Ask the Experts about Pharmacotherapy From Medscape Pharmacists Ask the Expert on . . . Acetylcysteine Question I work in a practice setting where the cardiologists are using oral acetylcysteine before each cardiac catheterization (diagnostic) procedure as a routine prophylactic measure against the dye. Are there any guidelines or recommendations for this? Can you suggest any other options? Response from Reza Taheri, PharmD Assistant Professor of Pharmacy Practice /Assistant Professor of Medicine, Schools of Pharmacy & Medicine, Loma Linda University, Loma Linda, California; Co-Director, Lipid Clinic, VA Loma Linda Healthcare System, Loma Linda, California. Data suggest that the use of contrast in various procedures results in about 150,000 cases of contrast-induced nephropathy (CIN) per year.[1,2] This has alarming economic and patient quality-of-life implications. While the exact mechanism of pathogenesis is not elucidated in the literature, a number of factors such as oxygen radical formation, medullary hypoxia due to intrarenal vasoconstriction, and direct tubular toxicity have been described as major contributors.[3,4] Individuals with certain comorbidities such as diabetes or renal insufficiency are at particularly high risk for nephropathy.[4] Other factors may also contribute to increased risk for CIN. A recent study by Marenzi and colleagues[5] assessed clinical predictors of CIN in patients undergoing primary angioplasty for acute myocardial infarction. The following factors were identified as contributors to increased risk of CIN: Age > 75 years Anterior myocardial infarction Time to reperfusion > 6 hours Contrast agent volume > 300 mL Use of intra-aortic balloon Although there are no clear guidelines for the use of preventative measures in patients undergoing percutaneous coronary interventions (PCI), data seem to suggest every effort should be taken to decrease the risk of CIN in patients undergoing PCI even if they have near normal renal function.[2,5,6] A number of preventative measures have been attempted with varying degrees of success. Agents such as dopamine,[7,8] fenoldopam,[9,10] and theophylline[11-14] have had inconsistent results with preponderance of data suggesting neutrality or negative outcomes; hence, routine use of these agents is not advisable. On the other hand, hydration seems to be one of the most effective preventative measures available. Although the majority of the hydration studies utilized half-isotonic (0.45%) saline at a rate of 1 mL/kg/hr,[15-21] there is some suggestion in the literature that isotonic (0.9%) saline may provide a more profound benefit.[22] The duration of hydration in these studies was from a few hours before to 24 hours after contrast exposure. As mentioned above, reactive oxygen species may play a significant role in the pathogenesis of CIN. This has led to a great deal of interest in assessing the role of N-acetylcysteine (NAC) for the prevention of CIN. Administration of NAC will result in replenishment of glutathione, which in turn leads to the formation of glutathione peroxidase, an important enzyme involved in the degradation of reactive oxygen radicals.[23] It is important to realize that there were significant differences among these trials in terms of patient population, the NAC regimen used, and the type and volume of contrast.[15,16,18-21,24-28] The results of 2 recent meta-analyses involving a number of trials suggest a clear benefit for the use of NAC in high-risk patients.[29,30] Conversely, the authors of 2 other meta-analyses warn against ubiquitous use of NAC in all patients receiving intravenous contrast stating borderline statistical significance and the heterogeneity of the trials as their reason for this cautious approach.[31,32] In summary, there is no doubt that use of radiocontrast dye in various procedures is associated with a risk for development of contrast-induced nephropathy (CIN). The degree of this risk can vary substantially according to patient characteristics as well as the volume and the type of contrast used. Of all the preventative measures tested in this setting, hydration (IV and/or oral) has consistently proven to be effective in decreasing the risk of CIN. Therefore, it would be advisable to utilize this simple and effective measure in all patients undergoing PCI (eg, angiography, angioplasty) unless there is a contraindication to do so (eg, exacerbated heart failure). The extent of benefit derived from NAC will largely depend on a number of factors, including the age and comorbidities of the patient, the degree of renal failure, the type and volume of contrast used in the procedure, the dosage and route of NAC, and perhaps other factors as well. Although the use of NAC in prevention of CIN has gained much popularity in recent years and its benefit in higher-risk patients has been confirmed by experts, its ubiquitous use in every case remains controversial and the subject of much debate. Posted 4/05 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.