Brinzolamide

Brinzolamide is a type of eye drop that treats glaucoma, or high pressure in the eye. In eyes with glaucoma, the amount of fluid in the eye is excessive, which raises the pressure inside the eye. This high intraocular pressure can cause loss of sight. Brinzolamide reduces the pressure inside eyes with glaucoma. The most common side effect is burning or stinging sensations in the eye. However, brinzolamide is less likely to cause eye irritation than are some other eye drops for glaucoma.

It was approved by the Food and Drug Administration on April 1, 1998.

Other Names

Brinzolamide is marketed in the U.S. by Alcon Laboratories under the brand name Azopt.

Uses/Indications

Brinzolamide is used to reduce the buildup of fluid in the eye, called intraocular pressure. It is used to reduce the pressure in eyes with a form of glaucoma called primary open-angle glaucoma, and also in ocular hypertension. Frequently, brinzolamide is used in patients who are not responding to treatment with beta-blockers such as timolol (Timoptic), or in patients who cannot take beta-blockers. Children or adolescents up to 17 years of age should not take brinzolamide unless directed to do so by a physician.

Diagram of an eye. Source: National Eye Institute, National Institutes of Health

How Brinzolamide Is Taken

Brinzolamide is a milky fluid of 1% brinzolamide, drops of which are placed in the eye two or three times a day. It is instilled under the eye by pulling down the lower eyelid. Sometimes brinzolamide leaks into the bloodstream and enters the circulation, or can cause a bad taste in the mouth. To reduce this risk, the patient should close the eye and press the corner of the eye next to the nose after instilling the drop. Brinzolamide is combined with other drops that reduce intraocular pressure, such as beta-blockers, if necessary.

How Brinzolamide Works

Glaucoma is caused by a buildup of fluid in the eye. This fluid accumulation increases pressure in the eye, called intraocular pressure, which can damage the retina, crush the optic nerve, and ultimately lead to vision loss. Brinzolamide reduces the amount of fluid secreted into the eye, and thus reduces the pressure. Intraocular pressure is measured in terms of mm Hg, or millimeters of mercury. Pressures over 20mm Hg are high.

Brinzolamide is a sulfa drug that inhibits the enzyme carbonic anhydrase, which pushes fluid into the eye. ^[1] In general, brinzolamide is as effective as other medications that reduce intraocular pressure, but it causes fewer side effects.

How The Body Affects Brinzolamide

Even though brinzolamide is an eye drop, it can enter the circulation, where it collects in red blood cells. Because of this accumulation, the time needed to reduce the amount of circulating brinzolamide by half (its half-life) is about 24 weeks. Brinzolamide in red blood cells can inhibit carbonic anhydrase in the red blood cells. Over half of brinzolamide is excreted in urine. Some brinzolamide is metabolized (broken down) in the liver, primarily by an enzyme called CYP3A4.

Side Effects

The most common side effect of brinzolamide is a bitter or unusual taste in the mouth. This can be reduced or prevented by gently closing the eye and pressing at the corner near the nose after instilling the drop. Several other mild side effects have been reported:

• Blurred vision
• Eye pain or discomfort
• Foreign body sensation in the eye
• Headache
• Dry or red eyes

Risks and Precautions

Because brinzolamide can cause some blurring of vision, a patient should not drive or operate heavy machinery after instilling a drop. Patients should notice how brinzolamide affects their vision before doing these tasks.

The effect of brinzolamide in eyes with contact lenses has not been studied. Brinzolamide may affect the water content of the cornea, so brinzolamide use in eyes with contact lenses should be monitored to reduce the risk of cornea problems. Contact lenses should be removed when instilling brinzolamide and replaced 15 minutes after the drop. Because of the effects on the cornea, a physician should monitor the use of brinzolamide if the patient has conditions that affect the cornea, such as diabetes.

Patients should notify a healthcare provider if they have hyperchloremic acidosis, severe kidney problems, or liver problems. Another drug might be preferred in patients with any of these conditions.

Brinzolamide is a sulfa drug, and it does enter the circulation. Thus, people who are allergic to sulfa drugs will also be allergic to brinzolamide.

Brinzolamide should not be used if another carbonic anhydrase inhibitor is being used.

The effects of brinzolamide during pregnancy have not been studied. However, brinzolamide should not be used during pregnancy or while breast-feeding.

Drug Interactions

Drugs that inhibit the enzyme that metabolizes brinzolamide, CYP3A4, may reduce the metabolism of brinzolamide. Some of these drugs include the antifungals ketoconazole (Nizarol), itraconazole (Sporanox), and the HIV/AIDS drug ritonavir (Norvir). Caution should be used when brinzolamide is given with these or other drugs that inhibit CYP3A4.

Research

Treatment with brinzolamide (1%) for two weeks was shown to reduce intraocular pressure by 16%.^[2] Similar effects were produced after three months of treatment.^[3] Brinzolamide is as effective as another carbonic anhydrase inhibitor, dorzolamide (Trusopt), for reducing intraocular pressure, but brinzolamide causes fewer burning sensations in the eye.

One study found that dorzolamide caused burning and stinging sensations in 11% of patients and brinzolamide caused the sensations in 3% of patients.^[3] An 18-month study found that brinzolamide reduced intraocular pressure between 2.7mm Hg to 3.9mm Hg.^[4] This reduction was equivalent to that seen with treatment with timolol, but brinzolamide caused less burning and stinging.

References

1. ↑ Sharir, M. Topical carbonic anhydrase inhibitors. In, Textbook of Ocular Pharmacology, (Zimmerman, T.J., ed.) Lippincott-Raven, Philadelphia, 1997, pp. 287-290.
2. ↑ Silver LH. Dose-response evaluation of the ocular hypotensive effect of brinzolamide ophthalmic suspension (Azopt). Brinzolamide Dose-Response Study Group. Surv Ophthalmol 2000 Jan;44 Suppl 2:S147-53. Abstract | Full Text
3. ↑ ^{3.0 3.1} Sall K. The efficacy and safety of brinzolamide 1% ophthalmic suspension (Azopt) as a primary therapy in patients with open-angle glaucoma or ocular hypertension. Brinzolamide Primary Therapy Study Group. Surv Ophthalmol. 2000 Jan;44 Suppl 2:S155-62. Abstract | Full Text
4. ↑ March WF, Ochsner KI. The long-term safety and efficacy of brinzolamide 1.0% (Azopt) in patients with primary open-angle glaucoma or ocular hypertension. The Brinzolamide Long-Term Therapy Study Group. Am J Ophthalmol 2000 Feb;129(2):136-43. Abstract | Full Text

External Links

Alcon Pharmaceuticals: Azopt

MedicineNet: Brinzolamide-Opthalmic Suspension, Azopt Side Effects, Medical Uses, and Drug Interactions

Web MD Carbonic Anhydrase Inhibitors

Aging Eye: Glaucoma Information and Glaucoma Risk Factors