Three oral antiviral medications treat herpes: acyclovir, valacyclovir (Valtrex), and famciclovir (Famvir). All three are FDA-approved and work against both HSV-1 (oral herpes) and HSV-2 (genital herpes). None of them cure the virus, but they shorten outbreaks, reduce symptoms, and can be taken daily to prevent flare-ups.
The Three Core Medications
Acyclovir has been around the longest and is the foundation of herpes treatment. It works well but needs to be taken more frequently, typically two to three times a day. Valacyclovir is essentially a more absorbable version of acyclovir. Your body converts it into acyclovir after you swallow it, but because it absorbs better through the gut, you can take it less often, sometimes just once daily. Famciclovir works through a similar mechanism and also absorbs well orally.
All three are considered equally effective. The practical differences come down to how many pills you take per day and cost. Valacyclovir’s once- or twice-daily dosing makes it the most commonly prescribed option for daily use. All three are available as generics.
How These Drugs Work
Herpes antivirals are activated inside virus-infected cells by an enzyme the virus itself produces. Once activated, they mimic the building blocks of DNA and trick the virus into incorporating them during replication. This stalls the copying process and prevents the virus from making more of itself. Healthy cells are largely spared because the drug has roughly 200 times more affinity for the viral enzyme than the human version, which is why side effects tend to be mild.
First Outbreak Treatment
A first herpes outbreak is usually the most severe. Treatment lasts 7 to 10 days and involves taking the medication multiple times daily. The CDC recommends starting antivirals as soon as possible after symptoms appear. For genital herpes, the standard first-outbreak course is valacyclovir twice daily, acyclovir three times daily, or famciclovir three times daily for that full 7-to-10-day window. Starting treatment early can meaningfully reduce how long the outbreak lasts and how painful it is.
Episodic Therapy for Recurring Outbreaks
If you get occasional outbreaks but not frequently enough to justify daily medication, episodic therapy lets you treat each flare-up as it comes. You keep a prescription on hand and start taking it at the first sign of symptoms, ideally during the tingling or burning stage before sores appear.
Episodic treatment courses are shorter than first-outbreak treatment. Depending on the medication and dose, they range from as little as one day to five days. For example, valacyclovir can be taken twice daily for just three days, while famciclovir has a regimen where you take a higher dose twice in a single day. The key is speed: the earlier you start, the more effective it is.
Daily Suppressive Therapy
For people who get frequent outbreaks or want to reduce the risk of transmitting the virus to a partner, daily suppressive therapy is the standard approach. You take a lower dose of medication every day, regardless of whether you’re having symptoms. Valacyclovir at 500 mg once daily is one of the most common suppressive regimens. For people with nine or fewer outbreaks per year, that lower dose is typically sufficient. Those with more frequent recurrences may use 1,000 mg once daily.
Daily suppressive therapy does two important things. It dramatically reduces the number of outbreaks, and it lowers the amount of virus your body sheds even when you have no visible symptoms. That asymptomatic shedding is one of the main ways herpes spreads, so daily medication reduces the chance of passing the virus to a sexual partner. Valacyclovir is the only one of the three specifically FDA-approved for reducing transmission, though all three suppress viral activity.
Long-term daily use has been studied extensively and is considered safe. Some people stay on suppressive therapy for years. Your prescriber may suggest stopping periodically to reassess whether your outbreak frequency has changed over time, since outbreaks naturally decrease for many people as years pass.
Oral Herpes (Cold Sores)
For cold sores, the treatment approach is similar but the courses tend to be even shorter. Valacyclovir for cold sores is taken as a high dose (2,000 mg) twice in a single day, 12 hours apart. That one-day course modestly but significantly reduces healing time and pain duration by roughly half a day to a full day compared to no treatment.
Famciclovir as a single high dose can cut healing time by close to two days. Acyclovir taken five times daily for five days reduces pain but hasn’t been shown to speed healing of cold sores as reliably.
Topical Creams vs. Oral Medication
Topical antivirals like acyclovir cream, penciclovir cream, and docosanol (Abreva, available over the counter) are used for cold sores. They modestly decrease healing time and pain, typically by less than half a day, and need to be applied multiple times daily. Oral antivirals generally provide a larger benefit, particularly valacyclovir and famciclovir. No head-to-head trials directly compare oral and topical treatments, but the data on each suggests oral medications produce more meaningful results.
For genital herpes, topical antivirals are not a standard treatment. Oral medication is the clear first choice.
When Standard Medications Don’t Work
Antiviral resistance is rare in people with healthy immune systems. It becomes a concern primarily in immunocompromised patients, such as those who have undergone organ or stem-cell transplants. In these cases, the virus can develop changes that make it invisible to the enzyme these drugs depend on for activation.
When resistance occurs, treatment shifts to medications that work through a different mechanism and don’t rely on that viral enzyme. These are typically given intravenously in a hospital setting and carry more significant side effects, particularly kidney strain. This scenario is uncommon for the vast majority of people with herpes.
What to Expect From Treatment
Antivirals don’t eliminate the herpes virus from your body. HSV hides in nerve cells in a dormant state that no current medication can reach. What these drugs do is limit the virus’s ability to replicate when it reactivates, which shortens outbreaks, reduces severity, and lowers the amount of virus present on the skin.
Most people tolerate all three medications well. They’ve been used for decades with a strong safety profile. The most common side effects are mild: headache, nausea, and occasionally stomach discomfort. People with kidney problems may need adjusted doses, since these drugs are cleared through the kidneys.
If you’re dealing with a first outbreak, treatment can cut days off your symptoms. If you’re managing recurrences, you have the flexibility to choose between treating each outbreak as it happens or taking a daily pill to prevent them. The right approach depends on how often outbreaks occur, how bothersome they are, and whether reducing transmission risk is a priority.