Contrast-induced nephropathy (CIN) is a leading cause of hospital-acquired renal failure and affects mortality and morbidity. There has been no study comparing the efficacy of N-acetylcysteine (NAC) and ascorbic acid that have potential for CIN prevention in patients with renal insufficiency.

We conducted a prospective randomized controlled trial. A total of 212 patients who had pre-existing renal impairment with basal creatinine clearance ≤60 mL/min and/or serum creatinine (SCr) level of ≥1.1 mg/dL, were randomized to have either high-dose NAC (1,200 mg orally twice a day before and on the day of coronary catheterization, n = 106) or ascorbic acid (3 g and 2 g orally before, and 2 g twice after coronary catheterization with a 12-hour interval, n = 106). The primary end point was the maximum increase of SCr level, and the secondary end point was the incidence of CIN.

The maximum increase of SCr level was significantly lower in NAC group than in ascorbic acid group as follows: −0.03 ± 0.18 mg/dL versus 0.04 ± 0.20 mg/mL, respectively (P = .026). Patients with diabetes or who had received a high dose of contrast media experienced significantly less rise of SCr level with NAC than ascorbic acid; in diabetic subgroup, −0.05 ± 0.22 mg/dL versus 0.09 ± 0.29 mg/mL, respectively (P = .020); in patients with high dose of dye, −0.03 ± 0.17 mg/dL versus 0.04 ± 0.21 mg/mL, respectively (P = .032). The incidence of CIN, the secondary end point, tended to be in favor of NAC rather than ascorbic acid, 1.2% versus 4.4%, respectively (P = .370). Notably, among the diabetes patients, the NAC significantly lowered CIN rate than ascorbic acid, 0% (0/38) versus 12.5% (4/32), respectively (P = .039).

High-dose NAC seems more beneficial than ascorbic acid in preventing contrast-induced renal function deterioration in patients, especially diabetic patients, with renal insufficiency undergoing coronary angiography.