Ciprofloxacin – synthesis and mechanism MCQs With Answer

Ciprofloxacin – synthesis and mechanism MCQs With Answer

Ciprofloxacin is a widely used fluoroquinolone antibiotic whose medicinal chemistry, synthesis and mechanism are essential topics for B. Pharm students. This introduction covers key keywords like ciprofloxacin, fluoroquinolone, synthesis route, piperazinyl substitution, SAR, DNA gyrase, topoisomerase IV, chelation, resistance mechanisms (gyrA/parC mutations, qnr, efflux), pharmacokinetics and adverse effects. Understanding core synthetic strategies, functional group transformations and the precise enzyme-DNA interactions helps link theory to formulation, analytical assay development and clinical use. The following targeted MCQs probe deeper concepts in synthesis, mechanism and pharmaceutical implications for thorough exam preparation. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What chemical class does ciprofloxacin belong to?

• Macrolide
• Aminoglycoside
• Fluoroquinolone
• Tetracycline

Correct Answer: Fluoroquinolone

Q2. Which primary bacterial enzymes are inhibited by ciprofloxacin?

• Peptidyl transferase and RNA polymerase
• DNA gyrase and topoisomerase IV
• Transpeptidase and carboxypeptidase
• MurA and MurB

Correct Answer: DNA gyrase and topoisomerase IV

Q3. The bactericidal action of ciprofloxacin results mainly from:

• Inhibition of cell wall synthesis
• Disruption of bacterial membranes
• Stabilization of enzyme–DNA cleavage complexes causing double-stranded DNA breaks
• Competitive antagonism of folate synthesis

Correct Answer: Stabilization of enzyme–DNA cleavage complexes causing double-stranded DNA breaks

Q4. Which structural feature at position C6 enhances antibacterial activity in fluoroquinolones?

• Methyl group
• Fluorine atom
• Nitro group
• Sulfhydryl group

Correct Answer: Fluorine atom

Q5. The piperazinyl moiety at C7 in ciprofloxacin primarily contributes to:

• Increased lipophilicity only
• Improved Gram-negative activity and pharmacokinetic properties
• Beta-lactamase inhibition
• Chelation of metal ions in plasma

Correct Answer: Improved Gram-negative activity and pharmacokinetic properties

Q6. Substitution at the N1 position with a cyclopropyl group in ciprofloxacin results in:

• Decreased oral absorption
• Enhanced activity against Gram-negative bacteria and some atypicals
• Loss of activity against Pseudomonas
• Increased protein binding only

Correct Answer: Enhanced activity against Gram-negative bacteria and some atypicals

Q7. Which functional group pair is essential for binding to the bacterial enzyme–DNA complex?

• Hydroxyl at C2 and methoxy at C3
• Carboxylic acid at C3 and ketone at C4
• Amino at C5 and aldehyde at C6
• Sulfone at C7 and ester at C8

Correct Answer: Carboxylic acid at C3 and ketone at C4

Q8. The most common chromosomal resistance mechanism to ciprofloxacin is:

• Overproduction of peptidoglycan
• Mutations in gyrA and parC genes altering target enzymes
• Plasmid-mediated beta-lactamase production
• Inactivation by acetyltransferases

Correct Answer: Mutations in gyrA and parC genes altering target enzymes

Q9. Plasmid-mediated qnr genes confer resistance by:

• Enzymatically degrading ciprofloxacin
• Protecting DNA gyrase from quinolone binding
• Pumping ciprofloxacin out via efflux pumps
• Altering cell wall permeability

Correct Answer: Protecting DNA gyrase from quinolone binding

Q10. Which resistance mechanism reduces intracellular drug concentration of ciprofloxacin?

• Target site mutation only
• Efflux pump overexpression
• Ribosomal methylation
• Biofilm formation exclusively

Correct Answer: Efflux pump overexpression

Q11. Ciprofloxacin’s killing kinetics are best described as:

• Time-dependent bactericidal
• Concentration-dependent bactericidal
• Bacteriostatic irrespective of concentration
• Post-antibiotic effect absent

Correct Answer: Concentration-dependent bactericidal

Q12. Which organism is ciprofloxacin particularly active against?

• Enterococcus faecalis primarily
• Pseudomonas aeruginosa
• Mycobacterium tuberculosis as first-line therapy
• Strict anaerobes only

Correct Answer: Pseudomonas aeruginosa

Q13. Oral absorption of ciprofloxacin is significantly reduced by coadministration of:

• Antacids containing calcium, magnesium or aluminum
• Vitamin C supplements
• Proton pump inhibitors without metal ions
• Oral contraceptives exclusively

Correct Answer: Antacids containing calcium, magnesium or aluminum

Q14. A clinically important adverse effect associated with ciprofloxacin is:

• Ototoxicity leading to irreversible hearing loss
• Tendonitis and risk of tendon rupture
• Severe hypoglycemia in all patients
• Immediate hemolytic anemia in normal G6PD individuals

Correct Answer: Tendonitis and risk of tendon rupture

Q15. Ciprofloxacin is generally contraindicated or used with caution in:

• Pregnancy and growing children due to cartilage toxicity
• Adults over 50 only
• Patients with hyperthyroidism
• Patients with hyperlipidemia exclusively

Correct Answer: Pregnancy and growing children due to cartilage toxicity

Q16. The primary elimination pathway for ciprofloxacin involves:

• Hepatic metabolism only with no renal excretion
• Significant renal excretion of unchanged drug
• Fecal elimination exclusively
• Exhalation via lungs

Correct Answer: Significant renal excretion of unchanged drug

Q17. In pharmaceutical formulations, ciprofloxacin is commonly used as:

• Free acid in aqueous injections
• Hydrochloride salt for oral and IV formulations
• As a sulfate ester prodrug only
• Topical ointment with no systemic forms

Correct Answer: Hydrochloride salt for oral and IV formulations

Q18. In synthetic routes, introduction of the piperazinyl group at C7 is typically achieved by:

• Electrophilic aromatic substitution at C2
• Nucleophilic aromatic substitution at C7 on an activated haloquinolone intermediate
• Free radical halogenation at N1
• Direct coupling with Grignard reagent at C4

Correct Answer: Nucleophilic aromatic substitution at C7 on an activated haloquinolone intermediate

Q19. A common method to construct the 4-quinolone core in fluoroquinolone synthesis is the:

• Gould–Jacobs reaction forming 4-hydroxyquinoline-3-carboxylates
• Wittig reaction to form quinolone directly
• Buchwald–Hartwig amination of benzene
• Ozonolysis of naphthalene derivatives

Correct Answer: Gould–Jacobs reaction forming 4-hydroxyquinoline-3-carboxylates

Q20. During synthesis, the final conversion to ciprofloxacin’s carboxylic acid moiety commonly involves:

• Oxidative cleavage of an alkene
• Ester hydrolysis followed by acidification to yield the carboxylic acid
• Direct nitration of the aromatic ring
• Reductive amination at C3

Correct Answer: Ester hydrolysis followed by acidification to yield the carboxylic acid

Q21. Which analytical technique is most suitable for routine assay and purity testing of ciprofloxacin in formulations?

• Paper chromatography only
• HPLC with UV detection
• Flame photometry
• Polarimetry exclusively

Correct Answer: HPLC with UV detection

Q22. Which spectroscopic method can directly detect the fluorine atom in ciprofloxacin and help in structural confirmation?

• 1H NMR only
• 19F NMR spectroscopy
• IR spectroscopy exclusively
• Mass spectrometry cannot detect fluorine

Correct Answer: 19F NMR spectroscopy

Q23. Divalent magnesium ions play what role in ciprofloxacin’s interaction with the bacterial target?

• They inactivate ciprofloxacin by oxidation
• They coordinate between drug, DNA and enzyme stabilizing the cleavage complex
• They act as a competitive antagonist at the active site
• They have no role in the mechanism

Correct Answer: They coordinate between drug, DNA and enzyme stabilizing the cleavage complex

Q24. Ciprofloxacin inhibits which cytochrome P450 enzyme, leading to drug interactions (e.g., with theophylline)?

• CYP3A4 exclusively
• CYP1A2
• CYP2D6 only
• No effect on cytochrome P450 enzymes

Correct Answer: CYP1A2

Q25. Which cardiac effect can be associated with ciprofloxacin therapy, warranting caution with other QT-prolonging drugs?

• Complete heart block universally
• QT interval prolongation and risk of torsades de pointes
• Immediate myocardial infarction onset
• No known cardiac effects

Correct Answer: QT interval prolongation and risk of torsades de pointes

Q26. For patients with significant renal impairment, ciprofloxacin dosing typically requires:

• No adjustment because it is entirely hepatic
• Dose reduction or extended dosing interval
• Switching to an aminoglycoside always
• Doubling the dose for efficacy

Correct Answer: Dose reduction or extended dosing interval

Q27. Regarding stereochemistry, ciprofloxacin is best described as:

• A racemic mixture of two enantiomers
• A single stereogenic center with R configuration
• Achiral (no stereogenic center)
• A diastereomeric mixture

Correct Answer: Achiral (no stereogenic center)

Q28. At physiological pH ciprofloxacin predominantly exists as a/an:

• Neutral nonpolar molecule only
• Zwitterion with both positive and negative charges
• Permanently anionic species only
• Permanently cationic species only

Correct Answer: Zwitterion with both positive and negative charges

Q29. In manufacturing and formulation, why is polymorphism of ciprofloxacin important?

• Polymorphs change the chemical formula
• Different polymorphs can alter dissolution rate and bioavailability
• Polymorphism only affects color and is clinically irrelevant
• Polymorphs eliminate the need for stability testing

Correct Answer: Different polymorphs can alter dissolution rate and bioavailability

Q30. Mechanistically, ciprofloxacin’s inhibition leads to cell death because it:

• Blocks protein synthesis at the 50S ribosomal subunit
• Prevents religation of cleaved DNA strands, causing lethal DNA damage
• Inhibits folate synthesis resulting in slow bacteriostasis
• Destroys the bacterial cell wall by inhibiting transglycosylation

Correct Answer: Prevents religation of cleaved DNA strands, causing lethal DNA damage

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