Shingles, also known as herpes zoster, is a painful, blistering skin disease caused by the varicella zoster virus, which also causes chickenpox in children. Following chickenpox, the virus lies dormant in nerve tissue and may reactivate later in life if a person becomes immuno-suppressed due to advanced age or disease. Shingles generally follows a nerve distribution area, affecting a limited part of the body.
Antiviral medicines are the main agents used to treat the virus; other drugs may also be given to relieve pain. A vaccine is available to help prevent herpes zoster and should be considered for adults 60 years of age and over, before shingles develops. According to the Mayo Clinic, all three commonly used antiviral agents for shingles help reduce the severity and duration of pain, speed rash healing and reduce the risk of developing postherpetic neuralgia, a long-lasting pain syndrome that sometimes follows shingles.
Acyclovir
Acyclovir (Zovirax®) should ideally be initiated within 48 hours of the onset of rash. This drug has the disadvantage of requiring administration every four hours, five times daily, generally for 5 to 10 days. It is available in tablets, capsules and a liquid formulation and can be obtained generically. It may be taken without regard to meals. Side effects are uncommon but include nausea, diarrhea and kidney problems.
Valacyclovir
Valacyclovir (Valtrex®) is converted in the body to acyclovir, so it shares many of the same properties with acyclovir, except that it may be taken less frequently. Therapy should be started within 48 hours of rash onset. Valacyclovir is administered three times daily at eight-hour intervals for seven days without regard to meals. It is available only in tablets by brand name, and side effects are similar to those of acyclovir.
Famciclovir
Famciclovir (Famvir®) also should be started as early as possible after appearance of rash and is taken every eight hours for seven days without regard to meals. It is available only in tablets, without a generic alternative. The most common side effect is headache. Nausea and diarrhea have also been reported.
References
- Mayo Clinic: Herpes Zoster (Shingles) and Postherpetic Neuralgia
- "AHFS Drug Information"; G.K. McEvoy GK; 2009
