These MCQs focus on Sulfamethizine, Sulfacetamide, Sulfamethoxazole and Sulphadiazine—important sulfonamide antibiotics studied in B. Pharm curricula. The introduction reviews structures, mechanisms of action, pharmacokinetics, therapeutic uses, resistance mechanisms, adverse effects, drug interactions and formulation considerations. Emphasis is on clinical applications, dosage calculations, topical and systemic preparations, and distinguishing spectrums of activity. Keywords such as sulfonamides, folate synthesis inhibition, bacteriostatic action, hypersensitivity, crystalluria, and drug monitoring are woven into questions to sharpen recall and critical thinking. These targeted MCQs will help you master pharmacology, medicinal chemistry, pharmaceutics and therapeutics related to Sulfamethizine, Sulfacetamide, Sulfamethoxazole and Sulphadiazine. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which is the primary molecular target of sulfamethizine, sulfacetamide, sulfamethoxazole and sulphadiazine in bacteria?
- DNA gyrase inhibition
- Dihydrofolate reductase inhibition
- Dihydropteroate synthase inhibition
- 30S ribosomal subunit binding
Correct Answer: Dihydropteroate synthase inhibition
Q2. The antibacterial action of classical sulfonamides is best described as:
- Bactericidal by cell wall disruption
- Bacteriostatic by competing with para-aminobenzoic acid (PABA)
- Bactericidal by producing free radicals
- Bacteriostatic via 50S ribosomal blockade
Correct Answer: Bacteriostatic by competing with para-aminobenzoic acid (PABA)
Q3. Which sulfonamide is commonly formulated as an ophthalmic preparation for bacterial conjunctivitis?
- Sulfamethizine
- Sulfacetamide
- Sulfamethoxazole
- Sulphadiazine
Correct Answer: Sulfacetamide
Q4. Sulfamethoxazole is most frequently combined with which drug to produce a synergistic bactericidal effect?
- Pyrimethamine
- Trimethoprim
- Ciprofloxacin
- Amoxicillin
Correct Answer: Trimethoprim
Q5. A major mechanism of bacterial resistance to sulfonamides involves:
- Production of beta-lactamases
- Mutation of dihydropteroate synthase or increased PABA production
- Efflux pumps specific for tetracyclines
- Methylation of 23S rRNA
Correct Answer: Mutation of dihydropteroate synthase or increased PABA production
Q6. Which adverse effect is characteristically associated with systemic sulfonamide therapy?
- Ototoxicity
- Stevens–Johnson syndrome
- Cardiac arrhythmia
- Pulmonary fibrosis
Correct Answer: Stevens–Johnson syndrome
Q7. Which sulfonamide is classically used with pyrimethamine to treat toxoplasmosis?
- Sulfamethizine
- Sulfacetamide
- Sulfamethoxazole
- Sulphadiazine
Correct Answer: Sulphadiazine
Q8. Crystalluria risk with sulfonamides can be minimized by:
- Administering with acidic beverages
- Increasing fluid intake and alkalinizing urine
- Giving the drug intramuscularly only
- Concomitant probenecid administration
Correct Answer: Increasing fluid intake and alkalinizing urine
Q9. Which pharmacokinetic property is common to many sulfonamides like sulfamethoxazole and sulphadiazine?
- High hepatic extraction ratio and biliary excretion
- Extensive plasma protein binding and renal excretion
- Rapid metabolism to active antibiotics in plasma
- Predominant excretion via lungs
Correct Answer: Extensive plasma protein binding and renal excretion
Q10. Sulfacetamide topical preparations are primarily used because they:
- Provide systemic bactericidal concentrations
- Have broad antifungal action
- Deliver high local concentrations with minimal systemic absorption
- Act as local anesthetics
Correct Answer: Deliver high local concentrations with minimal systemic absorption
Q11. Which drug interaction is important when sulfamethoxazole is co-administered with warfarin?
- Reduced anticoagulant effect due to enzyme induction
- Increased warfarin effect due to displacement and CYP inhibition
- No interaction—both act on different pathways
- Warfarin reduces sulfonamide absorption
Correct Answer: Increased warfarin effect due to displacement and CYP inhibition
Q12. Which patient group is at highest risk for kernicterus if given systemic sulfonamides?
- Elderly with renal impairment
- Neonates and premature infants
- Pregnant women in third trimester only
- Young adults with hypertension
Correct Answer: Neonates and premature infants
Q13. The principal therapeutic spectrum of sulfonamides primarily covers:
- Atypical mycobacteria
- Gram-positive and some gram-negative organisms that synthesize folate
- Obligate intracellular organisms only
- Fungal pathogens
Correct Answer: Gram-positive and some gram-negative organisms that synthesize folate
Q14. A formulation advantage of sulfacetamide over older systemic sulfonamides is:
- Lower water solubility enabling depot action
- Good topical tolerability for ocular use
- Intrinsic synergism with beta-lactams
- Longer plasma half-life for once-weekly dosing
Correct Answer: Good topical tolerability for ocular use
Q15. Which monitoring parameter is most relevant during long-term high-dose sulfadiazine therapy?
- Liver function tests and complete blood count
- Serum amylase only
- Fasting blood glucose
- Serum creatine kinase
Correct Answer: Liver function tests and complete blood count
Q16. Which structural feature is shared by most classical sulfonamides and is essential for activity?
- Beta-lactam ring
- Sulfonamide moiety attached to an aromatic amine
- Glycopeptide backbone
- Macrolide lactone ring
Correct Answer: Sulfonamide moiety attached to an aromatic amine
Q17. Which adverse reaction is a common local side effect of topical sulfacetamide eye drops?
- Systemic hemolysis
- Local irritation and allergic conjunctivitis
- Renal tubular necrosis
- Peripheral neuropathy
Correct Answer: Local irritation and allergic conjunctivitis
Q18. The combination of sulfamethoxazole and trimethoprim is considered bactericidal because:
- Both drugs inhibit the same enzyme producing redundancy
- Sequential blockade of folate pathway—DHPS and DHFR—leads to enhanced kill
- They both disrupt bacterial cell membranes
- Trimethoprim activates sulfonamide prodrugs
Correct Answer: Sequential blockade of folate pathway—DHPS and DHFR—leads to enhanced kill
Q19. Which clinical use is a classical indication for sulphadiazine?
- Treatment of fungal keratitis
- Treatment of toxoplasmosis (with pyrimethamine)
- Primary therapy for MRSA skin infections
- Management of peptic ulcer disease
Correct Answer: Treatment of toxoplasmosis (with pyrimethamine)
Q20. Sulfamethizine differs from some other sulfonamides mainly in its:
- Relatively longer duration of action and pharmacokinetic profile
- Exclusive use only as an ophthalmic agent
- Unique mechanism acting on ribosomes
Correct Answer: Relatively longer duration of action and pharmacokinetic profile
Q21. In formulation development, sulfonamides susceptible to precipitation are best addressed by:
- Using nonionic surfactants exclusively
- Adjusting pH and using appropriate cosolvents to maintain solubility
- Converting all drugs into suspension only
- Avoiding any buffering agents
Correct Answer: Adjusting pH and using appropriate cosolvents to maintain solubility
Q22. A laboratory indicator of sulfonamide hypersensitivity may include:
- Elevated creatine kinase
- Eosinophilia and elevated liver enzymes
- Low serum sodium only
- Decreased platelet count exclusively
Correct Answer: Eosinophilia and elevated liver enzymes
Q23. Which statement about protein binding of sulfonamides is correct?
- They are not protein bound and distribute freely
- They often exhibit significant plasma protein binding which affects free drug levels
- Protein binding prevents renal excretion completely
- Protein binding is irrelevant to drug interactions
Correct Answer: They often exhibit significant plasma protein binding which affects free drug levels
Q24. In managing severe sulfonamide-induced hemolysis in G6PD-deficient patients, the immediate step is to:
- Give high-dose sulfonamide to overcome resistance
- Stop the offending drug and provide supportive care including transfusion if needed
- Administer naloxone
- Start broad-spectrum antifungals
Correct Answer: Stop the offending drug and provide supportive care including transfusion if needed
Q25. Which analytical test is commonly used in quality control of sulfacetamide ophthalmic solutions?
- Assay by HPLC for concentration and impurities
- Gram staining for sterility
- Viscosity testing only
- Melting point determination exclusively
Correct Answer: Assay by HPLC for concentration and impurities
Q26. Which precaution is important when prescribing sulfamethoxazole-trimethoprim to an elderly patient?
- No need for renal dosing adjustments
- Assess renal function and consider dose adjustment due to renal clearance
- They are contraindicated in anyone over 60
- Always combine with high-dose NSAIDs to prevent side effects
Correct Answer: Assess renal function and consider dose adjustment due to renal clearance
Q27. Which laboratory finding suggests serious systemic sulfonamide toxicity?
- Transient mild headache
- Acute interstitial nephritis with rising serum creatinine and eosinophiluria
- Isolated decreased appetite
- Improved renal clearance
Correct Answer: Acute interstitial nephritis with rising serum creatinine and eosinophiluria
Q28. For topical ocular delivery of sulfacetamide, formulation aims typically include:
- Rapid systemic absorption for systemic therapy
- Preservation of sterility, isotonicity, and pH compatible with eye
- Highly alkaline pH for maximal stability
- Inclusion of strong detergents to enhance penetration
Correct Answer: Preservation of sterility, isotonicity, and pH compatible with eye
Q29. Which test organism or condition would predict poor activity of sulfonamides?
- Bacteria that can uptake preformed folate or overproduce PABA
- Organisms lacking a cell wall
- Gram-positive cocci sensitive to beta-lactams
- Fungal pathogens requiring ergosterol inhibition
Correct Answer: Bacteria that can uptake preformed folate or overproduce PABA
Q30. In the context of drug stability, exposure of sulfonamide solutions to sunlight may cause:
- No change—sulfonamides are photostable
- Photodegradation leading to loss of potency and formation of impurities
- Immediate crystallization and precipitation only
- Conversion to active antiviral compounds
Correct Answer: Photodegradation leading to loss of potency and formation of impurities
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com