Antivirals-acyclovir

Question 1

What are common indications?

Answer 1

1. acute episodes of herpesvirus (cold sores, genital ulcers, encephalitis)
   Varicella -zoster (chicken Pox and shingles)
2. Suppression of recurrent HSV attacks where these are occurring at a frequency of 6 or more a year.

Question 2

What does the Herpes virus family include?

Answer 2

HSV 1
HSV 2
varicella zoster

Question 3

What is the mechanism of action?

Answer 3

It enters infected cells and inhibits the herpes-specific DNA polymerase (enzyme needed for replication), stopping further viral DNA synthesis and replication

Question 4

What are common adverse effects of aciclovir?

Answer 4

Headache
dizziness
GI upset
skin rash

IV-
Inflammation or phlebitis at site of injection

Question 5

What are potential side effects of high dose IV acyclovir?

How can you prevent it from occurring?

Answer 5

As aciclovir is very water soluble

Delivery of high concentration of acyclovir into the renal tubules can cause precipitation

Leading to crystal induced acute renal failure

The risk of this can be reduced by slowing rate of infusion (over at least 1 hour) and good hydration.

Question 6

Who should be prescribed with caution/avoided?

Answer 6

Caution in breastfeeding and pregnant women

Dose/ frequency adjustment needed for severe renal failure ( excreted by kidneys dose) to prevent accumulation

Question 7

Why will acyclovir likely be given even though it may not be safe?

Answer 7

As infections such as viral encephalitis, varicella pneumonia, and genital herpes carry significant risk of mother and foetus, so the benefits of treatment.

Question 8

What are important interactions?

Answer 8

acyclovir can increase concentration of theophylline and aminophylline, increasing risk of adverse effects.

Renal function monitored (risk of crystal-induced renal failure)

Question 9

What are dosages?

Answer 9

Oral/genital herpes=
200mg five times a day

Recurrent infection=
400mg orally 12 hrly may be given

Herpes simplex encephalitis= 10mg/kg IV 8 hours for 14-21 days

Started immediately then stopped if CSF shows no signs of HSV

Question 10

Does acyclovir remove the virus from the body?

Answer 10

Not completely so risk of recurrence remains

But episodes of cold sore and genital infections may be less frequent

Question 11

What are self care options for herpetic lesions?

Answer 11

including keeping hydrated by using barrier preparations,

topical anaesthetics,
oral paracetamol, and/or NSAIDs to reduce pain.

risk of transmission to others and auto-inoculation of the eye when using contact lenses.

This is minimised by washing hands with soap and water after touching lesions, and avoiding kissing and sex until the lesions have healed.