Questions and Answers
What is the primary means of preventing influenza?
What is the enzyme that neuraminidase inhibitors target in influenza A and B viruses?
What is the benefit of starting neuraminidase inhibitor therapy as early as possible for patients with confirmed or suspected influenza?
What is the role of neuraminidase in the life cycle of influenza viruses?
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What is the effect of neuraminidase on the respiratory tract mucous?
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When are neuraminidase inhibitors most beneficial in reducing symptom severity and duration of illness?
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What type of patient should receive neuraminidase inhibitor therapy?
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What is the effect of neuraminidase inhibitors on the complications of influenza?
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What is the unique mechanism of action of Baloxavir Marboxil (Xofluza)?
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What is the primary reason the CDC recommended against prophylaxis for influenza?
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What is the main advantage of valacyclovir over acyclovir?
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Which of the following is NOT a nucleoside analogue used to treat herpesvirus infections?
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What is the main benefit of using antiviral medications to treat genital herpes?
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Which medication has the greatest bioavailability for treating herpesvirus infections?
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What is the primary indication for using Baloxavir Marboxil (Xofluza)?
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What is the benefit of the Zostavaz vaccine for older adults?
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What is the primary mechanism of action of NRTIs in the treatment of HIV?
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What is the benefit of using HAART in the treatment of HIV infection?
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What enzyme is responsible for cleaving polyproteins into smaller functional proteins during viral maturation?
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What is the result of the incorporation of viral DNA into the host genome?
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What is the primary mechanism of action of PIs in the treatment of HIV?
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What is the goal of recent developments in HAART regimens?
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What is the function of reverse transcriptase in the replication of HIV?
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What is the result of the entry of HIV into CD4 cells?
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What is the primary mechanism of action of enfuvirtide?
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Which of the following statements about non-nucleoside reverse transcriptase inhibitors (NNRTIs) is TRUE?
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What is the benefit of using maraviroc in HIV treatment?
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What is the mechanism of action of raltegravir?
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Which of the following is a unique characteristic of efavirenz?
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What is the main mechanism of action of protease inhibitors (PIs)?
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What is the advantage of using a regimen containing raltegravir for initial HIV treatment?
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Which of the following is a characteristic of atazanavir and darunavir?
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What is the primary indication for using enfuvirtide?
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What is the route of administration for enfuvirtide?
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What is the role of ritonavir in boosted therapy?
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What is a common side effect of enfuvirtide?
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What is the common adverse effect of nevirapine?
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Why is efavirenz avoided in pregnancy?
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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 unique characteristic of HIV protease?
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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 (e.g., HIV, influenza, and hepatitis)
- Antiviral drugs work in a variety of ways (e.g., prevent replication of viral nucleic acid; inhibit entry, uncoating, or release of virus)
Influenza
- 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, can shorten duration of illness in infected persons and prevent complications
Neuraminidase Inhibitors
- Reduce complications including otitis media (OM) and pneumonia (PNA)
- Drug therapy should be started as early as possible for any patient with confirmed or suspected influenza who is hospitalized, has severe illness, or is at higher risk of complications
- Most beneficial in reducing symptom severity and duration of illness if given < 3 days after 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
Prophylaxis
- 70-90% effective in preventing influenza, useful adjuncts to vaccines
- CDC recommended against prophylaxis because of risk of resistance
- Only prophylaxis, populations at risk of complications and control institutional outbreaks
Baloxavir Marboxil (Xofluza)
- Single dose PO treatment for influenza A and B
- First-in-class medication
- Unique mechanism of action (MOA) targets ribonuclease activity that affects transcription of viral RNA
- Approved in the US in 2018
- Potentially less side effects vs oseltamivir
Herpesviruses
- Cytomegalovirus (CMV) infections in immunocompetent are usually asymptomatic
- CMV retinitis, esophagitis, and colitis usually seen in immunocompromised patients
Drugs for Herpesviruses
- Nucleoside analogues:
- Acyclovir (Zovirax): IV acyclovir 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
- Ganciclovir (Cytovene)
- Trifluridine (Viroptic)
- Valacyclovir (Valtrex): prodrug that gets rapidly converted to acyclovir by intestinal and hepatic enzymes, more completely absorbed (55%)
- Famciclovir (Famvir): has the greatest bioavailability (80%)
- Other drugs:
- Foscarnet (Foscavir)
Treating Genital Herpes
- When given orally for genital herpes, prevents replication of HSV and reduces pain and other symptoms of acute infection
- Shortens time to healing of lesions, reduces the amount of viral shedding
- Does not eliminate the virus, recurrent episodes are common (can be treated with lesser doses)
Treating Shingles
- When given orally for shingles, shortens duration of acute illness and pain and lowers incidence of postherpetic pain
- Famciclovir and valacyclovir are more effective than acyclovir
- Newer drugs have less frequent administration, higher serum levels
- A vaccine is now available (Zostavaz) that reduces the incidence and severity of herpes zoster infections in older adults
Human Immunodeficiency Virus (HIV)
- Many remarkable advancements have been made in treating HIV infection and AIDS
- Combined use of 2 or more drugs from different classes have been shown to markedly reduce viral load and improve survival
- Multidrug treatment called highly active antiretroviral therapy (HAART)
HAART
- Initially were complicated regimens requiring multiple doses of several drugs every day
- Recent emphasis on developing drug regimens that require only a few doses each day or even a single pill (like Atripla)
- Guidelines continue to evolve as new regimens are developed and testing
Pathophysiology of HIV
- Enters CD4 cells, viral RNA produced double-stranded DNA via reverse transcriptase
- Viral DNA enters host cell nucleus and gets incorporated into host genome via HIV integrase
- Eventually, the viral DNA gets transcribed/translated to produce polyproteins that get packed into immature virions
- HIV protease cleaves polyproteins into smaller functional proteins during viral maturation where virions get released into plasma
Drug Classes
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- Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)
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- Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
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- Protease inhibitors (PIs)
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- Fusion and entry inhibitors
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- Integrase inhibitors
Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
- Do not require metabolic activation and are not incorporated into viral DNA
- Efavirenz is the most potent NNRTI available, preferred for initial treatment of people with HIV because it can be taken qd
- Nevirapine is used in combo with two NRTIs
- Delaviridine, 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 sq bid
- 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
This quiz covers the basics of antiviral drugs, including their mechanism of action and effectiveness against various viral infections such as HIV, influenza, and hepatitis.