Study of XPF-001 in the Treatment of Pain From Primary/Inherited Erythromelalgia (IEM)

Inclusion Criteria: The study requires you to: * Be18-75 years old * Have inherited erythromelalgia * Be experiencing pain caused by erythromelalgia (Moderate pain score 4/10) * Be generally healthy (apart from your pain) * Stop taking your usual pain medications for 9 days * Not be pregnant or breast-feeding Your role in the study includes: * An out-patient screening visit * 9-days/8 nights-in-patient treatment visit at Nijmegen Medical Center (where you will be closely monitored) * A follow up phone call (after your return home) * Taking the investigational medication daily * Recording your pain levels daily during stay at the Medical Center. Exclusion Criteria: * Coexistent source of pain from other conditions * Receiving professional psychological support for dealing with IEM * Treatment for significant depression within 6 months of screening * Active HIV, Hepatitis B or C * Use of prescription or OTC medication between check-in and discharge * Women who are pregnant, or lactating * Not currently using adequate contraception * Alcoholism or alcohol or substance abuse * Presence or history of major psychiatric disturbance * Unwilling or unable to comply with all dietary and activity restrictions * Any other condition or finding that may pose undue risk for participation * Use of any other investigational drug in the 60 days prior to dosing