Acyclovir: (Brand name: Zovirax) One of a group of antiviral drugs that acts against the herpes viruses, including:

• Herpes simplex 1 which causes cold sores
• Herpes simplex 2 which causes genital herpes
• Varicella-zoster which causes both chickenpox and shingles
• Epstein-Barr virus which causes infectious mononucleosis

Acyclovir inhibits the replication of viral DNA needed to reproduce itself. Virally infected cells absorb more acyclovir than normal cells and convert more of it to an active form which prolongs its antiviral activity where it is most needed. Acyclovir may reduce the severity and duration of a shingles attack if given soon after the onset of symptoms.

For more information, see: Acyclovir.