How long does it take valacyclovir to work?

In this article:

• How long does valacyclovir take to work?
• What can affect how long it takes valacyclovir to work?
• Tips for administration
• Who should avoid taking valacyclovir?
• The bottom line

In this article

• How long does valacyclovir take to work?
• What can affect how long it takes valacyclovir to work?
• Tips for administration
• Who should avoid taking valacyclovir?
• The bottom line

Valacyclovir, sold under the brand name Valtrex, is an antiviral medication that is approved to treat viral infections, including herpes simplex virus (genital and cold sores) and varicella-zoster virus, which can cause chickenpox and shingles.

 People who take valacyclovir may wonder: How long does it take for valacyclovir to work? Thankfully, valacyclovir works fairly quickly once you take it. “Valacyclovir typically begins to take effect within 2-3 days, sometimes sooner, after the first dose,” says Soma Mandal, MD, an internist at Summit Health.

 Here, we’ll go over everything you need to know about how long it takes valacyclovir to work, including factors that affect how long it takes, proper dosing of valacyclovir, and if there are certain situations where you should not take valacyclovir.

How long does valacyclovir take to work? 

If you are dealing with a herpes outbreak, chickenpox, or shingles, you want relief as soon as possible. The good news is that valacyclovir provides fairly quick relief from symptoms.

 So, how fast does valacyclovir work, exactly? “Within one to two hours of taking the first dose, valacyclovir is already working to shorten the course of your infection,” says Jacob Siegel, MD, assistant professor in Dermatology at Yale School of Medicine. “While you will not feel it working, you will know it helps when you start to notice lesions crusting over and healing more quickly.”

 Raman Madan, MD, chief of dermatology at Glen Cove Hospital, concurs. While valacyclovir is absorbed quickly and starts to work within hours of taking it, he says you may not notice results for a few days, noting that the sooner you take your first dose, the more effectively it will work. “It is best used within 72 hours of symptom onset,” he says.

Signs that valacyclovir is working

How might you know that the medication has started to work? “You can tell it’s working if you notice less pain, itching, and fewer sores,” says Raj Dasgupta, MD, a quadruple board-certified physician specializing in internal medicine, pulmonology, critical care, and sleep medicine, and reviewer at the National Council on Aging. “The medication has fully kicked in when your symptoms are mostly gone, which typically happens within a few days, but it might take longer for some people.”

 Most people can tell valacyclovir is starting to work when they observe a reduction in the severity and duration of their symptoms, Dr. Mandel says. “For example, in the case of HSV, there should be less pain, itching, and a reduction in the number of skin lesions,” she describes. “With shingles, people often notice a decrease in the intensity of pain and the size of the rash.” Dr. Mandel adds that full resolution of your symptoms and full healing of any rashes or skin lesions indicate the full effectiveness of valacyclovir.

What can affect how long it takes valacyclovir to work?

How fast valacyclovir works can depend on:

• When you take the first dose: Sooner is better, ideally within 72 hours of symptom onset
• Following the instructions exactly as prescribed
• Your immune system health: People with weaker immune systems may respond more slowly
• Kidney function: Impaired kidneys can affect how the drug is processed

Valacyclovir can be taken with or without food, but staying well-hydrated can help your body process the medication more safely and effectively.

Tips for administration

It is important to take valacyclovir exactly as prescribed. Doing so ensures the medication works safely and properly. The typical dose of valacyclovir for adults depends on the condition being treated and is as follows:

• Cold sores: Take 2000 mg two times a day for one day, 12 hours apart
• Genital herpes initial episode: Take 1000 mg two times a day for 10 days
• Genital herpes recurrence: 500 mg two times a day for three days
• Herpes zoster (shingles): 1000 mg three times daily for seven days

You can take the medication with or without food. But it’s important to drink lots of fluids during valacyclovir treatment. This is because valacyclovir can cause kidney problems, and the risk of kidney problems is higher if you aren’t well hydrated. 

If a dose is missed, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and take your next dose at your regularly scheduled time. You should not take two doses at the same time to make up for a missed dose. If you have questions about what to do after a missed dose, talk to your healthcare professional for medical advice. 

Who should avoid taking valacyclovir?

 Valacyclovir is well-tolerated by most people. “In general, valacyclovir is considered to be a safe medication,” says Dr. Soma Mandal, MD, an internist at Summit Health. Your dose may have to be adjusted if you have certain medical conditions like kidney impairment, she says. “If you have a known allergy to valacyclovir or acyclovir, then you should not take this medication,” she warns.

 Dr. Siegel agrees that valacyclovir is typically safe and has tolerable side effects. Still, he advises people to speak to their healthcare provider about any factors in their health that may put them at risk of serious side effects. According to Dr. Siegel, some of these risk factors include:

• Taking higher doses of the medication
• Older age
• History of kidney disease
• Hypertension (high blood pressure)
• Diabetes
• Concurrent use of any medications that may damage your kidneys

“Valacyclovir has few generally mild interactions with other medications and taking valacyclovir rarely requires holding another medication,” Dr. Siegel points out. “However, it may diminish the effectiveness of some vaccines, such as the varicella (chickenpox) or some forms of the zoster (shingles) vaccine.” Your physician may recommend waiting to get vaccinated until at least 24 hours after you finish valacyclovir treatment. If you were just vaccinated, they may recommend that you wait 14 days after you have taken either of these vaccines to start valacyclovir.

 Dr. Dasgupta says that valacyclovir can impact your kidneys. His recommendation is to stay well-hydrated and consider drinking extra fluids so you will pass more urine while you are taking valacyclovir. Doing so will “keep your kidneys working well and help prevent kidney problems,” Dr. Dasgupta explains.

 Pregnant and breastfeeding women should avoid valacyclovir, says Dr. Madan. You should avoid taking it with any medications that can be excreted by the kidneys, such as NSAIDs, Dr. Madan adds.

The bottom line

Valacyclovir starts to work almost immediately after you take it. However, you won’t notice results—such as reduced pain, less itching, and fewer rashes and sores—until about two or three days later. Valacyclovir works best if you take it at the first sign of symptoms and according to the dosing instructions given to you by your healthcare provider.

Want to save on your prescription? Find a discount for valacyclovir and start your treatment today.