A 14-year-old girl being treated with long-term nonsteroidal anti-inflammatory drugs for juvenile idiopathic arthritis develops a fever of 38.5°C (101.3°F), a maculopapular rash, and a rising serum creatinine. Urinalysis shows sterile pyuria and microscopic hematuria. If her kidney function fails to improve shortly after stopping the offending medication, what is the recommended treatment for suspected drug-induced acute tubulointerstitial nephritis?