Pharmacology Quiz: Influenza Antivirals
20 questions · exam conditions
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Influenza AntiviralsQuestion 1 of 20

Which of the following antiviral agents possesses an intrinsic spectrum of activity that is limited only to influenza A viruses, with no clinical activity against influenza B viruses?

Oseltamivir
Baloxavir
Peramivir
Rimantadine
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Pharmacology Quiz

Pharmacology Quiz: Influenza Antivirals

Practice Influenza Antivirals in Pharmacology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Influenza Antivirals, giving you a quick way to practice the rules, question types, and explanations that matter most for Pharmacology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

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Question 1

Which of the following antiviral agents possesses an intrinsic spectrum of activity that is limited only to influenza A viruses, with no clinical activity against influenza B viruses?

  1. Oseltamivir
  2. Baloxavir
  3. Peramivir
  4. Rimantadine (correct answer)
Explanation: The correct answer is D. Rimantadine belongs to the adamantane class of antivirals. These drugs target the M2 proton channel, a protein that is unique to influenza A viruses. Influenza B viruses lack the M2 protein and are therefore intrinsically resistant to adamantanes. A, B, C: Oseltamivir, peramivir (neuraminidase inhibitors), and baloxavir (endonuclease inhibitor) are all active against both influenza A and influenza B viruses because their respective targets (neuraminidase and polymerase acidic protein) are conserved in both types of influenza.

Question 2

A 19-year-old college student presents with a 24-hour history of fever, myalgia, and cough. A rapid influenza test is positive. The provider prescribes a single dose of baloxavir marboxil. Which concurrent self-medication should the patient be counseled to avoid for several hours before and after taking the baloxavir?

  1. An acetaminophen-containing product for fever and myalgia.
  2. A dextromethorphan-containing cough syrup for cough suppression.
  3. A calcium carbonate-containing antacid for heartburn. (correct answer)
  4. A pseudoephedrine-containing product for nasal congestion.
Explanation: The correct answer is C. Baloxavir marboxil's absorption is significantly reduced when co-administered with products containing polyvalent cations, such as calcium, magnesium, aluminum, iron, or zinc. Calcium carbonate is a polyvalent cation-containing antacid. Patients should be advised to avoid dairy products, antacids, or supplements containing these cations around the time of baloxavir administration. A, B, D: Acetaminophen, dextromethorphan, and pseudoephedrine do not contain polyvalent cations and do not have a clinically significant interaction with baloxavir.

Question 3

A 6-month-old infant is hospitalized with severe, complicated influenza B infection and requires mechanical ventilation. The infant is not able to take medications orally. Based on current FDA approvals and clinical practice guidelines, which antiviral regimen is the most appropriate choice?

  1. Intravenous peramivir, due to the severity of illness.
  2. Oral baloxavir, administered via nasogastric tube.
  3. Oral oseltamivir, administered via nasogastric tube. (correct answer)
  4. Inhaled zanamivir, delivered through the ventilator circuit.
Explanation: The correct answer is C. Oseltamivir is the preferred agent for treating severe influenza in infants. It has an Emergency Use Authorization (EUA) and standard approvals for use in infants as young as 2 weeks of age. It is available as an oral suspension that can be administered via a nasogastric (NG) tube if the patient cannot take it orally. A: Intravenous peramivir is only approved for patients aged 2 years and older. B: Oral baloxavir is not approved for children under 5 years old (approval is age-dependent, but generally not for infants) and data in severe, complicated influenza is limited. D: Use of inhaled zanamivir in mechanically ventilated patients is complex, not standard practice, and it is not approved for infants.

Question 4

A patient initiated on an influenza antiviral two days ago now reports acute confusion, hallucinations, and agitation. While rare, such neuropsychiatric events have been most frequently reported in association with which class of influenza antivirals, particularly in post-marketing surveillance?

  1. Adamantanes, such as amantadine.
  2. Neuraminidase inhibitors, such as oseltamivir. (correct answer)
  3. Cap-dependent endonuclease inhibitors, such as baloxavir.
  4. Broad-spectrum purine nucleoside analogues.
Explanation: The correct answer is B. Post-marketing surveillance, particularly from Japan, has identified reports of neuropsychiatric events (including delirium, hallucinations, and abnormal behavior) in patients, especially children and adolescents, taking neuraminidase inhibitors like oseltamivir. Although a direct causal relationship has not been definitively established and influenza itself can cause these symptoms, this association is a noted safety concern for this drug class. A: Adamantanes are known for CNS side effects like dizziness, insomnia, and ataxia, but the specific profile of acute psychosis is more strongly associated with NAIs in post-marketing reports. C: This is not a characteristic adverse effect profile for baloxavir. D: This refers to drugs like ribavirin, which are not first-line agents for seasonal influenza and have a different set of adverse effects.

Question 5

A 15-year-old patient with a history of moderate persistent asthma is diagnosed with influenza A. The provider wishes to prescribe an antiviral agent. Which agent carries a specific warning regarding its use in patients with underlying respiratory disease due to a risk of acute deterioration of respiratory function?

  1. Oseltamivir
  2. Zanamivir (correct answer)
  3. Baloxavir
  4. Peramivir
Explanation: The correct answer is B. Zanamivir is administered as an inhaled dry powder. Its use has been associated with bronchospasm and a decline in respiratory function, particularly in patients with underlying asthma or chronic obstructive pulmonary disease (COPD). Therefore, it is generally not recommended for this patient population. A: Oseltamivir is administered orally and does not carry this specific risk, although gastrointestinal side effects are common. C: Baloxavir is an oral agent not associated with bronchospasm. D: Peramivir is an intravenous agent not associated with bronchospasm.

Question 6

An experimental influenza antiviral is discovered that prevents newly formed virions from detaching from the surface of an infected host cell, causing them to aggregate on the cell membrane. The mechanism of this new drug most closely mimics which of the following approved agents?

  1. Amantadine
  2. Baloxavir marboxil
  3. Zanamivir (correct answer)
  4. Ribavirin
Explanation: The correct answer is C. Zanamivir is a neuraminidase inhibitor. The function of the viral neuraminidase enzyme is to cleave sialic acid residues on the host cell surface, which allows newly formed virions to be released. By inhibiting this enzyme, drugs like zanamivir cause virions to remain tethered to the host cell, preventing their spread. The experimental drug has the same functional effect. A: Amantadine blocks the M2 ion channel, interfering with viral uncoating after entry into the cell. B: Baloxavir marboxil inhibits viral mRNA transcription inside the host cell nucleus. D: Ribavirin is a broad-spectrum antiviral that interferes with viral nucleic acid synthesis and is not a first-line agent for influenza.

Question 7

A 28-year-old woman at 30 weeks gestation presents with a 24-hour history of symptoms consistent with influenza, which is confirmed by a rapid molecular assay. She is febrile to 39°C and has significant myalgia. What is the recommended course of action regarding antiviral therapy?

  1. Withhold antiviral therapy due to the unknown risks to the developing fetus.
  2. Initiate oral oseltamivir promptly due to the increased risk of complications in pregnancy. (correct answer)
  3. Prescribe single-dose baloxavir, as the shorter duration of exposure is safer for the fetus.
  4. Recommend supportive care only and reserve antiviral therapy for signs of pneumonia.
Explanation: The correct answer is B. Pregnant women are considered a high-risk group for severe complications from influenza. Prompt antiviral treatment is recommended. Oseltamivir is the preferred agent due to the most extensive available safety data from observational studies in pregnant women. The benefits of treatment are considered to outweigh the potential risks. A: Withholding therapy is not recommended, as influenza itself poses a significant risk to both the mother and the fetus. C: There are limited data on the safety of baloxavir in pregnancy; therefore, it is not the preferred agent. D: Waiting for complications is inappropriate in a high-risk patient population where early treatment is known to be most effective.

Question 8

A patient with influenza A (H1N1) is treated with oseltamivir but shows no clinical improvement after 72 hours. Viral genotyping reveals a mutation in the neuraminidase (NA) gene known to confer resistance. Which of the following antiviral agents would be most likely to demonstrate efficacy in this patient?

  1. Amantadine, because its mechanism of targeting the M2 protein is unaffected by NA mutations.
  2. Zanamivir, as it is administered via inhalation, leading to higher concentrations at the site of infection.
  3. Baloxavir marboxil, because it inhibits the cap-dependent endonuclease, a different viral target. (correct answer)
  4. Peramivir, as its intravenous administration achieves higher systemic levels than oral oseltamivir.
Explanation: The correct answer is C. Baloxavir marboxil has a unique mechanism of action, inhibiting the viral cap-dependent endonuclease of the polymerase acidic (PA) protein. This target is distinct from neuraminidase, so mutations conferring resistance to oseltamivir (a neuraminidase inhibitor) would not affect the activity of baloxavir. A: Amantadine targets the M2 protein, which is a different target. However, widespread resistance to adamantanes exists among circulating influenza A strains, making it an ineffective option. B: Zanamivir is also a neuraminidase inhibitor. Cross-resistance between neuraminidase inhibitors is common, so it is unlikely to be effective against an oseltamivir-resistant strain with a NA mutation. D: Peramivir is also a neuraminidase inhibitor. Despite its different route of administration, it targets the same enzyme as oseltamivir and would likely be ineffective due to cross-resistance.

Question 9

A 68-year-old male with severe chronic obstructive pulmonary disease (COPD) and a history of bronchospasm is diagnosed with influenza B in the emergency department. He is experiencing significant nausea and vomiting, precluding oral administration of medication. His symptoms began 36 hours ago. What is the most appropriate antiviral therapy for this patient?

  1. Oral oseltamivir administered with an antiemetic.
  2. Inhaled zanamivir administered via nebulizer.
  3. Intravenous peramivir as a single infusion. (correct answer)
  4. Oral baloxavir marboxil crushed and given in applesauce.
Explanation: The correct answer is C. This patient has several factors guiding therapy: inability to tolerate oral medications, severe underlying respiratory disease, and influenza B. Intravenous peramivir is the most appropriate choice as it bypasses the gastrointestinal tract, is effective against influenza B, and avoids the risks associated with inhaled medications in a patient with severe COPD. A: Although an antiemetic could be used, the patient's active vomiting makes the reliability of oral absorption questionable. IV administration is preferred in this scenario. B: Inhaled zanamivir is contraindicated in patients with underlying airway diseases like severe COPD due to the risk of inducing bronchospasm. D: The patient is unable to tolerate oral medications due to vomiting, making this option unsuitable regardless of how it is prepared.

Question 10

A 45-year-old unvaccinated healthcare worker has a significant, unprotected exposure to a patient with laboratory-confirmed influenza A. The worker is currently asymptomatic. Which of the following represents the most appropriate chemoprophylaxis regimen?

  1. A single oral dose of baloxavir marboxil initiated as soon as possible. (correct answer)
  2. A 5-day course of amantadine, as the exposure was specifically to influenza A.
  3. A 7-day course of oseltamivir, beginning only if influenza symptoms develop.
  4. A single intravenous infusion of peramivir to ensure maximal bioavailability.
Explanation: The correct answer is A. Baloxavir marboxil is approved for post-exposure prophylaxis of influenza as a single oral dose. This is a convenient and effective option for an asymptomatic individual after a known exposure. B: Amantadine is not recommended for prophylaxis or treatment due to high levels of resistance in circulating influenza A viruses. C: This describes a treatment regimen, not prophylaxis. Chemoprophylaxis is initiated before symptoms develop to prevent illness. D: Intravenous peramivir is indicated for treatment of influenza, not typically for post-exposure prophylaxis in an otherwise healthy individual.

Question 11

The therapeutic target of neuraminidase inhibitors, the viral neuraminidase enzyme, plays a critical and distinct role in the final stage of the influenza virus life cycle. This role is best described as:

  1. Cleaving the bond between viral hemagglutinin and host cell sialic acid receptors. (correct answer)
  2. Acidifying the virion interior to promote the release of viral genetic material.
  3. Facilitating the internalization of the virus into the host cell via endocytosis.
  4. Priming the transcription of the viral RNA genome into messenger RNA.
Explanation: When you encounter questions about neuraminidase inhibitors like oseltamivir (Tamiflu), focus on the influenza virus life cycle's final stage: viral release from infected cells. Neuraminidase is crucial for viral progeny release. After new viral particles are assembled inside infected host cells, they must escape to infect other cells. The newly formed virions initially remain attached to the host cell surface through bonds between viral hemagglutinin proteins and sialic acid receptors on the cell membrane. Neuraminidase acts as a molecular "scissors," cleaving these sialic acid linkages to free the viral particles. Without this cleavage, new virions would remain stuck to the host cell, unable to spread the infection. Answer A correctly describes this critical function—neuraminidase cleaves bonds between viral hemagglutinin and host sialic acid receptors, enabling viral release. Answer B incorrectly describes endosomal acidification, which occurs during viral entry, not release, and involves host cellular machinery rather than viral neuraminidase. Answer C describes the initial infection process where viruses enter cells through endocytosis—this happens at the beginning of the viral cycle, not the end, and doesn't involve neuraminidase. Answer D refers to viral transcription processes that occur inside infected cells during replication, which is mediated by viral RNA polymerase, not neuraminidase. Remember: neuraminidase inhibitors target the "exit strategy" of influenza viruses. Think of neuraminidase as the enzyme that cuts the viral "anchor lines" to the host cell, allowing newly formed viruses to sail away and infect neighboring cells.

Question 12

The emergence of resistance to baloxavir marboxil after a single dose of treatment has been documented. This resistance is most commonly associated with amino acid substitutions in which viral protein?

  1. Neuraminidase (NA)
  2. Hemagglutinin (HA)
  3. Matrix protein 2 (M2)
  4. Polymerase acidic protein (PA) (correct answer)
Explanation: The correct answer is D. Baloxavir marboxil's mechanism of action is the inhibition of the cap-dependent endonuclease activity of the polymerase acidic (PA) protein. Resistance to baloxavir is associated with specific amino acid substitutions (e.g., I38T) in this PA protein, which reduce the drug's ability to bind to its target. A: Neuraminidase is the target of oseltamivir, zanamivir, and peramivir. B: Hemagglutinin is the viral protein responsible for cell entry; mutations here can affect viral fitness and sometimes susceptibility to neuraminidase inhibitors, but it is not the target of baloxavir. C: The M2 protein is the target of the adamantane antivirals.

Question 13

A patient with influenza A (H1N1) is treated with oseltamivir but shows no clinical improvement after 72 hours. Viral genotyping reveals a mutation in the neuraminidase (NA) gene known to confer resistance. Which of the following antiviral agents would be most likely to demonstrate efficacy in this patient?

  1. Amantadine, because its mechanism of targeting the M2 protein is unaffected by NA mutations.
  2. Zanamivir, as it is administered via inhalation, leading to higher concentrations at the site of infection.
  3. Baloxavir marboxil, because it inhibits the cap-dependent endonuclease, a different viral target. (correct answer)
  4. Peramivir, as its intravenous administration achieves higher systemic levels than oral oseltamivir.
Explanation: The correct answer is C. Baloxavir marboxil has a unique mechanism of action, inhibiting the viral cap-dependent endonuclease of the polymerase acidic (PA) protein. This target is distinct from neuraminidase, so mutations conferring resistance to oseltamivir (a neuraminidase inhibitor) would not affect the activity of baloxavir. A: Amantadine targets the M2 protein, which is a different target. However, widespread resistance to adamantanes exists among circulating influenza A strains, making it an ineffective option. B: Zanamivir is also a neuraminidase inhibitor. Cross-resistance between neuraminidase inhibitors is common, so it is unlikely to be effective against an oseltamivir-resistant strain with a NA mutation. D: Peramivir is also a neuraminidase inhibitor. Despite its different route of administration, it targets the same enzyme as oseltamivir and would likely be ineffective due to cross-resistance.

Question 14

A 45-year-old unvaccinated healthcare worker has a significant, unprotected exposure to a patient with laboratory-confirmed influenza A. The worker is currently asymptomatic. Which of the following represents the most appropriate chemoprophylaxis regimen?

  1. A single oral dose of baloxavir marboxil initiated as soon as possible. (correct answer)
  2. A 5-day course of amantadine, as the exposure was specifically to influenza A.
  3. A 7-day course of oseltamivir, beginning only if influenza symptoms develop.
  4. A single intravenous infusion of peramivir to ensure maximal bioavailability.
Explanation: The correct answer is A. Baloxavir marboxil is approved for post-exposure prophylaxis of influenza as a single oral dose. This is a convenient and effective option for an asymptomatic individual after a known exposure. B: Amantadine is not recommended for prophylaxis or treatment due to high levels of resistance in circulating influenza A viruses. C: This describes a treatment regimen, not prophylaxis. Chemoprophylaxis is initiated before symptoms develop to prevent illness. D: Intravenous peramivir is indicated for treatment of influenza, not typically for post-exposure prophylaxis in an otherwise healthy individual.

Question 15

An influenza A virus is isolated from a patient who failed therapy. Genetic sequencing reveals a mutation in the M2 protein gene, conferring resistance to amantadine, and a separate mutation in the neuraminidase (NA) gene, conferring high-level resistance to oseltamivir. Which of the following statements is most accurate regarding this dual-resistant viral strain?

  1. It will likely remain susceptible to peramivir due to its different binding kinetics to the NA enzyme.
  2. It will be resistant to all currently available classes of FDA-approved influenza antivirals.
  3. Its replication cycle is effectively blocked at both the uncoating and budding stages by current drugs.
  4. It would most likely retain susceptibility to baloxavir marboxil. (correct answer)
Explanation: The correct answer is D. This virus is resistant to adamantanes (via M2 mutation) and neuraminidase inhibitors (via NA mutation). Baloxavir marboxil targets a completely different protein, the polymerase acidic (PA) protein's endonuclease function. Therefore, the virus would be expected to remain susceptible to baloxavir. A: While binding kinetics can differ among neuraminidase inhibitors, high-level oseltamivir resistance mutations often confer cross-resistance to other drugs in the same class, including peramivir. B: This statement is incorrect because the virus would likely be susceptible to baloxavir, which represents a different class of antiviral. C: This statement is the opposite of the situation described. The virus is resistant to drugs that target the uncoating (M2) and budding (NA) stages.

Question 16

A 6-month-old infant is hospitalized with severe, complicated influenza B infection and requires mechanical ventilation. The infant is not able to take medications orally. Based on current FDA approvals and clinical practice guidelines, which antiviral regimen is the most appropriate choice?

  1. Intravenous peramivir, due to the severity of illness.
  2. Oral baloxavir, administered via nasogastric tube.
  3. Oral oseltamivir, administered via nasogastric tube. (correct answer)
  4. Inhaled zanamivir, delivered through the ventilator circuit.
Explanation: The correct answer is C. Oseltamivir is the preferred agent for treating severe influenza in infants. It has an Emergency Use Authorization (EUA) and standard approvals for use in infants as young as 2 weeks of age. It is available as an oral suspension that can be administered via a nasogastric (NG) tube if the patient cannot take it orally. A: Intravenous peramivir is only approved for patients aged 2 years and older. B: Oral baloxavir is not approved for children under 5 years old (approval is age-dependent, but generally not for infants) and data in severe, complicated influenza is limited. D: Use of inhaled zanamivir in mechanically ventilated patients is complex, not standard practice, and it is not approved for infants.

Question 17

A 28-year-old woman at 30 weeks gestation presents with a 24-hour history of symptoms consistent with influenza, which is confirmed by a rapid molecular assay. She is febrile to 39°C and has significant myalgia. What is the recommended course of action regarding antiviral therapy?

  1. Withhold antiviral therapy due to the unknown risks to the developing fetus.
  2. Initiate oral oseltamivir promptly due to the increased risk of complications in pregnancy. (correct answer)
  3. Prescribe single-dose baloxavir, as the shorter duration of exposure is safer for the fetus.
  4. Recommend supportive care only and reserve antiviral therapy for signs of pneumonia.
Explanation: The correct answer is B. Pregnant women are considered a high-risk group for severe complications from influenza. Prompt antiviral treatment is recommended. Oseltamivir is the preferred agent due to the most extensive available safety data from observational studies in pregnant women. The benefits of treatment are considered to outweigh the potential risks. A: Withholding therapy is not recommended, as influenza itself poses a significant risk to both the mother and the fetus. C: There are limited data on the safety of baloxavir in pregnancy; therefore, it is not the preferred agent. D: Waiting for complications is inappropriate in a high-risk patient population where early treatment is known to be most effective.

Question 18

A patient initiated on an influenza antiviral two days ago now reports acute confusion, hallucinations, and agitation. While rare, such neuropsychiatric events have been most frequently reported in association with which class of influenza antivirals, particularly in post-marketing surveillance?

  1. Adamantanes, such as amantadine.
  2. Neuraminidase inhibitors, such as oseltamivir. (correct answer)
  3. Cap-dependent endonuclease inhibitors, such as baloxavir.
  4. Broad-spectrum purine nucleoside analogues.
Explanation: The correct answer is B. Post-marketing surveillance, particularly from Japan, has identified reports of neuropsychiatric events (including delirium, hallucinations, and abnormal behavior) in patients, especially children and adolescents, taking neuraminidase inhibitors like oseltamivir. Although a direct causal relationship has not been definitively established and influenza itself can cause these symptoms, this association is a noted safety concern for this drug class. A: Adamantanes are known for CNS side effects like dizziness, insomnia, and ataxia, but the specific profile of acute psychosis is more strongly associated with NAIs in post-marketing reports. C: This is not a characteristic adverse effect profile for baloxavir. D: This refers to drugs like ribavirin, which are not first-line agents for seasonal influenza and have a different set of adverse effects.

Question 19

A 15-year-old patient with a history of moderate persistent asthma is diagnosed with influenza A. The provider wishes to prescribe an antiviral agent. Which agent carries a specific warning regarding its use in patients with underlying respiratory disease due to a risk of acute deterioration of respiratory function?

  1. Oseltamivir
  2. Zanamivir (correct answer)
  3. Baloxavir
  4. Peramivir
Explanation: The correct answer is B. Zanamivir is administered as an inhaled dry powder. Its use has been associated with bronchospasm and a decline in respiratory function, particularly in patients with underlying asthma or chronic obstructive pulmonary disease (COPD). Therefore, it is generally not recommended for this patient population. A: Oseltamivir is administered orally and does not carry this specific risk, although gastrointestinal side effects are common. C: Baloxavir is an oral agent not associated with bronchospasm. D: Peramivir is an intravenous agent not associated with bronchospasm.

Question 20

A nursing home is experiencing a large influenza A outbreak. A 78-year-old resident who received the seasonal influenza vaccine 4 months prior is asymptomatic but shared a room with a resident who has a confirmed case. According to CDC guidelines, what is the most appropriate recommendation for post-exposure chemoprophylaxis with oseltamivir for this resident?

  1. Prophylaxis is unnecessary since the resident was appropriately vaccinated against seasonal influenza.
  2. Prophylaxis should be initiated and continued for a minimum of 2 weeks and until the outbreak is declared over. (correct answer)
  3. A standard 5-day treatment course of oseltamivir should be administered for prophylaxis.
  4. Prophylaxis should be given for 7 days, the typical duration for household exposure.
Explanation: The correct answer is B. In an institutional outbreak setting like a nursing home, chemoprophylaxis is recommended for all residents, regardless of vaccination status, because vaccine effectiveness can be variable. The recommended duration is for at least 2 weeks and should continue for at least 7 days after the last known case was identified. A: Vaccination does not provide 100% protection, so prophylaxis is still recommended during an outbreak. C: A 5-day course is for treatment, not prophylaxis in an outbreak setting. D: A 7- or 10-day course is recommended for prophylaxis after a household exposure, but the duration is extended during a confirmed institutional outbreak.