Penciclovir
"Best cold sore product available. I've been getting cold sores for years and each outbreak usually puts me in hiding for at least a week. Denavir usually keeps it from forming into breakouts and cuts breakout times by 2/3s. 

Coupons are available on the company's product site to help defray the substantial costs for the medicine. As someone who has suffered breakouts for years, I'd recommend this product at any price. But it's nice to have a coupon to make it more affordable."