Table 1.

The mechanisms of action and adverse reactions of drugs approved by Food and Drug Administration (FDA) for Alzheimer’s disease (AD) treatment.

Drugs	Mechanisms of Action	Main Limitations	Reference
Tacrine	Inhibition of acetylcholinesterase activity and increase in acetylcholine level	Oral administration leads to strong hepatotoxicity and gastrointestinal adverse reactions, which quickly leads to increase in transaminase activity	[11,12]
Donepezil	Inhibition of acetylcholinesterase activity and increase in acetylcholine level. Inhibition of aberrant glia cell activation to alleviate neuroinflammation	Low CNS selectivity, gastrointestinal toxicity (nausea, vomiting, anorexia, flatulence, loose stool, diarrhea, salivation, and abdominal colic)	[13,14,15]
Rivastigmine	Selective enhancement of Ach activity in the cerebral cortex and hippocampus. Improvements in cognitive function and deceleration of APP formation	Adverse reactions such as acute dystonia, nausea, vomiting, diarrhea, dizziness, and weight loss	[16,17,18]
Galantamine	Inhibition of acetylcholinesterase activity and increase in acetylcholine level. Regulation of nicotinic acid receptors outside the brain to increase Ach release	Severe cutaneous adverse drug reactions	[19]
Memantine	Antagonizing effect on NMDAR	Bradycardia	[20,21]
Aducanumab	Recognition of an epitope of Aβ, reduction of aggregated soluble and insoluble forms of Aβ.	ARIA, effusion, minor hemorrhage, and hemosiderosis	[22]

CNS, central nervous system; Ach, acetylcholine; APP, amyloid precursor protein; NMDAR, N-methyl-D-aspartate-receptor; ARIA, amyloid-associated imaging abnormality.