Antivirals Flashcards
The basic process of viral infection and virus replication occurs in 6 main steps
Adsorption - virus binds to the host cell.
Penetration - virus injects its genome into host cell.
Viral Genome Replication - viral genome replicates using the host’s cellular machinery.
Assembly - viral components and enzymes are produced and begin to assemble.
Maturation - viral components assemble and viruses fully develop.
Release - newly produced viruses are expelled from the host cell.
Acyclovir (Zovirax®)
Guanosine analog
Topical, oral, and IV
Treatment of choice for HSV Genital infections, HSV encephalitis, HSV infections in immunocompromised and pregnant patient
Anti-HSV/VZV (Herpes/Varicella/Zoster) agents
The analog inhibits viral DNA-polymerase
Only actively replicating viruses are inhibited
Poor bioavailabitiy
Acyclovir Mechanism of Action
Inhibition of viral synthesis of DNA
Competes with deoxyguanosine triphosphate for viral DNA polymerases
Acyclovir is thus selectively activated in cells infected with herpes virus.
Acyclovir (Zovirax®) Dosage
Varicella (chicken pox)/ zoster (shingles)
800mg PO 4-5x/day x 7days
Genital/mucocutaneous HSV
1st episode: 400mg PO 3-4x/day x 7-10 days
Recurrence: 400 mg PO TID X 5 days
Suppression: 400mg PO BID
Famciclovir (Famvir®)
Cyclic guanine analog
Converted to penciclovir in the liver and intestines
Penciclovir is used only topically whereas Famciclovir is only oral
Spectrum: HSV 1 and 2, VZV
Famciclovir MOA
The mechanism is similar to that of acyclovir;
however, famciclovir is converted to penciclovir triphosphate and compared to acyclovir triphosphate.
penciclovir triphosphate has a lower affinity for viral DNA polymerase but a longer intracellular half-life.
Valacyclovir (Valtrex®)
Valacyclovir is a prodrug of Acyclovir Rapidly and almost completely converted to acyclovir Same mechanism of action Same spectrum of activity Same mechanism of resistance Available orally only Advantage: better oral bioavailability More convenient dosing More pricey than Acyclovir
Valacyclovir (Valtrex®) Dosage
Zoster (shingles) 1000mg PO tid x 7days Genital/mucocutaneous HSV 1st episode: 1000mg PO bid x 7-10 days Recurrence: 500mg PO bid x 3-5 days Suppression: 1000mg PO qday
Ganciclovir (Cytovene®)
CMV retinitis in immunocompromised patient
Prevention of CMV disease in transplant patients
Ganciclovir MOA
Competes with deoxyguanosine triphosphate similar to acyclovir
However in CMV, viral-encoded phosphotransferase converts to ganciclovir triphosphate
Unlike acyclovir, ganciclovir contains a 3’-hydroxyl group, allowing for DNA to continue
Oseltamivir (Tamiflu®)
Oral neuraminidase inhibitor
Spectrum: Infuenza A and B in both children and adults, avian influenza, H5N1 disease
Adverse effects: NV, headache
Neuraminidase inhibitors : Oseltamivir / Zanamavir
Influenza contains an enzyme neuraminidase which is essential for the replication of the virus.
Neuraminidase inhibitors prevent the release of new virions and their spread from cell to cell.
Zanamivir (Relenza®)
Neuraminidase inhibitor
Given via inhalation
Spectrum: Uncomplicated influenza A and B, some strains of avian influenza
Adverse effects: nasal and throat discomfort, bronchospasm
Amantadine (Symmetrel®)Rimantadine (Flumadine®)
Not currently recommended in the US for influenza- too much resistance!
