N-acetylcysteine to Reduce Oxidative Stress and Improve Endothelial Function in HIV-infected Older Adults

Inclusion Criteria: * HIV-1 infection, documented by (1) any licensed rapid HIV test or HIV enzyme or chemiluminescence immunoassay (E/CIA) test kit at any time prior to study entry and confirmed by a licensed Western blot or a second antibody test by a method other than the initial rapid HIV and/or E/CIA, or (2) by two detectable HIV-1 antigens, or (3) two detectable plasma HIV-1 RNA viral loads. * Age equal to or greater than 50 years. * Receipt of antiretroviral therapy of any kind for at least 6 months prior to screening. * HIV-1 RNA level \< 75 copies/mL at screening. * For women who are still of reproductive potential, a negative urine pregnancy test at screening and willingness to use two forms of birth control during the course of the study. Acceptable forms of birth control include condoms (with or without a gel that can kill sperm), a diaphragm or cervical cap (with or without a gel that can kill sperm), an intrauterine device (IUD), or hormonal-based birth control ("the pill"). Exclusion Criteria: * Inability to complete written, informed consent. * Incarceration at the time of any study visit. * Known allergy or intolerance to n-acetylcysteine. * Use of n-acetylcysteine within 180 days of screening. * Diagnosed vascular disease (history of angina pectoris, coronary disease, peripheral vascular disease, cerebrovascular disease, aortic aneurysm, or otherwise known atherosclerotic disease). * History of congestive heart failure even if currently compensated. * History of portal hypertension or hepatic cirrhosis (either clinically diagnosed or histologically diagnosed). * Diagnosed disease or process, besides HIV infection, associated with increased systemic inflammation (including, but not limited to, systemic lupus erythematosis, inflammatory bowel diseases, other collagen vascular diseases). * Known or suspected malignancy requiring systemic treatment within six months of screening. * History of ADA-defined diabetes mellitus (115) * History of migraine headaches. * History of Raynaud's phenomenon. * History of cardiac arrhythmias or cardiomyopathy. * Uncontrolled hyperthyroidism or hypothyroidism, defined as TSH values outside of the local reference range on most recent clinical assessment. * Asthma or COPD requiring daily use of beta-2-agonist therapy (e.g. albuterol) * History of carotid bruits. * Creatinine clearance \< 50 mL/min (using the Cockcroft-Gault equation) using a serum creatinine level measured at screening. * Hemoglobin \< 9.0 g/dL at screening. * Alanine aminotransferase (ALT) level or aspartate aminotransferase (AST) \> 3 times ULN at screening. * Total bilirubin \> 2.5 times ULN at screening; if the participant is receiving atazanavir, then s/he would be excluded if total bilirubin is \> 3.5 times ULN at screening. * Therapy for serious medical illnesses within 14 days prior to screening. * Pregnancy or breastfeeding during the course of the study. * Uncontrolled hypertension, defined as systolic blood pressure \> 160 mmHg or diastolic blood pressure \> 100 mmHg at screening. * Receipt of investigational agents, cytotoxic chemotherapy, systemic glucocorticoids (of any dose), or anabolic steroids at screening. * Previous receipt of stavudine or didanosine for more than 7 cumulative days. * Receipt of daily Vitamin C or Vitamin E supplements at screening. * Alcohol intake more than the equivalent of one 8 oz. of wine daily for the 7 days prior to screening. * Active drug use or dependence that, in the opinion of the investigator, would interfere with adherence to study requirements.