Pharmacology Antimicrobial and Chemotherapeutic Agents 3 — Questions and Answers
Question 1: A patient taking isoniazid (INH) for tuberculosis develops peripheral neuropathy. This adverse effect is best prevented by supplementing with:
- Vitamin C
- Pyridoxine (Vitamin B6) (Correct answer)
- Folic acid
- Thiamine (Vitamin B1)
Correct answer: Pyridoxine (Vitamin B6)
INH inhibits pyridoxal phosphate synthesis and competes with pyridoxine, causing peripheral neuropathy that is prevented by concurrent pyridoxine supplementation.
Question 2: Which antibiotic class is contraindicated in children under 8 years of age due to risk of permanent tooth discoloration?
- Macrolides
- Tetracyclines (Correct answer)
- Cephalosporins
- Sulfonamides
Correct answer: Tetracyclines
Tetracyclines bind to calcium in developing teeth and bones, causing permanent yellow-gray-brown discoloration and enamel hypoplasia in children under 8.
Question 3: Trimethoprim-sulfamethoxazole (TMP-SMX) inhibits bacterial folate synthesis by blocking which two sequential steps?
- DNA gyrase and topoisomerase IV
- Dihydropteroate synthase and dihydrofolate reductase (Correct answer)
- RNA polymerase and ribosome assembly
- Transpeptidase and transglycosylase
Correct answer: Dihydropteroate synthase and dihydrofolate reductase
Sulfamethoxazole inhibits dihydropteroate synthase while trimethoprim inhibits dihydrofolate reductase; together they create sequential blockade of folate synthesis.
Question 4: Which antiviral drug is used as prophylaxis and treatment for influenza A and B and works by inhibiting neuraminidase?
- Acyclovir
- Oseltamivir (Correct answer)
- Zidovudine
- Ribavirin
Correct answer: Oseltamivir
Oseltamivir (Tamiflu) inhibits viral neuraminidase, preventing release of new virions from infected cells and limiting spread of influenza A and B.
Question 5: A patient develops gray baby syndrome after receiving which antibiotic?
- Erythromycin
- Chloramphenicol (Correct answer)
- Linezolid
- Clindamycin
Correct answer: Chloramphenicol
Chloramphenicol causes gray baby syndrome in neonates because their immature hepatic glucuronyl transferase cannot metabolize the drug, leading to toxic accumulation.
Question 6: Which antiparasitic drug is first-line for treatment of malaria caused by chloroquine-resistant Plasmodium falciparum?
- Primaquine
- Chloroquine
- Artemether-lumefantrine (Correct answer)
- Metronidazole
Correct answer: Artemether-lumefantrine
Artemisinin-based combination therapies (ACTs) such as artemether-lumefantrine are WHO first-line treatment for chloroquine-resistant P. falciparum malaria.
Question 7: What is the primary mechanism by which bacteria develop resistance to aminoglycosides?
- Alteration of ribosomal target site
- Production of modifying enzymes (acetyltransferases, phosphotransferases) (Correct answer)
- Efflux pump overexpression only
- Decreased outer membrane permeability only
Correct answer: Production of modifying enzymes (acetyltransferases, phosphotransferases)
The most common mechanism of aminoglycoside resistance is production of plasmid-encoded enzymes that acetylate, phosphorylate, or adenylate the drug, preventing ribosomal binding.
Pharmacology Antimicrobial and Chemotherapeutic Agents 3
A patient taking isoniazid (INH) for tuberculosis develops peripheral neuropathy.
This adverse effect is best prevented by supplementing with: