Brinzolamide is a carbonic anhydrase inhibitor used topically to lower intraocular pressure in patients with glaucoma or ocular hypertension. It works by inhibiting carbonic anhydrase in the ciliary body, reducing aqueous humor production and thereby decreasing intraocular pressure to protect the optic nerve and preserve vision. Developed in the late 20th century as a safer alternative to systemic carbonic anhydrase inhibitors like acetazolamide, brinzolamide was designed to provide effective IOP reduction with fewer systemic side effects. Approved for ophthalmic use in the early 2000s, it quickly became a widely used therapy for open-angle glaucoma and ocular hypertension, either alone or in combination with other agents, due to its favorable safety profile, convenient dosing, and ability to improve patient adherence.
BRAND NAMES
Azopt: The most recognized brand name for brinzolamide alone.
Simbrinza: is an eye drop formulation that combines brinzolamide and brimonidine.
Azarga: A combination eye drop containing brinzolamide and timolol.
MECHANISM OF ACTION
Brinzolamide is a carbonic anhydrase inhibitor that lowers intraocular pressure by selectively inhibiting carbonic anhydrase II in the eye’s ciliary body. This enzyme is responsible for the formation of bicarbonate ions, which are essential for aqueous humor production. By inhibiting carbonic anhydrase, brinzolamide reduces the formation of aqueous humor, leading to decreased intraocular pressure (IOP). Lowering IOP helps prevent optic nerve damage and slows the progression of glaucoma or ocular hypertension.
PHARMACOKINETICS
Absorption
When applied as an ophthalmic solution, brinzolamide is minimally absorbed systemically. Peak plasma concentrations are low, usually reached within 1-2 hours after ocular administration.
Distribution
It is widely distributed in the eye, particularly in the aqueous humor and ciliary body, with minimal systemic exposure.
Metabolism
Brinzolamide undergoes hepatic metabolism to a limited extent, primarily by cytochrome P450 enzymes.
Excretion
The drug is mostly excreted unchanged in the urine, with a long half-life of approximately 111 days due to strong binding to red blood cells.
PHARMACODYNAMICS
Brinzolamide is a selective carbonic anhydrase inhibitor that lowers intraocular pressure by reducing the production of aqueous humor in the eye. By inhibiting carbonic anhydrase in the ciliary body, it decreases the formation of bicarbonate ions, which in turn reduces fluid transport into the anterior chamber. This results in lower intraocular pressure, helping to prevent optic nerve damage and slow the progression of glaucoma or ocular hypertension. Its effects are dose-dependent and sustained with twice-daily topical administration.
DOSAGE AND ADMINISTRATION
Route: Ophthalmic (eye drops)
Typical dose: 1% solution, 1 drop in the affected eye(s) twice daily (approximately 12 hours apart)
Administration tips:
Wash hands before use.
Do not let the dropper tip come into contact with your eye or the surrounding skin.
Remove contact lenses prior to administration and wait at least 15 minutes before putting them back in.
Tilt head back, squeeze one drop into the conjunctival sac, and close eye for 1–2 minutes.
DRUG INTERACTIONS
Brinzolamide has minimal systemic absorption, so significant drug interactions are uncommon. Caution is advised when used with other sulfonamides or systemic carbonic anhydrase inhibitors, as additive effects or allergic reactions may occur.
FOOD INTERACTIONS
There are no clinically significant food interactions. Topical administration ensures effectiveness is unaffected by meals.
CONTRAINDICATIONS
It is contraindicated in patients with known sulfonamide hypersensitivity and those with severe renal impairment. Brinzolamide should be used with caution in patients with hepatic impairment, during pregnancy, and while breastfeeding.
SIDE EFFECTS
Eye-related:
Blurred vision (usually temporary).
Stinging or burning sensation when applied.
Eye irritation, redness, soreness, itching, or pain.
Dry eyes or feeling of something in the eye.
Eye discharge or increased tears after use.
Crusting in the corner of the eye or eyelid.
General side effects:
An unusual, bitter, or sour taste in the mouth.
Headache.
Dry mouth.
Runny or stuffy nose, sneezing, or cold symptoms.
OVERDOSE
Confusion.
Irregular heartbeat.
Muscle cramps or pain.
Neurological effects: May include numbness, tingling, pain, or weakness in the hands or feet.
Seizures.
Trembling.
Weakness and heaviness of the legs.
TOXICITY
Systemic toxicity is rare due to minimal absorption. Accidental high systemic exposure could theoretically cause metabolic acidosis or electrolyte imbalances, so monitoring is advised if this occurs.
