Ketamine for Multiple Sclerosis Fatigue

This study is testing whether low-dose ketamine — a medication already used for pain and depression — can reduce fatigue in people with multiple sclerosis (MS), a chronic condition of the nervous system. **You may be eligible if...** - You are between 18 and 65 years old with a diagnosis of multiple sclerosis - Fatigue is one of your main symptoms (measured by a standard questionnaire) - You are able to walk at least 20 feet, even with support - You have access to the internet and can use a computer, tablet, or smartphone - You are medically stable **You may NOT be eligible if...** - You have a history of psychosis or a condition that would make ketamine unsafe - You are pregnant or planning to become pregnant - You have certain liver or kidney problems - You have an active substance use disorder Talk to your doctor to see if this trial is right for you.