Questions and Answers
What is the recommended population for prophylaxis against influenza?
What is the unique mechanism of action of Baloxavir Marboxil?
What is the most effective treatment for serious herpesvirus infections?
What is the advantage of valacyclovir over acyclovir?
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What is the benefit of treating genital herpes with acyclovir, valacyclovir, or famciclovir?
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What is the benefit of treating shingles with famciclovir and valacyclovir?
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What is the bioavailability of acyclovir?
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What is the primary role of vaccines in preventing influenza?
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What is the name of the vaccine available for herpes zoster infections in older adults?
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What is the main function of neuraminidase in influenza A and B viruses?
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What is the benefit of starting neuraminidase inhibitors within 48 hours of onset of influenza symptoms?
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Why are antibacterial and antifungal drugs ineffective against viral infections?
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What is the primary target of neuraminidase inhibitors in the treatment of influenza?
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What is the benefit of neuraminidase inhibitors in the treatment of influenza?
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When is it most beneficial to administer neuraminidase inhibitors in the treatment of influenza?
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What is the mechanism of action of neuraminidase inhibitors in the treatment of influenza?
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Which of the following NRTIs is classified as a nucleotide RTI?
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What is the main mechanism of action of NRTIs?
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Which of the following NRTIs is associated with bone marrow suppression, anemia, and neutropenia?
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What is the recommended therapy for preventing in utero transmission of HIV?
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Which of the following is a common adverse effect of all NRTIs?
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What is the recommended initial treatment of HIV?
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Which of the following is a once-daily, single-pill regimen for HIV treatment?
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Why are NRTIs often more effective when combined with other NRTIs?
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Which of the following statements about Non-nucleoside RTIs (NNRTIs) is true?
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What is the primary mechanism of action of Protease inhibitors (PIs)?
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Which of the following NNRTIs has the lowest antiviral activity?
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What is the main reason for avoiding Efavirenz in pregnancy and women who can become pregnant?
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What is the role of Ritonavir in boosted therapy?
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Which of the following is a common side effect of NNRTIs?
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What is the current preferred PI for treating HIV?
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When was the first PI introduced?
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What is the main mechanism of action of enfuvirtide?
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What is a common side effect of enfuvirtide injection?
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What is the main advantage of maraviroc over other HIV therapies?
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What is the result of integrase inhibitors on HIV replication?
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What is the name of the combo drug product containing ritonavir and another PI?
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What is the role of integrase in HIV replication?
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What is the effect of maraviroc and other fusion and entry inhibitors on HIV infection?
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What is a recent recommendation for initial treatment of HIV infection?
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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.
- Acyclovir (Zovirax):
- 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.