Dorzolamide

Carbonic anhydrase inhibitor (topical), Glaucoma medication, Ocular hypotensive agent

Dorzolamide

Trusopt; with timolol as Cosopt

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Titration strategies

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Effects

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Summary

Classes

Carbonic anhydrase inhibitor (topical), Glaucoma medication, Ocular hypotensive agent

Common uses

Primary open-angle glaucoma▲0▼, Ocular hypertension▲0▼

Pharmacy

Starting dose

1 drop in affected eye(s) TID (monotherapy); BID with timolol (Cosopt)

Preparations

2% ophthalmic solution (Trusopt); 2%/0.5% fixed combination with timolol (Cosopt, Cosopt PF)

US FDA Max

TID per eye

Pharmacology

Routes

Topical ophthalmic

Onset

IOP lowering at 2 hours; max at 4 hours

Duration

8-12 hours (TID dosing needed)

Half-life

~4 months in erythrocytes (carbonic anhydrase binding in red cells; not relevant to topical IOP duration)

Bioavailability

Topical with measurable systemic absorption (small CA inhibition observed clinically with chronic use)

Pregnancy

Limited data; weigh against alternatives.^{[citation needed]}

Legal status

Rx-only in US

Purported mechanism

Dorzolamide selectively inhibits carbonic anhydrase II (CA-II) in the ciliary epithelium, reducing bicarbonate formation and aqueous humor production; IOP falls ~18-22% from baseline.▲0▼ Compared with oral acetazolamide, topical CAI provides similar local efficacy without the systemic acidosis, paresthesias, and kidney stone risk of systemic CA inhibition. Sulfonamide structural class — caution in severe sulfa allergy.