Dorzolamide is a sulfonamide and a highly specific carbonic anhydrase II (CA-II) inhibitor, which is the main CA isoenzyme involved in aqueous humor secretion. Dorzolamide is marketed under the trade name Trusopt, indicated in the treatment of elevated intraocular pressure in patients with ocular hypertension or open-angle glaucoma. Carbonic anhydrase (CA) is an enzyme found in many tissues of the body including the eye. It catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In humans, carbonic anhydrase exists as a number of isoenzymes, the most active being carbonic anhydrase II (CA-II), found primarily in red blood cells (RBCs), but also in other tissues. Inhibition of carbonic anhydrase in the ciliary processes of the eye decreases aqueous humor secretion, presumably by slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport. The result is a reduction in intraocular pressure (IOP). TRUSOPT Ophthalmic Solution contains dorzolamide hydrochloride, an inhibitor of human carbonic anhydrase II. Following topical ocular administration, TRUSOPT reduces elevated intraocular pressure. Elevated intraocular pressure is a major risk factor in the pathogenesis of optic nerve damage and glaucomatous visual field loss.

Methazolamide is topical carbonic anhydrase inhibitor. Methazolamide is indicated for the reduction of elevated intraocular pressure in patients with open-angle glaucoma or ocular hypertension who are insufficiently responsive to beta-blockers. Methazolamide is a sulfonamide derivative; however, it does not have any clinically significant antimicrobial properties. Although methazolamide achieves a high concentration in the cerebrospinal fluid, it is not-considered an effective anticonvulsant. Methazolamide has a weak and transient diuretic effect, therefore use results in an increase in urinary volume, with excretion of sodium, potassium and chloride. Methazolamide is a potent inhibitor of carbonic anhydrase. Inhibition of carbonic anhydrase in the ciliary processes of the eye decreases aqueous humor secretion, presumably by slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport. Methazolamide is used for treatment of chronic open-angle glaucoma and acute angle-closure glaucoma.

Pilocarpine is an alkaloid extracted from plants of the genus Pilocarpus. The drug stimulates the muscarinic receptors (especially M3, which is expressed in smooth muscles and glands) and thus induces salivation, hypertension and water intake. Pilocarpine was appoved by FDA for the alleviation of symptoms of xerostomia in patients who have undergone radiation therapy to their head and neck cancer and in patients with Sjogren's Syndrome. Ophthalmic solution of the drug is prescribed for the treatment of glaucoma, ocular hypertension, postoperative elevated intraocular pressure, etc.

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.

Acetazolamide, usually sold under the trade name Diamox in some countries. DIAMOX is used for adjunctive treatment of: chronic simple (open-angle) glaucoma, secondary glaucoma, and preoperatively in acute angle-closure glaucoma where delay of surgery is desired in order to lower intraocular pressure. DIAMOX is also indicated for the prevention or amelioration of symptoms associated with acute mountain sickness despite gradual ascent. DIAMOX is an enzyme inhibitor that acts specifically on carbonic anhydrase, the enzyme that catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In the eye, this inhibitory action of acetazolamide decreases the secretion of aqueous humor and results in a drop in intraocular pressure, a reaction considered desirable in cases of glaucoma and even in certain non-glaucomatous conditions. Evidence seems to indicate that DIAMOX has utility as an adjuvant in treatment of certain dysfunctions of the central nervous system (e.g., epilepsy). The diuretic effect of DIAMOX is due to its action in the kidney on the reversible reaction involving hydration of carbon dioxide and dehydration of carbonic acid. The result is renal loss of HCO3 ion, which carries out sodium, water, and potassium. It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.