Brinzolamide
Brinzolamide is a topical **carbonic anhydrase inhibitor** used primarily to control **glaucoma** in dogs and cats, either alone or in combination with other topical drugs. It is often better tolerated than dorzolamide due to its more physiological pH of 7.5. > **Clinical Pearl:** While brinzolamide is ineffective at lowering intraocular pressure in normal cats, it can successfully reduce IOP in glaucomatous cats. By contrast, dorzolamide is effective in both normal and glaucomatous cats and dogs.
Mechanism: Brinzolamide reduces intraocular pressure (IOP) by inhibiting the enzyme **carbonic anhydrase** within the ciliary body epithelium. Inhibition of carbonic anhydrase → decreased formation of bicarbonate ions → reduced fluid transport → decreased rate of **aqueous humour production**.
Dosing by species
- Glaucoma · 1 drop/eye · topical · q8-12h · Can be used alone or in combination with other topical drugs.
- Glaucoma · 1 drop/eye · topical · q8-12h · Ineffective in normal cats but may reduce IOP in glaucomatous cats.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Severe hepatic impairment
- Severe renal impairment
- Uveitis (specifically for the timolol combination, as timolol causes miosis)
- Anterior lens luxation (timolol combination)
- Pupil block (timolol combination)
Adverse effects
- Local ocular irritation
- Keratitis
- Blepharitis
- Hypokalaemia (cats, rare systemic effect)
- Metabolic acidosis (dogs, rare systemic effect)
- Bradycardia and hypotension (if using the timolol combination product)
Monitoring
- Intraocular pressure (IOP)
- Signs of local ocular irritation (keratitis, blepharitis)
- Serum potassium and acid-base status (if prolonged use or systemic signs occur)
- Heart rate and blood pressure (if using timolol combination)
Overdose
Excessive topical application may increase the risk of systemic absorption, potentially leading to **metabolic acidosis** or **hypokalaemia** (especially in cats). If the timolol combination is used, overdose may lead to significant **bradycardia** and **hypotension**. Treatment is supportive and symptomatic.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.