|Short description Overview Acyclovir is an antiviral medicine. It is used to treat infections caused by the herpes viruses. Common infections treated include shingles, genital herpes, chicken pox and cold sores. The drug works by slowing the growth and the spread of the herpes virus. All in all, this drug does not cure herpes. It works by lessening the symptoms.   It is also important to note that this drug will not treat such viral infections as common cold or flu. Acyclovir may also be prescribed to treat other conditions not mentioned in this guide.