WEDNESDAY, June 28 (HealthDay News) -- In myocardial infarction patients undergoing primary angioplasty, intravenous and oral doses of the antioxidant N-acetylcysteine may help prevent contrast-medium-induced nephropathy and improve outcomes, according to a study published in the June 29 issue of the New England Journal of Medicine.

Giancarlo Marenzi, M.D., of the University of Milan, Italy, and colleagues randomly assigned 354 angioplasty patients to one of three groups: 116 received a standard dose of N-acetylcysteine (a 600-mg intravenous bolus before primary angioplasty and 600 mg orally twice daily for the 48 hours after angioplasty); 119 received a double dose of N-acetylcysteine (a 1,200-mg intravenous bolus and 1,200 mg orally twice daily for the 48 hours after intervention); and 119 received a placebo.

The researchers found that five (4 percent) of the standard-dose group died compared to three (3 percent) of the high-dose group and 13 (11 percent) of the placebo group. They determined that the composite end point -- death, acute renal failure requiring temporary renal-replacement therapy or the need for mechanical ventilation -- was eight (7 percent), six (5 percent) and 21 (18 percent) in the three groups, respectively.

"The mechanisms underlying the improvement in the in-hospital clinical outcome have not been completely elucidated, and studies of potential extrarenal effects of N-acetylcysteine are warranted," the authors conclude.

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