This trial aims to test the hypothesis that 1) a single dose of zinc cysteine in a proprietary gastro-retentive form will produce sustained blood levels of zinc giving a larger bioavailable amount of zinc than an FDA approved preparation of inorganic zinc acetate; and 2) that the zinc cysteine gastro-retentive, sustained-release preparation will be better tolerated with significantly less gastrointestinal side effects than the zinc acetate capsules. The trial also tests the hypothesis that, after 6 months of once daily administration, the zinc cysteine subjects will show reduced serum non-ceruloplasmin copper. Additionally, subjects will perform tests of mental function,including the dementia rating scale, the Mini Mental Status Examination and the ADAS-cognitive performance test aimed at Alzheimer's status assessment. Tests will be administered at baseline, 3 and 6 months, and the performance results compared. Care-giver assessments will also be noted.

This multi-center study aims to determine the pharmacokinetics and pharmacodynamics of a novel gastro-retentive, sustained-release zinc cysteine preparation on the blood and urine measures of copper and zinc balance in Alzheimer's disease and mild cognitive impairment. Data expected to be derived include tolerability of the novel preparation in comparison with oral inorganic zinc salt, and long-term effects on primarily blood-measured copper-zinc balance. The study design is that of a prospective, randomized, double blind placebo-controlled clinical trial, with a duration for individual subjects of 6 months. The study will be performed at a total of 3 sites, under the direction of a single principal investigator, with a sub-investigator. The statistical plan calls for a comparison of data from the two long-term parallel groups using ANOVA and other applicable techniques. In addition to blood parameters, mental function assessments obtained at baseline, 3 and 6 months will be evaluated statistically.

Inclusion Criteria:

• Alzheimer's disease mild to moderate as diagnosed by standard clinical, functional and NINDA-ADRDA criteria
• Mild cognitive impairment diagnosed by standard clinical, functional and NINDA-ADRDA criteria
• All subjects able to swallow Tablets
• Subjects taking copper or zinc containing supplements must have a 30-day wash out before starting study materials
• Screening laboratory values either within normal limits or deemed not clinically significant by investigator

Exclusion Criteria:

• Subjects or their study companions/care givers unable to give adequate informed consent
• Presence of a disease or condition known to affect biometal homeostasis
• Presence of psychosis, substance abuse or other major medical or neurological issues
• Presence of vascular dementia
• Clinically significant anemia at the time of the screening visit
• Current use of a decoppering drug such as trientine or penicillamine