Acyclovir  is a guanosine analogue antiviral drug. It is one of the most commonly used antiviral drugs, that is primarily used for the treatment of herpes simplex virus infections, as well as in the treatment of varicella zoster (chickenpox) and herpes zoster (shingles).


Mechanism of action:

Acyclovir is converted by viral thymidine kinase to aciclovir monophosphate, which is then converted by host cell kinases to aciclovir triphosphate (ACV-TP). ACV-TP, in turn, competitively inhibits and inactivates HSV-specified DNA polymerase preventing further viral DNA synthesis without affecting the normal cellular processes


Acyclovir is poorly water soluble and has poor oral bioavailability  (15–30%), hence intravenous administration is necessary if high concentrations are required. When orally administered, peak plasma concentration occurs after 1–2 hours. Aciclovir has a high distribution rate; protein binding is reported to range from 9 to 33%.The elimination half -life  (t1/2) of acyclovir depends according to age group; neonates have a t1/2 of 4 hours, children 1–12 years have a t1/2 of 2–3 hours whereas adults have a t1/2 of 3 hours.

Medical Uses:

Acyclovir is used for the treatment of herpes simplex virus and varicella zoster virus infections, including:

  • Genital herpes simplex  (treatment and prevention)
  • Herpes simplex labialis (cold sores)
  • Shingles
  • Acute chickenpox  in immunocompromised patients
  • Herpes simplex encephalitis
  • Acute mucocutaneous HSV infections in immunocompromised patients
  • Herpes of the eye and herpes simplex blepharitis (a chronic (long-term) form of herpes eye infection)
  • Prevention of herpes viruses in immunocompromised people (such as people undergoing cancer chemotherapy)

Common adverse drug reactions include: nausea, vomiting, diarrhoea, encephalopathy, and headache.