NPC-06 to Acute Pain in Herpes Zoster

Inclusion Criteria: 1. 20 years old or over at the time of informed consent. 2. Both genders. 3. Patients who have acute rash (either erythema or papule or bulla or pustule, or more), except who have crust more than 20% of entire rash at just before the time of the first administration. 4. Patients who are administrated antiviral drug for herpes zoster at the time of the first administration. 5. Patients who are administrated non-opioid analgesics(acetaminophen, NSAIDs) for herpes zoster at the time of the first administration. 6. Patients who the NRS score at the time of below evaluation point is higher than 4. * 120 minutes before the start of infusion. * Just before the start of infusion. 7. Patients who the therapeutic effect of non-opioid analgesics for herpes zoster has been insufficient. 8. Patients who can admit to hospital for the all assessment duration from first administration until next day (including hospitalized patient). 9. Patients or his/her guardian who give a written informed consent in understanding and willingness after having received enough explanation regarding the study participation. Exclusion Criteria: 1. Patients who cannot evaluate NRS by themselves. 2. Patients who are suspected to intracranial pressure increase. 3. Patients who have epilepsy, serious psychiatric or serious neurological disease (i. e. dementia, Parkinson disease and schizophrenic disorder) or consciousness disorder. 4. Patients who have malignant tumors (except for patients who have no signs of recurrence under treatment) or patients who are under treatment for HIV or patients who are receiving immunosuppressant. 5. Patients who have complicated idiopathic trigeminal neuralgia. 6. Patients who have other serious pain which may affect the evaluation of acute herpetic pain. 7. Patients who are receiving opioids or steroids(systemic). 8. Patients who have sinus bradycardia or serious disturbance of conduction system. 9. Patients who have history of hypersensitivity against hydantoin compound. 10. Patients who are receiving tadalafil (for pulmonary hypertension), rilpivirine, asunaprevir, daclatasvir, vaniprevir, macitentan or sofosbuvir. 11. Patients who are receiving medications for neuropathic pain, antidepressants, antiarrhythmic drugs, N-methyl-D-aspartate receptor antagonists, muscle relaxants, local anesthetics, an extract from inflammatory rabbit skin inoculated by vaccinia virus, Chinese herbal medications for analgesia, vitamin B12. 12. Patients who are receiving amenamevir. 13. Patients who have meningitis or meningeal irritation signs. 14. Patients who have complications such as serious heart disease, hepatic function disorder or renal function disorder which severity are considered by investigator as grade 3 or more severe with reference to ''Concerning classification criteria for seriousness of adverse drug reactions of medical agents'' . 15. Patients who are receiving fosphenytoin, phenytoin or ethotoin and combination drug including these or have taken these drugs as adjuvant therapy for pain .