Herpes zoster, also known as shingles, results when the varicella-zoster virus, the same virus that causes chicken pox, reactivates within the roots of the sensory nerves. According to the American Academy of Dermatologists, herpes zoster produces symptoms similar to chicken pox, including a blistering skin rash and mild, flu-like illness. However, there are two key differences: with herpes zoster, pain is more prominent than itching and the rash usually strikes just one side of the body. Chicken pox follows the opposite pattern. Although herpes zoster, like chicken pox, usually resolves without treatment, doctors often prescribe prescription antiviral drugs to prevent complications.
Therapeutic Rationale
According to the Centers for Disease Control and Prevention, up to 70 percent of people with herpes zoster develop a chronic pain syndrome known as postherpetic neuralgia. Prompt initiation of antiviral drugs and, sometimes, corticosteroids reduce the risk of postherpetic neuralgia, in addition to reducing the severity and duration of zoster symptoms. According to the Mayo Clinic website, the drugs work best when started within 72 hours of symptom onset, so affected patients should contact their doctors as soon as symptoms appear.
Medications
According to University of Alabama Medical School professor of infectious diseases Richard J. Whitely, M.D., in the 2008 edition of "Harrison's Principles of Internal Medicine," doctors typically use one of three antiviral drugs--acyclovir, valacyclovir or famciclovir--to treat herpes zoster. Some patients, notes the American Academy of Dermatology, may receive a tapered course of steroids such as prednisone, or prescription pain medications such as fentanil.
Dosing and Administration
Depending on the drug used, patients may be required to take antiviral drugs by mouth, up to three times per day, says Whitely. Corticosteroids may be injected, applied topically or ingested orally. Injected corticosteroids are usually reserved for very severe symptoms. Topical steroids may be applied to the eye. Oral steroids complement the first two or may be used on their own. Steroid dosing may be complicated because patients usually take progressively smaller doses over the course of three weeks, rather than discontinuing the drugs outright.
Side Effects
In clinical trials for acyclovir, the manufacturer, Glaxo-Smith-Kline, reported that the most common side effects were nausea, vomiting, diarrhea and headache. The other two antiviral drugs used to treat herpes zoster, valacyclovir and famciclovir, produce similar side effects. Side effects of steroids, according to the Mayo Clinic website, include eye problems, weight gain, fluid retention, increased blood pressure and mood swings. Prescription pain medications often cause sedation and carry the risk of dependency.
Complications
In rare cases, says Whitely, herpes zoster can affect the brain, spinal cord or the internal organs, such as the lungs, liver and kidneys. Complications usually present three to five days after skin symptoms appear, continues Whitely. In addition to antiviral drugs, these patients require symptom-based treatment, such as supplemental oxygen for pneumonia or anticonvulsants for seizures due to brain inflammation.
References
- American Academy of Dermatology: Herpes Zoster
- "Harrison's Principles of Internal Medicine, 23rd Edition"; A.S. Fauci et al.; 2008
- MayoClinic: Prednisone and Other Corticosteroids: Balancing the Risks and Benefits
- MayoClinic: Shingles: Treatment and Drugs
- Centers for Disease Control and Prevention: Shingles: Q and As for Providers
