Famciclovir is a prescription antiviral medication used to treat HSV-1, including cold sores. It works by preventing the virus from multiplying, helping to reduce the duration and severity of outbreaks. For recurrent cold sores, a common dosing regimen is a single 1500 mg dose, taken at the first sign of symptoms. Like valacyclovir and acyclovir, it can also be used for suppressive therapy in frequent cases. Famciclovir is generally well tolerated and offers the convenience of a one-time treatment for outbreaks. While it doesn’t cure HSV-1, it effectively manages symptoms and may help prevent future flare-ups.