Even if you rarely get cold sores, the condition can feel stressful. You never know how large they’ll get, how long they’ll stay or how visible they’ll become.
Some over-the-counter (OTC) remedies such as ointments and creams may knock cold sores out. But what if you’ve tried that route with little success?
That’s when you may want to pivot to valacyclovir, brand name Valtrex®. It’s a prescription antiviral medication used to treat the cause of cold sores — the herpes simplex virus — as well as shingles and chickenpox. (Did you know that you may be able to save on medications such as Valtrex using the free Optum Perks prescription discount card?)
Valtrex isn’t a cure, and it can’t stop you from getting cold sores in the future. But it can slow the growth of the virus enough to help your sores heal faster and shorten the duration of a flare-up. It can also decrease itching and pain.
But how effective is this pill, really? To find out, we asked pharmacists to share everything they wished their patients knew.
Related reading: 6 common myths about cold sores.

What makes Valtrex unique?
In addition to Valtrex, there are 2 other antiviral medications that are used for cold sores: acyclovir (Zovirax®) and famciclovir (Famvir®). All 3 have been shown to be more effective at treating cold sores than OTC creams or ointments, says Beth Bryan, PharmD. She’s a pharmacist and the owner of Surgoinsville Pharmacy in Surgoinsville, Tennessee.
That said, Valtrex is often the first choice because it has better bioavailability, says Daniel Breisch, PharmD. He’s a pharmacist at Mountain View Pharmacy in Bountiful, Utah. “That means you can take less of the drug and have superior outcomes,” he says.
When and how much do you take?
Because Valtrex is a prescription, your dosage will depend on what your doctor decides is best for you. But most people take 2,000 milligrams twice a day, starting at the very first sign of a cold sore, Breisch says. (Compare that to a typical dosage of Zovirax, which is often taken 5 times a day.) If you get cold sores often, you’ll recognize the early “tingling” stage, when a sore is starting to form.
Even if you don’t catch the infection right away, Valtrex is still highly effective if you begin taking it within 48 hours of an outbreak, Bryan says.