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.

Rivastigmine (sold under the trade name Exelon) is a parasympathomimetic or cholinergic agent for the treatment of mild to moderate dementia of the Alzheimer's type and dementia due to Parkinson's disease. Rivastigmine, an acetylcholinesterase inhibitor, inhibits both butyrylcholinesterase and acetylcholinesterase (unlike donepezil, which selectively inhibits acetylcholinesterase). It is thought to work by inhibiting these cholinesterase enzymes, which would otherwise break down the brain neurotransmitter acetylcholine. Rivastigmine capsules, liquid solution, and patches are used for the treatment of mild to moderate dementia of the Alzheimer's type and for mild to moderate dementia related to Parkinson's disease. Rivastigmine has demonstrated treatment effects on the cognitive (thinking and memory), functional (activities of daily living) and behavioral problems commonly associated with Alzheimer's and Parkinson's disease dementia. In people with either type of dementia, rivastigmine has been shown to provide meaningful symptomatic effects that may allow patients to remain independent and ‘be themselves’ for longer. In particular, it appears to show marked treatment effects in patients showing a more aggressive course of the disease, such as those with younger-onset ages, poor nutritional status, or those experiencing symptoms such as delusions or hallucinations. Side effects may include nausea and vomiting, decreased appetite and weight loss.

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.

Acquired myasthenia gravis (MG) is a chronic autoimmune disorder of the neuromuscular junction, characterized clinically by muscle weakness and abnormal fatigability on exertion. Current guidelines and recommendations for MG treatment are based largely on clinical experience, retrospective analyses and expert consensus. Pyridostigmine (under the trade names Mestinon (Valeant Pharmaceuticals)), has been used as a treatment for MG for over 50 years and is generally considered safe. It is suitable as a long-term treatment in patients with generalized non-progressive milder disease, and as an adjunctive therapy in patients with severe disease who are also receiving immunotherapy. Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft by competing with acetylcholine for attachment to acetylcholinesterase, thus slowing down the hydrolysis of acetylcholine, and thereby increases efficiency of cholinergic transmission in the neuromuscular junction and prolongs the effects of acetylcholine. The side effects of Mestinon are most commonly related to over dosage and generally are of two varieties, muscarinic and nicotinic. Among those in the former group are nausea, vomiting, diarrhea, abdominal cramps, increased peristalsis, increased salivation, increased bronchial secretions, miosis and diaphoresis. Nicotinic side effects are comprised chiefly of muscle cramps, fasciculation and weakness. Muscarinic side effects can usually be counteracted by atropine, but for reasons shown in the preceding section the expedient is not without danger. As with any compound containing the bromide radical, a skin rash may be seen in an occasional patient. Such reactions usually subside promptly upon discontinuance of the medication.

Neostigmine is a cholinesterase inhibitor used in the treatment of myasthenia gravis and to reverse the effects of muscle relaxants such as gallamine and tubocurarine. Neostigmine, unlike physostigmine, does not cross the blood-brain barrier. By inhibiting acetylcholinesterase, more acetylcholine is available in the synapse, therefore, more of it can bind to the fewer receptors present in myasthenia gravis and can better trigger muscular contraction. Neostigmine is used for the symptomatic treatment of myasthenia gravis by improving muscle tone.

LADOSTIGIL, a rasagiline derivative, is a reversible acetylcholinesterase and butyrylcholinesterase inhibitor with neuroprotective properties. It also acts as an irreversible brain monoamine oxidases inhibitor. It is under development for the treatment of neurodegenerative disorders like dementia and Alzheimer's disease.

Suronacrine (also known as HP128) is a tetrahydroacridinol derivative patented by Hoechst-Roussel Pharmaceuticals, Inc for the treatment of various memory dysfunctions characterized by decreased cholinergic function. The activity ofHP128 is attributable to its inhibition of both norepinephrine uptake and cholinesterase enzyme activity. Suronacrine has enhanced memory in animals with combined cholinergic and adrenergic lesions. In preclinical models, Suronacrine blocks responses to nerve stimulation and to carbachol, but increased responses to acetylcholine. Extracellular recording of nerve terminal currents from triangularis sterni preparations revealed that Suronacrine had a selective blocking action on the waveform associated with K+ currents.

Icopezil (previously known as CP-118,954) was developed as a selective acetylcholinesterase inhibitor for the treatment of cognitive disorders. Phase II trials of icopezil were underway in Japan and in the USA for the treatment of patients with Alzheimer's disease. However, Pfizer has discontinued these studies.

Ganstigmine is an orally active, carbamate-based acetylcholinesterase (AChE) inhibitor developed for the treatment of Alzheimer's disease. It is a newer generation AChE than BChE inhibitor, derived from genserine, and has a long duration of action in vivo. Studies have shown it significantly prevented the progressive neuronal cell death due to growth factor deprivation and decreased neurodegeneration. Ganstigmine may be a suitable candidate for the treatment of cholinergic deficit in Alzheimer's disease because it was found to significantly increase basal extracellular concentrations of acetylcholine in rat prefrontal cortex, and does not affect the concentrations of serotonin, noradrenaline and levels of dopamine and metabolites. It is safe and well tolerated at 5–10 mg doses as the study conducted in Phase I randomized, double-blind, placebo-controlled clinical trial. It was dropped from phase II trials because of its adverse effects reported in some patients.

Quilostigmine (also known as NXX-066) is an isoquinolinecarboxylate patented by Hoechst-Roussel Pharmaceuticals Inc as a memory enhancer. Quilostigmine acts as acetylcholinesterase inhibitor and studies as a potential drug for treating Alzheimer’s disease. Quilostigmine is well absorbed from the gastrointestinal tract, but the oral bioavailability poor to moderate in rats and dogs because of pre-systemic metabolism. In preclinical studies has demonstrated activity in animal models of memory function. In clinical trials, Quilostigmine was well tolerated in healthy subjects up to a single dose of 64 mg and multiple doses of 60 mg QD for seven days