The purpose of this study is to compare the safety and efficacy of two doses of FV-100 to valacyclovir in patients with herpes zoster, or shingles. FV-100 has shown to be very potent in cells infected with varicella zoster virus, the virus that causes shingles. The study objectives include:

• Compare the safety of FV-100 to valacyclovir
• Compare the effect of FV-100, as compared to valacyclovir, on shingles pain
• Compare the effect of FV-100, as compared to valacyclovir, on shingles lesions

Inclusion Criteria:

• Men and women ≥ 50 years of age
• Patients with a clinical diagnosis of HZ as evidenced by a unilateral dermatomal rash
• Patients with zoster-related pain (ZBPI worst pain score > 0)
• Patients able to be enrolled into the study ≤ 72 hours from appearance of rash (i.e., lesions or vesicles)
• Patients providing written informed consent
• Patients who are able to complete all study visits per protocol
• Men and premenopausal women must agree to practice a barrier method of birth control plus the use of a spermicide for one month after the last dose of study drug (oral contraceptives are not permitted)

Exclusion Criteria:

• Women who are pregnant or lactating

• Patients with multidermatomal or disseminated HZ (i.e., > 20 vesicles beyond the dermatomes adjacent to the primarily involved dermatome)

• Patients with HZ ophthalmicus, defined as cutaneous lesions in the dermatome associated with the ophthalmic division of the trigeminal nerve

• Patients with history of impaired renal function, (e.g., calculated creatinine clearance <50 mL/min/1.73 m2)

• Patients taking narcotic analgesic routinely for a chronic pain condition

• Patients taking tricyclic antidepressants

• Patients who have received systemic antivirals with activity against VZV within the past 30 days, or a topical antiviral to treat their current HZ

• Patients who are immunosuppressed from:

  • disease (e.g., malignancy [present or remission < 5 years], HIV)
  • corticosteroid use (except intermittent or topical/inhaled beclomethasone dipropionate or equivalent < 800 mcg/day), or
  • other immunosuppressive/cytotoxic therapy (cancer chemotherapy or organ transplantation)

• Patients with gastrointestinal dysfunction that could interfere with drug absorption

• Patients with any other condition (e.g., extensive psoriasis, chronic pain syndrome, cognitive impairment) that, in the opinion of the site investigator, might interfere with the evaluations required by the study

• Patients who are not ambulatory (bed-ridden or homebound); hospitalized patients may be enrolled if they are ambulatory and able to complete the study requirements

• Patients with history of allergy to valacyclovir hydrochloride

• Patients unlikely to adhere to protocol follow-up

• 14. Subjects taking strong CYP3A4-inhibiting protease inhibitors (specifically including atazanavir, indinavir, nelfinavir, saquinavir, and ritonavir), strong CYP3A4 inhibitors (specifically including clarithromycin, itraconazole, ketoconazole, nefazodone, telithromycin) and all strong CYP3A4 inducers (specifically including rifampin, efavirenz, etravirine, phenobarbital, phenytoin, and carbamazepine)