The contrast induced nephropathy (CIN) has been known to be associated with significant clinical and economic consequences. Many studies were performed to find the pathophysiology and preventive measures for CIN. But the results were somewhat frustrating. Recently, it has been reported that the N-acetylcysteine and ascorbic acid might have preventive effects for CIN by their antioxidant effects.There have been no study to compare these two antioxidant.

N-acetylcysteine and ascorbic acid may prevent the CIN in the patients with underlying renal insufficiency who is undergoing the coronary angiography. The effect may derive from the antioxidant function of these two antioxidant. We studied to find which of the two antioxidants is more beneficial in prevention of CIN

Inclusion Criteria:

• Stable Angina pectoris patients
• Patients who required the coronary catheterization
• Creatinine clearance rates =<60 mL/min using the Cockcroft-Gault formula
• Age of 19 or over 19

Exclusion Criteria:

• Pregnancy
• Lactation
• Having received contrast media within 7 days of study entry
• Emergent coronary angiography
• Acute renal failure
• End-stage renal disease requiring dialysis
• History of hypersensitivity reaction to contrast media
• Cardiogenic shock
• Pulmonary edema
• Multiple myeloma
• Mechanical ventilation
• Parenteral use of diuretics
• Recent use of N-acetylcysteine
• Recent use of Ascorbic acid
• Recent use of statin
• Use of metformin or nonsteroidal anti-inflammatory drugs within 48 hours of the procedure.