Zovirax is an antiviral medication available in tablet form with strengths of 200mg, 400mg, and 800mg. Its active ingredient, Aciclovir, effectively treats infections caused by the herpes simplex virus, including cold sores, genital herpes, chickenpox (varicella), and shingles (herpes zoster). Zovirax tablets are also marketed under various names including Herpikind, Herpex, Herperax, Acylovir, and Acivir.