Shingles is a viral disease affecting the nerves. It causes painful blisters along the skin. The disease is caused by the same virus that causes chicken pox, called the VZV for varicella-zoster virus. In fact, people who have never contracted chicken pox will not get shingles. This is because after the course of chicken pox, the virus remains latent in the spinal cord. It is more likely to be reactivated and cause shingles, also known as zoster, with increasing age, cancer, immune suppression and chronic kidney and lung diseases. Some medications are available to combat the virus.
Acyclovir
Acyclovir is an antiviral medication used to treat shingles. Other indications include chicken pox, genital herpes, cold sores, and herpes infections elsewhere, such as the brain, eyes and eyelids. The drug mimics a component of DNA called gaunosine. Normal gaunosine is required for the shingles virus to replicate. The shingles virus incorporates acyclovir into its DNA instead of gaunosine, and it is unable to synthesize any more DNA. The drug has a much greater affinity for viral DNA than human DNA and has an excellent safety profile. Common side effects are headaches and gastrointestinal complaints such as nausea, vomiting and diarrhea. Confusion and allergic reactions are less common but possible. Acyclovir is typically given five times per day.
Valacyclovir
Valacyclovir is a similar drug to acyclovir, but it only needs to be taken three times per day orally. The drug is well tolerated, similarly to acyclovir. In the treatment of shingles, it appears that the skin lesions heal just as quickly for each acyclovir and valacyclovir, but the valacyclovir may decrease the duration of nerve pain compared to acyclovir according to an article in 2007 in the "Journal of the American Academy of Dermatology."
Famciclovir
Famciclovir is a third option. It's mechanism of action is similar to acyclovir and valacyclovir. Famciclovir is given one to three times per day. Its safety level is similar to acyclovir and valacyclovir . However, it use is limited because of higher cost.
Foscarnet
Foscarnet is a drug used to treat shingles infections in HIV patients who have strains of the shingles virus that are resistant to acyclovir and other more common drugs. Foscarnet is an intravenous drug rather than an oral one, and causes more side effects and toxicity. The drug causes nausea, decreased kidney function and changes in the concentrations of minerals such as potassium and calcium in the blood.
References
- "Basic and Clinical Pharmacology"; Bertram G. Katzung et al; 11th Ed 2009
- "Journal of the American Academy of Dermatology"; Management of herpes zoster and postherpetic neuralgia; Stephen K. Tyring, MD, PhD; December 2007
