Antiviral agents are drugs that inhibit viral replication by targeting specific stages of the virus life cycle. For B.Pharm students, mastering classification—entry/fusion inhibitors, uncoating (M2) inhibitors, nucleoside/nucleotide analogs, non-nucleoside inhibitors, protease and integrase inhibitors, neuraminidase and polymerase inhibitors—and mechanisms of action is essential for rational therapy and resistance management. Key keywords include mechanism of action, nucleoside analogs, viral polymerase, protease inhibitors, reverse transcriptase inhibitors, pharmacokinetics, prodrugs, activation by viral kinases, and drug–drug interactions. This concise review links mechanism-based classification with representative drugs and clinical relevance. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which classification groups antiviral agents based on the stage of the viral life cycle they inhibit?
- Entry/fusion, uncoating, replication, assembly/release
- Chemical structure only such as nucleosides or proteins
- Clinical route of administration like oral or IV
- Cost and availability
Correct Answer: Entry/fusion, uncoating, replication, assembly/release
Q2. Nucleoside analog antiviral drugs primarily inhibit viral replication by which mechanism?
- Blocking viral entry into host cells
- Acting as competitive inhibitors at viral proteases
- Incorporation into viral DNA/RNA causing chain termination
- Inhibiting host cell protein synthesis
Correct Answer: Incorporation into viral DNA/RNA causing chain termination
Q3. Activation of acyclovir into its active triphosphate requires which viral enzyme?
- Viral neuraminidase
- Viral thymidine kinase
- Viral protease
- Viral integrase
Correct Answer: Viral thymidine kinase
Q4. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) inhibit HIV reverse transcriptase by which principle?
- Chain termination after incorporation into DNA
- Allosteric inhibition of reverse transcriptase activity
- Blocking gp120 binding to CD4
- Inhibiting viral protease cleavage
Correct Answer: Allosteric inhibition of reverse transcriptase activity
Q5. Protease inhibitors reduce viral maturation by:
- Preventing viral attachment to host receptors
- Inhibiting cleavage of viral polyproteins into functional units
- Blocking viral DNA integration into host genome
- Inhibiting neuraminidase to prevent release
Correct Answer: Inhibiting cleavage of viral polyproteins into functional units
Q6. Integrase strand transfer inhibitors (INSTIs) such as raltegravir act by:
- Blocking viral entry at CCR5 receptor
- Inhibiting integrase-mediated insertion of viral DNA into host DNA
- Inhibiting RNA-dependent RNA polymerase
- Preventing capsid assembly
Correct Answer: Inhibiting integrase-mediated insertion of viral DNA into host DNA
Q7. Neuraminidase inhibitors like oseltamivir prevent influenza spread by:
- Inhibiting viral RNA polymerase
- Blocking viral uncoating in endosomes
- Preventing release of progeny virions from infected cells
- Inhibiting viral entry into respiratory epithelium
Correct Answer: Preventing release of progeny virions from infected cells
Q8. Amantadine and rimantadine act against influenza A by targeting which process?
- Inhibiting neuraminidase activity
- Blocking M2 ion channel and preventing uncoating
- Inhibiting viral protease
- Blocking host cell DNA synthesis
Correct Answer: Blocking M2 ion channel and preventing uncoating
Q9. Remdesivir is classified as which type of antiviral and targets which enzyme?
- Nucleoside analog targeting viral RNA-dependent RNA polymerase
- Protease inhibitor targeting viral protease
- Entry inhibitor blocking CCR5
- Integrase inhibitor blocking DNA integration
Correct Answer: Nucleoside analog targeting viral RNA-dependent RNA polymerase
Q10. Sofosbuvir is best described as:
- A neuraminidase inhibitor prodrug
- A nucleotide prodrug inhibitor of HCV RNA polymerase
- An HIV protease inhibitor
- A fusion inhibitor acting on gp41
Correct Answer: A nucleotide prodrug inhibitor of HCV RNA polymerase
Q11. Maraviroc exerts its antiretroviral effect by:
- Blocking reverse transcriptase active site
- Antagonizing CCR5 co-receptor to prevent HIV entry
- Inhibiting viral neuraminidase
- Inhibiting viral protease cleavage
Correct Answer: Antagonizing CCR5 co-receptor to prevent HIV entry
Q12. Enfuvirtide inhibits HIV by binding to:
- CCR5 receptor on host cells
- HIV gp41 to block fusion of viral and host membranes
- Reverse transcriptase allosteric site
- Integrase active site
Correct Answer: HIV gp41 to block fusion of viral and host membranes
Q13. Ritonavir is commonly used in HIV therapy primarily as a:
- Direct antiviral with high intrinsic potency against HIV
- Pharmacokinetic booster via CYP3A4 inhibition
- Reverse transcriptase inhibitor
- CCR5 antagonist
Correct Answer: Pharmacokinetic booster via CYP3A4 inhibition
Q14. A common molecular mechanism by which viruses develop resistance to nucleoside analogs is:
- Upregulation of host kinases
- Mutations in viral polymerase reducing drug incorporation
- Increased viral envelope glycoprotein expression
- Overexpression of neuraminidase
Correct Answer: Mutations in viral polymerase reducing drug incorporation
Q15. Which antiviral requires phosphorylation by viral thymidine kinase for activation?
- Acyclovir
- Oseltamivir
- Ritonavir
- Maraviroc
Correct Answer: Acyclovir
Q16. A notable adverse effect associated with many HIV protease inhibitors is:
- Bone marrow aplasia
- Lipodystrophy and metabolic disturbances
- Severe nephrotoxicity with hematuria
- Permanent vision loss
Correct Answer: Lipodystrophy and metabolic disturbances
Q17. Which pharmacokinetic consideration is most important for dosing of acyclovir and ganciclovir?
- Adjustment for hepatic impairment only
- No adjustment necessary for renal function
- Adjustment for renal impairment due to renal excretion
- Adjustment for gastric pH variability only
Correct Answer: Adjustment for renal impairment due to renal excretion
Q18. Which antiviral is a guanosine nucleoside analog used for herpesvirus infections?
- Acyclovir
- Oseltamivir
- Sofosbuvir
- Maraviroc
Correct Answer: Acyclovir
Q19. A drug with a high genetic barrier to resistance in HIV therapy refers to:
- Drug that is rapidly cleared and needs frequent dosing
- Drug requiring multiple viral mutations for resistance to develop
- Drug that is toxic at low concentrations
- Drug effective only in single-drug regimens
Correct Answer: Drug requiring multiple viral mutations for resistance to develop
Q20. NS5A inhibitors used in HCV therapy primarily disrupt:
- Viral entry by blocking host receptors
- Assembly of viral replication complexes and RNA replication modulation
- Host cell protein synthesis
- Neuraminidase activity
Correct Answer: Assembly of viral replication complexes and RNA replication modulation
Q21. Oseltamivir is administered as a prodrug and is activated by:
- Viral neuraminidase cleavage
- Host hepatic esterases to the active carboxylate form
- Phosphorylation by viral kinases
- Spontaneous activation in plasma
Correct Answer: Host hepatic esterases to the active carboxylate form
Q22. Chain-terminating nucleoside analogs lack which chemical group to prevent further elongation?
- 5′ phosphate group
- 3′ hydroxyl group
- 2′ hydrogen atom
- 1′ nitrogen atom
Correct Answer: 3′ hydroxyl group
Q23. Which drug is an integrase inhibitor used in first-line HIV regimens?
- Raltegravir
- Lopinavir
- Acyclovir
- Oseltamivir
Correct Answer: Raltegravir
Q24. Which laboratory parameter is most important to monitor during ganciclovir therapy?
- Serum bilirubin
- Complete blood count for neutropenia
- Thyroid function tests
- Fasting blood glucose
Correct Answer: Complete blood count for neutropenia
Q25. The antiviral activity of amantadine is limited clinically due to:
- High rates of viral resistance among influenza strains
- Severe renal toxicity in all patients
- Inhibition of host DNA polymerase
- Complete inactivity against influenza A
Correct Answer: High rates of viral resistance among influenza strains
Q26. Zanamivir differs from oseltamivir mainly in that zanamivir is administered by which route?
- Intravenous infusion only
- Inhalation (nebulizer/inhaler)
- Topical ocular drops
- Transdermal patch
Correct Answer: Inhalation (nebulizer/inhaler)
Q27. Combination antiviral therapy reduces the likelihood of resistance primarily by:
- Increasing the plasma half-life of drugs
- Targeting multiple distinct viral steps simultaneously
- Reducing the need for therapeutic drug monitoring
- Eliminating adverse effects
Correct Answer: Targeting multiple distinct viral steps simultaneously
Q28. Zidovudine (AZT) adverse effects commonly include:
- Macrocytic anemia and bone marrow suppression
- Severe hepatotoxicity in all patients
- Renal tubular acidosis as the main toxicity
- Visual hallucinations as an early sign
Correct Answer: Macrocytic anemia and bone marrow suppression
Q29. Which antiviral acts by binding viral gp120 or gp41 to prevent HIV entry/fusion?
- Enfuvirtide binds gp41 to block fusion
- Oseltamivir binds gp120
- Raltegravir binds gp120 to prevent CCR5 binding
- Ganciclovir binds gp41 to inhibit entry
Correct Answer: Enfuvirtide binds gp41 to block fusion
Q30. Protease inhibitor drug interactions are mainly due to their effect on which hepatic enzyme system?
- UDP-glucuronosyltransferases only
- CYP3A4 inhibition or induction altering metabolism of co-administered drugs
- Mitochondrial DNA polymerase gamma
- Monoamine oxidase inhibition
Correct Answer: CYP3A4 inhibition or induction altering metabolism of co-administered drugs
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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