BMA Concise Guide to Medicine & Drugs


Brand name Trusopt

Used in the following combined preparation Cosopt


Drug group Drug for glaucoma

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Dorzolamide is a carbonic anhydrase inhibitor (a kind of diuretic) that is used, in the form of eye drops only, to treat glaucoma. It is also used for ocular hypertension (high pressure inside the eye). The drug relieves the pressure by reducing production of aqueous humour, the fluid in the front chamber of the eye.

Dorzolamide may be used either alone or combined with a beta blocker by people who are resistant to the effects of beta blockers or for whom beta blockers are not suitable.

Most side effects of dorzolamide are local to the eye, but systemic effects may occur if enough of the drug is absorbed by the body.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Eye drops.

Frequency and timing of doses 3 x daily (on its own); 2 x daily (combined preparation).

Adult dosage range 1 drop in the affected eye(s) or as directed.

Onset of effect 15–30 minutes.

Duration of action 4–8 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light. Discard eye drops 4 weeks after opening.

Missed dose Use as soon as you remember. If your next dose is due, skip the missed dose and then go back to your normal dosing schedule.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra application is unlikely to cause problems. Excessive use may provoke side effects as described herebelow.


Local side effects of dorzolamide include inflammation of the surface of the eye and the skin of the eyelids, which may lead to burning, stinging, or watery eyes, inflamed or sore eyes, or blurred vision. The drug may also cause a bitter taste in the mouth. Consult your doctor if any of these become severe. Systemic side effects may also occur but are rare. If you develop an itchy rash, swelling of the lips or tongue, or breathing difficulties, you should consult your doctor urgently.




Be sure to tell your doctor if:

· You have liver or kidney problems.

· You are allergic to sulphonamide drugs.

· You are allergic to benzalkonium chloride.

· You are taking other medicines.

Pregnancy Not prescribed. Discuss with your doctor.

Breast-feeding Not recommended. Discuss with your doctor.

Infants and children Not recommended.

Over 60 No special problems.

Driving and hazardous work Avoid such activities until you have learned how dorzolamide affects you because the drug can affect your vision.

Alcohol No special problems.


Rarely, prolonged use of this drug may lead to development of kidney stones.