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.

Demecarium (HUMORSOL®) is an indirect-acting parasympathomimetic agent, also known as a cholinesterase inhibitor and anticholinesterase. Cholinesterase inhibitors prolong the effect of acetylcholine, which is released at the neuroeffector junction of parasympathetic postganglion nerves, by inactivating the cholinesterases that break it down. Application of demecarium (HUMORSOL®) to the eye produces intense miosis and ciliary muscle contraction due to inhibition of cholinesterase, allowing acetylcholine to accumulate at sites of cholinergic transmission. These effects are accompanied by increased capillary permeability of the ciliary body and iris, increased permeability of the blood-aqueous barrier, and vasodilation. Myopia may be induced or, if present, may be augmented by the increased refractive power of the lens that results from the accommodative effect of the drug. Demecarium (HUMORSOL®) indirectly produces some of the muscarinic and nicotinic effects of acetylcholine as quantities of the latter accumulate.

Ambenonium is a cholinesterase inhibitor with all the pharmacologic actions of acetylcholine, both the muscarinic and nicotinic types. It was marketed under the brand name Mytelase, but was withdrawn from the market in the United States in 2010. Ambenonium, similar to pyridostigmine and neostigmine, is used for the treatment of muscle weakness and fatigue in people with myasthenia gravis.Ambenonium exerts its actions against myasthenia gravis by competitive, reversible inhibition of acetylcholinesterase. The disease myasthenia gravis occurs when the body inappropriately produces antibodies against acetylcholine receptors, and thus inhibits proper acetylcholine signal transmission (when acetylcholine binds to acetylcholine receptors of striated muscle fibers, it stimulates those fibers to contract). Ambenonium reversibly binds acetylcholinesterase at the anionic site, which results in the blockage of the site of acetycholine binding, thereby inhibiting acetylcholine hydrolysis and enhancing cholinergic function through the accumulation of acetycholine at cholinergic synpases. In turn this facilitates transmission of impulses across the myoneural junction and effectively treats the disease.

Ambenonium is a cholinesterase inhibitor with all the pharmacologic actions of acetylcholine, both the muscarinic and nicotinic types. It was marketed under the brand name Mytelase, but was withdrawn from the market in the United States in 2010. Ambenonium, similar to pyridostigmine and neostigmine, is used for the treatment of muscle weakness and fatigue in people with myasthenia gravis.Ambenonium exerts its actions against myasthenia gravis by competitive, reversible inhibition of acetylcholinesterase. The disease myasthenia gravis occurs when the body inappropriately produces antibodies against acetylcholine receptors, and thus inhibits proper acetylcholine signal transmission (when acetylcholine binds to acetylcholine receptors of striated muscle fibers, it stimulates those fibers to contract). Ambenonium reversibly binds acetylcholinesterase at the anionic site, which results in the blockage of the site of acetycholine binding, thereby inhibiting acetylcholine hydrolysis and enhancing cholinergic function through the accumulation of acetycholine at cholinergic synpases. In turn this facilitates transmission of impulses across the myoneural junction and effectively treats the disease.

Hexafluorenium inhibits the enzyme cholinesterase in the plasms, but apparently not at the neuromuscular juntion. It also has some nondepolarizing activity (tubocurarine-like) at the postjunctional membrane. In man hexafluorenium potentiates the muscle relaxant effects of succinylcholine. As such, smaller doses of succinylcholine are required and fewer side effects like fasciculations, twitching and postoperative muscle pain are experienced.

Edrophonium is a short and rapid-acting cholinergic drug. Chemically, edrophonium is ethyl (m-hydroxyphenyl) dimethylammonium. Edrophonium is used for the differential diagnosis of myasthenia gravis and as an adjunct in the evaluation of treatment requirements in this disease. It may also be used for evaluating emergency treatment in myasthenic crises. Because of its brief duration of action, it is not recommended for maintenance therapy in myasthenia gravis. It is also useful whenever a curare antagonist is needed to reverse the neuromuscular block produced by curare, tubocurarine, gallamine triethiodide or dimethyl-tubocurarine. It is not effective against decamethonium bromide and succinylcholine chloride. It may be used adjunctively in the treatment of respiratory depression caused by curare overdosage.

Physostigmine (Phy) is one of the oldest drug isolated from Calabar beans and successfully used for the treatment of glaucoma in 1864. Since then, it has been widely employed for various therapeutic purposes. Recently, it has gained prominence because of its clinical trials in the treatment of Alzheimer's disease. Physostigmine was used to treat glaucoma. It can be applied topically to the conjunctiva. Phy is also considered to be a potent prophylactic antidote for organophosphate poisoning. It is a reversible cholinesterase (ChE) inhibitor and has a short duration of action. For the last 50 years, numerous authors have shown that pretreatment with Phy would rapidly improve the incapacitating effects of organophosphate intoxication in various animal species. Phy carbamylates to a portion of ChE enzyme and thus protects the enzyme from binding with organophosphate, which are irreversible ChE inhibitors. The carbamylated ChE enzyme decarbamylates to free the enzyme for normal functioning. The rates of decarbamylation of butyrylcholinesterase (BuChE) in plasma and ChE in brain and muscle are different and are related to the half-life of Phy in these tissues. In addition to ChE inhibition, Phy has a direct action on acetylcholine (ACh) receptor ionophore complex by interacting with the ACh-gated cation channels. A cholinesterase inhibitor that is rapidly absorbed through membranes. It also can cross the blood-brain barrier and is used when central nervous system effects are desired, as in the treatment of severe anticholinergic toxicity.

Physostigmine (Phy) is one of the oldest drug isolated from Calabar beans and successfully used for the treatment of glaucoma in 1864. Since then, it has been widely employed for various therapeutic purposes. Recently, it has gained prominence because of its clinical trials in the treatment of Alzheimer's disease. Physostigmine was used to treat glaucoma. It can be applied topically to the conjunctiva. Phy is also considered to be a potent prophylactic antidote for organophosphate poisoning. It is a reversible cholinesterase (ChE) inhibitor and has a short duration of action. For the last 50 years, numerous authors have shown that pretreatment with Phy would rapidly improve the incapacitating effects of organophosphate intoxication in various animal species. Phy carbamylates to a portion of ChE enzyme and thus protects the enzyme from binding with organophosphate, which are irreversible ChE inhibitors. The carbamylated ChE enzyme decarbamylates to free the enzyme for normal functioning. The rates of decarbamylation of butyrylcholinesterase (BuChE) in plasma and ChE in brain and muscle are different and are related to the half-life of Phy in these tissues. In addition to ChE inhibition, Phy has a direct action on acetylcholine (ACh) receptor ionophore complex by interacting with the ACh-gated cation channels. A cholinesterase inhibitor that is rapidly absorbed through membranes. It also can cross the blood-brain barrier and is used when central nervous system effects are desired, as in the treatment of severe anticholinergic toxicity.

Huperzine A is a plant alkaloid derived from Club moss plant, Huperzine serrata, which is a member or the Lycopodium species. Huperzine-A is in phase III clinical trial in the USA (Alzheimer disease) and is available as a dietary supplement. It selectively and reversibly inhibits acetylcholinesterase. Huperzine A is also a NMDA receptor antagonist, which protects the brain against glutamate induced damage, and it increases nerve growth factor levels. Huperzine A is used for Alzheimer's disease, memory and learning enhancement, and age-related memory impairment. It is also used for treating a muscle disease called myasthenia gravis, for increasing alertness and energy, and for protecting against agents that damage the nerves such as nerve gases. It can cause some side effects including nausea, diarrhea, vomiting, sweating, blurred vision, slurred speech, restlessness, loss of appetite, contraction and twitching of muscle fibers, cramping, increased saliva and urine, inability to control urination, high blood pressure, and slowed heart rate. Various medications used for glaucoma, Alzheimer's disease, and other conditions (Cholinergic drugs) interacts with Huperzine A.

Acotiamide (Acofide(®)), an oral first-in-class prokinetic drug, is under global development by Zeria Pharmaceutical Co. Ltd and Astellas Pharma Inc. for the treatment of patients with functional dyspepsia. The drug modulates upper gastrointestinal motility to alleviate abdominal symptoms resulting from hypomotility and delayed gastric emptying. It exerts its activity in the stomach via muscarinic receptor inhibition, resulting in enhanced acetylcholine release and inhibition of acetylcholinesterase activity. Acofide® is launched in Japan for treating functional dyspepsia.