Dorzolamide
Dorzolamide hydrochloride
Also known as: Trusopt · CoSopt · Dorzolamide hydrochloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Glaucoma | 1 drop/eye | topical | q8-12h | — | 🌍 EU |
- Glaucoma: Dorzolamide/timolol combination may be more effective in dogs than either drug alone.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Glaucoma | 1 drop/eye | topical | q8-12h | — | 🌍 EU |
- Glaucoma: Maximal IOP lowering efficiency occurs with dorzolamide alone.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Dorzolamide is a topical carbonic anhydrase inhibitor used primarily for the management of glaucoma in dogs and cats. It is available as a single agent or in combination with the beta-blocker timolol.
Clinical Pearl: While the combination product is often more effective in dogs, cats typically achieve maximal intraocular pressure (IOP) reduction with dorzolamide alone. Note that its acidic pH (5.6) may cause more stinging upon application compared to brinzolamide.
Mechanism of action
Inhibits the enzyme carbonic anhydrase in the ciliary body epithelium → reduces the formation of bicarbonate ions → decreases fluid transport → reduces aqueous humour production → lowers intraocular pressure (IOP).
Safety & warnings
Contraindications
- Severe hepatic impairment
- Severe renal impairment
- Uveitis (if using timolol combination)
- Anterior lens luxation (if using timolol combination)
Adverse effects
- Local irritation
- Blepharitis
- Keratitis
- Salivation
- Inappetance
- Bradycardia (with timolol combination)
- Hypotension (with timolol combination)
- Hypokalaemia (cats, rare)
- Metabolic acidosis (dogs, rare)
Precautions
Irritation: May cause more local irritation than brinzolamide due to its pH of 5.6. Systemic Absorption: Though applied topically, systemic absorption can occur, rarely leading to hypokalaemia in cats or metabolic acidosis in dogs. Timolol Combination: Timolol causes miosis and should be avoided in cases of uveitis or anterior lens luxation.
Monitoring
- Intraocular pressure (IOP)
- Signs of local irritation (blepharitis, keratitis)
- Serum potassium in cats (if used long-term)
- Acid-base status in dogs (if used long-term)
Pharmacokinetics
Absorption
Absorbed locally into the eye. Systemic absorption can occur via the nasolacrimal duct.
Distribution
Accumulates in red blood cells due to binding to carbonic anhydrase II.
Metabolism
Metabolized to N-desethyl dorzolamide, which also inhibits carbonic anhydrase.
Elimination
Excreted primarily unchanged in the urine.
Overdose
No specific information provided in the monograph. Excessive topical application may increase the risk of systemic absorption, potentially leading to metabolic acidosis or hypokalaemia.
Available products
Formulations
- Ophthalmic drops: 20 mg/ml (2%) (Trusopt)
- Ophthalmic drops: 2% dorzolamide + 0.5% timolol (CoSopt)
Human-labeled
- Trusopt 20 mg/ml (2%) ophthalmic drops
- CoSopt 2% dorzolamide + 0.5% timolol ophthalmic drops
Regulatory status
Human approved drug used off-label in veterinary medicine.
POM (Prescription Only Medicine)
POM (Prescription Only Medicine)
No regulatory data for: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature. Protect from light. Single-use vials should be used immediately after opening.
Client information
Administration: Wash hands before and after applying. Do not let the dropper tip touch the eye or any surface. Spacing: If using multiple eye drops, wait at least 5-10 minutes between applications. Side Effects: Your pet may experience temporary stinging, squinting, or increased salivation (especially in cats due to the bitter taste draining into the mouth).
Contact your vet if the eye becomes increasingly red, cloudy, or if your pet stops eating.
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.