the lateral site of the right leg as well as the dorsal and plantar sites of the right foot. The patient was initially treated at a dermatology clinic with oral valaciclovir (an antiviral agent) and diclofenac (an anti-inflammatory agent), and subsequently, with diclofenac alone for several weeks. Within a month of its onset, the pain in the leg and the dorsum of the foot subsided concomitantly with the skin rash healing. However, severe pain in the plantar site of the foot persisted.Three months after the initial onset, the patient presented at our pain clinic, in a wheelchair, because of intractable pain with severe tactile allodynia on the sole and on the heel of the right foot, which was so severe that it prevented her from walking normally. Resting spontaneous pain was moderate, being rated at 50 mm/ 100 mm on the visual analog scale (VAS). However, marked tactile allodynia was observed on the right heel, which was rated at 91/100 mm. Because of the severe touch-evoked allodynia, she could not stand on the right foot, nor could she wear a sock or shoe on the right foot. She could hardly walk, limping and relying mostly on the left foot, stepping on the right tiptoe, and she wore beach sandals. She was treated initially with oral amitriptyline and repeated (caudal) epidural blocks, which resulted in only a slight improvement in her pain status.Five months after the onset of pain, she was admitted to our hospital to study the mechanisms underlying her pain condition, and to seek potentially effective therapeutic measures. After obtaining institutional review board approval and written informed consent from the patient, we assessed various intravenous (IV) drugs for analgesic efficacy. Because the severe tactile allodynia was elicited most prominently when she was trying to walk, she was asked to rate her pain using VAS both at rest (for spontaneous pain) and when standing/stepping (for evoked tactile allodynia) before, during, and after administration of each test drug.