Glaucoma refers to multifactorial optical neuropathies, which cause complete loss of vision in individuals. The abnormal increase in intraocular pressure is the common reason for the onset of the disease and blindness in an individual. The only option to prevent the progression of the glaucoma disease is to decrease the intraocular pressure. At present, a wide range of drugs is available for glaucomas, such as prostaglandin analogues, carbonic anhydrase inhibitors, beta-receptor antagonists, adrenergic agonists, and parasympathomimetics. These anti-glaucoma drugs are used effectively in controlling eye pressure instead of surgery.
What Eye Drops Are Prescribed for Glaucoma?
Prostaglandins Analogues: Prostaglandins analogues are considered as first-choice antiglaucoma medications. It works by binding with receptors prostaglandins F and cause a relaxation in the inner eye muscles, this makes the uveoscleral fluid to flow better, thus results in a decrease of intraocular pressure. Bimatoprost, latanoprost, tafluprost, and travoprost are some of the anti-glaucoma drugs available which allow intraocular pressure to drop 20 to 35%. All prostaglandin analogues are commonly well tolerated with no general side effects. They are essential once in a day and hence among other eye drops, prostaglandins have the best user compliance. However, some local common side effects involved with the use of prostaglandins such as burning, conjunctival hyperemia, stinging, eyelash alterations, increased periocular skin pigmentation, and increased iris pigmentation.
Example for approved antiglaucoma prostaglandins – Xalatan (Pfizer), Lumigan (Allergan), Travatan Z (Alcon) and Rescula (Novartis).
Beta-receptor Antagonists: It works by minimizing the form of aqueous humor in the ciliary by reducing the intracellular cAMP concentration. The potential of the intraocular pressure reducing property has been defined to be between 20% and 25% from the initial values. For years, timolol is the most frequently used drugs followed by betaxolol, carteolol, metipranolol, and levobutaxolol. Beta-receptor antagonists have potent neuroprotective effect and improve the pulmonary and cardiovascular risk profile.
Example for approved antiglaucoma Beta-receptor antagonists: Timoptic XE (Merck), Istalol (ISTA) and Betoptic S (Alcon).
Carbonic Anhydrase Inhibitors: It works by reducing the formation of aqueous humor. It is a potential intraocular pressure reducing antiglaucoma drugs with an efficacy of between 15% and 20% of the initial value. Brinzolamide and dorzolamide are presently widely used to drop eye pressure. However, these inhibitors are sulfonamides chemical and distinctive care is must as it causes serious allergic reactions in individuals. Sometimes, it can manifest to urticaria, angioedema, or pruritus and also cause side effects like burning, stinging, bitter taste, superficial punctuate keratitis, blurred vision, tearing, headache, dizziness, paresthesia, and transient myopia.
Example for approved carbonic anhydrase inhibitors: Trusopt (Merck) and Azopt (Alcon).
Adrenergic Agonists: It stimulates the activity of alpha-2 receptors, which cause vasoconstriction in the ciliary body connected with a reduction in aqueous humor formation. The consequence is lost within a treatment period of 1 month. After that period, the effects of brimonidine on uveoscleral outflow predominate, increasing outflow by contraction of the ciliary muscle. The intraocular pressure lowering probability of brimonidine is approximately 20% to 25% from baseline. Adrenergic agonists seem to have neuroprotective properties may be caused by an upregulation of neurotrophic factors.
Example for approved anti-glaucoma adrenergic agonists: Iopidine (Alcon), Alphagan (Allergan). and Alphagan-P (Allergan).
Parasympathomimetics: It encourages the contraction of smooth muscle cells in the ciliary body, which cause a rise in aqueous humor discharge. The increase in the drain of the fluids is because of the wide opening of trabecular meshwork and Schlemm’s canal. Pilocarpine is the well-known FDA accepted drug candidate of this parasympathomimetics group of antiglaucoma drugs with an intraocular pressure lowering capability of 20% to 25%. Reported side effects are abdominal spasms, bronchospasm, retinal detachment, ciliary cramps, increased pupillary block, and several other topical symptoms.
Example for approved antiglaucoma parasympathomimetics: pilocarpine, carbachol, echothiophate, and demecarium.
Anti-glaucoma drugs also available in form of combination eyes drops because some patients need more than one type of prescription to control intraocular pressure.
Hence, “combination” eye drops which have the effect of two dissimilar anti-glaucoma drugs.
Examples of FDA-approved “combination” drugs: Cosopt (Merck), Combigan (Allergan) and DuoTrav (Alcon).