The main medicines for herpes are three prescription antiviral pills: acyclovir, valacyclovir, and famciclovir. All three are FDA-approved nucleoside analogs that work by blocking the virus’s ability to copy itself inside your cells. They don’t cure herpes, but they shorten outbreaks, reduce symptoms, and can prevent future flare-ups when taken daily.
The Three Prescription Antivirals
Acyclovir (brand name Zovirax) was the first antiviral developed for herpes and remains widely used. Valacyclovir (Valtrex) is essentially a more absorbable version of acyclovir, meaning your body takes in more of the drug from each dose, so you can take it less frequently. Famciclovir (Famvir) works through the same basic mechanism but is a separate compound with its own dosing schedule.
All three treat genital herpes outbreaks. For cold sores (oral herpes), valacyclovir and famciclovir are the most commonly prescribed, though a specialized tablet form of acyclovir called Sitavig can be applied directly to the gum above an upper front tooth. Each medication is most effective when started early. Valacyclovir loses effectiveness for a first genital outbreak if started more than 72 hours after symptoms appear. Famciclovir has an even tighter window of about 6 hours for recurrent episodes.
How These Medications Are Used
Doctors prescribe antivirals in three distinct ways depending on your situation.
For a first outbreak: A first episode of genital herpes is typically the most painful and longest-lasting. Antiviral treatment during this initial episode shortens the duration of sores and reduces the severity of symptoms. Acyclovir and valacyclovir are both approved for first episodes.
For recurrent outbreaks (episodic therapy): If you get occasional flare-ups, you can keep a prescription on hand and start taking it at the first sign of tingling, itching, or redness. All three antivirals are approved for this use. The goal is to shorten the outbreak by a few days and reduce discomfort.
For daily prevention (suppressive therapy): If you experience frequent recurrences, daily antiviral therapy reduces outbreaks by 70% to 80%. Valacyclovir and famciclovir are both approved for suppressive use. Valacyclovir is the only antiviral with FDA approval specifically for reducing transmission to a sexual partner. Taking 500 mg daily has been shown to decrease the rate of HSV-2 transmission in couples where one partner has herpes and the other does not.
Side Effects and Safety
These medications are generally well tolerated. The most common side effects of valacyclovir are headache, nausea, and abdominal pain, reported by more than 10% of adults in clinical trials. Acyclovir and famciclovir have a similar side effect profile.
The main safety concern involves kidney function. The drug is cleared through your kidneys, and in some cases it can crystallize in the kidney’s tiny tubes if you’re not drinking enough water. This makes adequate hydration important while taking any of these antivirals. People with existing kidney problems, older adults, and anyone on other medications that stress the kidneys need adjusted doses. In rare cases, particularly in elderly patients or those with reduced kidney function who take higher-than-recommended doses, nervous system side effects like confusion, agitation, or hallucinations can occur.
Over-the-Counter Options for Cold Sores
Docosanol (brand name Abreva) is the only FDA-approved over-the-counter treatment for herpes, and it’s approved only for cold sores on the lips and face. It works differently from prescription antivirals. Rather than blocking viral replication directly, it prevents the virus from fusing with your skin cells.
The honest picture on topical treatments is that their benefit is modest. A systematic review of topical acyclovir, penciclovir, and docosanol found that all three shorten pain duration by less than 24 hours compared to doing nothing. They’re safe and have no serious side effects, but if you’re looking for significant relief, oral prescription antivirals are more effective than anything you can apply to the skin.
Supplements With Some Evidence
L-lysine is the most studied supplement for herpes prevention. In a six-month trial, participants taking oral lysine averaged 2.4 times fewer outbreaks than those on placebo, with milder symptoms and shorter healing times. It’s available without a prescription and is generally considered safe, though the evidence base is smaller than for prescription antivirals.
Zinc has also shown some promise. Oral zinc supplements are associated with fewer and shorter outbreaks, and topical zinc applied to lesions may shorten healing time without side effects. However, high doses of oral zinc (above 100 mg) can deplete your body’s copper levels, so moderation matters.
Treatment for Drug-Resistant Herpes
In rare cases, usually in people with weakened immune systems, herpes can become resistant to standard antivirals. A newer drug called pritelivir is currently being made available through an expanded access program for immunocompromised patients with treatment-resistant HSV-1 or HSV-2. It works through a completely different mechanism than acyclovir and its relatives, targeting a different part of the virus’s replication machinery. It is not yet broadly approved but represents an option when standard treatments fail.