How Do Antiglaucoma Carbonic Anhydrase Inhibitors Work?

Antiglaucoma carbonic anhydrase inhibitors reduce the pressure inside the eye (intraocular pressure) by decreasing the production of aqueous humor. Carbonic anhydrase inhibitors inhibit the activity of carbonic anhydrase, an enzyme involved in the secretion of fluid in many parts of the body, including aqueous humor in the eyes.

Aqueous humor is a clear fluid that fills the space between the lens and the cornea in the eyes. A part of the eye known as the ciliary body produces aqueous humor, which supplies oxygen and nutrients to the lens and cornea and removes waste products.

Balancing the inflow and outflow of aqueous humor is essential to maintain optimum pressure in the eye.

Antiglaucoma carbonic anhydrase inhibitors work topically or systemically to reduce the production of aqueous humor. Topical applications work directly on the ciliary body to decrease the secretion of aqueous humor. Systemic carbonic anhydrase inhibitors work on the kidneys to increase urination and reduce the fluid content in the body, including the eyes.

Antiglaucoma carbonic anhydrase inhibitors are used to treat eye conditions with elevated intraocular pressure. In addition to eye conditions, systemic carbonic anhydrase inhibitors are also used to treat other conditions such as altitude sickness, congestive heart failure and seizures.

Antiglaucoma carbonic anhydrase inhibitors are usually administered along with other types of medications such as antiglaucoma beta blockers. Eye conditions treated with antiglaucoma carbonic anhydrase inhibitors include the following:

• Glaucoma: Glaucoma is a progressive disease that damages the optic nerve. Glaucoma is most often characterized by elevated intraocular pressure, although some people may develop glaucoma with normal pressure. Lowering the elevated pressure to reduce the risk of optic nerve damage is the primary treatment for glaucoma. Types of glaucoma treated with carbonic anhydrase inhibitors include:
  • Open-angle glaucoma: The most common type of glaucoma in which the drainage angle through which the aqueous humor drains remains open, but the drainage channels are partially blocked.
  • Closed-angle glaucoma: The iris bulges towards the cornea closing the drainage angle, which affects the drainage of aqueous humor and elevates the intraocular pressure. Angle closure glaucoma may be acute, or a chronic condition that develops slowly over time.
  • Secondary glaucoma: Secondary glaucoma results from an injury or other conditions that lead to elevated intraocular pressure.
• Ocular hypertension: Elevated intraocular pressure due to imbalance in the production and drainage of aqueous humor

Side effects of antiglaucoma carbonic anhydrase inhibitors may include the following:

Ocular side effects:

• Blurred vision
• Double vision (diplopia)
• Blepharitis (inflammation of the eyelids)
• Dry eyes
• Irritation, discomfort and foreign body sensation
• Pain, burning and stinging
• Tearing and/or discharge
• Eyelid margin crusting
• Light sensitivity
• Hyperemia (dilation of blood vessels)
• Itching and redness
• Corneal inflammation (keratitis)
• Allergic reactions in and around the eye
• Conjunctivitis (inflammation of the conjunctiva, the membrane that lines the eye and inner surface of eyelids)
• Keratoconjunctivitis (inflammation of cornea and conjunctiva)
• Eye fatigue
• Degeneration of cornea (keratopathy)

Systemic side effects:

• Confusion
• Dizziness
• Convulsions
• Drowsiness
• Bronchospasm and shortness of breath (dyspnea)
• Chest pain
• Muscle weakness
• Muscle stiffness (hypertonia)
• Flaccid paralysis (muscle weakness or paralysis with reduced muscle tone)
• General malaise
• Abnormal skin sensation (paresthesia)
• Hypersensitivity reactions such as:
  • Hives (urticaria)
  • Hair loss (alopecia)
  • Angioedema (swelling in the tissue below the skin or mucous membranes)
  • Toxic epidermal necrolysis (a rare and serious skin condition with skin peeling and blistering)
  • Stevens-Johnson syndrome (a rare medical emergency with flu-like symptoms and a painful rash)
• Dry mouth
• Bitter taste
• Nasal bleeding (epistaxis)
• Hearing issues or noises in the ears (tinnitus)
• Pharyngitis (inflammation of the pharynx)
• Lack of appetite
• Indigestion (dyspepsia)
• Nausea, vomiting and diarrhea
• Liver damage or disease
• Aplastic anemia (low red blood cell production)
• Leukopenia (low white blood cells)
• Agranulocytosis (dangerously low white
• blood cells)
• Thrombocytopenia (low platelet count)
• Thrombocytopenic purpura (bruising and bleeding due to thrombocytopenia)
• Dark tarry stools (melena)
• Acidosis (too much acid in body fluids)
• Electrolyte imbalance
• Excessive urination (polyuria)
• Blood in urine (hematuria)
• Excess sugar in urine (glycosuria)
• Kidney pain

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Antiglaucoma anhydrase inhibitors are available as ophthalmic suspensions or solutions which are topically administered in the eyes, and as tablets, capsules and injections that work systemically. Generic and brand names of some antiglaucoma carbonic anhydrase inhibitors include:

Topical:

• Brinzolamide (Azopt)
• Dorzolamide hydrochloride (Trusopt)

Systemic:

• Acetazolamide, Acetazolamide sodium
• Methazolamide