Three oral antiviral medications treat herpes effectively: acyclovir, valacyclovir, and famciclovir. All three work the same way, blocking the virus from copying itself inside your cells. None of them cure herpes, but they shorten outbreaks, reduce severity, and can lower the risk of transmitting the virus to a partner. The “best” one depends on your situation, how often you get outbreaks, and how simple you want your pill schedule to be.
The Three Core Medications
Acyclovir is the oldest of the three and has decades of safety data behind it. It works well, but the trade-off is frequency: you may need to take it every four to five hours during an active outbreak. Valacyclovir is essentially a newer form of acyclovir that your body absorbs more efficiently, which means fewer pills per day. Famciclovir is the third option and offers similar flexibility in dosing.
In terms of raw effectiveness, all three produce comparable results. Cold sores and genital herpes blisters typically start improving within two to three days of starting treatment, though full healing can take up to two weeks. The main practical difference is convenience. Valacyclovir’s simpler schedule (two to three times per day versus acyclovir’s more frequent dosing) makes it the most commonly prescribed option today.
First Outbreak vs. Recurring Outbreaks
Your first herpes outbreak is usually the most painful and longest-lasting, and treatment runs 7 to 10 days. If healing isn’t complete by day 10, your provider can extend the course. For a first episode, the CDC lists all three antivirals as equally appropriate options.
Recurring outbreaks are typically shorter and less severe. Treatment for a recurrence lasts just 1 to 5 days depending on which medication and dosing schedule you use. With famciclovir, for example, one regimen covers a recurrence in a single day. Valacyclovir can be taken for as few as three days. The key with episodic treatment is starting as early as possible, ideally at the first tingle or sign of an outbreak. Waiting even a day reduces how much the medication helps.
Daily Suppressive Therapy
If you get frequent outbreaks (roughly six or more per year), daily suppressive therapy is worth considering. Instead of treating each outbreak as it comes, you take a low dose of medication every day to prevent outbreaks from happening in the first place. This approach also reduces viral shedding, the periods when the virus is active on your skin without visible symptoms, which lowers the chance of passing herpes to a sexual partner.
For suppressive therapy, valacyclovir can be taken once daily, which makes it especially convenient. However, for people with very frequent recurrences (10 or more episodes per year), the lower once-daily valacyclovir dose may not be enough, and a higher dose or switching to acyclovir twice daily may work better. Famciclovir twice daily is another suppressive option.
There’s no set time limit on suppressive therapy. Many people take it for years. Providers sometimes suggest pausing once a year to reassess whether outbreaks have naturally become less frequent, which often happens over time.
Cold Sores: Oral vs. Topical
For cold sores (oral herpes), you have both oral pills and topical creams available. Topical options like penciclovir cream and docosanol (sold over the counter as Abreva) provide modest benefits. In clinical trials, penciclovir cream shortened healing by less than a day compared to placebo (4.8 days versus 5.5 days). Oral valacyclovir, by contrast, cut healing time of full-blown cold sore lesions by about 3.5 days compared to placebo. Oral antivirals are clearly more effective, so if cold sores are a recurring problem, pills are the better choice over creams.
Side Effects and Safety
All three herpes antivirals are well tolerated by most people. The most common side effects are mild: headache, nausea, and fatigue. Some people report body aches or a stuffy nose. These side effects are generally manageable and often fade as your body adjusts.
Rare but serious reactions can occur, particularly in people with weakened immune systems. These include kidney problems (especially if you’re not drinking enough water), confusion, and in very rare cases, a blood disorder called thrombotic thrombocytopenic purpura. People with kidney disease typically need adjusted doses. If you’ve had a bone marrow or kidney transplant, or are living with HIV, your provider will monitor you more closely.
Drug resistance is not a practical concern for most people. In the general population, fewer than 0.5% of herpes isolates show resistance to acyclovir. Among immunocompromised patients who’ve been treated repeatedly, that number rises to around 6%, which is when alternative medications become relevant.
How to Choose Between Them
For most people, valacyclovir is the most practical choice. It works as well as acyclovir with fewer pills per day, and it’s available as a generic, making it affordable. If cost is a major factor, acyclovir is typically the cheapest option and equally effective, just less convenient to take. Famciclovir is a solid third option, particularly for episodic treatment of recurrences, where its short-course regimens are appealing.
Your choice also depends on how you want to manage herpes day to day. If outbreaks are rare (a couple of times a year or less), keeping a prescription on hand and treating episodes as they arise is reasonable. If outbreaks are frequent or you want to minimize transmission risk to a partner, daily suppressive therapy with any of the three medications is the standard approach. The right medication is the one you’ll actually take consistently, since timing and adherence matter more than which specific antiviral you pick.
For Treatment-Resistant Cases
In rare situations, typically in immunocompromised patients, herpes can stop responding to standard antivirals. A newer drug called pritelivir works through a completely different mechanism and remains active against virus strains that have become resistant to acyclovir and related drugs. In a Phase 2 trial, 93% of immunocompromised patients with resistant herpes saw their lesions heal with pritelivir, compared to 57% with the current backup treatment. Phase 3 results are expected in 2026, and the drug is currently available through expanded access programs for patients who need it.