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.

Isofluorophate (diisopropyl fluorophosphate) is an irreversile acetylcholinesterase inhibitor. It was used in ophthalmology as a miotic agent in treatment of chronic glaucoma.

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.

Paraoxon is an odorless, reddish-yellow oil. Paraoxon is an aryl dialkyl phosphate where both the alkyl groups are ethyl and the aryl group is 4-nitrophenyl. It is a cholinesterase or acetylcholinesterase (AChE) inhibitor. It is an organophosphate oxon, and the active metabolite of the insecticide parathion. Paraoxon is one of the most potent acetylcholinesterase-inhibiting insecticides available, around 70% as potent as the nerve agent sarin, and so is now rarely used as an insecticide due to the risk of poisoning to humans and other animals. Exposure to Paraoxon can cause rapid, severe organophosphate poisoning with headache, sweating, nausea and vomiting, diarrhea, loss of coordination, and death. Paraoxon is on the Hazardous Substance List because it is cited by DOT and EPA. Parathion is converted in the body in part to paraoxon, a strong inhibitor of the enzyme acetyl cholinesterase. Upon inhibition of this enzyme in the tissues, acetylcholine, the substance responsible for transmission of nerve impulses in much of the nervous system, accumulates, producing an initial overstimulation and subsequent blockage of nerve stimuli. Paraoxon was once used as an opthamological drug against glaucoma.

Aceclidine is a parasympathomimetic agent used in the treatment of open-angle glaucoma as topical eye drop solution. It is as a muscarinic acetylcholine receptor agonist with weak anticholinesterase activity. Acting directly on the motor end-plate (cholinergic nerve endings) it decreases intraocular pressure and mediates the contraction of iris muscle. Aceclidine increased outflow facility in human eyes in vitro by a direct stimulation of the outflow tissues in the absence of an intact ciliary muscle. This effect was biphasic, occurring at concentrations of 10 uM and lower with no effect at higher concentrations. Passed numerous clinical trials in Russia, France, Italy and other countries and was widely used in Europe but never been in clinical use in USA.

Befunolol is a beta-adrenergic receptor blocker approved in Japan for the treatment of open-angle glaucoma. The current drug status is unknown.

AR-13503 is an active metabolite of Netarsudil

Tafluprost acid is a prostanoid selective FP receptor agonist that is believed to reduce the intraocular pressure (IOP) by increasing the outflow of aqueous humor. Studies in animals and humans suggest that the main mechanism of action is increased uveoscleral outflow. A prostaglandin analogue ester prodrug used topically (as eye drops) to control the progression of glaucoma and in the management of ocular hypertension. Tafluprost was approved for use in the U.S. on February 10, 2012. Tafluprost, preserved and preservative-free formulations, received marketing approval for the reduction of elevated intraocular pressure (IOP) in open-angle glaucoma and ocular hypertension in several European and Nordic countries as well as Japan, and some other Asia Pacific markets.

Travoprost, an isopropyl ester prodrug, is a synthetic prostaglandin F2 alpha analogue that is rapidly hydrolyzed by esterases in the cornea to its biologically active free acid. The travoporst free acid is potent and highly selective for the FP prostanoid receptor. Travoprost free acid is a selective FP prostanoid receptor agonist and is believed to reduce intraocular pressure by increasing the drainage of aqueous humor, which is done primarily through increased uveoscleral outflow and to a lesser extent, trabecular outflow facility. Travoprost ophthalmic solution is used for the reduction of elevated intraocular pressure in patients with open-angle glaucoma or ocular hypertension who are intolerant of other intraocular pressure lowering medications or insufficiently responsive (failed to achieve target IOP determined after multiple measurements over time) to another intraocular pressure lowering medication. Travoprost is known by the brand names of Travatan and Travatan Z, manufactured by Alcon.

Brinzolamide reduces the amount of fluid in the eye, which decreases pressure inside the eye. Brinzolamide is a carbonic anhydrase inhibitor that is FDA approved for the treatment of elevated intraocular pressure in patients with ocular hypertension or open-angle glaucoma. Common adverse reactions include abnormal taste in mouth and blurred vision. The concomitant administration of brinzolamide and oral carbonic anhydrase inhibitors is not recommended. Plus, in patients treated with oral carbonic anhydrase inhibitors, rare instances of acid-base alterations have occurred with high-dose salicylate therapy.