The Academy of General Dentistry reports that most Americans have been exposed to the herpes simplex virus that causes cold sores; however, only about 30 percent of people actually develop symptoms. Among those that do, the first outbreak is usually the most severe, lasting up to 14 days and producing numerous lesions on and inside the mouth. Although herpes cold sores usually resolve on their own, treatment can accelerate the process and provide relief from pain and itching.
Therapeutic Rationale
In a 2008 review published in the "Archives of Internal Medicine" internist Christina Cernik, M.D. explains that prescription antiviral drugs reduce the duration and severity of symptoms. Over-the-counter medications such as oral acetaminophen and topical lidocaine or benzocaine may improve pain and itching. Practicing good skin and mouth hygiene, states Cernik, can also promote healing and reduce the risk of secondary bacterial infections.
Mechanism of Action
In the 2008 edition of "Harrison's Principles of Internal Medicine," Lawrence Corey, M.D. explains that prescription antiviral drugs inhibit replication of the herpes simplex virus by substituting the drug for nucleic acids essential to DNA replication. Doctors don't know exactly how acetaminophen works. Topical pain medications typically work by blocking the transmission of pain signals within the nerve.
Administration
Antiviral drugs such as acyclovir, valacyclovir, famciclovir or penciclovir can be administered orally or applied topically, notes Cernik. Doctors usually prescribe a one-week course, adding additional doses if necessary. The drugs work best the sooner they are started, Cernik notes, so patients should contact their doctors for a prescription as soon as cold sores appear, or when they experience premonitory symptoms such as tingling, burning or sensitivity. In the case of over-the-counter medications, patients should read and follow the instructions in the package insert.
Safety
In the 2008 edition of "Basic and Clinical Pharmacology" University of California-San Francisco Professor of Medicine Sharon Safrin, M.D. explains that antiviral drugs used to treat cold sores are generally well tolerated. The most common side effects, which occur in less than 10 percent of people, include nausea, vomiting, diarrhea and headache. Safrin cautions that people with kidney problems may require topical preparations or reduced doses of oral drugs. Delusions, hallucinations, delirium and abnormal behavior have occurred among people with acute or chronic kidney failure.
Effectiveness
Cernik reports that, in clinical studies of children with cold sores, oral acyclovir cut healing time from 9 days to 4 days and reduced the severity of pain and itching during the interim. Similar results, says Cernik, occurred with oral valacyclovir and famciclovir. Topical preparations of acyclovir and penciclovir have shown mixed results, with some studies showing no benefit, and others showing results superior to no treatment at all, but inferior to oral drugs.
References
- "Archives of Internal Medicine"; "The Treatment of Herpes Simplex Infections; C. Cernik et al.; 2008
- "Harrison's Principles of Internal Medicine, 23rd Edition"; A.S. Fauci et al.; 2008
- "Basic and Clinical Pharmacology, 11th Edition"; B.G. Katzung et al.; 2008
- Academy of General Dentistry: What Are Cold Sores?
- Mayo Clinic: Cold Sore: Treatments and Drugs
