Treating a cold sore during the prodrome (tingle) stage is the best way to avoid a 2-week outbreak. One way to achieve that goal is with the use of doctor-prescribed medication.

Available in tablet form and topical cream, medication prescribed by your primary care physician can be beneficial. Many medications can also be used as a preventative measure.

While there are many cold sore treatments on the market, there are currently just four FDA-approved drugs (with brand variations) that your doctor can prescribe. Each of these drugs has an extended history of treating the herpes virus successfully.

In this guide, we will take a closer look at each drug, how they work, and what you can expect from your treatment plan.

What are the Different Types of Cold Sore Medication?

Prescription antiviral cold sore medications are available in tablet form and as a topical cream. The primary options are acyclovir (Zovirax/Sitavig), valacyclovir (Valtrex), famciclovir (Famvir), and penciclovir (Denavir).

Let’s explore each of these selections and discover the pros and cons of each option:

Acyclovir (Zovirax and Sitavig)

Slowing the growth and spread of HSV-1, acyclovir is an antiviral drug. First developed in the 1970s, Acyclovir can significantly reduce the symptoms of cold sores.

How Does Acyclovir Work?

This potent drug works by inhibiting the activation of active HSV-1 from attacking cells. Acyclovir prevents viral DNA synthesis without directly impacting the normal cellular process. True to its name, this antiviral prevents the virus from replicating and spreading to other areas of the mouth/lips.

How Long Does it Take to Work?

Acyclovir is fast-acting and can provide relief in as little as 24 hours.

Coming in tablet, capsule, and liquid form, this antiviral drug can be consumed with or without food 2-5 times per day for as many as ten days. If you begin a course of acyclovir as soon as your symptoms appear, you will have better results.

Acyclovir can also be used as a preventative measure. The drug is usually taken 2-5 times per day for an entire calendar year under this circumstance.

As with any drug, it is crucial to take acyclovir at the same time each day. Take the drug as directed and never take more or less than your prescription states. Never skip doses or stop consumption just because symptoms have cleared.

If you are consuming acyclovir in liquid form, you should always shake the bottle well to ensure an even mixture.

What Are the Ingredients?

Using the brand name Zovirax as our example for tablet and liquid forms, each tablet contains 200 mg of acyclovir.

Other ingredients include:

  • Cellulose
  • Indigotine
  • Lactose
  • Magnesium Stearate
  • Povidone
  • Sodium Starch Glycolate

One teaspoon of Zovirax contains 200 mg of acyclovir in addition to:

  • Cellulose
  • Glycerin
  • Methylparaben
  • Propylparaben
  • Sorbitol
  • Vanillin
  • Water

What Are the Side Effects?

The most common side effects of acyclovir can include but are not limited to, upset stomach, vomiting, diarrhea, fatigue, and dizziness.

Valacyclovir (Valtrex)

Approved for medical use in 1995, valacyclovir (commonly known as Valtrex) is an antiviral drug that can decrease the growth and spread of HSV-1. It can be used by adults and children (who are at least 12 years old.)

How Does Valacyclovir Work?

Valacyclovir directly interferes with viral reproduction. By stopping the virus from multiplying and spreading to healthy cells, an active cold sore outbreak can be contained.

While there is no cure for HSV, valacyclovir can quickly reduce the symptoms and pain. This drug can be used to heal viral outbreaks, decrease the risk of transmission, and prevent future occurrences.

How Long Does it Take to Work?

The effectiveness of valacyclovir depends on the severity of your outbreak. Typically prescribed for a 7-10 day period, it can begin to promote healing within 24-72 hours.

If you are in the midst of your first cold sore outbreak, it’s possible for your prescription to last longer than your symptoms. If this is the case, you should finish the prescription.

Recurring outbreaks will often heal much faster with valacyclovir. The drug may be prescribed for 4-5 days rather than the normal 7-10 days, for example.

What Are the Ingredients?

The core active ingredient in a single valacyclovir caplet is valacyclovir hydrochloride. All other ingredients (carnauba wax, colloidal, silicon dioxide, crospovidone, etc.) are inactive.

What Are the Side Effects?

  • Fever
  • Bruising and bleeding
  • Red spots
  • Diarrhea and vomiting (with blood)
  • Skin discoloration (yellow and pale)
  • Fatigue
  • Weak urination

Famciclovir (Famvir)

Famciclovir (branded as Famvir) is an antiviral drug. It was approved for medical use in 1994.

While it does not cure the herpes virus, it can slow its spread and replication. Famciclovir may reduce the most common symptoms associated with cold sores, such as pain, burning, itching, redness, etc.

How Does Famciclovir Work?

Famciclovir belongs to a group of drugs known as nucleoside analogs. These drugs can slow the replication of viral DNA which is required for viral spreading.

Regarded as a prodrug, famciclovir acts as a conversion piece. By transforming into the active antiviral drug penciclovir once inside the body, it is penciclovir that fights off the virus.

Famciclovir is known for its long-acting potency. It can be taken less often in a 24-hour window.

How Long Does it Take to Work?

Famciclovir typically begins to provide relief within 24-72 hours. Much depends on the severity of the outbreak. Your physician will assess your condition before issuing you with a prescription.

What Are the Ingredients?

Famvir’s active ingredient is famciclovir.

Noted inactive ingredients include:

  • Hydroxypropyl cellulose
  • Hydroxypropyl methylcellulose
  • Lactose
  • Magnesium stearate
  • Polyethylene glycols
  • Sodium starch glycolate
  • Titanium dioxide

What Are the Side Effects?

  • Headaches
  • Fatigue/Weakness
  • Nausea
  • Vomiting
  • Rash (Not related to HSV-1)
  • Diarrhea

Penciclovir (Denavir)

Penciclovir is a strong antiviral that minimizes pain and prevents viral spreading.

How Does Penciclovir Work?

It penetrates the skin and delivers healing at the site of the active virus. By targeting the cells that have been compromised by HSV-1, this drug can heal the area while preventing cell replication.

How Long Does it Take to Work?

Penciclovir can provide relief within 24-48 hours of initial application.

Unless directed by your physician, most courses of penciclovir only last for an average of 4-5 days. By applying a thin layer of cream to the problem area every 2 hours, you can relieve any discomfort.

For best results, apply penciclovir at the same time each day. Rub it in gently, ensuring that the site of the cold sore is covered completely.

What Are the Ingredients?

The active ingredient in Denavir is penciclovir. Each gram of Denavir contains 10 mg of penciclovir.

Inactive ingredients include…

  • Cetostearyl alcohol
  • Mineral oil
  • Polyoxyl 20 cetostearyl ethe
  • Propylene glycol
  • White petrolatum

What Are the Side Effects?

  • Headaches
  • Localized numbness
  • Changes in taste/inability to taste
  • Rashes and irritation

When Should Prescription Meds Be Avoided?

If you are allergic to the ingredients, active or otherwise, you should always avoid prescription medication. If your medication can prompt a negative reaction when mixed with an existing drug, you should also avoid consumption or application.

Let your physician know all the medications you are currently taking before accepting a prescription. The last thing you want to do is create any new health issues.

Because many things can go wrong with prescription drug use, the FDA has compiled a list of helpful tips.

Let’s explore each of them in turn:

1) Know the exact name of your medication

Never allow your doctor to prescribe something to you without first knowing the name. Ask for clarification, if necessary.

Cindi Fitzpatrick, who is a registered nurse and a consumer safety officer for the FDA, says that asking about your prescription will help you to notice if your pharmacy gives you something different.

It is impossible to know if you have received the wrong medicine if you did not know what it was in the first place. This knowledge will also help you when getting refills. You will be familiar with the packaging, the shape of the pill, the size of the pill, etc. If anything seems to be different, you should always ask the pharmacist.

2) Make your questions known before you leave your doctor

If you have been given a prescription, it is vital to ask any pertinent questions. What should I do if I miss a dosage? Is this medication better with or without food? How critical is timing between dosages? Given my personal situation, what side effects should I expect?

Ask your doctor to brief you on your medication. You’ll receive a crash course on what to expect before you ever use the drug. If you have a series of questions, you may find it better to take notes. Write things down and follow instructions.

Cold sore prescription Valtrex

3) Always read labels and follow all directions

Before you pop a pill or apply a cream, you should know how to do it. Never assume you know every step. The effectiveness of drugs so often depends on how they are consumed. The drug itself is only part of the equation.

4) Keep track of all your medications, vitamins, and supplements

If you can name (or show) all medications to your physician, you will be able to steer clear of specific prescriptions. Your physician will be able to bypass certain drugs altogether because they will know what is safe for your consumption or application based on your up-to-date list.

According to Dr. Douglas Paaw, a professor of medicine at the University of Washington, making a detailed list of your medications and supplying it to your physician should be done at least on an annual basis.

The concept of a “brown bag check-up” is highly recommended. This is where all of your medications and supplements are physically presented to your physician for evaluation.

5) Keep a list of your medications with you at all times.

Provide a copy of the list close family members. This list can come in handy during times of medical emergency.

What are the Non-Prescription Alternatives?

Virulite Cold Sore Machine

Using light technology to accelerate healing, the Virulite device is approved by the FDA.

Designed to be used only three times over the course of 48 hours, Virulite is arguably the best OTC treatment on the market today.


FDA-approved, Abreva cream can result in recovery in as little as 72 hours. It is one of the best known topical applications available.


Created by Hannah Yoseph, MD, HERP-B-GONE is fast-acting and FDA approved. It can heal active outbreaks while preventing future blister occurrences.

Essential Oils

Tea tree oil, peppermint oil, lemon balm oil, and oregano oil have the potential to heal your cold sores faster.

Applied directly via a cotton swab, essential oils can dry out fluid-filled blisters and halt the spread of the herpes simplex virus.

Aloe Vera Gel

Complete with anti-inflammatory, antibacterial, and antiviral properties, aloe vera gel can alleviate pain and help the skin to recover.

During the scab stage, the use of aloe vera gel can keep your scab moist and prevent cracking due to excessive dryness.

Laser Technology

Penetrating the skin without contact or pain, laser technology can be used to heal cold sores. Conducted in the professional setting of a dentistry, laser treatment can provide pain and symptom relief immediately.

Destroying the active virus on contact, light energy heats the area without compromising healthy skin. HSV-1 carriers who undergo a laser treatment not only find instant relief but prolonged prevention.

Key benefits…

  • Reduces the chances of scarring.
  • Destruction of the viral nerve channel. This makes a future recurrence in a specific location of the lip nearly impossible.
  • Active blisters are completely healed within 24-72 hours.
  • Immediate pain relief

Although there is no known cold sore cure, a doctor or other healthcare professional can give you a prescription for a cold sore medication.  The length of time that you will take them will vary, depending on how often you experience the symptoms.


  1. Cunningham A, Griffiths P, Leone P, et al. Current management and recommendations for access to antiviral therapy of herpes labialis. Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology. 2012; 53(1):6-11. doi:10.1016/j.jcv.2011.08.003.
  2. Emmert D.H., Lancaster M.D. Treatment of common cutaneous herpes simplex virus infections. Am. Fam. Physician. 2000; 61:1697–1607.

Last update on 2024-04-24 / Affiliate links / Images from Amazon Product Advertising API