The effect of ketamine as an additive in epidural block on the intractable herpetic neuralgia: a case report.

Ketamine has been shown to have analgesic effect by blocking N-methyl-D-aspartate receptor, thus preventing and reducing central sensitization caused by peripheral nociceptive stimulation. However, due to lack of knowledge about its safety and toxicity in the central nervous system, either epidural or intrathecal injection of ketamine still remains controversial. Here, we describe a case report of satisfactory pain relief after the addition of ketamine in epidural injection in a patient with severe herpes zoster pain that was refractory to conventional medication, intravenous opioids and continuous epidural block. This case indicates the viability of epidural ketamine injection in patients with intractable herpetic neuralgia.