Methods of treating postherpetic neuralgia in a mammal with a pharmaceutical composition comprising a spiro-oxindole compound of the formula: are disclosed. The methods provide excellent penetration of the spiro-oxindole compound into the affected skin area to effectively reduce the severity of the postherpetic neuralgia and/or to alleviate the postherpetic neuralgia with minimal or negligible systemic exposure of the spiro-oxindole compound.本發明揭示以包含下式之螺吲哚酮化合物之醫藥組合物治療哺乳動物之帶狀疱疹後遺神經痛的方法:該等方法以該螺吲哚酮化合物之最小或可忽略之全身曝露量提供該螺吲哚酮化合物極佳地滲透進入患部皮膚區域中,以有效地降低帶狀疱疹後遺神經痛之嚴重度及/或緩解帶狀疱疹後遺神經痛。