Drugs for Cold Sores: How Well Do They Work?

They are sometimes referred to as fever blisters, oral herpes or herpes labialis. No matter what you call them, cold sores can be painful and embarrassing.

Cold sores are caused by a contagious virus called herpes simplex. Some people show no symptoms from cold sores, but others develop blisters on the face that last for a week or more.

While there is no cure for cold sores, medicines can relieve some of the pain and discomfort associated with the infection. These include topical products that numb the blisters, antibiotics that control secondary bacterial infections and ointments that soften the crusts of the sores.

The Food and Drug Administration (FDA) has approved five drugs for recurrent cold sores. These drugs have been proven to minimally shorten the duration of, but not to cure, herpes simplex virus infections.

Below, we evaluate how well these products work and detail their side effects.

Comparison of cold sore products

The Table compares the effectiveness of the five products approved for cold sores in the U.S. In the studies that generated the data in the Table, patients began treatment within one to two hours of developing cold sore symptoms.

Timing is important when using these drugs. For instance, there is no evidence that the oral drug valacyclovir (VALTREX) will work when taken after a cold sore appears. The FDA requires the label for this drug to state that: "The efficacy of VALTREX initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer) has not been established."

Overall, the effect of these drugs compared to placebo treatment is quite modest. Patients using one of these drugs can expect their cold sores to heal and symptoms to disappear only 12 to 24 hours faster than without treatment (31 hours with FAMVIR).

Patients taking these drugs must weigh a slightly shorter duration of cold sore symptoms against the risk of side effects, the most common of which are headache and dizziness. Less common side effects include nausea, diarrhea, upset stomach, dry mouth and flatulence.

What You Can Do

Patients who do not wish to use medications to treat cold sores can take some simple steps to control discomfort, allow healing and avoid complications:

• Moisturize the cold sore to prevent drying and cracking. Drying and cracking may allow a bacterial infection to develop and delay healing.
• Apply local pain relievers (anesthetics) containing drugs such as benzocaine (available over-the-counter) to reduce discomfort.
• Clean the cold sore by gently washing with soap and water.

When you do have a cold sore, wash your hands frequently to prevent spreading the virus to other people or to other parts of your body.

Table. Products Currently Approved in the U.S. for Treatment of Cold Sores