Three oral antiviral medications form the backbone of herpes treatment: acyclovir, valacyclovir, and famciclovir. All three work by blocking the virus’s ability to copy itself, which shortens outbreaks, reduces pain, and lowers the chance of spreading the infection. Which one your provider prescribes, and how you take it, depends on whether you’re treating a first episode, a recurrent outbreak, or trying to prevent flare-ups altogether.
The Three Main Oral Antivirals
Acyclovir was the first antiviral developed for herpes and remains widely used. It’s effective but requires more frequent dosing, typically multiple times per day. Valacyclovir is a newer form of acyclovir that the body absorbs more efficiently, meaning you can take it less often for the same effect. Famciclovir works through a slightly different pathway but produces similar results.
For cold sores (HSV-1), clinical trials show these medications shorten healing by roughly half a day to two days, depending on the drug and dosing schedule. In one large trial, famciclovir at a single high dose reduced healing time by 1.8 days and pain duration by 1.2 days. Valacyclovir taken as two doses over 24 hours shortened both healing and pain by about half a day to just under a day. Acyclovir taken five times daily for five days reduced pain duration by close to a day but didn’t significantly speed up healing of the sore itself.
For genital herpes (HSV-2), the same three drugs are used, but dosing and duration differ. A first genital outbreak is typically treated for 7 to 10 days because initial episodes tend to be more severe and longer lasting. Recurrent episodes use shorter courses, often 3 to 5 days, since the body’s immune system already recognizes the virus and outbreaks are milder.
Why Timing Matters
Antivirals work best when you start them at the earliest sign of an outbreak. Many people learn to recognize a “prodrome,” the tingling, burning, or itching sensation that appears before sores develop. Starting medication during this window gives the drug the best chance of shortening or even preventing a full outbreak. Once blisters have already formed and begun to crust over, antivirals have much less impact.
This is why many providers give patients a prescription to keep on hand. Having pills ready means you can take them the moment symptoms start rather than waiting for a pharmacy visit or appointment.
Daily Suppressive Therapy
If you experience frequent outbreaks, typically six or more per year, daily suppressive therapy is an option. This means taking a low dose of an antiviral every day, whether or not you have symptoms. Suppressive therapy significantly reduces the number of outbreaks per year and also lowers the risk of transmitting the virus to a sexual partner.
Valacyclovir taken once daily is the most common suppressive regimen because of its convenient dosing. Acyclovir works too but requires doses two to three times per day. Most people tolerate long-term suppressive therapy well, and some stay on it for years. Providers will occasionally reassess whether it’s still needed, since outbreak frequency often decreases naturally over time.
Topical Treatments and Over-the-Counter Options
For cold sores specifically, several topical options are available. Docosanol 10% cream (sold as Abreva) is the main over-the-counter treatment in the United States. In a multicenter clinical trial of 737 patients, docosanol shortened healing time by about 18 hours compared to a placebo cream. That’s a real but modest benefit.
Prescription topical creams containing acyclovir or penciclovir produce similar results to docosanol, typically shaving less than a day off healing time. A combination cream with acyclovir and hydrocortisone (a mild steroid to reduce inflammation) showed a slight edge over placebo, shortening healing by about 0.8 days, but didn’t outperform acyclovir cream alone.
No head-to-head trials have directly compared oral antivirals against topical treatments. However, looking across studies, oral antivirals consistently produce larger reductions in healing time and pain. Topical creams are a reasonable choice for mild, infrequent cold sores, but oral medications are the stronger option, especially for genital herpes or frequent outbreaks.
Lysine and Other Supplements
L-lysine is the supplement you’ll see mentioned most often for herpes prevention. It’s an amino acid that may interfere with the virus’s ability to replicate. In a six-month double-blind trial, participants taking oral lysine averaged 2.4 times fewer outbreaks than those on placebo, with milder symptoms and faster healing. That’s a meaningful difference, though the evidence base is smaller and less consistent than what exists for prescription antivirals.
Some people take lysine daily as a preventive measure, while others use it only when they feel an outbreak coming on. It’s generally considered safe, but it’s not a replacement for antiviral medication in people with frequent or severe outbreaks.
Treatment During Pregnancy
Herpes during pregnancy raises specific concerns because the virus can be passed to the baby during delivery. The CDC recommends that pregnant women with recurrent genital herpes begin suppressive antiviral therapy at 36 weeks of gestation. The two recommended options are acyclovir taken three times daily or valacyclovir taken twice daily. This approach reduces the likelihood of an active outbreak at the time of delivery, which in turn lowers the chance of needing a cesarean section. However, suppressive therapy doesn’t eliminate all risk of transmission to the newborn.
When Standard Treatments Don’t Work
For the vast majority of people, one of the three oral antivirals will control herpes effectively. Antiviral resistance is rare in people with healthy immune systems. It becomes a concern primarily in immunocompromised individuals, such as those with advanced HIV or organ transplant recipients on immunosuppressive drugs, whose bodies can’t help fight the virus alongside the medication.
When resistance to acyclovir and related drugs develops, treatment options narrow considerably. Intravenous foscarnet is the most reliably effective alternative, though it requires hospital administration and carries more side effects. Topical trifluridine can help with small lesions but needs frequent application and is difficult to use on larger affected areas. These situations are managed by infectious disease specialists rather than through routine care.