Acetazolamide

Acetazolamide is a white to yellowish-white fine crystalline powder that is slightly soluble in acetone, insoluble in chloroform, diethyl ether and carbon tetrachloride. The chemical name of it is 2-acetamido-1,3,4-thiadiazole-5-sulfonamide. Acetazolamide is a first-generation carbonic anhydrase (CA) inhibitor, which is most commonly used in the treatment of glaucoma. The structure is shown in fig. 1.

Fig. 1 Structure of acetazolamide

Application in the treatment of glaucoma

• Introduction of glaucoma

Glaucoma is a group of eye diseases that damage the optic nerve, leading to vision loss. Glaucoma includes open-angle glaucoma and closed-angle glaucoma. Open-angle glaucoma develops slowly without pain, whereas closed-angle glaucoma appears suddenly and can be accompanied by severe eye pain, blurred vision, mid-dilated pupils, eye redness and nausea. The common features of all forms of glaucoma are loss of retinal ganglion cells, thinning of the retinal nerve fiber layer, and cupping of the optic disc (fig. 2)[1]. Glaucoma is the leading cause of irreversible blindness in the world, with an estimated 67 million people suffering from glaucoma. Therefore, prevention and treatment of glaucoma are very important for eye protection.

• Mechanism of action

As an enzyme in the eyes, CA reversibly catalyzes the reaction of H2O and CO2 to form carbonic acid and subsequently the HCO3-. As shown in the following equation:

The HCO3- is responsible for the movement of Na+ into the eyes. Water follows Na+ to form the aqueous humor. Acetazolamide is a CA inhibitor that decreases HCO3- concentration and therefore the flow of Na+ and H2O into the posterior chamber, resulting in a decreased production of aqueous humor and hence a lowering of intraocular pressure. Low intraocular pressure is beneficial for treating glaucoma.

• Side effects

Common side effects of acetazolamide mainly include:

Less common side effects of acetazolamide mainly include:

Application in the treatment of other diseases

Acetazolamide plays an unparalleled role in the treatment of diseases. In addition to glaucoma, acetazolamide is also used in the treatment of drug-induced edema, heart failure-induced edema, epilepsy, altitude sickness, Ménière's disease, increased intracranial pressure and neuromuscular disorder.