Anticholinesterase Health Dictionary

An ANTICHOLINESTERASE drug which enhances neuromuscular transmission – the passage of chemical messages between nerve and muscle cells – in voluntary and involuntary muscles in patients with the disorder MYASTHENIA GRAVIS. Its e?ect lasts for about four hours. A disadvantage is that it has a marked cholinergic action – affecting heart rhythm, causing excessive salivation and tear secretion, constricting the BRONCHIOLES and stimulating the gastrointestinal tract.... neostigmine

These drugs produce partial or complete paralysis of skeletal muscle (see under MUSCLE – Structure of muscle). Drugs in clinical use are all reversible and are used to help insert a breathing tube into the TRACHEA (endotracheal tube) during general ANAESTHESIA and ARTIFICIAL VENTILATION OF THE LUNGS. They may be broadly divided into depolarising and nondepolarising muscle relaxants. Depolarising muscle relaxants act by binding to acetylcholine receptors at the motor end-plate where nerves are attached to muscle cells, and producing a more prolonged depolarisation than acetylcholine, which results in initial muscle fasciculation (overactivity) and then ?accid paralysis of the muscle. The only commonly used depolarising drug is succinylcholine which has a rapid onset of action and lasts approximately three minutes. Non-depolarising muscle relaxants bind to the acetylcholine receptors, preventing acetylcholine from gaining access to them. They have a slower onset time and longer duration than depolarisers, although this varies widely between di?erent drugs. They are competitive antagonists and they may be reversed by increasing the concentration of acetylcholine at the motor end-plate using an anticholinesterase agent such as neostigmine. These drugs are broken down in the liver and excreted through the kidney, and their action will be prolonged in liver and renal failure. Other uses include the relief of skeletal muscle spasms in TETANUS, PARKINSONISM and spastic disorders. The drugs dantrolene and diazepam are used in these circumstances.... muscle relaxants

In clinical practice, the transmission of impulses at the NEUROMUSCULAR JUNCTION may be blocked to paralyse temporarily a patient for a surgical procedure, or to assist treatment on the intensive care unit. There are two main types of drug, both of which competitively block the ACETYLCHOLINE receptors on the motor end plates. (1) Depolarising neuromuscular blocking agents: these act by ?rst producing stimulation at the receptor, and then by blocking it. There are characteristic muscle fasciculations before the rapid onset of paralysis which is of short duration (less than ?ve minutes with the commonly used drug, suxamethonium). The drug is removed from the receptor by the enzyme, CHOLINESTERASE.

(2) Non-depolarising neuromuscular blocking agents: these drugs occupy the receptor and prevent acetylcholine from becoming attached to it. However, in su?ciently high concentrations, acetylcholine will compete with the drug and dislodge it from the receptor; the e?ect of these drugs is reversed by giving an anticholinesterase, which allows the amount of acetylcholine at the neuromuscular junction to build up. These drugs have varying durations of action, but all are slower in onset and of longer duration than the depolarisers.... neuromuscular blockade

n. the acetic acid ester of the organic base choline: the *neurotransmitter released at the synapses of parasympathetic nerves and at *neuromuscular junctions. After relaying a nerve impulse, acetylcholine is rapidly broken down by the enzyme *cholinesterase. *Antimuscarinic drugs block the action of acetylcholine at receptor sites; *anticholinesterases and *acetylcholinesterase inhibitors prolong the activity of acetylcholine by blocking cholinesterase.

A pharmaceutical preparation of acetylcholine is instilled into the anterior chamber of the eye as a *miotic during intraocular surgery.... acetylcholine

n. an *anticholinesterase drug that is used after surgery to reverse the effects of nondepolarizing *muscle relaxants and in a test for diagnosis of *myasthenia gravis. Side-effects can include nausea and vomiting, increased saliva flow, diarrhoea, and stomach pains.

EDTA (ethylenediaminetetraacetic acid) see edetate.... edrophonium

n. a drug that has the effect of stimulating the *parasympathetic nervous system. The actions of parasympathomimetic drugs are cholinergic (resembling those of *acetylcholine) and include stimulation of skeletal muscle, *vasodilatation, depression of heart rate, increasing the tension of smooth muscle, increasing secretions (such as saliva), and constricting the pupil of the eye. They are used in the treatment of *myasthenia gravis (see anticholinesterase) and glaucoma (see miotic).... parasympathomimetic

n. an *anticholinesterase drug used in the treatment of *myasthenia gravis. Side-effects may include nausea, vomiting, abdominal pain, diarrhoea, sweating, and increased salivation.... pyridostigmine

a chronic disease marked by abnormal fatigability and weakness of selected muscles, which is relieved by rest. The degree of fatigue is so extreme that these muscles are temporarily paralysed. The muscles initially affected are those around the eyes, mouth, and throat, resulting in drooping of the upper eyelids (*ptosis), double vision, *dysarthria, and *dysphagia. Myasthenia gravis is an *autoimmune disease in which acetylcholine-receptor autoantibodies bind to cholinergic receptors on muscle cells, which impairs the ability of the neurotransmitter acetylcholine to induce muscular contraction. Treatment with *anticholinesterase drugs and surgical removal of the thymus in younger patients (under the age of 45 years) lessen the severity of the symptoms. Steroid therapy, intravenous immunoglobulin treatment, and plasma exchange may be used to treat the more severely affected patients.... myasthenia gravis