Anticholinesterase Agents

Anticholinesterase Agents 

a group of medicinal substances that slow the activity of cholinesterase (an enzyme that decomposes acetylcholine, a substance that transmits stimuli in the nervous system). The mechanism of anticholinesterase activity consists in the intensification of the effect of acetycholine on the glands, heart, nerve ganglia, and smooth and skeletal musculature. Also significant is the direct effect of anticholinesterase remedies on tissue. Anticholinesterase agents are conventionally divided into substances of reversible or irreversible effect, according to the way they interact with cholinesterase. To those of the first group belong physostigmine (or eserine), galanthamine, proserine methyl sulfate, and others; to those of the second group belong phosphacol, “armine,” “pyrophos,” insecticides (for example, “chlorophos,” parathion), and also certain chemical warfare agents (tabun, “zarin,” and “zoman”). Anticholinesterase remedies intensify contractions of the smooth musculature of the eyes, bronchi, gastrointestinal tract, biliary and urinary tracts, and uterus. They increase secretion of the digestive and sweat glands and stimulate the autonomic nervous system, increasing the tonus of the sympathetic and parasympathetic nerves. Anticholinesterase agents that act on the eye cause extreme miosis, the decrease of intraocular pressure, and an accommodation cramp. Contraction of the striated (skeletal muscles is also intensified under the influence of anticholinesterase agents.

Certain anticholinesterase agents (phosphacol, “armine,” “pyrophos,” physostigmine) are used in ophthalmology to decrease intraocular pressure in the treatment of glaucoma; galanthamine and eserine in the treatment of myasthenia, myopathy, and other diseases accompanied by reduction in the strength of skeletal muscle contraction.

Anticholinesterase agents used as chemical warfare agents and also toxic doses of anticholinesterase agents in medical practice are capable of causing excitation of the central nervous system manifested by convulsions, which may be followed by paralysis. If the paralysis spreads to the respiratory center, death results. Atropine and other preparations are used for treatment of poisoning with anticholinesterase agents.

REFERENCES

Zakusov, V. V. Farmakologiia, 2nd ed. Moscow, 1966.
Mashkovskii, M. D. Lekarstvennye sredstva, 6th ed., parts 1–2. Moscow, 1967.

IU. V. BUROV