• The incidence of contrast induced nephropathy, defined as an increase of serum creatinine of at least 0.5 mg/d and/or 25% within 48 hours of contrast-medium application (comparison of treatment groups to placebo) [ Time Frame: 48h after the application of contrast-medium ]
  

• Change in serum creatinine 48h after contrast medium compared to pre-contrast serum creatinine. Multiple regression analysis of risk-factors of CIN with “Y=Maximum increase of serum creatinine compared to baseline within 48h” [ Time Frame: 48h ]
  

Contrast-induced nephropathy (CIN) is the third leading cause of hospital-acquired acute renal failure (ARF). Accounting for 12% of ARF cases, CIN is defined as an increase of serum creatinine of at least 0.5 mg/d (“Barrett´s definition”) and/or 25% within 48 hours of contrast-medium application. CIN is associated with prolonged hospitalisation and increased mortality. CIN frequency depends on several risk-factors including pre-existing renal dysfunction, high amounts of contrast-medium, diabetes, and concurrent use of nephrotoxic drugs. CIN incidence is low in the absence of risk-factors; however, in high-risk patients, CIN occurs in more than 50% of patients. A variety of prophylactic approaches have been investigated. Despite nephro-protective effects of hydration with saline or with sodium bicarbonate, other trials reported CIN-incidences between 20 and 50% despite hydration. Several studies and two recent meta-analyses demonstrated a significant reduction of renal impairment after contrast-medium using medical prophylaxis with the adenosine antagonist theophylline. However, a recent trial failed to prove prophylactic effects of theophylline. The antioxidant acetylcysteine (ACC) was effective in patients with impaired renal function in at least six studies, but it was not preventive in at least 21 trials and two recent meta-analyses. A recent study comparing the prophylactic efficacy of theophylline and acetylcysteine demonstrated superior prophylactic effects of theophylline. Nevertheless, this study did not include a placebo group, was not restricted to patients with impaired renal function and exclusively enrolled ICU-patients. Therefore, we performed a double-blinded study to compare the effects of acetylcysteine, theophylline, a combination of both, and placebo in patients with impaired renal function (serum creatinine >=1.3mg/dl) parenterally receiving >=100ml of contrast-medium.