and prevent polymerisation. Hypersensitivity needs premedication, and neuropathy and neutropenia are common.

   • A: Irinotecan inhibits topoisomerase I.
   • B: Cross-linking of DNA is the action of cisplatin and alkylating agents.
   • C: Preventing tubulin polymerisation is the vinca alkaloid action.

   Remember this

   Taxanes stabilise microtubules; vinca alkaloids prevent their assembly.

3. Question 3 · Medium

   Terbinafine is effective for onychomycosis because it:

   1. AInhibits 14-alpha-demethylase in the membrane
   2. BBlocks squalene epoxidase, so squalene builds up
   3. CInhibits glucan synthase
   4. DBinds ergosterol and forms membrane pores

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   Answer: B · Blocks squalene epoxidase, so squalene builds up

   Terbinafine inhibits squalene epoxidase, an early step in ergosterol synthesis, so ergosterol falls and squalene builds up, which is fungicidal for dermatophytes. It collects in nails and skin. Hepatotoxicity needs consideration, and baseline liver tests are advised.

   • A: 14-alpha-demethylase is the azole target.
   • C: Glucan synthase is the target of echinocandins.
   • D: Ergosterol binding is the action of polyenes.

   Remember this

   Terbinafine blocks squalene epoxidase and is a preferred oral treatment for dermatophyte nail infection.

4. Question 4 · Easy

   The bactericidal effect of amoxicillin depends on its action on which bacterial structure or process?

   1. ABinding to the 30S ribosomal subunit
   2. BPeptidoglycan cross-linking
   3. CUnwinding of DNA by gyrase
   4. DSynthesis of dihydrofolate

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   Answer: B · Peptidoglycan cross-linking

   Beta-lactams acylate penicillin-binding proteins, which blocks the cross-linking of peptidoglycan. The weakened wall cannot withstand osmotic pressure and the growing cell lyses. They act only on actively dividing bacteria and are time-dependent killers.

   • A: 30S binding is the action of aminoglycosides and tetracyclines.
   • C: DNA gyrase inhibition is the action of fluoroquinolones.
   • D: Folate synthesis is blocked by trimethoprim and sulfonamides.

   Remember this

   Beta-lactams block peptidoglycan cross-linking by binding penicillin-binding proteins.

5. Question 5 · Hard

   A patient with Pseudomonas sepsis receives piperacillin-tazobactam. Which dosing strategy makes the best use of its pharmacodynamics?

   1. AA single large daily bolus to reach a high peak level
   2. BOral dosing to give constant absorption
   3. CUsing a long dose interval to reduce toxicity risk
   4. DExtended infusion to keep free drug above the MIC longer

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   Answer: D · Extended infusion to keep free drug above the MIC longer

   Beta-lactams show time-dependent killing, so efficacy depends on the percentage of the dosing interval that the free drug concentration exceeds the MIC. Extended or continuous infusion raises this fraction, particularly for organisms with higher MICs. Aminoglycosides and quinolones are concentration-dependent and are given in high peak doses.

   • A: A high peak suits concentration-dependent drugs, not beta-lactams.
   • B: Piperacillin-tazobactam is not absorbed orally.
   • C: A long interval would lengthen the time below MIC.

   Remember this

   Beta-lactams are time-dependent (T>MIC); aminoglycosides are concentration-dependent (peak/MIC).

6. Question 6 · Medium

   A child receives ifosfamide, and the oncology team orders mesna with each dose. What is the purpose of mesna?

   1. AIt binds acrolein and protects the bladder
   2. BIt restores reduced folate in marrow cells
   3. CIt raises urinary pH to dissolve uric acid crystals
   4. DIt protects the heart from free radicals

   Answer and explanation in LearnFree account

7. Question 7 · Medium

   Co-trimoxazole combines sulfamethoxazole with trimethoprim because together they:

   1. ABlock two sequential steps in bacterial folate synthesis
   2. BBlock two different ribosomal subunits
   3. CInhibit both transpeptidase and beta-lactamase
   4. DBlock both DNA gyrase and RNA polymerase

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8. Question 8 · Easy

   Methotrexate exerts its antineoplastic effect by inhibiting:

   1. AThymidylate synthase by a fluorouracil metabolite
   2. BMicrotubule assembly
   3. CDihydrofolate reductase
   4. DTopoisomerase II

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9. Question 9 · Medium

   How does metronidazole kill susceptible anaerobic bacteria?

   1. AIt binds the 50S subunit and blocks translocation
   2. BIt inhibits folate synthesis
   3. CIt binds penicillin-binding proteins
   4. DNitro-group reduction to DNA-damaging free radicals

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10. Question 10 · Medium

    Which toxicity limits the cumulative dose of doxorubicin and requires cardiac monitoring?

    1. APeripheral sensory neuropathy
    2. BHaemorrhagic cystitis of the bladder
    3. CDose-related cardiomyopathy
    4. DPulmonary fibrosis

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11. Question 11 · Medium

    Clavulanic acid is combined with amoxicillin because it:

    1. AIrreversibly inhibits many beta-lactamases
    2. BBinds penicillin-binding proteins more strongly
    3. CPrevents efflux of amoxicillin from bacteria
    4. DIncreases the renal excretion of amoxicillin

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12. Question 12 · Hard

    Carboplatin is dosed to a target AUC of 5 mg/mL x min with the Calvert formula (dose = AUC x [GFR + 25]). A patient has a measured GFR of 75 mL/min. What dose should be prepared?

    1. A500 mg
    2. B375 mg
    3. C625 mg
    4. D400 mg

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13. Question 13 · Medium

    A patient on linezolid for a resistant infection has been taking it for 4 weeks and his platelet count has fallen to 60 x 10^9/L. Which statement is correct?

    1. AThe platelet fall shows an allergic reaction to the oxazolidinone
    2. BMyelosuppression is duration-related, so blood counts are checked weekly
    3. CThrombocytopenia occurs only in the first week
    4. DLinezolid binds the 30S subunit and damages platelets directly

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14. Question 14 · Easy

    Vancomycin inhibits cell wall synthesis by binding to:

    1. ABacterial DNA-dependent RNA polymerase
    2. BPenicillin-binding protein 2a
    3. CThe 50S ribosomal subunit of bacteria
    4. DThe D-Ala-D-Ala end of precursors

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15. Question 15 · Hard

    A man starting capecitabine develops severe mucositis, diarrhoea and neutropenia after the first cycle. Testing shows he carries a non-functional DPYD variant. Which statement explains this and gives the right approach?

    1. AThymidylate synthase overactivity causes toxicity; double the dose
    2. BDHFR deficiency causes the toxicity; give high-dose folic acid rescue
    3. CDPD deficiency slows fluorouracil breakdown; reduce the dose markedly
    4. DTPMT deficiency slows fluorouracil breakdown; add allopurinol at once

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16. Question 16 · Medium

    Dolutegravir is used in HIV infection. Which step of the viral life cycle does it block?

    1. AReverse transcription of RNA to DNA by the nucleoside analogue route
    2. BBinding to the CCR5 co-receptor
    3. CCleavage of viral polyproteins
    4. DStrand transfer by integrase

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17. Question 17 · Hard

    A candidaemic patient who failed fluconazole prophylaxis has Candida krusei in the blood culture. Which statement is correct?

    1. AFlucytosine alone is the standard first-line treatment
    2. BC. krusei is intrinsically resistant, so use an echinocandin
    3. CTerbinafine is the drug of choice for invasive disease
    4. DFluconazole at a double dose overcomes the resistance

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18. Question 18 · Easy

    Rifampicin acts by inhibiting:

    1. AMycolic acid synthesis in the cell wall
    2. BArabinosyl transferase of the cell wall
    3. CThe beta subunit of bacterial RNA polymerase
    4. DThe 30S subunit of the ribosome

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19. Question 19 · Medium

    A hospital isolate of Staphylococcus aureus is resistant to flucloxacillin. What is the usual mechanism?

    1. ALoss of the thymidine kinase gene
    2. BAcquisition of mecA, which codes for low-affinity PBP2a
    3. CA plasmid-borne beta-lactamase that cleaves the penicillin ring
    4. DMutation of the 23S ribosomal RNA gene

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20. Question 20 · Medium

    Imatinib is effective in chronic myeloid leukaemia because it:

    1. ABinds CD20 on B cells
    2. BInhibits the BCR-ABL tyrosine kinase
    3. CInhibits the proteasome
    4. DBlocks the HER2 receptor on tumour cells

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21. Question 21 · Medium

    A patient started on isoniazid for latent tuberculosis is also given pyridoxine. Which mechanism links the two?

    1. AIsoniazid depletes pyridoxine; the vitamin prevents neuropathy
    2. BPyridoxine increases the bactericidal effect of isoniazid
    3. CPyridoxine prevents hepatitis from isoniazid and rifampicin
    4. DPyridoxine activates isoniazid through the KatG enzyme

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22. Question 22 · Medium

    Which measure best reduces the risk of cisplatin nephrotoxicity?

    1. AReducing the gentamicin dose at the same time
    2. BAdding a loop diuretic without any hydration
    3. CSaline hydration before and after each cisplatin dose
    4. DRestricting fluids to 1 litre a day

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23. Question 23 · Medium

    Caspofungin acts against Candida by:

    1. AInhibiting beta-(1,3)-D-glucan synthase
    2. BBlocking ergosterol synthesis at squalene epoxidase
    3. CInhibiting thymidylate synthase after conversion to 5-fluorouracil
    4. DBinding ergosterol

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24. Question 24 · Medium

    Colistin is used for carbapenem-resistant Gram-negative infections. What is its mechanism, and what is its main adverse effect?

    1. AOuter membrane disruption; nephrotoxicity
    2. BIt inhibits DNA gyrase; tendon rupture
    3. CIt inhibits 30S translation; hepatotoxicity
    4. DIt inhibits peptidoglycan cross-linking; ototoxicity

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25. Question 25 · Medium

    A blood culture grows an ESBL-producing Escherichia coli resistant to ceftriaxone. Which treatment is the most reliable?

    1. ACefotaxime at a higher dose
    2. BAmpicillin plus gentamicin
    3. CMeropenem
    4. DAmoxicillin

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