The ACT Trial was a large, pragmatic randomized controlled trial that investigated whether acetylcysteine reduces the risk of contrast-induced nephropathy (CIN) in over 2,300 patients undergoing coronary angiography. The trial found no difference in the primary outcome of CIN or other clinical outcomes like mortality between patients receiving acetylcysteine or placebo. Subgroup and sensitivity analyses also found no benefit of acetylcysteine. An updated meta-analysis of high-quality trials, including the ACT Trial, similarly found no effect of acetylcysteine on reducing CIN risk. The results suggest acetylcysteine is not effective in preventing CIN and may inform updating clinical guidelines.