Aciclovir (ACV), also known as acyclovir and acycloguanosine, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include prevention of cytomegalovirus infections following transplant and infections due to Epstein-Barr virus. It is available by mouth and intravenously.
The discovery of aciclovir was announced in 1977. It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.It is available as a generic medication and is marketed under many brand names worldwide.

Aciclovir 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)

Acyclovir is an antiviral drug. It slows the growth and spread of the  in the body. Acyclovir will not cure herpes, but it can lessen the symptoms of the infection.
Acyclovir may also be used for other purposes not listed in this medication guide.