Valacyclovir
herpes simplex, mucocutaneous/immunocompromised host
"It's well worth it to ask your doctor to prescribe 1gm daily Valtrex for recurring cold sores.  You can easily take from your daily prescribed to help immediately when you notice a cold sore start by then taking 1gm 3 times in 24 hours.  The prescription for 3 pills costs the same as 30 days so I recommend to talk to your doctor."