Topical carbonic anhydrase II inhibitor for ophthalmic use
ATC code: S01EC03 (Dorzolamide)
Brand names
Trusopt, Cosopt
Selective inhibitor of carbonic anhydrase isoenzyme II in the ciliary body. Blocks bicarbonate formation needed for aqueous humour secretion and reduces production by 30–50%. Instillation of a 2% solution 2–3 times daily lowers IOP by 14–20% from baseline. Activity depends solely on reduced secretion, not on outflow. Systemic absorption is minimal, but accumulation may occur in severe renal impairment (CrCl below 30 mL/min).
Second line
Dorzolamide is a second-line topical carbonic anhydrase inhibitor for primary open-angle glaucoma. EGS 2024 and SEG/SEO 2023 recommend it as monotherapy for patients with contraindications to prostaglandins and beta blockers or as add-on when IOP control is insufficient. IOP reduction of 14–20% is weaker than with prostaglandins. Frequently used in a fixed combination with timolol (Cosopt) for two-mechanism synergy.
Second line
Dorzolamide lowers IOP in ocular hypertension when prostaglandins and beta blockers are contraindicated or do not reach target reduction. EGS 2024 positions it as second-line monotherapy or add-on.
Sources
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Dorzolamide is a topical carbonic anhydrase inhibitor and AEMPS registered it solely for IOP lowering. Marketing as a drug that «improves vision» or «nourishes the retina» has no evidence base: dorzolamide affects only aqueous production and does not change visual acuity, visual fields or exert RCT-confirmed neuroprotection. Off-label use for cystoid macular oedema after cataract surgery (CME) has weak evidence – case series and small open trials, without large RCTs (Cochrane 2018). It does not work in macular oedema of other aetiologies. If dorzolamide was suggested «for vision» or «for the retina» without a diagnosis of glaucoma or ocular hypertension, consider seeking a second opinion.
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FDA Category C. No controlled trials in pregnant patients. Dorzolamide contains a sulphonamide group and high systemic doses are teratogenic in animals. Systemic exposure from ophthalmic instillation is modest. AEMPS permits use when benefit outweighs risk; a topical beta blocker is preferred when possible.
Compatible with caution. Hale L3. Systemic absorption from ophthalmic instillation is modest. Milk concentrations have not been studied. Punctal occlusion for 1–2 minutes after instillation reduces infant exposure.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Dorzolamide is evaluated for the following indications with varying evidence strength: Open-angle glaucoma (evidence tier A), Ocular hypertension (evidence tier B), Vision improvement and retinal nutrition marketing (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of Dorzolamide (≥ 1 in 100): Burning and stinging after instillation, Bitter metallic taste, Superficial punctate keratitis, Tearing, Conjunctivitis, Allergic blepharitis. See the Safety section for uncommon and serious reactions.
FDA category C. FDA Category C. No controlled trials in pregnant patients. Dorzolamide contains a sulphonamide group and high systemic doses are teratogenic in animals. Systemic exposure from ophthalmic instillation is modest. AEMPS permits use when benefit outweighs risk; a topical beta blocker is preferred when possible.
Compatible with caution. Hale L3. Systemic absorption from ophthalmic instillation is modest. Milk concentrations have not been studied. Punctal occlusion for 1–2 minutes after instillation reduces infant exposure.
Dorzolamide is contraindicated in: Hypersensitivity to dorzolamide or sulphonamides; Severe renal impairment (CrCl under 30 mL/min); Hyperchloraemic acidosis; Under 1 year of age without paediatric supervision. Full list in the Safety section.