The mainstay of therapy for patients with Alzheimer disease (AD) is the use of centrally acting cholinesterase inhibitors to attempt to compensate for the depletion of acetylcholine (ACh) in the cerebral cortex and hippocampus. A partial N -methyl-D-aspartate (NMDA) antagonist is approved for treatment of moderate and severe AD. Various medications are used for treatment of secondary symptoms of AD, including antidepressants, anti-anxiety agents, and antipsychotic agents.
Cholinesterase inhibitors (ChEIs) are used to palliate cholinergic deficiency. All 4 currently approved ChEIs (ie, tacrine, donepezil, rivastigmine, galantamine) inhibit acetylcholinesterase (AChE) at the synapse (specific cholinesterase). Tacrine was the first agent that was approved for AD, but because of its potential to cause hepatotoxicity, it is now rarely used.
Tacrine and rivastigmine also inhibit butyrylcholinesterase (BuChE). Although BuChE levels may be increased in AD, it is not clear that rivastigmine and tacrine have greater clinical efficacy than donepezil and galantamine.
Galantamine has a different second mechanism of action; it is also a presynaptic nicotinic modulator. No data exist to indicate that this second mechanism is of clinical importance.
Rivastigmine is indicated for the treatment of mild to moderate dementia of the Alzheimer type. Initial dosing recommendations are 1.5 mg given twice daily, with a maximum dose of 12 mg/day. Rivastigmine is a potent, selective inhibitor of brain AChE and BChE. Rivastigmine is considered a pseudo-irreversible inhibitor of AChE.
While the precise mechanism of rivastigmine’s action is unknown, it is postulated to exert its therapeutic effect by enhancing cholinergic function. This is accomplished by increasing the concentration of acetylcholine through reversible inhibition of its hydrolysis by cholinesterase.
Galantamine is indicated for the treatment of mild to moderate dementia of the Alzheimer type. It enhances central cholinergic function and likely inhibits AChE. There is no evidence that galantamine alters the course of the underlying dementing process. The dosing recommendation for the immediate-release formulation is 4 mg twice daily. The extended-release formulation is given at a dose of 8 mg once daily. The maintenance dose after dose titration is 16-24 mg/day.
The only drug in the N -methyl-D-aspartate (NMDA) antagonist class that is approved by the US Food and Drug Administration is memantine. This agent may be used alone or in combination with AChE inhibitors.
Namenda is approved for the treatment of moderate to severe dementia in patients with AD. The initial dose for the immediate-release formulation is 5 mg once daily, and it can be titrated to a maximum dose of 20 mg/day. The initial dose for the extended-release formulation is 7 mg once daily, and it can be titrated to a maximum dose of 28 mg/day.
Medical foods are dietary supplements intended to compensate specific nutritional problems caused by a disease or condition. Caprylidene is a prescription medical food that is metabolized into ketone bodies. The brain can use these ketone bodies for energy when its ability to process glucose is impaired, which brain-imaging scans suggest is the case in AD.
Caprylidene is indicated for clinical dietary management of metabolic processes associated with mild to moderate AD. General dosing recommendations include administering 40 g/day (1 packet of caprylidene powder, containing 20 g of medium-chain triglycerides) during breakfast.
Radioactive diagnostic agent for use with PET brain imaging. Binds to beta-amyloid neuritic plaques and the F 18 isotope produces a positron signal that is detected by a PET scanner.