Galantamine (RAZADYNE®, galantamine hydrobromide) is a benzazepine derived from norbelladine. It is found in Galanthus and other Amaryllidaceae. It is a reversible, competitive acetylcholinesterase inhibitor that is used for the treatment of mild to moderate dementia of the Alzheimer’s type. Although the etiology of cognitive impairment in Alzheimer’s disease is not fully understood, it has been reported that acetylcholine-producing neurons degenerate in the brains of patients with Alzheimer’s disease. The degree of this cholinergic loss has been correlated with degree of cognitive impairment and density of amyloid plaques (a neuropathological hallmark of Alzheimer’s disease). While the precise mechanism of galantamine’s (RAZADYNE®, galantamine hydrobromide) 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 acetylcholinesterase. If this mechanism is correct, galantamine’s (RAZADYNE®, galantamine hydrobromide) effect may lessen as the disease process advances and fewer cholinergic neurons remain functionally intact. There is no evidence that galantamine (RAZADYNE®, galantamine hydrobromide) alters the course of the underlying dementing process.

Donepezil, marketed under the trade name Aricept, is a medication used in the palliative treatment of Alzheimer's disease. Aricept is indicated for the treatment of dementia of the Alzheimer’s type. Efficacy has been demonstrated in patients with mild to moderate Alzheimer’s Disease, as well as in patients with severe Alzheimer’s Disease. Donepezil 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 acetylcholinesterase. Donepezil has been tested in other cognitive disorders including Lewy body dementia and Vascular dementia, but it is not currently approved for these indications. Donepezil has also been studied in patients with Mild Cognitive Impairment, schizophrenia, attention deficit disorder, post-coronary bypass cognitive impairment, cognitive impairment associated with multiple sclerosis, and Down syndrome.

Malathion is an organophosphate insecticide, an inhibitor of cholinesterase. In low doses (0.5%) malathion is used for treatment of pediculosis and scabies.

Tacrine is a parasympathomimetic- a reversible cholinesterase inhibitor that is indicated for the treatment of mild to moderate dementia of the Alzheimer's type. An early pathophysiological feature of Alzheimer's disease that is associated with memory loss and cognitive deficits is a deficiency of acetylcholine as a result of selective loss of cholinergic neurons in the cerebral cortex, nucleus basalis, and hippocampus. Tacrine is postulated to exert its therapeutic effect by enhancing cholinergic function. This is accomplished by increasing the concentration of acetylcholine at cholinergic synapses through reversible inhibition of its hydrolysis by acetylcholinesterase. If this proposed mechanism of action is correct, tacrine's effect may lessen as the disease progresses and fewer cholinergic neurons remain functionally intact. There is no evidence that tacrine alters the course of the underlying dementing process. The mechanism of tacrine is not fully known, but it is suggested that the drug is an anticholinesterase agent which reversibly binds with and inactivates cholinesterases. This inhibits the hydrolysis of acetylcholine released from functioning cholinergic neurons, thus leading to an accumulation of acetylcholine at cholinergic synapses. The result is a prolonged effect of acetylcholine. is used for the palliative treatment of mild to moderate dementia of the Alzheimer's type. Tacrine was marketed under the trade name Cognex. Because of its liver toxicity and attendant requirement for monitoring liver function, tacrine prescriptions dropped after other acetylcholinesterase inhibitors were introduced, and its use has been largely discontinued.

NAMENDA (marketed under the brands Namenda among others) is an N-methyl-D-aspartate (NMDA) receptor antagonist indicated for the treatment of moderate to severe dementia of the Alzheimer’s type. Persistent activation of central nervous system N-methyl-D-aspartate (NMDA) receptors by the excitatory amino acid glutamate has been hypothesized to contribute to the symptomatology of Alzheimer’s disease. Memantine is postulated to exert its therapeutic effect through its action as a low to moderate affinity uncompetitive (open-channel) NMDA receptor antagonist which binds preferentially to the NMDA receptor-operated cation channels. There is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer’s disease. Memantine showed low to negligible affinity for GABA, benzodiazepine, dopamine, adrenergic, histamine and glycine receptors and for voltage-dependent Ca2+, Na+ or K+ channels. Memantine also showed antagonistic effects at the 5HT3 receptor with a potency similar to that for the NMDA receptor and blocked nicotinic acetylcholine receptors with one-sixth to one-tenth the potency. In vitro studies have shown that memantine does not affect the reversible inhibition of acetylcholinesterase by donepezil, galantamine, or tacrine.