Compare Famciclovir vs. Valacyclovir

Famciclovir (generic for the discontinued brand Famvir) and valacyclovir (Valtrex) are both antiviral medications used to treat infections caused by the herpes simplex virus and varicella-zoster virus, such as cold sores, genital herpes, and shingles. However, they differ in several ways. Famciclovir is converted in the body to penciclovir, while valacyclovir is converted to acyclovir. Famciclovir is typically taken as a single dose for cold sores and genital herpes, whereas valacyclovir requires multiple doses over a day or several days, depending on the condition. Valacyclovir is also approved for treating chickenpox in children, which is not an indication for famciclovir. Both medications are available as generics, but valacyclovir can be compounded into a liquid form for those who have trouble swallowing tablets. Common side effects for both include headache and nausea, but valacyclovir has additional risks like rare blood clotting problems and nervous system-related side effects, especially in older adults or those with kidney issues.