L25. Pharma - Antivirals I
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Which of the following antiviral agents specifically targets Herpes-simplex-virus 2 (HSV2)?

  • Acyclovir (correct)
  • Indinavir
  • Ribavirin
  • Oseltamivir

    • What is the mechanism of action for nucleoside analogues like Acyclovir?

  • Inhibit host cell RNA polymerase
  • Compete with nucleotide bases for viral DNA polymerase (correct)
  • Enhance host immune response
  • Block viral entry into host cells

    • Which of the following is a class of antiviral agents used to inhibit DNA polymerase non-nucleosidely?

  • Integrase inhibitors
  • NRTIs
  • NNRTIs (correct)
  • Protease inhibitors

    • What step in the activation of Acyclovir requires viral enzymes?

    <p>First phosphorylation step</p> Signup and view all the answers

    Which of the following antiviral medications is likely to be affected by viral resistance mechanisms of thymidine kinase?

    <p>Valacyclovir</p> Signup and view all the answers

    What is a common adverse effect associated with antiviral medications like Ganciclovir?

    <p>Bone marrow suppression</p> Signup and view all the answers

    Which antiviral agent is the best choice for treating infections caused by Varicella-zoster virus (VZV)?

    <p>Acyclovir</p> Signup and view all the answers

    Which mechanism explains cross-resistance among antiviral drugs targeting HSV?

    <p>Resistance to viral DNA polymerase</p> Signup and view all the answers

    What is the primary mechanism of action of interferons as antiviral agents?

    <p>They produce enzymes that degrade viral mRNA.</p> Signup and view all the answers

    Which adverse effect is commonly associated with the use of Simeprevir?

    <p>Anaemia</p> Signup and view all the answers

    What is the significance of pegylation when it comes to the administration of interferons?

    <p>It prolongs the action and enables once weekly dosing.</p> Signup and view all the answers

    Which drug specifically inhibits the non-structural 3/4A protease required for viral replication?

    <p>Simeprevir</p> Signup and view all the answers

    What common adverse effect is associated with Entecavir?

    <p>Dizziness</p> Signup and view all the answers

    Which of the following drugs is associated with nephrotoxicity as a side effect?

    <p>Tenofovir</p> Signup and view all the answers

    Which class of drugs includes agents that act through interfering with viral protein synthesis?

    <p>Interferons</p> Signup and view all the answers

    Which of the following adverse effects is least likely to be caused by interferons?

    <p>Nephrotoxicity</p> Signup and view all the answers

    What are the main classes of human interferons?

    <p>Alpha, beta, and gamma</p> Signup and view all the answers

    How do antiviral agents inhibit virus resistance mechanisms?

    <p>By disrupting viral protein processing</p> Signup and view all the answers

    Which antiviral agent is primarily effective against CMV and is about 100 times more active than acyclovir?

    <p>Ganciclovir</p> Signup and view all the answers

    What is the primary mechanism of action for acyclovir in targeting infected cells?

    <p>Selective phosphorylation by viral thymidine kinase</p> Signup and view all the answers

    Which of the following adverse effects is common with high doses or intravenous administration of acyclovir?

    <p>Acute renal failure</p> Signup and view all the answers

    Which statement about the resistance mechanisms in viruses related to antiviral agents is accurate?

    <p>Resistance to acyclovir typically arises from mutations in DNA polymerase.</p> Signup and view all the answers

    What distinguishes penciclovir from acyclovir in terms of its phosphorylation and activity?

    <p>Penciclovir is phosphorylated more efficiently but has lower affinity to viral DNA polymerase.</p> Signup and view all the answers

    Which antiviral agent is specifically ineffective against influenza B?

    <p>Amantadine</p> Signup and view all the answers

    What is the primary mechanism of action of oseltamivir?

    <p>Inhibition of viral neuraminidase</p> Signup and view all the answers

    What type of side effects are primarily associated with amantadine?

    <p>CNS-related side effects</p> Signup and view all the answers

    How does ribavirin exert its antiviral effects?

    <p>By directly inhibiting viral mRNA polymerase</p> Signup and view all the answers

    What is a significant advantage of neuraminidase inhibitors over amantadine?

    <p>Broader activity against both influenza A and B</p> Signup and view all the answers

    Which hepatitis virus is categorized as a single-stranded RNA virus?

    <p>Hepatitis C</p> Signup and view all the answers

    Phosphorylation to di- or tri-phosphate forms is necessary for which of the following drug classes?

    <p>Nucleotide/nucleoside analogues</p> Signup and view all the answers

    Which drug class is associated with less resistance compared to amantadine?

    <p>Neuraminidase inhibitors</p> Signup and view all the answers

    Which of the following is NOT a side effect associated with oseltamivir?

    <p>CNS toxicity</p> Signup and view all the answers

    What is the role of neuraminidase in influenza viral replication?

    <p>Cleaves sialic acid to release new virions</p> Signup and view all the answers

    What is the primary mechanism of action of foscarnet as an antiviral agent?

    <p>It interacts at the pyrophosphate site of viral DNA polymerase and reverse transcriptase.</p> Signup and view all the answers

    What significant selectivity characteristic does foscarnet possess?

    <p>It has ~100-fold greater inhibitory effects against herpesvirus DNA polymerases than the host's.</p> Signup and view all the answers

    Which of the following adverse effects is commonly associated with foscarnet treatment?

    <p>Nephrotoxicity.</p> Signup and view all the answers

    What type of viruses does amantadine primarily target and how?

    <p>It targets influenza A viruses by blocking the M2 proton channel.</p> Signup and view all the answers

    Which mechanism describes the resistance of herpesviruses to foscarnet?

    <p>Mutations in the viral DNA polymerase.</p> Signup and view all the answers

    How do neuraminidase inhibitors, such as oseltamivir, function in treating influenza?

    <p>By preventing the release of virions from the host cell.</p> Signup and view all the answers

    What is a common property of M2 inhibitors like amantadine?

    <p>They provide a late-stage inhibition effect in viral replication.</p> Signup and view all the answers

    Which statement best distinguishes between the mechanisms of action of foscarnet and amantadine?

    <p>Foscarnet interacts with viral polymerases, whereas amantadine blocks viral M2 channels.</p> Signup and view all the answers

    What is the expected outcome of using a neuraminidase inhibitor during an influenza infection?

    <p>Decrease in symptomatic viral shedding.</p> Signup and view all the answers

    What metabolic abnormalities are associated with foscarnet's nephrotoxicity?

    <p>Decreased levels of calcium and magnesium.</p> Signup and view all the answers

    Study Notes

    Antiviral Agents I - Case Study

    • A 27-year-old man developed painful, itchy sores on his genitals after meeting a woman.
    • He also experienced fever and headaches.
    • After testing, he was diagnosed with Herpes simplex virus 2 (HSV-2).
    • It was his first HSV-2 infection.

    Antiviral Medications for Herpes

    • Anti-herpes medications target viruses like HSV-1, HSV-2, VZV, CMV, and EBV.
    • These viruses are DNA viruses.
    • The main drug types against HSV viruses are:
      • Nucleoside Analogues (acyclovir, valacyclovir, famciclovir)
      • Non-Nucleoside DNA Polymerase Inhibitors (foscarnet)
      • Helicase-Primase Inhibitors (pitelivir - investigational)
      • Immune Modulators (interferons - rarely used)
      • Topical Agents (docosanol, penciclovir)

    Mechanism of Action of Nucleoside Analogues

    • These drugs compete with nucleotides for the DNA polymerase substrate site.
    • Acyclovir, valacyclovir, etc., are analogues of deoxyribonucleoside triphosphates (dGTP).
    • They need viral enzymes to be phosphorylated and activated.
    • This inhibition of viral DNA synthesis is selective, meaning it does not affect host cells.
    • Nucleoside analogues go through 3 steps of phosphorylation to become active.
    • The first step is by a viral kinase (e.g., thymidine kinase or UL-97 kinase).
    • The next 2 steps are by host cell kinases to a nucleotide (e.g., guanosine) analogue.

    Other Antiviral Medications

    • Famciclovir and penciclovir are similar to acyclovir in their spectrum of activity but are more efficient at phosphorylation.
    • Valganciclovir/Ganciclovir: potent against CMV, requires less frequent dosing.
    • Foscarnet: a non-nucleoside DNA polymerase inhibitor that does not require phosphorylation.
    • Simeprevir: inhibits the non-structural 3/4A protease, essential for generating mature viral proteins required for replication.

    Anti-influenza Drugs

    • Influenza virus types are A, B, and C.
    • Influenza viruses use hemagglutinin to attach to host cells.
    • The virus is internalized into the endosome and genetic material is released.
    • Anti-influenza drugs include Amantadine (M2 inhibitor) and Oseltamivir (neuraminidase inhibitor).
    • Amantadine affects the M2 proton channel, preventing viral uncoating.
    • Oseltamivir inhibits neuraminidase, preventing viral release.

    Anti-Hepatitis Drugs

    • Hepatitis viruses include A, B, C, D.
    • Hepatitis B is a DNA virus.
    • Hepatitis C is an RNA virus.
    • Anti-hepatitis medications include nucleotide/nucleoside analogues (ribavirin, entecavir, adefovir).
    • Interferons are also used in Hepatitis treatments.
    • Drugs like simeprevir inhibit the NS3/4A protease.

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    Pharma - Antivirals I (OA) PDF

    Description

    Explore the case study of a 27-year-old man diagnosed with HSV-2, detailing his symptoms and the latest antiviral medications used for treatment. Understand the mechanisms of action of nucleoside analogues and their role in managing herpes infections. This quiz delves into critical antiviral agents targeting DNA viruses.

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