Effect of oral cyclosporin on renal function in Crohn's disease

Twenty-one patients with Crohn's disease were followed prospectively for 24 weeks to examine the effect of a low-dose cyclosporin regime on renal function (initial dose 5 mg/kg reduced by 1 mg/kg every two months to a maintenance of 2 mg/kg). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by radioisotope clearance at 0, 6 and 24 weeks. GFR and ERPF fell significantly (mean GFR at baseline: 120.9 ml/min/1.73 m2; at six weeks: 100.9 ml/min/1.73 m2; mean ERPF at baseline: 497.3 ml/min/1.73 m2; at six weeks: 398.5 ml/min/1.73 m2). Following dose reduction, the ERPF remained lower than baseline (mean 408.6 ml/min/1.73 m2), and there was a trend towards the GFR remaining low (mean 111.8 ml/min/1.73 m2). Serum creatinine rose significantly (median pretreatment 72 mumol/liter; median at four weeks 86 mumol/liter) but returned to baseline after dose reduction. Plasma cyclosporin levels and serum creatinine did not help predict the extent of changes in renal function. At low doses, cyclosporin causes changes in renal hemodynamics that may not be reversed by dose reduction.