Antiviral Drugs — MCQs
6 year old son of pregnant woman is suffering from chicken pox. Which of the following is given to pregnant woman?
What is the recommended regimen for post-exposure prophylaxis for HIV?
Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
Which antiretroviral drug should be avoided in a known sputum-positive pulmonary tuberculosis patient who is currently on INH, rifampicin, pyrazinamide, and ethambutol, and has a CD4 count of 100 cells/dL and a viral load of more than 50,000 copies/mL, given that the patient is HIV-positive?
Topical antiviral drugs are not indicated in:
Administration of which of the following drugs would increase the bioavailability of saquinavir?
What is an example of an entry inhibitor?
Idoxuridine is used for treatment of?
Which of the following drugs inhibits post-translational modification of viral proteins?
Why is a regimen of four drugs recommended for a TB patient on the first visit?
Antiviral Drugs Indian Medical PG Practice Questions and MCQs
Question 1: 6 year old son of pregnant woman is suffering from chicken pox. Which of the following is given to pregnant woman?
- A. Acyclovir + immunoglobulin
- B. Only immunoglobulin (Correct Answer)
- C. Vaccination
- D. Acyclovir
Explanation: ***Only immunoglobulin*** - Giving **immunoglobulin** to a pregnant woman exposed to **chickenpox** provides immediate passive immunity, which is crucial as she is at risk of infection from her child. - This is particularly important because chickenpox during pregnancy can lead to severe maternal disease and congenital varicella syndrome in the fetus. *Acyclovir + immunoglobulin* - **Acyclovir** is an antiviral that treats active varicella infection but is not typically given prophylactically in combination with immunoglobulin for exposure unless the woman is already immunocompromised or develops symptoms. - The primary goal for exposed pregnant women is preventing infection through passive immunity, not immediately treating a potential infection. *Vaccination* - **Varicella vaccine** is a live attenuated vaccine and is **contraindicated** during pregnancy due to the theoretical risk of fetal infection. - It is used for pre-conception immunity or post-exposure prophylaxis in non-pregnant individuals if given within a short window, but not for pregnant women. *Acyclovir* - **Acyclovir** is an antiviral medicine used to treat active chickenpox infections, not to prevent infection immediately after exposure. - It would be considered if the pregnant woman develops symptoms of chickenpox, but not as a primary prophylactic measure in this scenario.
Question 2: What is the recommended regimen for post-exposure prophylaxis for HIV?
- A. Zidovudine + Lamivudine + Lopinavir/ritonavir for 28 days
- B. Tenofovir disoproxil fumarate + Emtricitabine + Raltegravir for 28 days
- C. Single dose Tenofovir + Emtricitabine + Raltegravir
- D. Tenofovir disoproxil fumarate + Emtricitabine + Dolutegravir for 28 days (Correct Answer)
Explanation: ***Tenofovir disoproxil fumarate + Emtricitabine + Dolutegravir for 28 days*** - This is the **current first-line recommended regimen** for **HIV post-exposure prophylaxis (PEP)** according to WHO (2021), CDC, and Indian NACO guidelines. - It includes two **nucleoside reverse transcriptase inhibitors (NRTIs)** and an **integrase strand transfer inhibitor (INSTI)**. - **Dolutegravir** is preferred over Raltegravir due to **superior efficacy, better tolerability, higher barrier to resistance, once-daily dosing**, and fewer drug interactions. - The duration of **28 days** is crucial for effective PEP to cover the window period for potential HIV integration and replication. *Tenofovir disoproxil fumarate + Emtricitabine + Raltegravir for 28 days* - This was the **previous standard PEP regimen** and is still an acceptable alternative if Dolutegravir is contraindicated or unavailable. - Raltegravir requires **twice-daily dosing** compared to Dolutegravir's once-daily regimen, which may affect adherence. - The 28-day duration is correct, but Raltegravir is no longer the first-line INSTI choice in current guidelines. *Single dose Tenofovir + Emtricitabine + Raltegravir* - A **single dose** of these medications is insufficient for **post-exposure prophylaxis (PEP)** as HIV replication needs to be suppressed over an extended period to prevent seroconversion. - PEP typically requires a **28-day course** to be effective. *Zidovudine + Lamivudine + Lopinavir/ritonavir for 28 days* - While this is an older, effective **antiretroviral regimen**, it is **not the preferred first-line PEP regimen** due to a higher incidence of side effects, particularly with zidovudine (anemia, nausea). - Modern guidelines favor regimens with **Tenofovir/Emtricitabine + Dolutegravir** due to better tolerability and superior efficacy.
Question 3: Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
- A. Amantadine
- B. Rimantadine
- C. Oseltamivir
- D. Acyclovir (Correct Answer)
Explanation: ***Acyclovir*** - **Acyclovir** is an antiviral medication specifically used to treat infections caused by **herpes viruses** (e.g., HSV, VZV), not influenza viruses. - It works by inhibiting **viral DNA polymerase**, a mechanism distinct from how anti-influenza drugs act. - **This drug has never been indicated for influenza** - it is the correct answer to this "not indicated" question. *Amantadine* - **Amantadine** is an M2 ion channel inhibitor that **was indicated** for influenza A treatment and prophylaxis. - Although no longer recommended due to widespread **resistance** among circulating influenza strains, it remains a drug that was formally indicated for seasonal influenza. *Rimantadine* - **Rimantadine** is also an M2 ion channel inhibitor, structurally related to amantadine, with a similar mechanism of action. - Like amantadine, it **was indicated** for influenza treatment or prophylaxis but is no longer recommended due to high rates of **resistance** in circulating influenza A viruses. *Oseltamivir* - **Oseltamivir** is a **neuraminidase inhibitor** currently approved and recommended for the treatment and prophylaxis of both influenza A and B. - It reduces viral spread by preventing the release of new virions from infected cells and remains a first-line agent for seasonal influenza.
Question 4: Which antiretroviral drug should be avoided in a known sputum-positive pulmonary tuberculosis patient who is currently on INH, rifampicin, pyrazinamide, and ethambutol, and has a CD4 count of 100 cells/dL and a viral load of more than 50,000 copies/mL, given that the patient is HIV-positive?
- A. Indinavir
- B. Ritonavir (Correct Answer)
- C. Lamivudine
- D. Efavirenz
Explanation: ***Ritonavir (Correct Answer)*** - **Ritonavir** is the most critical drug to avoid due to severe drug-drug interactions with **rifampicin** - **Rifampicin** is a potent CYP3A4 inducer that dramatically reduces ritonavir plasma concentrations by 75-90%, rendering it completely ineffective - Ritonavir is commonly used as a pharmacokinetic booster for other protease inhibitors, making this interaction particularly significant - **Contraindicated** with rifampicin-based TB regimens *Indinavir* - Also a protease inhibitor metabolized via CYP3A4 - Should also be **avoided with rifampicin** as levels are reduced by approximately 90% - However, indinavir is rarely used in modern ART regimens due to high pill burden, need for dietary restrictions, and significant side effects (nephrolithiasis) - Less commonly used than ritonavir, making ritonavir the better answer *Lamivudine* - Nucleoside reverse transcriptase inhibitor (NRTI) with **renal elimination** - Not metabolized by CYP450 enzymes - **No significant interactions** with rifampicin or other anti-TB drugs - Safe and commonly used in TB/HIV co-infection *Efavirenz* - Non-nucleoside reverse transcriptase inhibitor (NNRTI) that **can be safely co-administered** with rifampicin - Standard dose (600 mg daily) is generally adequate, though some guidelines recommend considering 800 mg in patients >60 kg - **Preferred NNRTI** for TB/HIV co-infection according to WHO guidelines - Well-studied and effective combination with rifampicin-based TB therapy
Question 5: Topical antiviral drugs are not indicated in:
- A. Metaherpetic ulcer (Correct Answer)
- B. Dendritic ulcer
- C. Stromal necrotizing keratitis
- D. All of the options
Explanation: ***Metaherpetic ulcer*** - Metaherpetic ulcers are **neurotrophic ulcers** that develop as a result of chronic epithelial damage and impaired healing after a herpes simplex virus (HSV) infection, but they are not an active viral replication process. - Topical antivirals are ineffective because there is **no replicating virus** to target; management focuses on promoting corneal healing and preventing secondary infections. *Dendritic ulcer* - A dendritic ulcer is a classic sign of **active HSV keratitis** with replicating virus in the epithelial cells. - Topical antiviral drugs (e.g., acyclovir, ganciclovir) are the **first-line treatment** to inhibit viral replication and promote epithelial healing. *Stromal necrotizing keratitis* - This condition involves **inflammation and necrosis** in the corneal stroma, often due to an immune reaction to HSV antigens rather than direct viral invasion. - While topical antivirals may be used to suppress any residual replicating virus, **topical corticosteroids are often necessary** to control the inflammation, and close monitoring is crucial due to the risk of steroid-induced complications. *All of the options* - This option is incorrect because topical antiviral drugs *are* indicated for **dendritic ulcers** and sometimes as adjunctive therapy for **stromal necrotizing keratitis** where active viral replication might be contributing.
Question 6: Administration of which of the following drugs would increase the bioavailability of saquinavir?
- A. Cimetidine
- B. Vitamin C
- C. Ritonavir (Correct Answer)
- D. Ganciclovir
Explanation: **Ritonavir** - **Ritonavir** is a potent **CYP3A4 inhibitor**, which is the primary enzyme responsible for the metabolism of saquinavir. - By inhibiting **saquinavir** metabolism, ritonavir significantly **increases its plasma concentrations and bioavailability**, making it an effective pharmacokinetic enhancer. - This combination (saquinavir/ritonavir) is a clinically established strategy in antiretroviral therapy. *Cimetidine* - **Cimetidine** inhibits various cytochrome P450 enzymes but is a less potent and more general inhibitor compared to ritonavir, particularly for **CYP3A4**. - While it could theoretically have some effect on drug metabolism, its impact on saquinavir's bioavailability would be **clinically insignificant** compared to ritonavir. *Vitamin C* - **Vitamin C** (ascorbic acid) is an antioxidant and plays various roles in the body. - It has **no significant interaction** with cytochrome P450 enzymes and would not affect the metabolism or bioavailability of saquinavir. *Ganciclovir* - **Ganciclovir** is an antiviral drug primarily used to treat cytomegalovirus (CMV) infections. - It does not significantly inhibit or induce cytochrome P450 enzymes and would therefore **not affect the bioavailability** of saquinavir.
Question 7: What is an example of an entry inhibitor?
- A. Abacavir
- B. Amprenavir
- C. Enfuvirtide (Correct Answer)
- D. Etravirine
Explanation: ***Enfuvirtide*** - **Enfuvirtide** is a **fusion inhibitor** that blocks **HIV-1** from entering target cells by binding to the gp41 subunit of the viral envelope glycoprotein. - It works by preventing the conformational change in gp41 required for fusion of the viral and cellular membranes. *Abacavir* - **Abacavir** is a **nucleoside reverse transcriptase inhibitor (NRTI)**. - NRTIs incorporate into the growing viral DNA chain, causing chain termination and preventing viral replication. *Etravirine* - **Etravirine** is a **non-nucleoside reverse transcriptase inhibitor (NNRTI)**. - NNRTIs bind directly to the reverse transcriptase enzyme, altering its structure and inhibiting its function. *Amprenavir* - **Amprenavir** is a **protease inhibitor (PI)**. - Protease inhibitors prevent the cleavage of viral polyproteins into functional proteins, which is essential for the assembly of new infectious virions.
Question 8: Idoxuridine is used for treatment of?
- A. Influenza
- B. RSV
- C. HSV (Correct Answer)
- D. HIV
Explanation: ***HSV*** - **Idoxuridine** is a **pyrimidine analog** that inhibits viral DNA synthesis, making it effective against **herpes simplex virus (HSV)** infections, particularly **herpes keratitis** (ophthalmic use). - Its mechanism involves being incorporated into viral DNA, leading to errors in replication and transcription. - It is applied **topically** for ocular HSV infections due to systemic toxicity concerns. *Influenza* - **Idoxuridine** is not active against **influenza viruses**. - **Antiviral drugs** like **oseltamivir** or **zanamivir** are typically used for influenza treatment. *RSV* - **Idoxuridine** is not indicated for the treatment of **respiratory syncytial virus (RSV)**. - **Ribavirin** is the primary antiviral agent used for severe RSV infections, especially in immunocompromised patients. *HIV* - **Idoxuridine** has no significant activity against **human immunodeficiency virus (HIV)**. - **Antiretroviral therapy (ART)**, a combination of drugs targeting various stages of the HIV life cycle, is used for HIV treatment.
Question 9: Which of the following drugs inhibits post-translational modification of viral proteins?
- A. Indinavir (Correct Answer)
- B. Lamivudine
- C. Zalcitabine
- D. Enfuvirtide
Explanation: ***Indinavir*** - This drug is a **protease inhibitor** that specifically targets the **HIV protease** enzyme [1]. - By inhibiting protease, Indinavir prevents the cleavage of viral polyproteins into functional individual proteins, thereby inhibiting the **post-translational modification** necessary for viral maturation and infectivity [2]. *Enfuvirtide* - Enfuvirtide is a **fusion inhibitor** that prevents HIV from entering CD4+ T-cells by blocking the fusion of the viral envelope with the host cell membrane. - Its mechanism of action is upstream of protein synthesis and modification, directly impacting viral entry, not post-translational processing. *Lamivudine* - Lamivudine is a **nucleoside reverse transcriptase inhibitor (NRTI)** that acts as a chain terminator during reverse transcription. - It interferes with the conversion of viral RNA into DNA, affecting an earlier stage of the HIV life cycle, not post-translational modification. *Zalcitabine* - Similar to Lamivudine, Zalcitabine is also a **nucleoside reverse transcriptase inhibitor (NRTI)**. - It incorporates into the newly synthesized viral DNA strand, causing premature termination because it lacks a 3'-hydroxyl group, thereby inhibiting DNA synthesis rather than protein modification.
Question 10: Why is a regimen of four drugs recommended for a TB patient on the first visit?
- A. To prevent emergence of drug-resistant strains (Correct Answer)
- B. To reduce bacterial load effectively
- C. To minimize treatment duration
- D. None of the options
Explanation: ***To prevent emergence of drug-resistant strains*** - Using a **four-drug regimen** at the initial stage significantly reduces the likelihood of **Mycobacterium tuberculosis** developing resistance to any single drug. - This strategy ensures that even if a small number of bacteria are naturally resistant to one drug, the other drugs will still be effective in killing them, preventing the proliferation of **resistant strains**. *To minimize treatment duration* - While a multi-drug regimen is effective, its primary goal is not to minimize treatment duration but rather to ensure **eradication of the infection** and prevent resistance. - Treatment duration is determined by the need to kill both actively multiplying and dormant bacteria, which typically takes several months even with multiple drugs. *To reduce bacterial load effectively* - Reducing bacterial load is certainly a goal of TB treatment, but the use of four drugs is specifically aimed at achieving this while simultaneously preventing **drug resistance**. - A single effective drug could reduce bacterial load, but it would quickly lead to the emergence of resistant bacteria, making the long-term goal of **cure** impossible. *None of the options* - This option is incorrect because the primary reason for a **four-drug regimen** in TB treatment is indeed to prevent the emergence of **drug-resistant strains**.
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