Carbonic Anhydrase Inhibitor (Topical) Pregnancy: Should not be used during pregnancy — there are no or limited data in pregnant women; in rabbits dorzolamide produced teratogenic effects at maternotoxic doses (§4.6). Breast-feeding: excretion in human milk unknown (present in animal milk); decide whether to stop breast-feeding or the medicine.

Dorzolamide

Brand names: Trusopt, Cosopt (with timolol)

Dorzolamide is a topical carbonic anhydrase inhibitor eye drop used to lower intraocular pressure in ocular hypertension and open-angle glaucoma.

Adult dose

Dose: One drop of dorzolamide 20 mg/ml eye drops into the conjunctival sac of the affected eye(s)

Route: Ocular (topical) — instil into the conjunctival sac

Frequency: Three times daily when used as monotherapy; two times daily when used as adjunctive therapy with an ophthalmic beta-blocker

When substituting dorzolamide for another ophthalmic anti-glaucoma agent, discontinue the other agent after proper dosing on one day and start dorzolamide on the next day. Using nasolacrimal occlusion or closing the eyelids for 2 minutes reduces systemic absorption — this may decrease systemic side effects and increase local activity. If more than one topical ophthalmic drug is used, administer at least ten minutes apart. Patients should wash their hands before use and avoid contact between the container tip and the eye or surrounding structures (contaminated solutions can cause serious eye damage and loss of vision). Concomitant administration of dorzolamide with an ORAL carbonic anhydrase inhibitor is NOT recommended (additive systemic carbonic anhydrase inhibition, §4.4). Contains benzalkonium chloride — remove contact lenses before instillation and wait at least 15 minutes before reinsertion. Paediatric population: only limited clinical data are available in paediatric patients with administration three times a day (see §5.1); no separate paediatric mg/kg dose is stated. Dorzolamide has not been studied below 36 weeks gestational age or under one week of age.

Dose adjustments

Renal

Contraindicated in severe renal impairment (CrCl < 30 ml/min); not studied in this population (§4.3). Not studied in hepatic impairment — use with caution (§4.4).

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Severe renal impairment (CrCl < 30 ml/min) — not studied; dorzolamide and its metabolites are excreted predominantly by the kidney
Hyperchloraemic acidosis

Side effects

Burning and stinging (very common)
Headache (common)
Superficial punctate keratitis, tearing, conjunctivitis, eyelid inflammation, eye itching, eyelid irritation, blurred vision (common)
Nausea and bitter taste (common)
Asthenia / fatigue (common)
Rare/serious: Stevens-Johnson syndrome, toxic epidermal necrolysis, urolithiasis, corneal oedema, choroidal detachment following filtration surgery

Interactions

Oral carbonic anhydrase inhibitors — potential additive systemic effect of carbonic anhydrase inhibition; concomitant administration is not recommended (§4.4)
This interaction list may be incomplete — check the full SPC.

Clinical monograph

How it works

It inhibits carbonic anhydrase in the ciliary processes, reducing aqueous humour production and thereby lowering intraocular pressure.

Prescribing in practice

As a sulfonamide derivative it can cause hypersensitivity reactions, and serious sulfonamide-type adverse effects may occur, so it should be avoided in patients with relevant sulfonamide allergy.
It should be used with caution in significant renal impairment and is not generally recommended in severe renal impairment.
Local effects such as a bitter taste and transient ocular stinging or burning are common.

Monitoring

Monitor intraocular pressure to confirm response and review for local intolerance or hypersensitivity reactions.

Counselling the patient

A bitter taste and brief stinging after instillation are common.
If you also use other eye drops, leave a gap between them as advised.
Report any persistent eye irritation, rash or signs of an allergic reaction.

Evidence & guidelines

Topical carbonic anhydrase inhibitors are an established option for lowering intraocular pressure, supported by glaucoma guidance and the SPC.

Reference: Royal College of Ophthalmologists Glaucoma Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways