Chemotherapy of sexually transmitted diseases is a focused area of pharmacology covering antibiotics, antivirals, and antifungals used to treat STDs such as syphilis, gonorrhea, chlamydia, trichomoniasis, and genital herpes. This introduction highlights mechanisms of action, drug choices (penicillins, cephalosporins, macrolides, tetracyclines, metronidazole, acyclovir), dosing principles, pregnancy considerations, adverse effects, pharmacokinetics, and growing issues of antimicrobial resistance. B. Pharm students will find clinical correlations, treatment guidelines, and stewardship principles essential for rational prescribing and monitoring drug interactions. Emphasis is placed on interpreting MIC, therapeutic regimens, and partner management in public health. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which is the drug of choice for primary syphilis?
- Benzathine penicillin G single intramuscular dose
- Oral azithromycin single dose
- Doxycycline 100 mg twice daily for 14 days
- Ceftriaxone intramuscular single dose
Correct Answer: Benzathine penicillin G single intramuscular dose
Q2. First-line therapy for uncomplicated gonorrhea (current standard)?
- Oral ciprofloxacin single dose
- Intramuscular ceftriaxone single dose
- Oral azithromycin single dose
- Oral doxycycline for 7 days
Correct Answer: Intramuscular ceftriaxone single dose
Q3. Preferred single-dose regimen for uncomplicated chlamydial infection in non-pregnant patients?
- Azithromycin 1 g orally single dose
- Doxycycline 100 mg orally once daily for 3 days
- Amoxicillin 500 mg three times daily for 7 days
- Cefixime 400 mg single dose
Correct Answer: Azithromycin 1 g orally single dose
Q4. What is the primary mechanism of action of penicillins against bacteria?
- Inhibition of DNA gyrase
- Inhibition of folate synthesis
- Inhibition of peptidoglycan cross-linking by binding penicillin-binding proteins
- Disruption of 30S ribosomal protein synthesis
Correct Answer: Inhibition of peptidoglycan cross-linking by binding penicillin-binding proteins
Q5. Which agent is most appropriate for treating Trichomonas vaginalis infection?
- Metronidazole 2 g orally single dose
- Fluconazole 150 mg orally single dose
- Amoxicillin 500 mg orally for 7 days
- Azithromycin 1 g orally single dose
Correct Answer: Metronidazole 2 g orally single dose
Q6. First-line antiviral therapy for acute genital herpes outbreaks?
- Acyclovir oral
- Oseltamivir oral
- Ribavirin inhaled
- Zanamivir inhaled
Correct Answer: Acyclovir oral
Q7. A common adverse effect associated with doxycycline relevant to counselling patients is:
- Ototoxicity
- Photosensitivity
- Nephrotoxicity
- Red man syndrome
Correct Answer: Photosensitivity
Q8. The Jarisch–Herxheimer reaction is most commonly seen after treatment of which infection?
- Gonorrhea treated with ceftriaxone
- Syphilis treated with penicillin
- Trichomoniasis treated with metronidazole
- Genital warts treated with imiquimod
Correct Answer: Syphilis treated with penicillin
Q9. A major mechanism of resistance in Neisseria gonorrhoeae to beta-lactams involves:
- Increased efflux of tetracyclines
- Methylation of 23S rRNA
- Alteration of penicillin-binding proteins (PBPs)
- Inactivation of aminoglycosides by acetylation
Correct Answer: Alteration of penicillin-binding proteins (PBPs)
Q10. Preferred treatment for chlamydial infection in pregnancy is:
- Doxycycline 100 mg twice daily for 7 days
- Azithromycin 1 g orally single dose
- Levofloxacin 500 mg daily for 7 days
- Tetracycline 250 mg four times daily for 7 days
Correct Answer: Azithromycin 1 g orally single dose
Q11. How do macrolides such as azithromycin exert antibacterial effects?
- Inhibit DNA replication by targeting DNA gyrase
- Inhibit cell wall synthesis by binding PBPs
- Block translocation by binding the 50S ribosomal subunit and inhibiting protein synthesis
- Interfere with folate synthesis by inhibiting dihydropteroate synthase
Correct Answer: Block translocation by binding the 50S ribosomal subunit and inhibiting protein synthesis
Q12. Which antibiotic class is contraindicated in pregnancy and children due to teeth discoloration and bone effects?
- Penicillins
- Tetracyclines
- Macrolides
- Cephalosporins
Correct Answer: Tetracyclines
Q13. Topical immune-response modifier commonly used to treat external genital warts is:
- Imiquimod cream
- Topical acyclovir cream
- Oral fluconazole
- Topical metronidazole gel
Correct Answer: Imiquimod cream
Q14. The most sensitive laboratory method for diagnosing chlamydia and gonorrhea is:
- Gram stain of urethral discharge
- Culture on blood agar
- Nucleic acid amplification test (NAAT)
- Rapid antigen detection by latex agglutination
Correct Answer: Nucleic acid amplification test (NAAT)
Q15. What is the primary antimicrobial action of metronidazole?
- Inhibition of peptidoglycan synthesis
- Generation of free radicals that cause DNA strand breakage in anaerobes and protozoa
- Inhibition of 30S ribosomal subunit
- Blockade of folate synthesis
Correct Answer: Generation of free radicals that cause DNA strand breakage in anaerobes and protozoa
Q16. Neonatal ocular prophylaxis to prevent gonococcal conjunctivitis typically uses:
- Tetracycline ointment
- Erythromycin ophthalmic ointment
- Topical azithromycin eye drops
- Silver nitrate 1% drops
Correct Answer: Erythromycin ophthalmic ointment
Q17. Which regimen is recommended for HIV pre-exposure prophylaxis (PrEP)?
- Oral tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC)
- Oral zidovudine monotherapy
- Weekly intramuscular zidovudine
- Topical acyclovir use before exposure
Correct Answer: Oral tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC)
Q18. A serious hypersensitivity adverse effect associated with sulfonamide antibiotics is:
- Stevens–Johnson syndrome
- Ototoxicity
- Thyroid suppression
- Hyperglycemia
Correct Answer: Stevens–Johnson syndrome
Q19. First-line therapy for chancroid caused by Haemophilus ducreyi is:
- Azithromycin 1 g orally single dose
- Fluconazole 150 mg orally single dose
- Metronidazole 2 g orally single dose
- Penicillin V orally for 10 days
Correct Answer: Azithromycin 1 g orally single dose
Q20. Acyclovir primarily targets which viral enzyme or process in HSV?
- Neuraminidase inhibition
- Inhibition of viral DNA polymerase after phosphorylation to active triphosphate
- Integration inhibition of viral DNA into host genome
- Capsid disassembly prevention
Correct Answer: Inhibition of viral DNA polymerase after phosphorylation to active triphosphate
Q21. Which antifungal is commonly used orally to treat vulvovaginal candidiasis?
- Metronidazole single dose
- Fluconazole 150 mg orally single dose
- Oral acyclovir
- Topical imiquimod
Correct Answer: Fluconazole 150 mg orally single dose
Q22. Common molecular mechanism of macrolide resistance in bacteria involves:
- Beta-lactamase production
- Methylation of 23S rRNA in the 50S ribosomal subunit
- Mutation of DNA gyrase
- Overexpression of DHFR enzyme
Correct Answer: Methylation of 23S rRNA in the 50S ribosomal subunit
Q23. Which of the following antibiotics is bactericidal against Neisseria gonorrhoeae?
- Ceftriaxone
- Doxycycline
- Azithromycin
- Clindamycin
Correct Answer: Ceftriaxone
Q24. Recommended treatment for latent syphilis of unknown duration is:
- Oral doxycycline for 7 days
- Benzathine penicillin G weekly for 3 weeks
- Azithromycin weekly for 3 weeks
- Single dose ceftriaxone intramuscularly
Correct Answer: Benzathine penicillin G weekly for 3 weeks
Q25. A Tzanck smear showing multinucleated giant cells suggests infection with:
- Treponema pallidum
- Herpes simplex virus
- Neisseria gonorrhoeae
- Trichomonas vaginalis
Correct Answer: Herpes simplex virus
Q26. First-line therapy for bacterial vaginosis is:
- Metronidazole 500 mg orally twice daily for 7 days
- Fluconazole 150 mg single dose
- Azithromycin 1 g single dose
- Amoxicillin 500 mg three times daily for 7 days
Correct Answer: Metronidazole 500 mg orally twice daily for 7 days
Q27. A major pharmacokinetic concern when prescribing HIV protease inhibitors is:
- They are strong CYP3A4 inhibitors causing significant drug–drug interactions
- They induce renal tubular secretion of penicillins
- They have no hepatic metabolism
- They increase gastric pH and impair absorption of all antibiotics
Correct Answer: They are strong CYP3A4 inhibitors causing significant drug–drug interactions
Q28. A pregnant patient with syphilis and a documented penicillin allergy should be managed by:
- Using doxycycline as alternative therapy
- Administering azithromycin instead of penicillin
- Desensitization to penicillin and then treatment with penicillin
- Withholding treatment until after delivery
Correct Answer: Desensitization to penicillin and then treatment with penicillin
Q29. Doxycycline inhibits bacterial protein synthesis by binding to which ribosomal subunit?
- 50S ribosomal subunit
- 30S ribosomal subunit
- 23S rRNA directly
- 16S rRNA methylase
Correct Answer: 30S ribosomal subunit
Q30. Which pharmacokinetic property of azithromycin allows single-dose regimens for some STDs?
- Extensive renal excretion and short tissue half-life
- High oral bioavailability but poor tissue penetration
- Long tissue half-life with high intracellular accumulation
- Rapid hepatic metabolism with no intracellular accumulation
Correct Answer: Long tissue half-life with high intracellular accumulation
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