Tetracyclines are broad-spectrum antibiotics that inhibit bacterial protein synthesis by binding reversibly to the 30S ribosomal subunit, producing a bacteriostatic effect. B. Pharm students should understand tetracycline pharmacology, mechanisms of action, resistance mechanisms, pharmacokinetics (absorption, distribution, chelation with divalent cations), and clinical uses of doxycycline, minocycline and tetracycline. Recognizing adverse effects — gastrointestinal upset, teeth discoloration, hepatotoxicity, nephrotoxicity, photosensitivity and vestibular symptoms — and important drug interactions is essential for safe dispensing and counseling. This concise, focused set of MCQs emphasizes mechanism, adverse reactions, clinical considerations and exam-relevant facts to strengthen recall and application. Questions cover pharmacodynamics, resistance mechanisms, dosing adjustments, contraindications and counseling points relevant to pharmacy practice.
Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which molecular target do tetracyclines primarily bind to in bacteria?
- 50S ribosomal subunit
- 30S ribosomal subunit
- Peptidoglycan transpeptidase
- DNA gyrase
Correct Answer: 30S ribosomal subunit
Q2. The primary antibacterial effect produced by tetracyclines is best described as:
- Bactericidal by cell wall lysis
- Bacteriostatic by inhibiting protein synthesis
- Bactericidal by inhibiting DNA synthesis
- Bacteriostatic by disrupting folate synthesis
Correct Answer: Bacteriostatic by inhibiting protein synthesis
Q3. Which mechanism is a common form of acquired bacterial resistance to tetracyclines?
- Production of beta-lactamases
- Modification of drug target in 23S rRNA
- Active efflux pumps removing tetracyclines
- Increased permeability to tetracyclines
Correct Answer: Active efflux pumps removing tetracyclines
Q4. Chelation reduces oral absorption of tetracyclines when co-administered with which of the following?
- Proton pump inhibitors
- Calcium-containing antacids
- Metoclopramide
- Paracetamol
Correct Answer: Calcium-containing antacids
Q5. Which tetracycline is least affected by renal impairment and often preferred in patients with renal dysfunction?
- Tetracycline
- Oxytetracycline
- Doxycycline
- Chlortetracycline
Correct Answer: Doxycycline
Q6. Teeth discoloration and enamel hypoplasia in children exposed to tetracyclines occur because the drug:
- Interferes with vitamin D metabolism
- Deposits in developing bone and teeth as calcium complexes
- Causes direct bacterial overgrowth in the oral cavity
- Blocks fluoride uptake in enamel
Correct Answer: Deposits in developing bone and teeth as calcium complexes
Q7. Which adverse effect is particularly associated with minocycline compared with other tetracyclines?
- Photosensitivity rash
- Vestibular toxicity causing dizziness and vertigo
- Severe nephrotoxicity
- Ototoxicity with permanent hearing loss
Correct Answer: Vestibular toxicity causing dizziness and vertigo
Q8. What is the main reason tetracyclines are contraindicated in pregnancy?
- High risk of maternal hepatotoxicity only
- Teratogenic neural tube defects
- Fetal teeth discoloration and inhibition of bone growth
- Increased risk of gestational diabetes
Correct Answer: Fetal teeth discoloration and inhibition of bone growth
Q9. Which laboratory monitoring is most relevant when a patient is on long-term tetracycline therapy?
- Serum potassium levels monthly
- Liver function tests for hepatotoxicity
- Fasting blood glucose weekly
- Serum amylase for pancreatic toxicity
Correct Answer: Liver function tests for hepatotoxicity
Q10. The predominant route of elimination for doxycycline is:
- Renal excretion unchanged
- Biliary and fecal excretion
- Excretion via lungs
- Rapid metabolism to inactive metabolites in plasma
Correct Answer: Biliary and fecal excretion
Q11. Doxycycline is often chosen for treatment of infections with intracellular organisms because it:
- Accumulates poorly in tissues
- Has good intracellular penetration into host cells
- Is highly active only in anaerobes
- Is rapidly bactericidal in serum
Correct Answer: Has good intracellular penetration into host cells
Q12. A pharmacy student counsels a patient starting doxycycline. Which point is most important to prevent reduced absorption?
- Take with milk to reduce gastric upset
- Avoid taking with iron or calcium supplements within 2 hours
- Crush tablets for faster absorption
- Double the dose if a dose is missed
Correct Answer: Avoid taking with iron or calcium supplements within 2 hours
Q13. Which clinical indication is tetracycline class commonly used for due to activity against atypical organisms?
- Uncomplicated urinary tract infections with E. coli
- Rickettsial infections like Rocky Mountain spotted fever
- Acute streptococcal pharyngitis first-line
- Severe MRSA bloodstream infections
Correct Answer: Rickettsial infections like Rocky Mountain spotted fever
Q14. Which drug interaction increases risk of photosensitivity when taken with tetracyclines?
- Concurrent isotretinoin
- Concurrent fluoroquinolones
- Concurrent sulfonylureas
- Concurrent corticosteroids
Correct Answer: Concurrent fluoroquinolones
Q15. Mechanistically, tetracyclines inhibit protein synthesis by preventing:
- Peptidyl transferase activity at 50S
- Attachment of aminoacyl-tRNA to the acceptor site on the 30S ribosome
- Initiation complex formation at the 50S subunit
- Termination of translation at the stop codon
Correct Answer: Attachment of aminoacyl-tRNA to the acceptor site on the 30S ribosome
Q16. Which adverse reaction is a recognized but uncommon severe toxicity of tetracyclines requiring immediate discontinuation?
- Drug-induced lupus
- Severe hepatotoxicity with jaundice
- Bilateral cataract formation
- Progressive peripheral neuropathy
Correct Answer: Severe hepatotoxicity with jaundice
Q17. Resistance mediated by ribosomal protection proteins against tetracyclines functions by:
- Enzymatically degrading the antibiotic
- Altering lipopolysaccharide to reduce uptake
- Displacing tetracycline from the ribosome
- Methylating 23S rRNA binding sites
Correct Answer: Displacing tetracycline from the ribosome
Q18. Which statement about tigecycline (a glycylcycline) compared with classical tetracyclines is correct?
- Tigecycline is less active against tetracycline-resistant organisms
- Tigecycline overcomes common efflux and ribosomal protection resistance mechanisms
- Tigecycline is primarily renally excreted and contraindicated in renal failure
- Tigecycline has superior activity against Pseudomonas aeruginosa
Correct Answer: Tigecycline overcomes common efflux and ribosomal protection resistance mechanisms
Q19. Which feature differentiates doxycycline from older tetracyclines in clinical use?
- Poor oral bioavailability
- Increased photosensitivity risk only
- Less renal excretion and safer in renal impairment
- Lack of activity against atypical pathogens
Correct Answer: Less renal excretion and safer in renal impairment
Q20. A patient reports severe sunburn-like reaction after starting doxycycline. This adverse effect is best classified as:
- Type I immediate hypersensitivity
- Photosensitivity reaction
- Fixed drug eruption
- Serum sickness-like reaction
Correct Answer: Photosensitivity reaction
Q21. In pediatrics, why are tetracyclines avoided in children under 8 years old?
- They cause growth hormone suppression
- They irreversibly stain developing teeth and affect bone growth
- They have no activity against common pediatric pathogens
- They induce severe behavioral side effects
Correct Answer: They irreversibly stain developing teeth and affect bone growth
Q22. Which pharmacokinetic property explains once- or twice-daily dosing of doxycycline?
- Very short half-life requiring continuous infusion
- Long half-life and high tissue penetration
- Extensive first-pass metabolism eliminating oral effect
- Rapid renal clearance necessitating frequent dosing
Correct Answer: Long half-life and high tissue penetration
Q23. Which of the following is a notable counseling point for patients taking oral tetracyclines?
- Take with antacids to improve absorption
- Complete the full course even if symptoms resolve early
- Avoid fluids for two hours after dosing
- Use only with dairy to mask taste
Correct Answer: Complete the full course even if symptoms resolve early
Q24. Which laboratory finding might suggest tetracycline-associated hepatotoxicity?
- Elevated ALT and AST
- Low serum creatinine kinase
- Decreased serum bilirubin only
- Elevated hematocrit
Correct Answer: Elevated ALT and AST
Q25. Which organism is inherently resistant or poorly susceptible to tetracyclines?
- Rickettsia rickettsii
- Chlamydia trachomatis
- Pseudomonas aeruginosa
- Mycoplasma pneumoniae
Correct Answer: Pseudomonas aeruginosa
Q26. How does food affect the absorption of tetracyclines generally?
- All tetracyclines are unaffected by food
- Food always doubles their bioavailability
- Food may reduce absorption of some tetracyclines but less effect on doxycycline
- Food converts them to inactive metabolites
Correct Answer: Food may reduce absorption of some tetracyclines but less effect on doxycycline
Q27. A pharmacy student is asked which adverse effect requires immediate discontinuation and urgent evaluation:
- Mild nausea after dose
- Onset of jaundice and right upper quadrant pain
- Moderate photosensitivity rash
- Transient dizziness with minocycline
Correct Answer: Onset of jaundice and right upper quadrant pain
Q28. Which structural property of tetracyclines contributes to chelation with divalent cations?
- Hydrophobic aromatic rings only
- Polyketide-like multi-hydroxy and keto functional groups
- Peptide backbone similar to beta-lactams
- Cationic quaternary amine group
Correct Answer: Polyketide-like multi-hydroxy and keto functional groups
Q29. For acne treatment, which tetracycline is commonly prescribed with good efficacy and better tolerability?
- Oxytetracycline
- Tetracycline oral suspension
- Doxycycline
- Chlortetracycline topical only
Correct Answer: Doxycycline
Q30. Which counseling instruction is correct regarding storage and administration of oral tetracycline capsules?
- Store in high humidity and keep bottle open
- Take at bedtime with dairy to increase absorption
- Store in a cool, dry place and avoid expired tablets due to increased toxicity
- Crush and mix with antacids for children under 8
Correct Answer: Store in a cool, dry place and avoid expired tablets due to increased toxicity
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.
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