Used primarily as an antiviral agent, particularly in the treatment of herpes simplex virus (HSV) infections. It is effective in reducing the duration and severity of symptoms associated with cold sores and genital herpes. Penciclovir works by inhibiting viral DNA replication, thereby limiting the spread of the virus within the body. It is commonly formulated in topical creams for localized application, allowing for targeted treatment with minimal systemic absorption. Due to its mechanism of action and safety profile, it is also explored for use in other herpesvirus-related conditions.