Duloxetine for PHN

Inclusion Criteria: * ages more than 50 years; * diagnosed with uncomplicated acute herpes zoster; * presents with vesicles within 72 hours; * has an average pain score of at least 40/100 mm on a visual analog scale (VAS, 0 = no pain, 100 = worst possible pain, at opposite ends of a 100-mm line). Exclusion Criteria: * refuses to participate or to provide written informed consent; * Zung Self-Rating Depression Scale raw score of more than 50 points; * herpes zoster that involves with head, neck, ocular, mucous membrane, cranial nerve, or central nervous system; * has hemorrhagic or necrotizing lesions, satellite lesions, abnormal vesicles or acute retinal necrosis; * has been on immunosuppressive therapy or mono- or multi-pharmacotherapy that involves any tricyclic antidepressant, valacyclovir, duloxetine or cytotoxic medications before acute HZ onset; * has been diagnosed with hepatic, renal or immune dysfunction; * during pregnancy or breastfeeding at the time; * hypersensitivity to the study drugs; * has contraindications to valacyclovir or duloxetine; * HZ vaccinated.