If you child does not respond well to nonsteroidal anti-inflammatory drugs, the doctor may prescribe a new drug called Xatmep. Xatmep is the first ready-to-use oral solution formulation of methotrexate to be approved for use in children with polyarticular juvenile idiopathic arthritis. An aggressive therapy, this medicine helps reduce further joint damage and helps preserve joint function. Side effects can include dizziness, fatigue, chills and fever.