Three prescription antiviral medications treat herpes effectively: acyclovir, valacyclovir, and famciclovir. All three are FDA-approved, taken as pills, and work by stopping the virus from copying itself in your body. They shorten outbreaks, reduce symptoms, and can be taken daily to prevent flare-ups. For cold sores specifically, one over-the-counter cream (docosanol, sold as Abreva) is also available without a prescription.
The Three Prescription Antivirals
Acyclovir was the first antiviral developed for herpes and remains effective, but it requires the most frequent dosing, up to five times per day. That schedule is hard to maintain, which is why it’s generally not the first choice for most people despite being the least expensive option.
Valacyclovir is a modified form of acyclovir that your body absorbs much more efficiently. This means you take fewer pills per day, typically two or three times daily during an outbreak and once daily for suppression. It’s the most commonly prescribed herpes medication for this reason. Famciclovir is the third option, also well-absorbed and taken less frequently than acyclovir. It works comparably for treating outbreaks, though it appears slightly less effective at reducing viral shedding between outbreaks compared to valacyclovir.
All three medications are available only by prescription. Your provider will consider cost, convenience, and how often you have outbreaks when recommending one over the others.
Treating an Active Outbreak
When you feel an outbreak starting, the goal is to begin medication as quickly as possible. Antivirals work best when taken at the first sign of symptoms: the tingling, itching, or burning sensation that often appears before sores develop. Starting treatment during this early window shortens how long the outbreak lasts and can reduce how severe it becomes. If you wait until sores are fully formed, the medication still helps, but the benefit is smaller.
Episodic treatment typically lasts between 1 and 5 days depending on the medication and dosing schedule your provider prescribes. Many people who get occasional outbreaks keep a prescription on hand so they can start treatment the moment symptoms appear, without waiting for a doctor’s appointment.
First outbreaks tend to be the most severe and longest-lasting. Antiviral treatment during a first episode is strongly recommended regardless of which medication you use, as it can significantly reduce the duration and intensity of symptoms.
Daily Suppressive Therapy
If you experience frequent outbreaks (roughly six or more per year), or if reducing the risk of passing herpes to a partner is a priority, daily suppressive therapy is an option. This means taking a low dose of antiviral medication every day, whether or not you have symptoms.
Daily therapy dramatically reduces the number of outbreaks most people experience. Many people on suppressive therapy have no outbreaks at all, or very few. It also lowers the amount of virus your body sheds between outbreaks, which is significant because herpes can be transmitted even when no visible sores are present. Valacyclovir taken once daily is the most common suppressive regimen because of its convenience.
There’s no set time limit for how long you can stay on suppressive therapy. Some people take it for years. Providers sometimes suggest pausing treatment periodically to reassess whether your outbreak frequency has changed on its own, since outbreaks often become less frequent over time regardless of medication.
Over-the-Counter Options for Cold Sores
Docosanol 10% cream (brand name Abreva) is the only FDA-approved over-the-counter treatment for oral herpes (cold sores). It works differently from prescription antivirals. Rather than targeting the virus directly, it helps prevent the virus from entering healthy skin cells around the sore.
In clinical trials, docosanol reduced healing time by about 18 hours compared to placebo, bringing the median time to healing down to roughly 4 days. It also shortened the duration of pain, itching, burning, and tingling. To get the most benefit, you need to apply it five times daily starting at the earliest sign of a cold sore, ideally during the tingling or redness stage before a blister forms.
For cold sores that are severe or frequent, prescription antivirals are more effective than docosanol. But for occasional cold sores, the cream offers a convenient option you can pick up at any pharmacy without a prescription.
Side Effects and Safety
Oral antivirals for herpes are generally well tolerated. The most common side effects are mild: headache, nausea, and stomach discomfort. Most people take these medications without any noticeable problems.
The one important safety consideration involves kidney function. Acyclovir and valacyclovir are cleared from the body through the kidneys, so they can build up to higher-than-intended levels in people with reduced kidney function. When levels get too high, the medication can cross into the brain and cause neurological symptoms like confusion, agitation, excessive drowsiness, hallucinations, or in rare cases seizures. These effects are generally reversible once the medication is stopped. Staying well hydrated while taking these medications helps your kidneys process them efficiently. If you have known kidney problems, your provider will adjust the dose accordingly.
Supplements and Complementary Approaches
L-lysine is the most commonly discussed supplement for herpes. It’s an amino acid available over the counter, and some preliminary research suggests it may help control herpes outbreaks. However, the evidence is limited and inconsistent. Lysine is generally safe to take, but it should not be treated as a substitute for proven antiviral medications, particularly during active outbreaks or if you’re trying to reduce transmission risk.
Keeping the affected area clean and dry during outbreaks, avoiding known personal triggers (common ones include stress, illness, sun exposure, and lack of sleep), and using sunscreen on your lips if sun triggers cold sores can all complement your medication strategy. None of these replace antivirals, but they can reduce how often you need them.