The FDA IND application is paused due to additional required testing. The IRB protocol was closed prior to research starting.

The purpose of this research is to obtain data or information on the safety and effectiveness of low dose naltrexone (LDN) for treating the symptoms of juvenile primary fibromyalgia syndrome. This is a dose finding study to find whether LDN helps the symptoms of juvenile fibromyalgia, and at what dose it does so.

In this pilot dosage-finding and efficacy study, we will experimentally test whether LDN reduces the symptoms of JPFS. We will recruit 40 children with JPFS. Participants will be screened via the JPFS criteria of Yunus and Masi. The study will be an open-label test of various doses of LDN to determine whether LDN reduces JPFS symptoms, and the appropriate dose at which it does so. Primary endpoints will be daily pain, fatigue, and sleep.

The protocol is designed to take 18 weeks. There are a total of 10 study visits, taking place approximately every 2 weeks.

Inclusion Criteria:1. Generalized musculoskeletal aching for over 3 months duration 2. Moderate-severe pain in 5 of 11 tender points 3. Age 7 - 17 4. Male or female Exclusion Criteria:1. Diagnosed rheumatic or autoimmune condition contributing to pain 2. Abnormal laboratory results (Rf, ANA, ESR) 3. Use of opioid analgesics in the last 6 months 4. Severe depression and/or anxiety as evidenced by a diagnosis of either disorder, or by evidence based on a clinical interview with the patient and parent at the time of screening. 5. Current or previous psychiatric disorder requiring hospitalization 6. Inability to operate Palm OS® handheld device for self-reports 7. Inability to understand English 8. Inability to attend sessions at Stanford lab every 3 weeks 9. Pregnancy or planned pregnancy, or breastfeeding 10. Abnormal liver functioning tests