Anti Herpes/Zoster

Question 1

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents

Answer 1

Acyclovir
Valacyclovir
Famciclovir

Primarily used in
HSV- herpes simplex virus
VZV- varicella-zoster virus
Active against some others

Acyclovir poorly absorbed orally; must be given up to five times a day

Valacyclovir and famciclovir are pro drugs with better absorption; can be given less frequently

Only acyclovir can be given IV
Agent of choice for serious HSV infections (like encephalitis)

Question 2

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents MOA

Answer 2

Nucleoside analogs; after phosphorylation are incorporated into the elongated viral DNA strand just like cellular nucleotides; lack the functional group that allows the next nucleotide to be added- halts replication

Question 3

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents Spectrum

Answer 3

Good
HSV 1 and 2

Moderate
VZV

Poor
Epstein-Barr (EBV)
Cytomegalovirus (CMV)
HIV

Question 4

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents Adverse Effects

Answer 4

Generally well tolerated with few effects

Most concerning is nephrotoxicity through either crystallization or AIN (most commonly associated with IV acyclovir in higher doses)
Crystallization is preventable (hydration and correct dosing in renally impaired)

CNS effects can occur- seizures, tremors, or others

Most common- nausea, diarrhea, rash

Thrombotic thrombocytopenic purpura has been reported with valacyclovir in HIV patients

Question 5

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents Important Facts

Answer 5

Valacyclovir pro drug- improved bioavailability and less frequent dosing
Higher cost

Famciclovir is pro drug of penciclovir (pen only available topically)

Acyclovir dose varies widely by indication and host status

Acyclovir is most nephrotoxic in combo with diuretics or other nephrotoxins
Keep patients hydrated (especially if on higher IV doses)

Question 6

Anti-Herpes Simplex Virus and Varicella-Zoster Virus Agents Good For

Answer 6

Acyclovir drug of choice for severe or difficult to treat HSV infections (like encephalitis or severe HSV outbreaks among HIV patients)

Any of the agents can be used for HSV2 infections (genital herpes), to prevent outbreaks or decrease symptom duration

All effective in VZV infection