Chlortetracycline – chemistry and use MCQs With Answer

Chlortetracycline – chemistry and use MCQs With Answer

Chlortetracycline is a broad‑spectrum tetracycline antibiotic with a polycyclic naphthacene carboxamide core. B. Pharm students should focus on its chemical structure, functional groups, stereochemistry, chelation with metal ions, degradation pathways, analytical assays (HPLC, microbiological), mechanism of action (30S ribosomal inhibition), pharmacokinetics, resistance mechanisms, formulations and stability considerations. Key topics include pH‑dependent solubility, photodegradation, assay validation, and clinical/excipients interactions. This concise yet detailed overview prepares you for both practical lab work and theory exams. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which structural feature is characteristic of chlortetracycline and responsible for its antibiotic activity?

• A linear peptide backbone
• A naphthacene (four fused rings) carboxamide core
• A β‑lactam ring
• An aminoglycoside sugar moiety

Correct Answer: A naphthacene (four fused rings) carboxamide core

Q2. Chlortetracycline primarily inhibits bacterial growth by:

• Inhibiting cell wall synthesis
• Blocking 50S ribosomal subunit formation
• Inhibiting DNA gyrase
• Binding the 30S ribosomal subunit and preventing protein synthesis

Correct Answer: Binding the 30S ribosomal subunit and preventing protein synthesis

Q3. One major chemical property of chlortetracycline is its ability to:

• Form covalent bonds with fatty acids
• Chelate divalent and trivalent metal ions
• Undergo rapid methylation in neutral pH
• Reduce to an alcohol in aqueous media

Correct Answer: Chelate divalent and trivalent metal ions

Q4. Which analytical technique is commonly used for the assay and purity determination of chlortetracycline in formulations?

• Gas chromatography with FID
• Reverse‑phase high performance liquid chromatography (HPLC)
• Polarimetry
• Size exclusion chromatography

Correct Answer: Reverse‑phase high performance liquid chromatography (HPLC)

Q5. Chlortetracycline is most unstable under which condition?

• Dry, dark storage
• Acidic aqueous medium and high temperature
• Freezing at −20°C
• Encapsulation in liposomes

Correct Answer: Acidic aqueous medium and high temperature

Q6. A common degradation pathway for chlortetracycline involves:

• Hydrolysis of an amide to an amine
• Photochemical epimerization and dehydration
• Oxidative cleavage of an ether bond
• β‑elimination of a sulfate group

Correct Answer: Photochemical epimerization and dehydration

Q7. In formulation development, which excipient concern is most relevant for chlortetracycline tablets?

• Interaction with anionic surfactants to form soluble complexes
• Chelation with calcium and magnesium contaminants in fillers
• Alkylation by common binders
• Incompatibility with polyethylene glycol due to peroxidation

Correct Answer: Chelation with calcium and magnesium contaminants in fillers

Q8. The official compendial methods for chlortetracycline often require control of which parameter during HPLC analysis?

• Strong basic mobile phase (pH > 10)
• Use of a neutral organic solvent without aqueous buffer
• Buffered mobile phase at controlled pH and a C18 column
• Normal phase silica column with nonpolar solvents

Correct Answer: Buffered mobile phase at controlled pH and a C18 column

Q9. Which statement about the microbial spectrum of chlortetracycline is correct?

• It is effective only against Gram‑positive bacteria
• It has broad‑spectrum activity against many Gram‑positive and Gram‑negative organisms
• It is primarily antifungal
• It targets only anaerobic bacteria

Correct Answer: It has broad‑spectrum activity against many Gram‑positive and Gram‑negative organisms

Q10. Resistance to chlortetracycline commonly arises via:

• Target site methylation of 23S rRNA
• Efflux pumps and ribosomal protection proteins
• Increase in cell wall thickness
• Production of β‑lactamase enzymes

Correct Answer: Efflux pumps and ribosomal protection proteins

Q11. Which formulation type can reduce light‑induced degradation of chlortetracycline?

• Clear, single‑layer blister packs
• Opaque or amber glass containers with desiccant
• Open plastic bottles exposed to daylight
• Sachets made of clear polyethylene

Correct Answer: Opaque or amber glass containers with desiccant

Q12. The presence of multiple ionizable groups in chlortetracycline causes:

• pH‑dependent ionization and solubility changes
• Complete insolubility in water at all pH
• Perpetual neutral charge across pH range
• Spontaneous polymerization in aqueous solutions

Correct Answer: pH‑dependent ionization and solubility changes

Q13. During microbiological assay for potency, the principle is based on:

• Measuring optical rotation changes caused by drug
• Zone of inhibition produced against a susceptible organism
• Colorimetric reaction with ferrous ions
• Measuring pressure change in culture vials

Correct Answer: Zone of inhibition produced against a susceptible organism

Q14. Chlortetracycline can form insoluble complexes in the presence of which coadministered agents, reducing absorption?

• Proton pump inhibitors
• Divalent cations such as calcium, magnesium and iron
• Non‑steroidal anti‑inflammatory drugs
• β‑blockers

Correct Answer: Divalent cations such as calcium, magnesium and iron

Q15. Which spectroscopic feature is typically used for qualitative identification of tetracyclines including chlortetracycline?

• Strong IR absorption at 2900 cm‑1 only
• Characteristic UV‑visible absorption bands due to conjugated ring system
• Unique NMR signal at 0 ppm
• Fluorescence in the red region only

Correct Answer: Characteristic UV‑visible absorption bands due to conjugated ring system

Q16. The role of magnesium in tetracycline pharmacology is most associated with:

• Enhancing gastrointestinal absorption
• Forming chelates that reduce oral bioavailability
• Acting as a preservative in formulations
• Serving as a cofactor for ribosomal binding

Correct Answer: Forming chelates that reduce oral bioavailability

Q17. For tablet assay by HPLC, selection of internal standard is important. Which property is most desirable?

• Completely different retention time and no structural similarity
• Chemical stability, similar extraction behavior and distinct peak from analyte
• Being an impurity of chlortetracycline
• Having identical retention time to the analyte

Correct Answer: Chemical stability, similar extraction behavior and distinct peak from analyte

Q18. What is an expected adverse effect associated with tetracyclines like chlortetracycline?

• Ototoxicity resembling aminoglycosides
• Tooth discoloration and inhibition of bone growth in children
• Severe hyperglycemia
• Permanent alopecia in all patients

Correct Answer: Tooth discoloration and inhibition of bone growth in children

Q19. Which storage recommendation helps maintain chlortetracycline stability in bulk powder?

• Store at high humidity and room temperature
• Store in airtight, light‑protected containers at controlled low humidity
• Store dissolved in aqueous solution at pH 2
• Store mixed with alkaline buffers

Correct Answer: Store in airtight, light‑protected containers at controlled low humidity

Q20. Incompatibility studies, chlortetracycline is likely to react with which functional excipient class?

• Neutral hydrocarbons with no polar groups
• Strong acids or bases that catalyze degradation
• Non‑ionic surfactants that are inert
• Silica fillers that are chemically inert

Correct Answer: Strong acids or bases that catalyze degradation

Q21. The term ‘epimerization’ in tetracycline chemistry refers to:

• Loss of a methyl group
• Conversion of one stereoisomer to another at a chiral center
• Formation of a new double bond
• Hydrolysis of an ester linkage

Correct Answer: Conversion of one stereoisomer to another at a chiral center

Q22. Which pharmacokinetic property is typical for chlortetracycline?

• Extensive hepatic metabolism with no renal excretion
• Moderate oral absorption with significant tissue binding and renal excretion
• Complete oral bioavailability and no protein binding
• Rapid inhalational absorption as main route

Correct Answer: Moderate oral absorption with significant tissue binding and renal excretion

Q23. During forced‑degradation studies, identifying degradation products helps primarily to:

• Increase the potency beyond label claim
• Understand stability pathways and develop stability‑indicating assays
• Eliminate the need for storage studies
• Prove that the drug is inert to all conditions

Correct Answer: Understand stability pathways and develop stability‑indicating assays

Q24. Which excipient can help stabilize chlortetracycline in a solid oral dosage form?

• Reactive metal salts
• Antioxidants and light‑protective coatings
• Strongly alkaline fillers
• Free divalent metal ions

Correct Answer: Antioxidants and light‑protective coatings

Q25. In quality control, the related substances test for chlortetracycline aims to detect:

• Only inorganic impurities
• Degradation products, synthesis impurities and related tetracycline analogs
• Only microbial contamination
• Only residual solvents

Correct Answer: Degradation products, synthesis impurities and related tetracycline analogs

Q26. Which of the following explains why chlortetracycline solutions should not be mixed with milk?

• Milk causes rapid oxidation to inactive species
• Calcium in milk forms insoluble chelates reducing drug absorption
• Milk significantly lowers pH causing precipitation
• Proteins in milk enzymatically degrade the drug instantly

Correct Answer: Calcium in milk forms insoluble chelates reducing drug absorption

Q27. For a stability‑indicating HPLC method, what must be demonstrated?

• The method quantifies only the excipients
• Resolution between chlortetracycline and its degradation products
• That the analyte coelutes with its impurities
• That the method ignores all related substances

Correct Answer: Resolution between chlortetracycline and its degradation products

Q28. A lab student observes a color change in chlortetracycline solution upon standing in light. This suggests:

• Formation of stable salts that increase potency
• Photodegradation and possible formation of inactive products
• Sterilization of the solution by light
• Complete stabilization by light exposure

Correct Answer: Photodegradation and possible formation of inactive products

Q29. Which mobile phase modifier is often used to improve peak shape for tetracyclines in RP‑HPLC?

• Strong oxidizing agents
• Volatile acidic buffers (e.g., formic or phosphate buffers at controlled pH)
• Concentrated strong bases like NaOH
• Pure water without buffer

Correct Answer: Volatile acidic buffers (e.g., formic or phosphate buffers at controlled pH)

Q30. In teaching labs, why is it important to emphasize drug‑excipient compatibility testing for chlortetracycline?

• Because excipients always improve drug stability
• To prevent unwanted chemical reactions that reduce efficacy or safety
• Compatibility testing is optional and rarely useful
• Because it allows substitution of the active with excipient

Correct Answer: To prevent unwanted chemical reactions that reduce efficacy or safety

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