Antiviral Drugs and Influenza

Questions and Answers

What is the recommended population for prophylaxis against influenza?

Healthy individuals

Populations at risk of complications and control institutional outbreaks (correct)

Immunocompromised patients only

Pregnant women only

What is the unique mechanism of action of Baloxavir Marboxil?

Inhibiting neuraminidase activity

Interfering with viral DNA replication

Targeting ribonuclease activity that affects transcription of viral RNA (correct)

Inhibiting viral release from infected cells

What is the most effective treatment for serious herpesvirus infections?

IV acyclovir (correct)

Oral valacyclovir

Foscarney aka Foscavir

Topical acyclovir

What is the advantage of valacyclovir over acyclovir?

Higher oral bioavailability Signup and view all the answers

What is the benefit of treating genital herpes with acyclovir, valacyclovir, or famciclovir?

Prevents replication of HSV and reduces pain and other symptoms Signup and view all the answers

What is the benefit of treating shingles with famciclovir and valacyclovir?

Shortens duration of acute illness and pain and lowers incidence of postherpetic pain Signup and view all the answers

What is the bioavailability of acyclovir?

22% Signup and view all the answers

What is the primary role of vaccines in preventing influenza?

To serve as the primary means of prevention Signup and view all the answers

What is the name of the vaccine available for herpes zoster infections in older adults?

Zostavax Signup and view all the answers

What is the main function of neuraminidase in influenza A and B viruses?

To catalyze reactions that promote viral spreading and infection Signup and view all the answers

What is the benefit of starting neuraminidase inhibitors within 48 hours of onset of influenza symptoms?

To reduce the symptom severity and duration of illness Signup and view all the answers

Why are antibacterial and antifungal drugs ineffective against viral infections?

They have little to no effect on viral infections Signup and view all the answers

What is the primary target of neuraminidase inhibitors in the treatment of influenza?

The enzyme neuraminidase Signup and view all the answers

What is the benefit of neuraminidase inhibitors in the treatment of influenza?

They reduce the severity of complications such as OM and PNA Signup and view all the answers

When is it most beneficial to administer neuraminidase inhibitors in the treatment of influenza?

As early as possible for any patient with confirmed or suspected influenza Signup and view all the answers

What is the mechanism of action of neuraminidase inhibitors in the treatment of influenza?

They inhibit the enzyme neuraminidase Signup and view all the answers

Which of the following NRTIs is classified as a nucleotide RTI?

Tenofovir disoproxil fumarate Signup and view all the answers

What is the main mechanism of action of NRTIs?

Competition with endogenous nucleoside triphosphate for incorporation into DNA Signup and view all the answers

Which of the following NRTIs is associated with bone marrow suppression, anemia, and neutropenia?

Zidovudine Signup and view all the answers

What is the recommended therapy for preventing in utero transmission of HIV?

Combination therapy with two NRTIs and an NNRTI Signup and view all the answers

Which of the following is a common adverse effect of all NRTIs?

Lactic acidosis, hepatic steatosis, and lipodystrophy Signup and view all the answers

What is the recommended initial treatment of HIV?

Tenofovir disoproxil fumarate and Emtricitabine Signup and view all the answers

Which of the following is a once-daily, single-pill regimen for HIV treatment?

Atripla Signup and view all the answers

Why are NRTIs often more effective when combined with other NRTIs?

They are antimetabolites for different purine and pyrimidine bases of DNA Signup and view all the answers

Which of the following statements about Non-nucleoside RTIs (NNRTIs) is true?

They do not require metabolic activation and are not incorporated into viral DNA. Signup and view all the answers

What is the primary mechanism of action of Protease inhibitors (PIs)?

They bind to the active site of the HIV protease enzyme. Signup and view all the answers

Which of the following NNRTIs has the lowest antiviral activity?

Delaviridine Signup and view all the answers

What is the main reason for avoiding Efavirenz in pregnancy and women who can become pregnant?

It is teratogenic. Signup and view all the answers

What is the role of Ritonavir in boosted therapy?

It inhibits the metabolism of other PIs, increasing their plasma levels and duration. Signup and view all the answers

Which of the following is a common side effect of NNRTIs?

All of the above Signup and view all the answers

What is the current preferred PI for treating HIV?

Atazanavir Signup and view all the answers

When was the first PI introduced?

1995 Signup and view all the answers

What is the main mechanism of action of enfuvirtide?

Blocking fusion of HIV with CD4 cells Signup and view all the answers

What is a common side effect of enfuvirtide injection?

Injection site reactions Signup and view all the answers

What is the main advantage of maraviroc over other HIV therapies?

It is active against HIV strains resistant to RTIs and PIs Signup and view all the answers

What is the result of integrase inhibitors on HIV replication?

Prevention of DNA strand transfer Signup and view all the answers

What is the name of the combo drug product containing ritonavir and another PI?

Kaletra Signup and view all the answers

What is the role of integrase in HIV replication?

Incorporates viral DNA into CD4 cells Signup and view all the answers

What is the effect of maraviroc and other fusion and entry inhibitors on HIV infection?

Decrease in viral loads and increase in CD4 cells Signup and view all the answers

What is a recent recommendation for initial treatment of HIV infection?

Regimen containing raltegravir Signup and view all the answers

Study Notes

Antiviral Drugs

Antibacterial and antifungal drugs have little to no effect on viral infections.
Compounds have been developed to treat some viral infections, such as HIV, influenza, and hepatitis.
Antiviral drugs work in various ways, including:
- Preventing replication of viral nucleic acid.
- Inhibiting entry, uncoating, or release of the virus.

Influenza Drugs

Influenza is one of the most common causes of infectious disease-related deaths.
Vaccines are the primary means of prevention.
Neuraminidase inhibitors are useful for prophylaxis during outbreaks and can:
- Shorten the duration of illness in infected persons.
- Prevent complications.

Neuraminidase Inhibitors

These drugs inhibit the enzyme neuraminidase in influenza A and B viruses.
Neuraminidase catalyzes reactions that promote viral spreading and infection, including:
- Enabling the release of virions from the surface of infected cells.
- Inactivating respiratory tract mucous that would prevent the spreading of virions.
Neuraminidase inhibitors:
- Reduce complications, including otitis media (OM) and pneumonia (PNA).
- Are most beneficial in reducing symptom severity and duration of illness if given within 3 days of onset, preferably within 48 hours.
- May still provide benefit in reducing respiratory failure and death in pregnant women if started 3-4 days after onset.

Baloxavir Marboxil (Xofluza)

Single-dose oral treatment for influenza A and B.
First-in-class medication.
Unique mechanism of action (MOA): prodrug gets converted to baloxavir acid (BXA), which targets ribonuclease activity affecting transcription of viral RNA.
Approved in the US in 2018.
Potentially has fewer side effects compared to oseltamivir.

Herpesvirus Infections

Cytomegalovirus (CMV) infections in immunocompetent individuals are usually asymptomatic.
CMV retinitis, esophagitis, and colitis are usually seen in immunocompromised patients.

Drugs for Herpesviruses

Nucleoside analogues:
- Acyclovir (Zovirax):
  - IV acyclovir is most effective for serious herpesvirus infections, including encephalitis and infections in immunocompromised patients.
  - Topical acyclovir can be used to treat genital herpes and mild mucocutaneous infections.
- Valacyclovir (Valtrex):
  - Prodrug that gets rapidly converted to acyclovir by intestinal and hepatic enzymes.
  - More completely absorbed (55%) compared to acyclovir.
- Famciclovir (Famvir):
  - Greatest bioavailability (80%).
  - Gets rapidly hydrolyzed to penciclovir after absorption.
Other drugs:
- Foscarney (Foscavir).
Treating genital herpes:
- When given orally, prevents replication of HSV and reduces pain and other symptoms of acute infection.
- Shortens time to healing of lesions and reduces viral shedding.
- Does not eliminate the virus; recurrent episodes are common (can be treated with lesser doses).
Treating shingles:
- When given orally, shortens duration of acute illness and pain and lowers incidence of postherpetic pain.
- Famciclovir and valacyclovir are more effective than acyclovir.

Integrase Strand Transfer Inhibitors

Reverse transcriptase inhibitors:
- Nucleoside reverse transcriptase inhibitors (NRTIs).
- Non-nucleoside reverse transcriptase inhibitors (NNRTIs).
Nucleoside reverse transcriptase inhibitors (NRTIs):
- First class of drugs developed for treating HIV+ individuals.
- Included in almost all regimens.
- Serve as antimetabolites for different purine and pyrimidine bases of DNA.
- More effective when combined with other NRTIs.
- Examples:
  - Zidovudine (AZT, ZDV) aka Retrovir.
  - Lamivudine (3TC) aka Epivir.
  - Emtricitabine (FTC) aka Emtriva.
  - Tenofovir disoproxil (TDF) aka Viread.

AZT/ZDV

First NRTI to be developed, still one of the most widely used drugs in this class.
Always combined with other drugs.
In utero transmission:
- AZT treatment significantly reduces in utero transmission of HIV from infected pregnant women to their offspring.

Initial Treatment of HIV

Newer NRTIs are now recommended for initial treatment of HIV:
- Tenofovir disoproxil fumarate (TDF).
- Emtricitabine (FTC).
Combo drug containing TDF, FTC, and efavirenz called Atripla is now available, once a day therapy with a single pill.

Non-Nucleoside RTIs (NNRTIs)

Efavirenz is the most potent NNRTI available, preferred for initial treatment of people with HIV because it can be taken once daily.
Nevirapine is used in combo with two NRTIs.
Delaviridine is not recommended for most patients, has lower antiviral activity compared to others in this class.

Protease Inhibitors (PIs)

HIV protease is responsible for maturation of the virus.
Protease inhibitors bind to the active site of the enzyme and inhibit its activity, resulting in production of immature, non-infectious virus particles.
First PI introduced in 1995, ushered in a new era of HIV treatment.
Newer PIs like atazanavir are better tolerated and have improved pharmacokinetic properties.
Atazanavir and darunavir are the preferred PIs for treating HIV today.

Fusion and Entry Inhibitors

Enfuvirtide (Fuzeon, T-20):
- Large peptide that binds to HIV glycoprotein 41 and blocks fusion process.
- Not active when given orally, must be injected subcutaneously (sc) twice daily.
- Often causes injection site reactions (ISRs), so change the injection site.
Maraviroc (Selzentry):
- Newer drugs that inhibit fusion and entry of HIV.
- Active against HIV strains resistant to RTIs and PIs.
- Approved to treat HIV infection caused by drug-resistant strains.

Integrase Inhibitors

Integrase incorporates viral DNA formed by reverse transcriptase into DNA of CD4 cells.
Raltegravir (Isentress) is the first integrase strand inhibitor approved to treat HIV.
Works by preventing DNA strand transfer.
Potent in vitro activity against wild-type and MDR HIV strains.
Recent recommendations for initial treatment include a regimen containing raltegravir.

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Description

Antiviral drugs are used to treat viral infections such as HIV, influenza, and hepatitis. Learn about how they work and their effects on these diseases. Also, discover the impact of influenza as one of the most common causes of infectious diseases.