Ketamine in Chronic Kid's (KiCK) Pain

Inclusion Criteria: * Subject, parent, or guardian willing and able to give informed consent * NRS for pain over the past 24 hours \>4 at baseline * Chronic pain, which has been present for \>3 months, or persisting longer than is normal for the underlying diagnosis * Chronic pain related to physiologic diagnoses including but not limited to: cancer, rheumatologic disease, sickle cell anemia, cystic fibrosis, pancreatitis, and neuromuscular disease (e.g. Duchenne muscular dystrophy) * Able to tolerate and cooperate with neurocognitive assessment * Age 8-20 years old Exclusion Criteria: * If they are known or suspected to have drug addiction * Uncontrolled psychiatric disorder such as depression, schizophrenia, or bipolar disorder * Uncontrolled hypertension * Known liver disease or elevation of AST or ALT greater than 3 times the upper limit of normal. * Previous intolerance or allergic reaction to ketamine * Pregnancy * Use of CYP3A4 inhibitors or inducers within the 2-week period prior the study drug administration or within 5 half-lives of the respective medication, whichever is longer, until study conclusion. * Consumption of grapefruit or grapefruit products from at least 2 weeks prior to study drug administration until study conclusion.