Low Dose Naltrexone for Chronic Pain in Osteoarthritis and Inflammatory Arthritis

Inclusion Criteria: * One or more of the following chronic conditions: osteoarthritis, rheumatoid arthritis, or non-axial spondyloarthritis * Average daily pain interference with function (average of the 7 parts of question 9 on the Brief Pain Inventory) rated at least 4 on a scale of 0-10, and no higher than 9 * No change in medication in the past 8 weeks made with the expectation of improving pain * No plan to start another medication or a non-pharmacologic treatment regimen likely to affect pain during the next 16 weeks * Age at least 18 * Capable of informed consent, and willingness to comply with study procedures, including receipt of weekly phone calls from the study coordinator Exclusion Criteria: * Use of opioids including tramadol, in the past 7 days * Pregnant, breast feeding, or unwilling to engage in contraceptive practices if sexually active and capable of conceiving * Schizophrenia, bipolar disorder, or poorly controlled depression or anxiety * Previous use of low-dose naltrexone for more than 8 weeks or in the past 2 weeks * Back pain described by the patient as greater in severity than arthritic pain in all peripheral locations * Significant kidney disease, defined as glomerular filtration rate \< 30 ml/min * Liver cirrhosis. There is no specific screening procedure to exclude cirrhosis. * Peripheral neuropathy described by the patient as greater in severity than arthritic pain. There is no specific screening procedure. * Plan to have surgery during the next 16 weeks * Other qualitative circumstances that the investigator feels would make the patient a poor candidate for this clinical trial, such as an unstable social situation or unreliable transportation