Since aciclovir works by decreasing the production of the virus's DNA, one might fear that it also damages DNA of healthy cells. I know that it is usually said that aciclovir doesn't affect healthy cells, but I heared recently rumors that there might be a longterm negative effects on the DNA of the patient.

So my question is the following:

  • Are there any scientific studies which evaluated the longterm effects on DNA of aciclovir and what are the results.
  • What are the mechanisms which ensure that it indeed doesn't affect healthy cells?
  • 2
    Can you link to the source that says aciclovir can damage human DNA?
    – Jan
    Aug 2, 2019 at 13:17
  • @Jan - The OP said "one might fear" indicating that it is a hypothesis rather than from a reputable source. However, prior research info is needed regarding the rumours of "long term negative effects on the DNA of the patient". Aug 4, 2019 at 11:17
  • Welcome to MedicalSciences.SE! Please take the tour and read the help center. For reasons mentioned in this post and in How to Ask, we require prior research information when asking questions. Please help us to help you and edit your question to provide more information on what you have read on this subject, and any problems you are having understanding your research. This helps to provide an answer which will be more helpful. If you found nothing, what did you Google? Aug 4, 2019 at 11:20

1 Answer 1


Aciclovir is a prodrug, which means that it has to be converted to an active form before having its desired effect.

It is converted to this active form (aciclovir triphosphate) by a process called phosphorylation. This process requires an enzyme called herpes simplex virus (HSV) thymidine kinase, which competes for endogenous deoxyguanosine triphosphate and acts as a chain terminator in the synthesis of viral DNA. Source: Science Direct

This enzyme is not present in humans, so the conversion does not occur. In viruses, it interferes with DNA synthesis to reduce viral replication.

Incidentally, viral resistance to the drug is due to a mutation in the thymidine kinase enzyme.

There have been studies demonstrating the safety of aciclovir. Here is an example demonstrating safety over a five-year period in the suppression of genital herpes.

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