Latanoprost (free acid) is a metabolite of latanoprost which has been approved for use as an ocular hypotensive drug. Latanoprost is an isopropyl ester prodrug which is converted to the Latanoprost-acid by endogenous esterase enzymes. The free acid is pharmacologically active and is 200 times more potent than latanoprost as an agonist of the human recombinant Prostaglandin F receptor. However, the free Latanoprost-acid is more irritating and less effective than Latanoprost when applied directly to the eyes of human glaucoma patients.

Timolol is the non-selective Beta antagonist used as eye drops to treat increased pressure inside the eye such as in ocular hypertension and glaucoma. Timolol is also used for high blood pressure, chest pain due to insufficient blood flow to the heart, to prevent further complications after a heart attack, and to prevent migraines. Timolol is a beta1 and beta2 (non-selective) adrenergic receptor antagonist that does not have significant intrinsic sympathomimetic, direct myocardial depressant, or local anesthetic (membrane-stabilizing) activity. Timolol, when applied topically on the eye, has the action of reducing elevated, as well as normal intraocular pressure, whether or not accompanied by glaucoma. Elevated intraocular pressure is a major risk factor in the pathogenesis of glaucomatous visual field loss and optic nerve damage. The precise mechanism of the ocular hypotensive action of Timolol is not clearly established at this time. Tonography and fluorophotometry studies of the timolol maleate ophthalmic solution in man suggest that its predominant action may be related to the reduced aqueous formation. However, in some studies, a slight increase in outflow facility was also observed. In a study of plasma drug concentration in six subjects, the systemic exposure to timolol was determined following once daily administration of Timolol Maleate Ophthalmic Gel Forming Solution 0.5% in the morning. The mean peak plasma concentration following this morning dose was 0.28 ng/mL. Side effects, when given in the eye, include burning sensation, eye redness, superficial punctate keratopathy, corneal numbness.

Carbachol is a potent cholinergic (parasympathomimetic) agent which produces constriction of the iris and ciliary body resulting in reduction in intraocular pressure.

Epinephrine is a sympathomimetic catecholamine. It acts as a naturally occurring agonist at both alpha and beta-adrenergic receptors. Three pharmacologic types have been identified: alpha 1-, alpha 2-, and beta-adrenergic receptors. Each of these has three subtypes, characterized by both structural and functional differences. The alpha 2 and beta receptors are coupled negatively and positively, respectively, to adenylyl cyclase via Gi or Gs regulatory proteins, and the alpha 1 receptors modulate phospholipase C via the Go protein. Subtype expression is regulated at the level of the gene, the mRNA, and the protein through various transcriptional and postsynthetic mechanisms. Through its action on alpha-adrenergic receptors, epinephrine lessens the vasodilation and increased vascular permeability that occurs during anaphylaxis, which can lead to loss of intravascular fluid volume and hypotension. Through its action on beta-adrenergic receptors, epinephrine causes bronchial smooth muscle relaxation and helps alleviate bronchospasm, wheezing and dyspnea that may occur during anaphylaxis. Epinephrine also alleviates pruritus, urticaria, and angioedema and may relieve gastrointestinal and genitourinary symptoms associated with anaphylaxis because of its relaxer effects on the smooth muscle of the stomach, intestine, uterus and urinary bladder. Epinephrine increases glycogenolysis, reduces glucose up take by tissues, and inhibits insulin release in the pancreas, resulting in hyperglycemia and increased blood lactic acid.

Metipranolol is a beta-adrenergic antagonist effective for both beta-1 and beta-2 receptors. It is used as an antiarrhythmic, antihypertensive, and antiglaucoma agent. Metipranolol blocks beta1 and beta2 (non-selective) adrenergic receptors. It does not have significant intrinsic sympathomimetic activity, and has only weak local anesthetic (membrane-stabilizing) and myocardial depressant activity. Orally administered beta-adrenergic blocking agents reduce cardiac output in both healthy subjects and patients with heart disease. In patients with severe impairment of myocardial function, beta-adrenergic receptor antagonists may inhibit the sympathetic stimulatory effect necessary to maintain adequate cardiac output. Metipranolol when applied topically in the eye, has the action of reducing elevated as well as normal intraocular pressure (IOP), whether or not accompanied by glaucoma. Elevated intraocular pressure is a major risk factor in the pathogenesis of glaucomatous visual field loss. The higher the level of intraocular pressure, the greater the likelihood of glaucomatous visual field loss and optic nerve damage. The primary mechanism of the ocular hypotensive action of Metipranolol is most likely due to reduction in aqueous humor production. A slight increase in outflow may be an additional mechanism. Metipranolol reduces IOP with little or no effect on pupil size or accommodation. Metipranolol is known as the brand OptiPranolol. Brand-name OptiPranolol is manufactured by Bausch & Lomb Incorporated. However, the patents for OptiPranolol have expired, and this medication is currently available in generic form. Generic OptiPranolol eye drops are available in one strength -- metipranolol 0.3 percent solution. It is made by Falcon Pharmaceuticals.

Guanethidine belongs to the general class of medicines called antihypertensives. It was used to treat high blood pressure (hypertension). It is believed to act mainly by preventing the release of norepinephrine at nerve endings and causes depletion of norepinephrine in peripheral sympathetic nerve terminals as well as in tissues. It is taken up by norepinephrine transporters. It becomes concentrated in NE transmitter vesicles, replacing NE in these vesicles.