BCHE and Alzheimer disease: To date, there are only five FDA-approved drugs available for AD, three of which are cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) [2], the fourth being an N-methyl-D-aspartate (NMDA) receptor antagonist [3], and the fifth a combination of cholinesterase inhibitor and NMDA-receptor antagonist.