6/11- Antiviral Therapy Flashcards
Options for the Control of Viral Infections (broad)?
- Antivirals
- Isolation/quarantine (depends on pathogenesis and transmission route)
- Immunization (active; passive*)
- Immunomodulators
- Other: drug/alcohol use, physical activity, risky behaviors…
* e.g. Hep B in babies born to chronic Hep B mothers given Hep B Ig
Potential targets for antiviral agents?
- Adsorption
- Penetration
- Uncoating
- Early transcription
- Early translation
- Genome replication
- Late transcription
- Late translation
- Assembly
- Release
Want to target unique viral functions (limits toxicity)
What is key for the treatment of acute viral infections?
Early initiation of therapy (similar to Abx)
What are the most common causes of viral respiratory infections?
- Influenza
- RSV
Disease course of influenza?
Typical treatment?
What are some complications of influenza?
(Outbreaks each year)
Course of disease:
- Uncomplicated influenza typ gets better w/ or w/out treatment (symptomatic treatment- rest, OTC meds, fluids)
Complications:
- Bacterial infections
- Viral pneumonia
Treatment for influenza (1 method…oldish)? Mechanism?
Route?
Indications?
Resistance?
Amantidine and Ramantidine (trycyclic amines)
(not used anymore)
- Mechanism: interferes with uncoating
- Indications: prevention and treatment of influenza A virus infections
- Resistance: associated with mutations in the M2 protein (why these aren’t used so much)
**not effective for Influenza B
How many strains of influenza circulate in a year?
Three:
- A (H1N1)
- A (H3N2)
- B
Efficacy of amantadine/rimantidine for influenza?
- Drugs decreased fever and virus shedding
- More rapid improvement in symptoms and activity levels
What other drugs (not targeting uncoating) can be used to treat Influenza?
- Mechanism:
- Route:
- Adverse effects:
- Indications:
- Neuraminidase inhibitors (sialic acid analogs)
- Mechanism: inhibit viral neuraminidase
- Route: oral (oseltamivir) or inhaled (zanamivir)
- Adverse effects: nausea/vomiting with oral oseltamivir; bronchospasm with inahled zanamivir
- Indications: Influenze A AND B infections (treatment and prophylaxis)
Which are preferred for the routine prevention of influenza: vaccines or antivirals?
Vaccines!
Which strains of influenza are resistant to Amantadine? (those that inhibit uncoating)
Alternative?
- A: H3N2
- A: H1N1
Alternatively use Oseltamivir or Zanamivir
Those at high risk for influenza complications?
- Children < 2 or adults > 65
- Chronic pulmonary (asthma), cardiovascular (not just HTN), renal, hepatic, hematological (sickle cell), metabolic (DM), or neurologic/neurodevelopment conditions
- Immunosuppression
- Pregnant/postpartum women (within 2 wks)
- < 19 and receiving long-term aspirin
- American Indians/Alaskan natives
- Morbidly obese (BMI > 40)
- Residents of nursing homes and other chronic-care facilities
What is Tamiflu?
Oseltamivir
What is Ribavirin?
- Mechanism
- Route
- Adverse effects
- FDA Indications
- Uses
Guanosine analog
- Mechanism: multifactorial; alters nucleotide pools and mRNA formation
- Route: aerosol (RSV), oral (HCV), IV
_- Adverse effect_s: anemia, bronchospasm, teratogenic and mutagenic
- FDA Indications:
—-Severe RSV dz in infants
—-Chronic HCV (with PEG-IFN)
(also Lassa fever and Hantavirus infections)
Treatment for bronchiolitis: allowed earlier termination of ventilation
What are some common herpes viruses to consider?
- Herpes simplex
- Varicella-zoster
- CMV
What can be used to treat herpes viruses?
Acyclovir (guanasine analog; anti-viral)
What is acyclovir?
- Mechanism
- Route
- Adverse effects
- Indications
Guanosine analog (anti-viral)
- Mechanism: inhibits VIRAL TK, DNA pol; results in DNA chain termination
- Route: oral, IV, and topical form
- Adverse effects: phlebitis, headache, nausea, CNS toxicity, and crystalluria
Indications:
- Genital, perinatal, and CNS HSV
- Varicella and zoster
- HSV infections in immunocompromised hosts
What is one of the worst complications of HSV?
What can be used to prevent this?
HSV Encephalitis
(high morbidity/mortality rate)
Acyclovir
- Better results than older methods for all Glasgow levels
- Should start IV acyclovir for anyone who presents with altered mental status who may have HSV encephalitis until diagnostics come back
Who should be treated for Varicella?
- Immunocompromised
- Possibly pregnant women
- Adolescents and adults
- Patients at high risk for complications
(Acyclovir for normal toddlers and children under 10 is efficacious but often not necessary)
What are some “off-label” uses of acyclovir?
Herpes simplex viruses:
- Gingivostomatitis
- Cold sores (penciclovir)
- Whitlow
- Ocular infections*
- Proctitis
- Eythema multiforme
*topical therapy is approved for use; other drugs available
Varicella-zoster virus
- Pneumonia
- Encephalitis
How do famciclovir and valacyclovir differ from acyclovir?
They are prodrugs and have greater oral bioavailability than acyclovir
What are famciclovir and valaciclovir used for?
Treatment of shingles
Suppression of genital HSV
Valacyclovir: primary genital HSV
Famciclovir: mucocutaneous HSV in immunocompromised
What is a drawback of acyclovir? Which form?
If given orally, have to take many times a day (poor compliance)
Valacyclovir has been associated with what in certain types of patients? Which patients?
TTP/HUS (hemolytic uremic syndrome)
- Pts with advanced HIV infection
- Bone marrow and renal transplant recipients
What drugs can be used to treat/suppress CMV infections? Routes of administration?
- Ganciclovir (IV)
- Valganciclovir (PO)
- Cidofovir (IV)
- Foscarnet (IV)