Antivirals Flashcards
What are one of the biggest challenges with treating viruses?
Most drugs work best when the virus is replicating, however most symptoms don’t appear until the virus load has already peaked in the blood.
- viral latency integrated into genome, can’t target
- virus uses host cellular machinery, limited targets
What are the most important keys in using antivirals?
- unable to target latent infections
- all drugs are viralstatic, requires competent immune system
What are two drugs that are used to prevent Influenza A and B adsorption/penetration of cells?
- Amantadine
- Oseltamivir
What drug is used to prevent and treat Influenza A?
Amantadine - blocks uncoating by inhibiting M2 protein from lowering the pH in the vesicle.
(Becoming more resistant every year)
What is the key in administering Amantadine and Oseltamivir?
- Must be started within 48 hours of the illness to effectively reducing fever and duration of the illness by several days.
What antiviral can be used to prevent infection of Influenza A and B?
Oseltamivir - Prodrug
–used as prevention in children under the age of 1–
What are the common side effects of Amantadine and Oseltamivir?
Amantadine - CNS Effects - slurred speech, anxiety, confusion
Oseltamivir - n/v/d, bronchitis
What antiviral can be used to treat occular herpes simplex 1 and 2?
Trifluridine - Thymidine Analog, inhibits virus DNA synthesis
–OPHTHALMIC only. Too toxic for systemic.
What are unique enzymes encoded by herpes virus family?
- *- Thymidine Synthase -**
- DNA Polymerase
- Ribonucleotide Reductase
How does Acyclovir selectively target infected cells?
Herpes Virus encodes Thymidine Synthase, which phosphorylates Acyclovir activating it.
- Targets Viral DNA Polymerase, preventing chain elongation by becoming incorporated into DNA
What are the uses for different modes of administering Acyclovir?
IV use - systemic herpes simplex, HSV encepholitis
Oral use - primary genital herpes, recurrent HSV1
topical - primary genital herpes
–Overall, well tolerated with n/v/ and HA
How is Famciclovir different from Acyclovir?
Famciclovir has similar mechanism of activation and targeting DNA Polymerase, but has a higher bioavailability. Tolerated Well.
What is used for treating acute herpes zoster?
Famciclovir.
Also used for treatment and suppression of recurrent genital herpes.
What antiviral is used topically to prevent recurrent oral herpes simplex?
Penciclovir, same mechanism as Acyclovir
What kind of people should be concerned with CMV infection?
- HIV - 80% of the time = Retinitis
- Organ transplant patients
- Most common infection in both patient populations, depends on CD4+ count.
What drug is used to treat CMV retinitis in AIDs patient and prevention of CMV in transplant patients?
Ganciclovir
How does Ganciclovir work and what are the adverse effects?
Activated my CMV Kinase, works like Acyclovir
Adverse Effects: Bone Marrow Suppression - enhances suppression of Zidovudine
What drug would be used if a herpes virus is resistant to Acyclovir?
Foscarnet - mimics pyrophosphate binding CMV DNA Polymerase
Also used for CMV Retinitis
What is the most concerning adverse side effect of Foscarnet?
Renal Damange and electrolyte imbalances. (30-50% of pts)
What is the best CMV Retinitis treatment?
HIV Treatment to elevate CD4+ counts, Foscarnet and Ganciclovir only slow progression of the retinitis causing many side effects.
What drugs are approved for treating Hepatitis B?
Lamivudine - nucleoside analog - inhibits HBV Reverse transcriptase
Tenofovir - AMP analog, inhibiting HBV Reverse Transcriptase
What drug is phosphorylated in vivo to treat RSV and Hep C?
Ribavirin -
- interferes with viral mRNA synthesis
- inhibits GTP Synthesis
- Inhibits GTP-capping of mRNA
How is Ribavirin used to treat Hepatitis C?
Ribavirin is used in combination with interferon-alpha and Boceprevir
What is the risk associated with Ribavirin?
- aerosol can clog airways and tubings while treating RSV
- IV/PO versions can cause Bone Marrow Suppression
