Cholinesterase inhibitors glaucoma treatment

L The answer is b. (Hardman, pp 166-167.) Echothiophate iodide is a long-acting (irreversible) cholinesterase inhibitor. It is used topically in the eye for the treatment of various types of glaucoma. Maximum reduction of intraocular pressure occurs within 24 h, and the effect may persist for several days. The drug is a water-soluble compound, which affords it a practical advantage over the lip id-soluble isofluorphate (another cholinesterase inhibitor used to treat glaucoma). 

Because anticholinesterase agents also inhibit plasma pseudo-ChE, they will potentiate the effects of succinylcholine by inhibiting its breakdown. This is important, for example, when succinylcholine is to be employed in patients who have previously received cholinesterase inhibitors for the treatment of myasthenia gravis or glaucoma. 

The major therapeutic uses of the cholinomimetics are for diseases of the eye (glaucoma, accommodative esotropia), the gastrointestinal and urinary tracts (postoperative atony, neurogenic bladder), the neuromuscular junction (myasthenia gravis, curare-induced neuromuscular paralysis), and very rarely, the heart (certain atrial arrhythmias). Cholinesterase inhibitors are occasionally used in the treatment of atropine overdosage. Several newer cholinesterase inhibitors are being used to treat patients with Alzheimer s disease. 

Reversible cholinesterase inhibitors find their greatest clinical use in the treatment of open-angle glaucoma. Relief is achieved by enhancing the contraction of the ciliary muscle and the iris sphincter. This contracture pulls the iris off the lens and facilitates fluid movement through the canal of Schlemm. The result is decreased pressure with reduced distortion of the lens and increased movement of aqueous humor out of the anterior chamber of the eye. 

Echothiophate iodide is a long-lasting cholinesterase inhibitor of the irreversible type, as is isofluorphate. Unlike the latter, however, it is a quaternary salt, and when applied locally, its distribution in tissues is limited, which can be very de.sirablc. It is used as a long-acting anticholinesterase agent in the treatment of glaucoma. 

Echothiophate is a cholinesterase inhibitor that causes miosis, increase in facility of outflow of aqueous humor, a fall in lOP, and potentiation of accommodation by enhancing the effect of endogenously liberated acetylchohne in the iris, ciliary muscle, and other parasympathetic innervated structures of the eye. It is indicated in the treatment of chronic open-angle glaucoma and treatment of accommodative esotropia (see also Figure 12). 

DFP is also knovm as a cholinesterase inhibitor for glaucoma treatment, Floropryl Ophthalmic. 

Plant-originated anti-ChEs, such as huperzine A, have been used for thousands of years in the treatment of aging-induced memory impairment (Haviv et al., 2007). In 1877, prior to the discovery of ACh as a neurotransmitter in the brain, physostigmine (eserine)— a carbamate extracted from the seeds of Physostigma venenosum—became the first cholinesterase inhibitor used therapeutically to control increased ocular pressure caused by wide-angle glaucoma (Taylor, 1996). 

Difluorophate (diisopropyl fluorophosphate) is an irreversible inhibitor of cholinesterase. It has been used in the treatment of glaucoma (Figure 8.87). 

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