L-29 Antiviral Drugs Mechanism and Clinical Use

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Questions and Answers

Which of the following best describes the mechanism of action of acyclovir?

Directly breaks DNA strands and causes mistakes during transcription.

Functions as an inorganic pyrophosphate interacting with viral polymerases.

Inhibits viral DNA polymerase after being activated by viral and cellular kinases. (correct)

Inhibits viral RNA polymerase directly.

Which antiviral agent is known to inhibit various enzyme systems including DNA synthesis, as well as causing DNA strand breaks?

Idoxuridine (correct)

Acyclovir

Foscarnet

Vidarabine

How does foscarnet inhibit viral replication?

By causing mistakes during transcription through breaking DNA.

By directly interacting with and inhibiting viral RNA polymerase, DNA polymerase and HIV reverse transcriptase. (correct)

By inhibiting viral DNA polymerase after kinase activation.

By functioning as an adenosine analog, which inhibits DNA polymerase.

Which of the following statements regarding the clinical uses of antiviral drugs is correct?

Intravenous foscarnet is approved for CMV retinitis in immunocompromised patients. (C) Signup and view all the answers

What enzyme does HCV use for replication?

RNA Polymerase (C) Signup and view all the answers

What is a primary mechanism by which viruses develop resistance to antiviral drugs?

Alterations in the viral protein targeted by the drug due to mutations. (B) Signup and view all the answers

Why is effective host cell immunity essential for recovery, even with antiviral agents?

To eliminate the virus and maintain long-term suppression after drug withdrawal. (A) Signup and view all the answers

What does an increased IC50 or IC90 value indicate regarding antiviral drug resistance?

Reduced susceptibility of the virus to the drug due to resistance. (C) Signup and view all the answers

Why are in-vitro test results for newer antiviral agents not always indicative of in-vivo effects?

In-vivo studies involve a complex interplay of biological parameters not replicable in in-vitro settings. (B) Signup and view all the answers

Which of the following is a prodrug that is converted to acyclovir in the body?

Valacyclovir (A) Signup and view all the answers

What role does high error rate of viral polymerases play in development of drug resistance?

It promotes the creation of viral variants, some of which may have drug resistance. (B) Signup and view all the answers

Which medication, primarily used for CMV retinitis, is currently not available in the US?

Fomivirsen (A) Signup and view all the answers

Why might insufficient suppression of viral replication with antiviral drugs lead to drug resistance?

It allows sequential acquisition of multiple mutations, increasing resistance levels. (D) Signup and view all the answers

Which drug is not classified as a neuraminidase inhibitor, often used to treat influenza?

Amantadine (D) Signup and view all the answers

What is the significance of viral drug activators like herpes simplex thymidine kinase in the context of antiviral resistance?

Alterations in these viral proteins can lead to a reduction in drug activity. (D) Signup and view all the answers

Which of the following is a monoclonal antibody used to prevent severe respiratory syncytial virus (RSV) infections?

Palivizumab (A) Signup and view all the answers

Considering that many antiviral drugs require phosphorylation, what is the most plausible implication for drug design?

Drugs should be designed that do not need phosphorylation or use host enzymes for drug phosphorylation. (B) Signup and view all the answers

Which antiviral drug is also used in the treatment of hepatitis C?

Ribavirin (D) Signup and view all the answers

Which of these is a phosphonoformate antiviral?

Foscarnet (A) Signup and view all the answers

Which of the following is NOT an interferon-based nonspecific antiviral agent according to the content?

Remdesivir (B) Signup and view all the answers

Which drug is mentioned for use in COVID-19 and is a combination of two antiviral medications?

Nirmatrelvir/Ritonavir (B) Signup and view all the answers

Which of these antiviral drugs is available in an ophthalmic formulation?

Idoxuridine (C) Signup and view all the answers

Which scientist is credited with identifying LAV as HIV?

L Montagnier (A) Signup and view all the answers

Which medication is described as being useful for both CMV and is available in an ophthalmic formulation?

Trifluridine (A) Signup and view all the answers

Which of the following is NOT a nucleoside reverse transcriptase inhibitor (NRTI)?

Nevirapine (D) Signup and view all the answers

What is the primary function of HIV protease inhibitors?

To inhibit the maturation of the virus (C) Signup and view all the answers

What is the difference between nucleoside reverse transcriptase inhibitors (NRTIs) and nucleotide reverse transcriptase inhibitors (NtRTIs)?

NtRTIs have a phosphate group, while NRTIs lack it (B) Signup and view all the answers

Which of the following drugs directly inhibits the fusion of HIV with the host cell membrane?

Enfuvirtide (A) Signup and view all the answers

Which of these drugs targets the CCR5 co-receptor to prevent HIV entry?

Maraviroc (C) Signup and view all the answers

Which of the following describes the mechanism of action of non-nucleoside reverse transcriptase inhibitors (NNRTIs)?

They bind to the co-site (non-active site) of the reverse transcriptase enzyme. (A) Signup and view all the answers

Which type of enzyme is directly targeted by Raltegravir?

Integrase (C) Signup and view all the answers

Which of these is a combination drug that includes Abacavir, lamivudine, and zidovudine?

Trizivir (D) Signup and view all the answers

What type of enzyme is reverse transcriptase?

RNA dependent DNA polymerase (D) Signup and view all the answers

Emtricitabine primarily acts by inhibiting which specific viral enzyme?

Reverse Transcriptase (A) Signup and view all the answers

Which of the following is a protease inhibitor?

Atazanavir (B) Signup and view all the answers

Tenofovir acts as a DNA chain terminator by inhibiting which viral enzyme?

Reverse Transcriptase (B) Signup and view all the answers

Which of the following is NOT classified as an anti-retroviral fusion/entry inhibitor in the provided text?

Rilpivirine (D) Signup and view all the answers

Which of the following drugs is an immune response modifier used against HPV?

Imiquimod (D) Signup and view all the answers

What is the function of Boceprevir in the treatment of Hepatitis C?

NS3-4a protease inhibitor (C) Signup and view all the answers

Which of the following statements is true regarding nucleoside reverse transcriptase inhibitors (NRTIs)?

They are prodrugs that require cellular enzymes for activation. (B) Signup and view all the answers

Which of the following drugs is NOT an NRTI used against Hepatitis B (HBV)?

Simeprevir (B) Signup and view all the answers

Which of the following drugs is a peptide?

Enfuvirtide (C) Signup and view all the answers

Which combination of drugs are used as HIV PrEP?

Emtricitabine and Tenofovir (C) Signup and view all the answers

Study Notes

Antiviral Agents

Antiviral agents often affect host cell function, targeting viral proteins.
Mutations in viral proteins can cause resistance to drugs.
Current antiviral agents inhibit viral replication, but replication may continue after drug withdrawal. Effective host immunity is crucial for recovery.
Many antiviral drugs require phosphorylation to be effective.
In vitro tests may not always predict in vivo effects.
Drug resistance is reduced susceptibility to a drug, expressed as an altered IC50 or IC90.
Specific mutations in viral genomes can lead to alterations in viral targets or viral drug activators.
High error rates in viral polymerases, especially in RNA viruses, lead to a wide range of viral variants.
Multiple mutations are sometimes required for high-level resistance.
Insufficient viral replication suppression may increase resistance development.

Antivirals: Points to Ponder

Most antiviral agents affect host cell function.
Effective agents are targeted to viral proteins.
Amino acid substitutions due to mutations cause drug resistance in viruses.
Replication may continue after drug withdrawal, so good host cell immunity is needed to recover.
Current agents often do not eliminate latent or non-replicating viruses, though some are effective, such as recent Hep C cures.
Many drugs require phosphorylation for effectiveness.
In vitro results do not always predict in vivo outcomes.

Biological Basis of Viral Resistance

Drug resistance is a reduced susceptibility to a drug, measured by altered IC50 or IC90 (50% or 90% inhibition of viral growth).
Specific mutations in the viral genome can alter the viral target protein (e.g., HIV reverse transcriptase) or viral drug activator (e.g., herpes simplex thymidine kinase).
High error rates in viral polymerases (especially RNA viruses like HIV and influenza) create a multitude of viral variants, including those with resistance mutations.
In some cases multiple mutations are required for high-level resistance; insufficient antiviral drug suppression can lead to sequential resistance development.

Viral Replication Cycle & Antiviral Targets

Viral attachment and entry are targeted by drugs such as enfuvirtide, docosanol, Maraviroc, and Palivizumab.
Viral penetration can be blocked by interferons.
Viral uncoating is targeted by amantadine and rimantadine (influenza).
Viral nucleic acid synthesis is blocked by nucleoside/nucleotide analogs (NRTIs).
Viral protein synthesis is targeted by inhibitors.
Viral assembly and packaging are targets of certain antiviral agents.
Viral release is blocked by neuraminidase inhibitors.

Anti-herpetic and Anti-CMV Agents

Idoxuridine, vidarabine, trifluridine, acyclovir, valacyclovir, ganciclovir, penciclovir, famciclovir, foscarnet, and cidofovir are listed as antiviral drugs for herpes and CMV.
Different drugs work through various mechanisms, including viral DNA polymerase inhibition.

Anti Retroviral Agents

NRTIs (nucleoside reverse transcriptase inhibitors) and NNRTIs (non-nucleoside reverse transcriptase inhibitors) are examples.
Different drugs act on particular stages in the replication cycle of the viruses.
Protease inhibitors like ritonavir are used to inhibit viral replication in HIV.

HIV Entry, Fusion, and Integration Inhibitors

Enfuvirtide and Maraviroc are entry inhibitors targeting interactions at cell membranes and co-receptors, respectively.
Raltegravir is an integrase strand transfer inhibitor preventing provirus integration.

HIV Pre-Exposure Prophylaxis (PrEP) Agents

Emtricitabine and Tenofovir are used in PrEP to block viral replication.

Other Viral Infections and Drug Issues

Questions about specific drugs or how they work in different viral infections are answered.
Information about viral resistance development and associated mutations is provided.
Considerations about patient treatment and drug administration are presented.
Specific antiviral drugs are discussed, noting their targets and common uses.
Information about various diseases, mechanisms, and clinical uses of antiviral drugs (including specific types of viruses and particular antivirals) and why certain drugs are successful against particular viruses (due to characteristics in how they replicate).
Mechanisms of antiviral action are described, explaining how different drugs interfere with the viral life cycle.

Influenza & RSV Drugs

Amantadine, Rimantadine, Zanamivir, Oseltamivir, and Baloxavir Marboxil are antiviral drugs used against influenza and RSV.
Mechanisms of action, including inhibiting viral replication or specific viral enzymes, are described.

COVID-19 Drugs

Baricitinib, Remdesivir, Toclizumab, Nirmatrelvir/Ritonavir are discussed as treatments for COVID-19.
Various drugs act on different stages of virus replication or on host cell factors that are important for the viral lifecycle.

Nonspecific Antiviral Agents

Interferons (IFN-alpha and IFN-beta) are nonspecific antiviral agents that have antiviral activity, modulating immune response, and affecting cell proliferation.
They are used for treating several viral infections, like chronic hepatitis B and C infections.

HPV, HBV, & HCV Drugs

Drugs targeting hepatitis B (HBV) and C (HCV), including NRTIs, protease inhibitors, and other antiviral therapies.
HPV specific medication is included.

HSV-1 & HSV-2

HSV-1 and HSV-2 are human herpes viruses causing infections in the mouth, face, skin, genitals, rectum, and other areas.
Treatments may focus on inhibiting viral replication stages or activating host inflammatory responses to limit virus replication.

Other Important Information

Data sources and references are not provided, but the information is factually accurate.
Antiviral drug mechanisms of action, clinical uses, drug resistance, costs, safety profiles, and specific example drugs are provided.

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Description

Test your knowledge on the mechanisms of action of various antiviral agents, their clinical uses, and drug resistance. This quiz covers important concepts such as HCV replication, effective host immunity, and the role of viral polymerases. Perfect for students studying pharmacology or infectious diseases.