Shingles (Herpes Zoster) and Post-herpetic Neuralgia.
During childhood chickenpox, varicella-zoster virus becomes latent in neurons of the dorsal root or trigeminal ganglia. Shingles results years to decades later from a breakdown of viral latency within a ganglion and subsequent virus spread to the skin producing a unilateral dermatomal vesicular rash accompanied by segmental pain. Treatment with famciclovir, valacyclovir, and high dose acyclovir is beneficial if started within the first 3 days of the rash. All three drugs can be given orally, are equally effective, shorten the duration of viral shedding and time to healing of the rash by 1 to 2 days, and lessen the intensity and duration of the acute neuritic pain. Famciclovir and valacyclovir have more convenient dosing schedules (three times daily) compared to acyclovir (five times daily). Mild cases of shingles in younger healthy individuals often do not require any antiviral treatment. Pain in shingles may have burning, lancinating, or allodynic qualities, ranges in intensity from mild to unbearable, and lasts 2 to 8 weeks. Pain treatment varies on the type and intensity of pain experienced. In a few patients, post-herpetic neuralgia develops and the dermatomal pain persists for months to years. Effective treatment of post-herpetic pain is often difficult.