Treatment of Chronic Itch in Patients Under Arsenic Exposure With Naloxone

Inclusion Criteria

• Aged 18 years or over and without diseases except arsenic-related pruritus
• Ability to study protocol and to give informed consent by himself/herself voluntarily
• The number of male or female subjects is required more than 1/3 of the total number of subjects
• Numeric Rating Sscale≥3 at the baseline
• Subjects taking hormone-containing medications must be on a stable dose for 6 months prior to study start to avoid any confounding influence on sensory and pain perception

Exclusion Criteria

• Use of oral anti-inflammatory medications for 2 weeks prior to the study start.
• Use of oral anti-histamines for 2 weeks prior to the study start.
• Use of topical or oral anti-pruritic agents for 2 weeks prior to the study start.
• Use of oral neuromodulatory agents for 2 months prior to study start.
• Current use of chronic pain medications (including opioids, antidepressants and anti-epileptic drugs).
• Use of nicotine-containing products for the past 6 months prior to study start.
• History of basic itchy dermatological diseases before such as eczema wich may influence the judgement of drug efficacy.
• Unstable thyroid function within the past 6 months prior to study start to exclude thyroid-related neuropathy.
• Known history of central or peripheral nervous system dysfunction.
• History of acute hepatitis, chronic liver disease or end stage liver disease.
• History of human immunodeficiency virus (HIV) or acquired immune deficiency syndrome.
• History of neuropathy associated with chronic obstructive pulmonary disease, diabetes mellitus, documented exposure to organophosphates or heavy metals or polychlorinated biphenyls.
• Known nutritional deficiency (vitamin B12, vitamin D, iron or zinc) within 3 months prior to the study start.
• Use of illicit drugs within the past 6 months prior to study start.
• Lyme disease, porphyria, rheumatoid arthritis, Hansen's disease (leprosy) or use of antineoplastic chemotherapeutic agents.
• Patients considered by researchers that are not suitable to the study.