Medically reviewed by Mary Lucas, RN
Written by Our Editorial Team
Last updated 4/26/2020
Valacyclovir (commonly sold as Valtrex) is one of the most widely used and effective drugs on the market for treating and controlling cold sores, shingles and genital herpes.
While valacyclovir isn’t a cure for herpes, it can help to treat the physical symptoms of HSV-1 and HSV-2. Valacyclovir is also commonly prescribed for chickenpox, which is caused by the varicella zoster virus (VZV).
The amount of time required for valacyclovir to start working can vary based on a number of factors, ranging from the type of infection you have to your valacyclovir dosage and the total amount of time that passes after you notice symptoms but before you start treatment.
In this guide, we’ll look at some of the most common situations in which you’d use valacyclovir for treatment, as well as the approximate amount of time it should take for valacyclovir to offer relief.
>>MORE: How to get rid of a cold sore quickly.
For first-time herpes outbreaks, valacyclovir is most effective when it’s used within 48 hours of symptoms appearing. Once valacyclovir has converted into acyclovir, it has a half-life of 2.5 to 3.3 hours in people with normal renal function. Meaning Valacyclovir stay in your system from 2.5 to 3.3 hours for normal people.
The standard dosage of valacyclovir for first-time herpes outbreaks is 1,000 mg two times per day over a period of 10 days. Valacyclovir usually starts treating herpes symptoms as soon as it’s in your system, but can take several days to produce a noticeable improvement.
It can take up to 10 days (or, in some cases, even longer) for herpes blisters to heal even with valacyclovir treatment. This makes it important to start treatment as soon as you notice herpes symptoms.
In some cases, your doctor might prescribe valacyclovir for a longer period than 10 days or at a different dosage. In this case, follow your doctor’s instructions and make sure you complete the full course of the medication, even if the herpes blisters heal before the end of the period.
Herpes can remain dormant in the body for weeks, months or years in between outbreaks. On average, people with HSV-1 experience about one outbreak per year, while people with HSV-2 will usually experience four to five outbreaks per year.
When these outbreaks occur, valacyclovir can provide fast and effective relief, helping to control herpes outbreak symptoms.
The typical valacyclovir dosage for recurrent herpes outbreaks is 500 mg two times per day over a period of three days. Like with first-time herpes outbreaks, valacyclovir is most effective when it’s taken as soon as you notice a herpes outbreak developing.
When taken as soon as you notice a herpes outbreak, valacyclovir can provide relief in as little as two to three days, minimizing symptoms and reducing the risk of you passing genital herpes to sexual partners.
>>MORE: HSV 1 vs. HSV 2 - What's the difference?
Valacyclovir is usually prescribed for seven days for shingles, with a typical dosage of 1,000 mg three times per day.
Just like with HSV-1 and HSV-2, it’s important to start treatment as soon as you notice shingles symptoms. Most experts recommend starting valacyclovir within 72 hours of noticing symptoms for the best results.
For cold sores, valacyclovir or valtrex is usually taken in two large doses of 2,000 mg, split 12 hours apart from each other. Like with other outbreaks of HSV, valacyclovir will speed up the speed at which cold sores heal, but it can still take seven to 10 days for them to fully disappear.
From cold sores to genital herpes, acting quickly helps you treat and control a herpes outbreak in the shortest amount of time. For this reason, most doctors recommend using valacyclovir in the first 24-72 hours after noticing a cold sore or other herpes blister developing.
If you’ve noticed a cold sore or any of the other symptoms of a herpes outbreak, it’s best to talk to your doctor about treatment and relief options as soon as possible.
>>MORE: Is valacyclovir your best option? Read about others here.