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:
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?
Which of the following antimalarial drugs is a slow-acting erythrocytic schizonticidal drug for malaria?
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: 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 7: 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 8: 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 9: 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**.
Question 10: Which of the following antimalarial drugs is a slow-acting erythrocytic schizonticidal drug for malaria?
- A. Lumefantrine
- B. Chloroquine
- C. Pyrimethamine (Correct Answer)
- D. Artemether
Explanation: ***Pyrimethamine*** - **Pyrimethamine** is a **slow-acting** antimalarial drug, primarily effective as an **erythrocytic schizonticide**, meaning it targets the parasite's asexual blood stages. - It works by inhibiting **dihydrofolate reductase**, an enzyme crucial for **folate synthesis** in the malaria parasite, thus disrupting DNA and RNA production. *Lumefantrine* - **Lumefantrine** is a rapidly acting erythrocytic schizonticide, usually co-formulated with **artemether** (as **artemether-lumefantrine**) to provide both fast action and a longer half-life. - It is known for causing rapid clearance of parasites, particularly in uncomplicated **falciparum malaria**. *Chloroquine* - **Chloroquine** is a well-known and historically effective **fast-acting** erythrocytic schizonticide, but its use is now limited due to widespread **parasite resistance**, especially concerning **Plasmodium falciparum**. - It works by preventing the detoxification of **heme** into **hemozoin** within the parasite's food vacuole, leading to parasite death. *Artemether* - **Artemether** is a **rapidly acting** erythrocytic schizonticide derived from artemisinin, known for its quick onset of action and potent antiparasitic effects by producing **free radicals**. - It is typically used in combination therapies, such as **artemether-lumefantrine**, to prevent resistance and enhance efficacy against **malaria**.
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