AimsThe objective of this study is to determine the effect of intravenous (i.v.) or oral N-acetylcysteine (NAC) in preventing contrast-induced nephropathy (CIN) in patients with moderate-to-severe renal insufficiency undergoing intra-arterial interventions.Materials and methodsWe studied 307 patients with estimated glomerular filtration rate of less than 60 ml/min/1.73 m(2) undergoing an elective intra-arterial procedure. Patients were assigned randomly to three groups according to the prophylactic regimen used. In group 1, patients were administered an i.v. infusion of 0.9% saline (n=103); in group 2, patients were administered oral NAC in addition to an i.v. saline infusion (n=102); and in group 3, patients were administered i.v. NAC in addition to an i.v. saline infusion (n=102). Serum creatinine (SCr) and cystatin C levels were measured at baseline and 4, 24, and 48 h after the application of contrast media. The primary endpoint was defined as an increase in the SCr or cystatin C concentration of at least 0.5 mg/dl and/or of at least 25% from the baseline value at 48 h after administration of the contrast dye.ResultsThe overall incidence of SCr-based CIN was 11.1%: 6.8% in the saline group, 13.7% in the oral NAC group, and 12.7% in the i.v. NAC group (P=0.231). That of cystatin C-based CIN was 8.1%: 6.8% in the saline group, 6.9% in the oral NAC group, and 10.8% in the i.v. NAC group (P=0.491).ConclusionIn this study, there was no detectable benefit of either high-dose oral or i.v. NAC over an aggressive hydration protocol in patients with moderate-to-severe renal insufficiency.