Background Prevention of contrast media (CM) induced nephropathy (CIN) by pharmacological prophylaxis (e.g. N-acetylcysteine; NAC) is controversially discussed. So far, in all interventional studies assessment of kidney function was based on measurements of serum creatinine although this surrogate biomarker has several limitations. We investigated the antioxidants NAC and zinc (Zn) for the prevention of CIN by monitoring concomitantly serum levels of creatinine and cystatin C.

In a prospective, placebo-controlled, double blind trial patients with moderate impaired kidney function receiving hypoosmolar, nonionic contrast medium were randomly assigned to an oral treatment for 2 days with 1.2g/day of NAC (n=19), for 1 day with 60mg/day of Zn (n=18) or placebo (n=17). All patients were periprocedural hydrated with 1ml/kg/h of 0.45% saline for 24h. At baseline (before hydration), prior to exposure of CM as well as 2 and 6 days after CM serum levels of creatinine and cystatin C have been measured.

Inclusion Criteria:

1. older than 18 years of age,
2. serum creatinine > 1.2 mg/dl or a creatinine clearance < 50 ml/min (measured by a 12 or 24 hour urine collection).

Exclusion Criteria:

1. acute inflammatory disease,
2. medication with NSAID or metformin until 3 days before entering study,
3. abnormal findings in physical examinations, e.g. signs of dehydration or decompensated heart failure.