Antivirals
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Questions and Answers

Which of the following is NOT a characteristic of protease inhibitors?

  • They inhibit HIV viral protease.
  • They are biotransformed by CYP 3A4 enzymes.
  • They can lead to altered body fat distribution.
  • They are exclusively derived from natural sources. (correct)

    • What is the primary mechanism of action for integrase inhibitors?

  • They enhance the immune response to HIV.
  • They bind to viral integrase, blocking DNA integration. (correct)
  • They alter the structure of human proteases.
  • They inhibit the replication of viral RNA.

    • Which of the following statements regarding the adverse effects of protease inhibitors is accurate?

  • PIs can lead to elevated levels of free drug in circulation. (correct)
  • All PIs can increase renal function.
  • PIs always reduce the risk of body fat redistribution.
  • Altered body fat distribution does not occur with PIs.

    • How does Ritonavir influence the levels of other protease inhibitors?

    <p>It increases protease inhibitor levels significantly.</p> Signup and view all the answers

    What is a significant concern when combining protease inhibitors with drugs that inhibit CYP3A4?

    <p>Increased plasma levels of PIs.</p> Signup and view all the answers

    Which of the following drugs is classified as a non-nucleoside reverse transcriptase inhibitor (NNRTI)?

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

    What can result from drug displacement from alpha-1-acid-glycoprotein (AAG) regarding protease inhibitors?

    <p>Elevated free plasma levels of PIs.</p> Signup and view all the answers

    What is a primary mechanism of resistance to protease inhibitors in HIV?

    <p>Alteration of the protease enzyme itself.</p> Signup and view all the answers

    What role do intracellular kinases play in the pharmacokinetics of prodrugs?

    <p>They convert the prodrug into an active compound.</p> Signup and view all the answers

    Which of the following is a common adverse effect associated with NRTIs?

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

    What is a primary mechanism of resistance for NRTIs?

    <p>Mutations in reverse transcriptase enzyme</p> Signup and view all the answers

    Which drug is an adenosine analog with the same mechanism of action as other NRTIs?

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

    What characterizes Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)?

    <p>They induce conformational change in reverse transcriptase.</p> Signup and view all the answers

    Which statement accurately describes the pharmacokinetics of NNRTIs?

    <p>They do not require phosphorylation for activation.</p> Signup and view all the answers

    What is a significant clinical application of NNRTIs?

    <p>Adjunctive therapy in HAART.</p> Signup and view all the answers

    How do NNRTIs impact other medications through their mechanism of action?

    <p>They induce CYP 3A4, lowering other drug concentrations.</p> Signup and view all the answers

    What is the primary mechanism through which acyclovir exerts its antiviral effect?

    <p>Inhibits viral nucleic acid synthesis by acting as a substrate for viral enzymes.</p> Signup and view all the answers

    Which of the following herpes virus types is NOT effectively targeted by acyclovir?

    <p>Cytomegalovirus (CMV)</p> Signup and view all the answers

    Acyclovir undergoes phosphorylation to become active. Which enzyme initiates this process?

    <p>Viral thymidine kinase</p> Signup and view all the answers

    What is the bioavailability (F) percentage of acyclovir after an oral dose?

    <p>15-20%</p> Signup and view all the answers

    Which of the following statements is true regarding the adverse effects of long-term acyclovir use?

    <p>Daily doses for up to 10 years have not been linked to significant untoward effects.</p> Signup and view all the answers

    What characterizes the structure of acyclovir?

    <p>It is a synthetic guanosine derivative.</p> Signup and view all the answers

    Which adverse reaction is most closely associated with acute high doses of acyclovir?

    <p>Nephrotoxicity due to crystallization in renal tubules</p> Signup and view all the answers

    Which of the following actions does acyclovir NOT perform?

    <p>Inhibits assembly of viral particles.</p> Signup and view all the answers

    What is the mechanism of action of Amantadine and Rimantadine in the context of antiviral treatment?

    <p>They block a proton ion channel in the virus.</p> Signup and view all the answers

    Which of the following best describes the role of Pegylated Interferon Alpha?

    <p>It enhances the stability and duration of action of the drug in the body.</p> Signup and view all the answers

    What kind of drug is Adefovir dipivoxil and how does it function?

    <p>A prodrug that is converted to an adenine analog to inhibit HBV DNA polymerase.</p> Signup and view all the answers

    Which of the following correctly identifies the role of Sofosbuvir in the treatment of Hepatitis C?

    <p>It is a nucleotide analog that inhibits HCV RNA polymerase.</p> Signup and view all the answers

    Which of the following statements about HIV entry into host cells is accurate?

    <p>HIV requires a co-receptor in addition to the CD4 receptor for entry into the host cell.</p> Signup and view all the answers

    What does the role of HIV protease entail in the lifecycle of the virus?

    <p>It processes viral polyproteins into functional proteins necessary for the assembly of new virions.</p> Signup and view all the answers

    Which class of drugs is specifically utilized as polymerase inhibitors for Hepatitis C?

    <p>Sofosbuvir and dasabuvir.</p> Signup and view all the answers

    What aspect of HIV is primarily targeted by the combination of drugs used in treatment?

    <p>The prevention of viral genome replication.</p> Signup and view all the answers

    Which of the following classes of drugs includes dolutegravir?

    <p>Integrase Strand Transfer Inhibitors</p> Signup and view all the answers

    What is one of the primary causes of drug failure in HIV treatment?

    <p>Sub-therapeutic plasma levels</p> Signup and view all the answers

    Which combination is recommended for HAART therapy?

    <p>At least two different NRTIs and one or more PIs</p> Signup and view all the answers

    Which of the following statements about tenofovir is true?

    <p>It is used in combination therapies for both HIV and HBV.</p> Signup and view all the answers

    What is a potential consequence of poor compliance in a patient taking over 20 pills a day?

    <p>Sub-therapeutic drug levels leading to viral replication</p> Signup and view all the answers

    Which of the following is NOT typically included in HAART therapy?

    <p>Entry Inhibitor</p> Signup and view all the answers

    Which drug is classified as an NNRTI?

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

    What is the necessary monitoring for a patient on tenofovir and emtricitabine?

    <p>Kidney function and pregnancy status</p> Signup and view all the answers

    What is herpes zoster?

    <p>A viral infection also known as shingles</p> Signup and view all the answers

    What is the mechanism of action (MOA) of acyclovir?

    <p>Inhibits DNA polymerase</p> Signup and view all the answers

    How is acyclovir eliminated from the body after oral dosing?

    <p>Renal excretion</p> Signup and view all the answers

    What is the name of the acyclovir prodrug that is converted to acyclovir in the body?

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

    What is the mechanism that provides the specificity of acyclovir’s actions for viral DNA and not for human DNA?

    <p>Acyclovir is only activated by viral thymidine kinase.</p> Signup and view all the answers

    Which of the following are methods of administering acyclovir? (Select all that apply)

    <p>Oral tablet</p> Signup and view all the answers

    What are three possible adverse drug reactions (ADRs) of acyclovir? (Select all that apply)

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

    Match each drug to its description

    <p>Valacyclovir = prodrug of the drug acyclovir converted to acyclovir in the liver Famciclovir = prodrug converted in the liver to penciclovir, similar in use and actions to acyclovir Penciclovir = Activated form of famciclovir Docosanol = inhibit fusion of virus with host cell membrane preventing entry into the host cell</p> Signup and view all the answers

    Which of the following antivirals are used for Cytomegalovirus (CMV)? (Select all that apply)

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

    What is the world's first anti-HIV drug?

    <p>Zidovudine (AZT)</p> Signup and view all the answers

    What is the purpose of Nevirapine?

    <p>Prevent transmission of the virus from mother to baby</p> Signup and view all the answers

    What is an adverse drug reaction (ADR) associated with protease inhibitors?

    <p>Buffalo hump</p> Signup and view all the answers

    What is a characteristic of indinavir?

    <p>Best absorption on an empty stomach</p> Signup and view all the answers

    What is an ADR (adverse drug reaction) of indinavir?

    <p>Precipitation of drug crystals in the kidney</p> Signup and view all the answers

    What is the mechanism of action (MOA) of enfuvirtide?

    <p>Binds to the gp41 subunit of the gp 160 viral protein and blocks entry of the HIV into the CD4 white cell</p> Signup and view all the answers

    What should dolutegravir not be given with?

    <p>St. John's Wort</p> Signup and view all the answers

    What does peglated interferon do for antihepatitis agents?

    <p>Slows absorption and increases the half-life of the interferon alpha</p> Signup and view all the answers

    Which drugs are approved for Hep B treatment? (Select all that apply)

    <p>pegylated interferon alfa 2a</p> Signup and view all the answers

    What is the mechanism of action (MOA) of adefovir dipivoxil?

    <p>phosphorylated adefovir inhibits viral DNA polymerase</p> Signup and view all the answers

    What drugs are approved for Hepatitis C treatment? (Select all that apply)

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

    What is the mechanism of action (MOA) for sofosbuvir?

    <p>inhibits Hepatitis C virus (HCV) RNA dependent RNA polymerase</p> Signup and view all the answers

    What is the mechanism of action (MOA) of boceprevir?

    <p>inhibits HCV protease and prevents cleavage of proteins required for viral development</p> Signup and view all the answers

    What is the mechanism of action (MOA) of ribavirin?

    <p>Inhibits RNA and DNA virus replication</p> Signup and view all the answers

    What is an adverse drug reaction (ADR) of ribavirin?

    <p>Hemolytic anemia</p> Signup and view all the answers

    Which of the following are anti-influenza neuraminidases?

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

    Which of the following are anti-influenza proton ion channel blockers?

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

    What is the mechanism of action (MOA) of maraviroc?

    <p>Binds to host CCR5</p> Signup and view all the answers

    What is an adverse drug reaction (ADR) of raltegravir?

    <p>Stevens-Johnson syndrome</p> Signup and view all the answers

    Study Notes

    Antivirals

    • Antivirals are drugs that target specific stages of a virus's life cycle, such as entry into a host cell, uncoating, or assembly of viral particles.
    • Herpesviruses are a family of DNA viruses including Herpes simplex, Varicella-zoster, Cytomegalovirus, Epstein-Barr, and Herpes Virus Type 6.
    • Acyclovir was the first synthetic antiviral drug, it is a guanosine derivative that resembles a guanosine monophosphate molecule.
    • Acyclovir inhibits DNA synthesis by competitively inhibiting deoxyGTP for viral DNA polymerase and halting DNA chain elongation.
    • Acyclovir is effective against HSV-1, HSV-2, and VZV, and is clinically used to reduce frequency and severity of symptoms of genital herpes.
    • Acyclovir has a low oral bioavailability of 15-20%, it is also available in IV and topical forms for herpetic lesions.
    • Zanamivir and amantadine/rimantadine are antiviral agents against influenza.
    • Zanamivir is a neuraminidase inhibitor, while amantadine and rimantadine are tricyclic amines that block a proton ion channel within the virus.
    • Interferon Alpha is a cytokine that binds to host cells and disrupts viral replication.
    • Hepatitis B (HBV) drugs like adefovir dipivoxil are prodrugs that are converted to adefovir, an adenine analogue that inhibits HBV DNA polymerase and viral replication.
    • Hepatitis C (HCV) drugs include polymerase inhibitors, protease inhibitors and guanosine analogue agents.
    • Sofosbuvir is a nucleotide analogue that inhibits HCV RNA polymerase.
    • Boceprevir is a protease inhibitor that prevents viral development by inhibiting HCV protease.
    • Ibavirin is a guanosine analogue that inhibits the synthesis of guanosine triphosphate, which is required for viral replication.

    Antiretroviral Drugs

    • HIV infection has affected over 42 million people worldwide, and 20+ different drugs are available to treat it.
    • The standard of care for HIV treatment includes three drug combinations, resulting in 1140 possible combinations.
    • There are two major families of HIV: HIV-1 (most common) and HIV-2 (found mostly in West Africa).
    • HIV enters host cells by attaching to the CD4 receptor using its spike protein (gp120) and then fusing with the host cell membrane.
    • After entry, the virus releases its RNA which is converted to DNA using HIV reverse transcriptase.
    • HIV integrase then inserts the viral DNA into the host cell's DNA, which then is used to produce more viral proteins and assembly new virions.
    • Antiretroviral drugs typically require intracellular kinases to phosphorylate the drug into its active form, often a triphosphorylated compound.

    NRTIs (Nucleoside Reverse Transcriptase Inhibitors)

    • NRTIs are analogues of nucleosides that inhibit HIV reverse transcriptase by competitively inhibiting the incorporation of natural nucleotides into viral DNA.
    • This class of drugs includes abacavir, didanosine, emtricitabine, lamivudine, stavudine, tenofovir, and zidovudine.
    • NRTIs are commonly used in HAART therapy, but can cause adverse effects such as myelosuppression, headache, insomnia, myopathy, anxiety, confusion, anorexia, fatigue, nausea, and malaise.
    • Resistance to NRTIs can develop due to mutations in the reverse transcriptase enzyme, requiring HIV genotyping for all isolates.

    NNRTIs (Non-Nucleoside Reverse Transcriptase Inhibitors)

    • Unlike NRTIs, NNRTIs bind to a different site on the reverse transcriptase enzyme, inducing conformational changes that inactive the enzyme.
    • Delavirdine, efavirenz, etravirine, nevirapine, and rilpivirine are examples of NNRTIs.
    • NNRTIs are typically used as adjunct drugs in HAART therapy, but can be inducers of CYP 3A4, which lowers the Cp of other drugs.
    • Resistance to NNRTIs arises from mutations in the reverse transcriptase enzyme.

    PIs (Protease Inhibitors)

    • PIs are synthetic peptidomimetic hydroxylamines that inhibit HIV viral protease, preventing the cleavage and assembly of viral proteins required for new virus formation.
    • This class of drugs includes atazanavir, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and tipranavir.
    • PIs can cause altered body fat distribution (Buffalo Hump) and are typically used as adjunct drugs in HAART therapy.
    • The Cp of PIs can significantly vary due to food interactions and can be affected by other drugs that interact with CYP 3A4 enzymes.
    • PIs are highly bound to alpha-1-acid-glycoprotein (AAG), levels of which can vary widely between patients, leading to potential interactions with other drugs that displace PIs from AAG.
    • Resistance to PIs is caused by mutations in the protease enzyme.

    Integrase Inhibitors

    • Integrase strand transfer inhibitors bind to viral integrase, inhibiting strand transfer and blocking the insertion of reversed transcribed HIV DNA into the host's DNA.
    • Dolutegravir, elvitegravir, and raltegravir are examples of integrase inhibitors.

    HAART Therapy

    • Highly active antiretroviral therapy (HAART) typically comprises at least two different NRTIs, 1 or more PIs, and sometimes 1 fusion inhibitor (FI).
    • HAART can result in more than 20 pills per day with variations in dosing frequency food interactions, and adverse drug reactions between patients.

    Causes of Drug Failure

    • Drug failure can occur due to sub-therapeutic Cp levels, lack of compliance, drug resistance, individual differences in metabolism and clearance, and drug-drug or drug-food interactions.

    HIV Drugs Required

    • Zidovudine, lamivudine, tenofovir, delaviridine, nevirapine, saquinavir, indinavir, ritonavir, enfuvirtide, maraviroc, and raltegravir are essential drugs for HIV management.

    Case Study

    • A 35-year-old HIV and HBV positive female, on methadone therapy for heroin addiction, with a low CD4 count of 278/uL and a high viral load (HIV RNA) of 110,000 copies/mL, required treatment with a three-drug combination considering her conditions.
    • Tenofovir and emtricitabine were chosen for treating both her HIV and HBV. Efavirenz was added for HIV treatment, provided she was not pregnant, and adjustments to her methadone dose may be required to account for drug-drug interactions.

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