N-acetylcysteine alone doesn't prevent contrast nephropathy after angiography

More than 40 small, middling-quality studies (n~80, some randomized) showing inconsistent results as to whether antioxidant therapy with acetylcysteine or other drugs reduces the risk for contrast nephropathy / acute kidney injury after angiography or CT-angiography. A 2008 meta-analysis concluded Mucomyst was helpful, reducing risk of nephropathy by almost 40% vs saline alone. However, the authors noted a troublesome degree of heterogeneity in the included studies.

Berwanger and the ACT investigators seem to have settled this question. They randomized a whopping 2,308 patients undergoing angiography at 46 sites in Brazil to receive either Mucomyst (oral N-acetylcysteine 1200 mg twice daily for 2 days before and 2 days after the procedure), or placebo. All patients were high-risk (older than 70, or with diabetes, CHF, or hypotension). 98% of patients were hydrated (received at least the recommended amount of 1 mL/kg/hr of saline for at least 6 hours before and after the procedure).

The incidence of acute kidney injury (>25% increase in creatinine) was exactly 12.7% in both groups. Mortality/need for dialysis at 30 days (2' endpoint) was ~2.25% in both groups. There was no benefit of acetylcysteine in even higher-risk subgroups (like those with renal failure or who got the highest dye loads).

These were all patients undergoing invasive angiography (67% cardiac catheterizations), but one would think the lower dye load in CT-angiography would preclude any benefit of acetylcysteine for those patients, either.

Investigators gave NAC orally and didn't give intravenous sodium bicarbonate, leaving the door open a tiny crack on this question (although not to me).

Berwanger et al. Acetylcysteine for Prevention of Renal Outcomes in Patients Undergoing Coronary and Peripheral Vascular Angiography. Circulation 2011; 124: 1250-1259. 

In related news, use of the proprietary RenalGuard system -- which gives furosemide and normal saline in precise realtime adjusted doses to maintain urine output at desired levels -- did reduce contrast nephropathy by an absolute 9% in a study published in the same issue. This has more biological plausibility as an effective method than oral NAC alone.