Pharmacologic and Biologic Therapy, Including Toxicity Monitoring
Conventional therapy
NSAIDs control symptoms but do not alter disease course. Intra-articular corticosteroids are highly effective in oligoarthritis. Methotrexate is the anchor disease-modifying drug and must be given weekly, never daily; co-prescribe folic acid and monitor CBC and liver enzymes. Leflunomide, sulfasalazine, and azathioprine are alternatives, with thiopurine methyltransferase testing before azathioprine. Mycophenolate is teratogenic. Cyclophosphamide treats severe lupus nephritis and vasculitis but risks gonadotoxicity and hemorrhagic cystitis. Hydroxychloroquine should not exceed 5 mg/kg/day and requires retinal screening. Corticosteroids cause growth suppression, osteoporosis, avascular necrosis, cataract, and adrenal suppression needing stress dosing.
Biologics
Screen for tuberculosis and hepatitis B before TNF inhibitors and check immunization status before any biologic. IL-1 blockade treats systemic JIA and autoinflammatory syndromes; IL-6 blockade causes neutropenia and lipid changes; abatacept blocks co-stimulation; rituximab depletes B cells and can cause hypogammaglobulinemia; belimumab targets BAFF. Live vaccines are contraindicated during most immunosuppression; inactivated vaccines are safe and encouraged.
Traps
Daily methotrexate is a fatal medication error. Do not attribute fever in a biologic-treated child to disease flare without considering infection.
Rule of thumb
Weekly methotrexate, folic acid, and a written monitoring schedule - every time.