Miscellaneous urinary anti-infectives – Furazolidone, Nitrofurantoin, Methenamine MCQs With Answer

Miscellaneous urinary anti-infectives – Furazolidone, Nitrofurantoin, Methenamine MCQs With Answer

Miscellaneous urinary anti-infectives such as Furazolidone, Nitrofurantoin, and Methenamine are essential topics for B. Pharm students studying urinary tract infection pharmacotherapy. This concise, focused set of MCQs reviews mechanisms of action, pharmacokinetics, spectrum of activity, clinical indications, dosing considerations, adverse effects, contraindications, and drug interactions relevant to these agents. Emphasis is placed on nitrofurantoin’s renal-dependent activation, furazolidone’s historical use and toxicity, and methenamine’s urinary conversion to formaldehyde for prophylaxis. These questions integrate therapeutic principles and clinical reasoning to build exam-ready knowledge and practical application. Clear explanations follow each correct answer to reinforce learning. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which best describes the antimicrobial mechanism of methenamine?

• Inhibits bacterial cell wall synthesis
• Acts as a folate antagonist
• Is hydrolyzed to formaldehyde in acidic urine producing nonspecific bactericidal activity
• Blocks bacterial protein synthesis at the 50S ribosomal subunit

Correct Answer: Is hydrolyzed to formaldehyde in acidic urine producing nonspecific bactericidal activity

Q2. Nitrofurantoin’s antibacterial activity depends on:

• Direct inhibition of DNA gyrase without activation
• Activation by bacterial flavoproteins to reactive intermediates that damage DNA
• Competitive antagonism of para-aminobenzoic acid
• Alkalinization of urine to prevent bacterial growth

Correct Answer: Activation by bacterial flavoproteins to reactive intermediates that damage DNA

Q3. Furazolidone belongs to which class and primary mechanism?

• Macrolide that blocks 50S ribosomal subunit
• Nitrofuran that undergoes nitro-reduction producing reactive intermediates that damage bacterial DNA
• Beta-lactam that inhibits transpeptidase enzymes
• Glycopeptide that disrupts cell wall synthesis

Correct Answer: Nitrofuran that undergoes nitro-reduction producing reactive intermediates that damage bacterial DNA

Q4. Nitrofurantoin is primarily indicated for which condition?

• Acute pyelonephritis requiring high serum levels
• Acute uncomplicated lower urinary tract infection (cystitis)
• Septicemia caused by Pseudomonas aeruginosa
• Systemic anaerobic infections

Correct Answer: Acute uncomplicated lower urinary tract infection (cystitis)

Q5. Methenamine is most effective when urine pH is:

• Alkaline (pH ≥8.0)
• Neutral (pH ~7.0)
• Acidic (pH ≤5.5)
• Any pH; pH has no effect

Correct Answer: Acidic (pH ≤5.5)

Q6. Nitrofurantoin is generally contraindicated in which pregnancy situation?

• First trimester use only
• Near-term pregnancy and in neonates (risk of hemolysis)
• Use throughout pregnancy is safe
• Only contraindicated in the second trimester

Correct Answer: Near-term pregnancy and in neonates (risk of hemolysis)

Q7. A serious long-term adverse effect associated with nitrofurantoin is:

• Renal papillary necrosis
• Pulmonary fibrosis and chronic interstitial pneumonitis
• Ototoxicity similar to aminoglycosides
• Cardiac arrhythmias due to QT prolongation

Correct Answer: Pulmonary fibrosis and chronic interstitial pneumonitis

Q8. The most common urinary adverse effect seen with methenamine therapy is:

• Systemic bone marrow suppression
• Urinary tract irritation and dysuria
• Severe hepatotoxicity
• Peripheral neuropathy

Correct Answer: Urinary tract irritation and dysuria

Q9. Which adverse event is a concern with furazolidone, especially in predisposed individuals?

• Hyperkalemia
• Hemolytic anemia in G6PD deficient patients
• Renal tubular acidosis
• Tendon rupture

Correct Answer: Hemolytic anemia in G6PD deficient patients

Q10. Traditional guidance recommends avoiding nitrofurantoin when creatinine clearance is below:

• 90 mL/min
• 60 mL/min
• 30 mL/min
• 10 mL/min

Correct Answer: 60 mL/min

Q11. Which coadministered agent can increase methenamine efficacy by acidifying urine?

• Acetazolamide
• Ascorbic acid (vitamin C)
• Sodium bicarbonate
• Proton pump inhibitor

Correct Answer: Ascorbic acid (vitamin C)

Q12. Nitrofurantoin has reliable activity against which common urinary pathogens?

• Pseudomonas aeruginosa and Proteus mirabilis
• E. coli and Staphylococcus saprophyticus
• Enterobacter and Serratia species
• Acinetobacter and Klebsiella pneumoniae

Correct Answer: E. coli and Staphylococcus saprophyticus

Q13. The primary mechanism by which bacteria develop resistance to nitrofurantoin is:

• Production of beta-lactamases
• Efflux pump overexpression only
• Loss or alteration of bacterial nitroreductases that activate the drug
• Acetylation of the drug by bacterial enzymes

Correct Answer: Loss or alteration of bacterial nitroreductases that activate the drug

Q14. Furazolidone may interact adversely with which of the following due to MAOI-like activity?

• Vitamin D supplements
• Tyramine-rich foods and sympathomimetics
• ACE inhibitors causing hyperkalemia
• Antacids reducing absorption

Correct Answer: Tyramine-rich foods and sympathomimetics

Q15. Methenamine is unlikely to be effective against infections with which organism due to urinary alkalinization by urease?

• Escherichia coli
• Proteus mirabilis
• Staphylococcus saprophyticus
• Enterococcus faecalis

Correct Answer: Proteus mirabilis

Q16. Regarding pharmacokinetics, nitrofurantoin achieves:

• High serum concentrations suitable for systemic infections
• High urinary concentrations with minimal systemic exposure
• Predominantly hepatic accumulation
• Extensive distribution into CSF

Correct Answer: High urinary concentrations with minimal systemic exposure

Q17. Historically, furazolidone was commonly used for:

• Systemic fungal infections
• Intestinal and enteric infections (e.g., some diarrheal illnesses)
• Central nervous system infections
• Viral hepatitis

Correct Answer: Intestinal and enteric infections (e.g., some diarrheal illnesses)

Q18. Which formulation characteristic of nitrofurantoin reduces GI side effects?

• Macrocrystalline formulation that slows absorption
• Intravenous formulation only
• Immediate-release syrup
• Combination with a proton pump inhibitor

Correct Answer: Macrocrystalline formulation that slows absorption

Q19. The commonly used urinary salt form of methenamine for prophylaxis is:

• Methenamine acetate
• Methenamine hippurate
• Methenamine sulfate
• Methenamine chloride

Correct Answer: Methenamine hippurate

Q20. Important monitoring for patients on nitrofurantoin includes:

• Regular ophthalmologic exams only
• Monitoring for pulmonary symptoms and liver function tests
• No monitoring is required
• Continuous ECG monitoring

Correct Answer: Monitoring for pulmonary symptoms and liver function tests

Q21. A common benign side effect of nitrofurantoin is:

• Blue-green skin discoloration
• Brownish urine discoloration
• Marked hyperglycemia
• Severe photosensitivity

Correct Answer: Brownish urine discoloration

Q22. Resistance to methenamine is uncommon because:

• It inhibits a single specific enzyme that bacteria cannot mutate
• Formaldehyde exerts nonspecific, multi-target denaturation of proteins and nucleic acids
• It is always combined with a beta-lactam
• It is not actually antibacterial

Correct Answer: Formaldehyde exerts nonspecific, multi-target denaturation of proteins and nucleic acids

Q23. Furazolidone use in pregnancy is generally:

• Recommended for all trimesters
• To be avoided due to potential fetal harm and maternal toxicity
• Required to prevent UTI in pregnancy
• Safe after the first trimester only

Correct Answer: To be avoided due to potential fetal harm and maternal toxicity

Q24. Nitrofurantoin should not be given to which pediatric group?

• Children older than 12 years
• Infants under 1 month of age (neonates)
• Children between 2–5 years for skin infections
• All pediatric patients without exception

Correct Answer: Infants under 1 month of age (neonates)

Q25. Which bacterial enzyme activity reduces methenamine efficacy by increasing urinary pH?

• Lactamase
• Beta-galactosidase
• Urease (e.g., Proteus species)
• Nitroreductase

Correct Answer: Urease (e.g., Proteus species)

Q26. Which nitrofurantoin formulation is marketed as twice-daily dosing (e.g., Macrobid)?

• Nitrofurantoin macrocrystals only
• Nitrofurantoin monohydrate/macrocrystals combination
• Intravenous nitrofurantoin
• Immediate-release syrup

Correct Answer: Nitrofurantoin monohydrate/macrocrystals combination

Q27. Long-term use of furazolidone has been associated with which neurological adverse effect?

• Acute meningitis
• Peripheral neuropathy
• Extrapyramidal movement disorder
• Grand mal seizures only

Correct Answer: Peripheral neuropathy

Q28. Which of the following would most likely decrease methenamine effectiveness?

• Administration with ascorbic acid
• Concomitant use of sodium bicarbonate that alkalinizes urine
• Taking methenamine with food
• Splitting dose into multiple small doses

Correct Answer: Concomitant use of sodium bicarbonate that alkalinizes urine

Q29. Which drug is most appropriate for chronic prophylaxis of recurrent lower urinary tract infections?

• Methenamine hippurate
• Intravenous ceftazidime daily
• Oral amphotericin B
• High-dose systemic gentamicin long term

Correct Answer: Methenamine hippurate

Q30. Which statement correctly matches the drug with a characteristic adverse property?

• Nitrofurantoin — commonly causes nephrolithiasis
• Methenamine — requires acidic urine to generate formaldehyde
• Furazolidone — safe in G6PD deficiency
• Nitrofurantoin — reliably treats systemic gram-negative sepsis

Correct Answer: Methenamine — requires acidic urine to generate formaldehyde

G S Sachin

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