Herpes zoster (HZ) is characterized by a painful dermatomal rash and significantly affects quality of life, with acute pain increasing the risk of postherpetic neuralgia. Although early antiviral therapy limits viral replication, its analgesic effect is insufficient, and many patients experience inadequate relief despite stepwise use of non-opioids and opioids. Recent attention has focused on the potential role of antidepressants, which have central antinociceptive property and may offer analgesic benefits by modulating central nervous system pain pathways through increased serotonin and norepinephrine availability. Therefore, investigators hypothesize that tulodesvenlafaxine may effectively reduce the severity of HZ pain without significantly increasing adverse events.