Oxytetracycline – chemistry and use MCQs With Answer

Oxytetracycline – chemistry and use MCQs With Answer

Oxytetracycline is a broad‑spectrum tetracycline antibiotic widely studied for its chemistry, pharmacology, and clinical applications. B.Pharm students should understand its four‑ring naphthacene core, functional groups (dimethylamino, keto‑enol system, multiple hydroxyls), stereochemistry, and susceptibility to epimerization and chelation. Key pharmacokinetic and pharmacodynamic aspects include absorption, protein binding, renal elimination, 30S ribosomal binding and bacteriostatic action. Learn important topics such as antimicrobial spectrum, resistance mechanisms, drug interactions (divalent cations, antacids), adverse effects (teeth discoloration, hepatotoxicity, photosensitivity), formulations and analytical assays. This concise review prepares you for applied questions and practical pharmacy use. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which antibiotic class does oxytetracycline belong to?

• Tetracyclines
• Aminoglycosides
• Macrolides
• Fluoroquinolones

Correct Answer: Tetracyclines

Q2. Which structural feature is characteristic of oxytetracycline?

• Four fused rings (naphthacene) with multiple hydroxyl and keto groups
• Beta‑lactam ring fused to a thiazolidine
• Large lactone ring with glycosidic sugars
• Quinolone core with a fluorine atom at C‑6

Correct Answer: Four fused rings (naphthacene) with multiple hydroxyl and keto groups

Q3. What is the primary mechanism of action of oxytetracycline?

• Inhibition of DNA gyrase
• Inhibition of 30S ribosomal subunit, blocking tRNA binding
• Inhibition of peptidoglycan cross‑linking
• Disruption of cell membrane via pore formation

Correct Answer: Inhibition of 30S ribosomal subunit, blocking tRNA binding

Q4. Oxytetracycline is generally classified as which type of antimicrobial agent?

• Bactericidal
• Bacteriostatic
• Fungistatic
• Virucidal

Correct Answer: Bacteriostatic

Q5. Which of the following reduces oral absorption of oxytetracycline?

• Concurrent ingestion of antacids containing aluminum or magnesium
• Taking with a glass of water
• Administration with a fatty meal
• Co‑administration with vitamin C

Correct Answer: Concurrent ingestion of antacids containing aluminum or magnesium

Q6. Which ion commonly chelates with oxytetracycline causing reduced absorption?

• Sodium (Na+)
• Calcium (Ca2+)
• Potassium (K+)
• Chloride (Cl-)

Correct Answer: Calcium (Ca2+)

Q7. Which adverse effect is classically associated with oxytetracycline use in children?

• Permanent tooth discoloration and enamel hypoplasia
• Serotonin syndrome
• Ototoxicity leading to irreversible deafness
• Permanent alopecia

Correct Answer: Permanent tooth discoloration and enamel hypoplasia

Q8. Oxytetracycline is contraindicated in which patient group?

• Pregnant women and children under 8 years
• Patients with hyperthyroidism
• Individuals with lactose intolerance
• Patients taking beta blockers

Correct Answer: Pregnant women and children under 8 years

Q9. The dimethylamino group responsible for antibacterial activity in tetracyclines is located at which carbon position?

• C‑4
• C‑1
• C‑7
• C‑12

Correct Answer: C‑4

Q10. Which mechanism commonly causes bacterial resistance to oxytetracycline?

• Ribosomal protection proteins and efflux pumps
• Production of beta‑lactamases
• Altered folate synthesis enzymes
• Mutations in DNA gyrase only

Correct Answer: Ribosomal protection proteins and efflux pumps

Q11. Oxytetracycline is most reliably assayed by which analytical technique in quality control?

• High‑performance liquid chromatography (HPLC)
• Paper chromatography
• Turbidimetric assay only
• Simple gravimetric analysis

Correct Answer: High‑performance liquid chromatography (HPLC)

Q12. Which formulation of oxytetracycline is commonly used for topical ophthalmic infections?

• Ointment
• Enteric‑coated tablet
• Dry powder inhaler
• Transdermal patch

Correct Answer: Ointment

Q13. Oxytetracycline is eliminated primarily by which route?

• Renal excretion
• Exhalation via lungs
• Complete hepatic metabolism only
• Faecal elimination exclusively

Correct Answer: Renal excretion

Q14. Which property of oxytetracycline makes it prone to form complexes with metal ions?

• Multiple chelating functional groups including hydroxyl and keto‑enol systems
• Strong basic tertiary amine that forms salts with acids
• Highly lipophilic chain that dissolves in oils
• Quaternary ammonium center that binds halides

Correct Answer: Multiple chelating functional groups including hydroxyl and keto‑enol systems

Q15. Exposure to which environmental factor accelerates oxytetracycline degradation and requires protection in storage?

• Light (photodegradation)
• Low temperature refrigeration
• Dry, desiccated air
• Presence of inert nitrogen

Correct Answer: Light (photodegradation)

Q16. Which statement about oxytetracycline pharmacodynamics is correct?

• It binds reversibly to the 30S subunit preventing aminoacyl‑tRNA attachment
• It irreversibly binds penicillin‑binding proteins
• It inhibits folate synthesis by dihydropteroate synthase
• It depolarizes bacterial membranes causing lysis

Correct Answer: It binds reversibly to the 30S subunit preventing aminoacyl‑tRNA attachment

Q17. Epimerization at C‑4 of tetracyclines leads to loss of activity and is promoted by which condition?

• Acidic solutions and heat
• Strongly reducing agents only
• Anhydrous conditions at low temperature
• Contact with non‑polar solvents

Correct Answer: Acidic solutions and heat

Q18. Which microorganism is least likely to be reliably treated with oxytetracycline?

• Pseudomonas aeruginosa
• Chlamydia trachomatis
• Mycoplasma pneumoniae
• Brucella species

Correct Answer: Pseudomonas aeruginosa

Q19. A common phototoxic effect of oxytetracycline involves:

• Skin erythema and exaggerated sunburn reaction
• Severe urticarial anaphylaxis
• Permanent skin hyperpigmentation only
• Immediate blistering independent of sunlight

Correct Answer: Skin erythema and exaggerated sunburn reaction

Q20. Which analytical property makes UV spectrophotometry useful for preliminary oxytetracycline estimation?

• Strong UV absorbance due to conjugated keto‑enol and aromatic systems
• Intrinsic fluorescence identical to all antibiotics
• High volatility allowing GC‑MS direct quantitation
• No absorption in UV range requiring IR instead

Correct Answer: Strong UV absorbance due to conjugated keto‑enol and aromatic systems

Q21. Which is a clinically relevant drug interaction of oxytetracycline?

• Reduced absorption when given with iron supplements
• Increased effect when combined with penicillin V
• Synergistic cardiac conduction slowing with digoxin
• Neutralization by oral vitamin E

Correct Answer: Reduced absorption when given with iron supplements

Q22. Which adverse reaction requires dose adjustment or caution in hepatic or renal impairment?

• Increased risk of nephrotoxicity and accumulation leading to toxicity in renal impairment
• Sudden hypoglycemia in diabetics
• Immediate hemolytic anemia in G6PD deficiency only
• Complete prevention of vitamin K activation

Correct Answer: Increased risk of nephrotoxicity and accumulation leading to toxicity in renal impairment

Q23. Which formulation is NOT commonly used for oxytetracycline?

• Transdermal patch
• Oral tablets and capsules
• Injectable solutions
• Topical ointments

Correct Answer: Transdermal patch

Q24. The presence of which functional group contributes to keto‑enol tautomerism in oxytetracycline?

• Beta‑diketone (keto‑enol) moiety
• Ether linkage only
• Simple alkane chain with no heteroatoms
• Quaternary ammonium salt

Correct Answer: Beta‑diketone (keto‑enol) moiety

Q25. Which lab monitoring may be important during high‑dose or prolonged therapy with oxytetracycline?

• Liver and renal function tests
• Fasting blood glucose only
• Serial coagulation times exclusively
• Daily serum magnesium only

Correct Answer: Liver and renal function tests

Q26. Oxytetracycline’s antibacterial spectrum includes which of the following atypical organisms?

• Mycoplasma species
• Cryptococcus neoformans
• Influenza A virus
• Treponema pallidum only

Correct Answer: Mycoplasma species

Q27. Which statement about oxytetracycline stability is correct?

• It is light‑sensitive and can degrade to inactive products if exposed to sunlight
• It is completely stable in concentrated acid at high temperature
• It is unaffected by metal ions in solution
• It does not undergo epimerization under any conditions

Correct Answer: It is light‑sensitive and can degrade to inactive products if exposed to sunlight

Q28. In formulation design, oxytetracycline oral suspensions should avoid which excipient to prevent chelation?

• Calcium‑containing salts
• Povidone (polyvinylpyrrolidone)
• Sodium carboxymethylcellulose
• Sorbitol

Correct Answer: Calcium‑containing salts

Q29. Which bacteria would oxytetracycline typically be effective against?

• Staphylococcus aureus (susceptible strains)
• All strains of Enterococcus faecalis without resistance
• Most strains of Mycobacterium tuberculosis as first line
• Pneumocystis jirovecii

Correct Answer: Staphylococcus aureus (susceptible strains)

Q30. Regarding dosing in renal impairment, oxytetracycline usually requires which consideration?

• Dose adjustment or increased dosing interval due to renal excretion
• No change; always metabolized completely in the liver
• Immediate discontinuation because it is exclusively hepatotoxic
• Doubling the daily dose to overcome renal loss

Correct Answer: Dose adjustment or increased dosing interval due to renal excretion

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