To reduce the risk of contrast-induced nephrotoxicity, patients should be adequately hydrated before exposure to contrast. Varying regimens have been used. One common regimen consists of 0.45% saline pre-exposure at 1 mL/kg/h for 12 hours for inpatients or 2 mL/kg/h for at least 4 hours for outpatients and postexposure at 75 mL/h for 12 hours. In addition to hydration, consideration should be given to administering N-acetylcysteine (NAC), especially in patients with renal insufficiency. One recent meta-analysis showed that NAC (which is relatively inexpensive and has few side effects if taken by mouth) reduced the risk of contrast-induced nephrotoxicity in patients with pre-existing chronic renal insufficiency. However, in this analysis, single doses varied widely, with oral doses of 400 to 1,500 mg and IV doses of 50 to 150 mg/kg given at varying intervals and durations. Some clinicians say that if oral dosing is used, apparently more than one pre-exposure dose is needed. One common regimen consists of pre-exposure NAC 600 mg orally for two doses at least 4 hours apart and postexposure
two doses 12 hours apart. For oral administration, NAC is best administered in a strongly flavored drink such as a carbonated cola or Fresca to partially mask the disagreeable odor and taste. In emergencies, IV administration of 150 mg/kg in 500 mL of 0.9% saline over 30 minutes pre-exposure and 50 mg/kg in 500 mL of 0.9% saline over 4 hours postexposure has been used, although IV use is more common for the treatment of acetaminophen overdose. Intravenous NAC has a higher risk of anaphylactoid reactions than does oral administration and the physician must consider the risk-to-benefit ratio of using IV NAC for renal prophylaxis.