Antivirals Flashcards
Describe the mechanism of action of guanine analogues
Once activated by phosphorylation, they inhibit the viral DNA polymerase enzyme, preventing synthesis + gets incorporated into growing DNA chain, terminating the chain
Common ADRs of guanine analogues?
Headache, vomiting, diarrhoea
Famiciclovir dose for cold sores?
1500mg stat. Single dose.
Shingles = 500mg tds for 7 days
Genital herpes = 250mg tds for 10 days
When to reduce the dose of famciclovir?
In renal impairment (reduction depends on degree of impairment) and in immunocompromised patients
Which 3 main viruses are guanine analogues active against?
Herpes simplex type 1 (HSV1)
Herpes simplex type 2 (HSV2)
Varicella zoster virus (VZV)
All are DNA viruses
Why do you need to drink lots of water when taking aciclovir or Valaciclovir?
To prevent crystallisation (kidney stones)
Potential rare side effects of aciclovir and valaciclovir?
Neurotoxic effects like hallucinations, confusion, dizziness, etc
Dose for aciclovir for cold sores?
Cream.
Apply the 5% cream 5 times a day (every 4 hours) for 7 days
S3 product
Compare the dose of aciclovir for shingles vs genital herpes
Genital herpes = 400mg tds for 10 days
Shingles = 800mg 5 times a day for 7 days
How to take a med 5 times a day?
Every 4 hours
Causative virus for shingles?
Varicella zoster
First line choice for shingles?
Valaciclovir
Dose for Valaciclovir in shingles?
1g tds for 7 days
True or false: Valaciclovir is the prodrug of famaciclovir
False. It’s the prodrug of aciclovir
Genital herpes dose for Valaciclovir?
500mg bd for 10 days
