Cosopt (20mg/5mg) Eye Drops

Cosopt is used to lower raised pressure in the eye and to treat glaucoma. Glaucoma is a condition in which the pressure of the fluid in the eye may be high. However, some people with glaucoma may have normal eye pressure. Also, some people with raised eye pressure may not have glaucoma.

Although Cosopt helps control your glaucoma it does not cure it.


Pharmacist - M.B.A. (Public Health) D.I.C.

Cosopt (20mg/5mg) Eye Drops

Cosopt eye drops (timolol, dorzolomide) Cosopt…

Garvan J. Lynch
MBA (Public Health)

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Cosopt eye drops (timolol, dorzolomide)

  • Cosopt eye drops contain two active ingredients, timolol and dorzolamide. These are both medicines that decrease raised pressure within the eye.

What is it used for?

  • Open angle glaucoma.
  • Pseudo-exfoliative glaucoma.

How does it work?

  • Cosopt eye drops contain two active ingredients, timolol and dorzolamide. These are both medicines that decrease raised pressure within the eye.
  • The pressure within the eyeball is normally maintained by a continuous flow of liquid called aqueous humour through the eyeball. Aqueous humour is produced by a part of the eye called the ciliary body. If aqueous humour builds up inside the eyeball, this increases the pressure within the eyeball. This pressure needs to be reduced, as otherwise it can damage the optic nerve and impair vision.
  • Timolol and dorzolamide work in different ways to reduce the production of aqueous humour and so decrease its build-up inside the eyeball. They both therefore decrease the pressure in the eyeball.
  • Timolol is a type of medicine called a beta-blocker. These medicines block beta receptors in various parts of the body. Blocking the beta receptors in the eye reduces the amount of aqueous humour that is produced.
  • Dorzolamide is a type of medicine called a carbonic anhydrase inhibitor. It works by blocking the action of an enzyme in the body called carbonic anhydrase. Carbonic anhydrase is usually responsible for the production of a salt called bicarbonate in the body. Bicarbonate is needed for the production of the aqueous humour. By decreasing the production of bicarbonate, dorzolamide also decreases the production of aqueous humour.
  • Cosopt eye drops are used to treat glaucoma when treatment with a beta-blocker eye drop on its own has not lowered the pressure in the eye sufficiently.

How do I use it?

  • Cosopt eye drops are available in multi-dose bottles or preservative-free single-dose containers.
  • Cosopt eye drops in a multi-dose bottle contain the preservative benzalkonium chloride, which can be absorbed by soft contact lenses and cause eye irritation. If you wear soft contact lenses, you should remove them before putting in these eye drops. You should wait at least 15 minutes after using the drops before putting your contact lenses back in.
  • One drop should be put into the affected eye(s) twice a day. Click here for instructions on how to put in the eye drops.
  • Each preservative-free single-use vial contains enough solution to put one drop in both eyes. However, only treat both eyes if you have been told to do so by your doctor. If there is any medicine remaining in the single-use container after you have used it this should be thrown away and not kept for future use.


  • This medicine must not be taken by mouth.
  • This medicine may cause temporary blurred vision after you have applied it into the eye(s). If affected, do not drive or operate machinery until this has worn off. You should also take into account that this medicine can sometimes cause other visual disturbances, eg double vision, and dizziness or fatigue, all of which may affect your ability to drive or operate machinery.
  • When using the eye drops you should take care to not touch the dropper tip to any surface, or to your eye, in order to avoid contaminating the eye drops with germs that could cause eye infections.
  • Cosopt eye drops are sterile until opened. The multi-dose bottles contain a preservative that helps keep the eye drops sterile. Any medicine remaining in the bottle four weeks after the first opening should be carefully disposed of, as after this time it is likely to be contaminated with germs. You may find it helpful to write the date of first opening on the packet. Dispose of carefully, preferably by returning to your pharmacy. Cosopt single dose containers do not contain a preservative and are for single use only. They should be disposed of after use, even if there is some solution remaining.
  • Beta-blockers such as timolol can be absorbed into the bloodstream after being applied into the eye. They may mask the symptoms of low blood sugar (hypoglycaemia) such as increased heart rate, sweating, tremor and nausea. For this reason, people with diabetes should carefully monitor their blood sugar while using these eye drops.
  • Beta-blockers such as timolol can increase sensitivity to substances which cause allergy and the seriousness of severe allergic reactions (anaphylaxis). People who experience an anaphylactic reaction while using this medicine may need larger than normal doses of adrenaline to treat the reaction. Seek further medical advice from your doctor if you have a history of allergies.
  • While using this medicine you should have regular eye examinations.

Use with caution in

  • People with a history of heart disease.
  • People with a severe form of angina pectoris, not caused by exertion (Prinzmetal's angina).
  • Low blood pressure (hypotension).
  • People with poor blood circulation in the arteries of the extremities, eg hands and feet (peripheral arterial disorders such as Raynaud's syndrome or intermittent claudication).
  • Decreased liver function.
  • History of allergies.
  • Psoriasis.
  • Diabetes mellitus.
  • Overactive thyroid gland (hyperthyroidism).
  • Abnormal muscle weakness (myaesthenia gravis).
  • History of kidney stones.
  • Chronic defects of the transparent circular part of the front of the eyeball (cornea).
  • People who have had eye surgery.
  • Not to be used in
  • History of asthma.
  • Severe chronic obstructive pulmonary disease (COPD).
  • People with a slow heart rate caused by the pacemaker of the heart (sinus bradycardia).
  • People with a serious defect in the heart's electrical message pathways resulting in decreased function of the heart (2nd or 3rd degree heart block).
  • Uncontrolled heart failure.
  • Failure of the heart to maintain adequate circulation of blood (cardiogenic shock).
  • Severely decreased kidney function.
  • Peopel with high acid levels in the blood and tissues (acidosis).
  • Pregnancy.
  • Breastfeeding.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

  • This medicine can pass into the bloodstream after application into the eye. It should not be used during pregnancy as it may be harmful to a developing baby. Seek further medical advice from your doctor.
  • This medicine can pass into breast milk after application into the eye. It should not be used by mothers who are breastfeeding. Seek further medical advice from your doctor.

Side effects

  • Eye burning, stinging or itching.
  • Bitter taste.
  • Watering eyes.
  • Blurred vision.
  • Inflammation or irritation of the eyelids.
  • Inflammation of the surface of the eye (keratitis).
  • Headache.
  • Inflammation of the sinuses (sinusitis).
  • Disorders of the front layer of the eye (cornea).
  • Dry eyes.
  • Nausea.
  • Visual disturbances.
  • Feeling weak or fatigued.
  • Dizziness.
  • Slow heart rate (bradycardia).
  • Low blood pressure (hypotension).
  • Kidney stones.
  • Breathing difficulties due to a narrowing of the airways (bronchospasm).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

  • The timolol and dorzolamide in these eye drops can be absorbed into the bloodstream after application to the eye and it is possible they could affect other medicines that you are taking by mouth. It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while using this one, to make sure that the combination is safe.

If you are using more than one type of eye drop you should administer them at least five minutes apart, to prevent the second drop washing away the first. Use eye gels or ointments last.

Timolol may have an additive effect with medicines that decrease blood pressure, particularly medicines that are used to treat high blood pressure (antihypertensives). This may cause dizziness, which can usually be relieved by lying down until the symptoms pass. If you feel dizzy while using this medicine in combination with medicines that can lower blood pressure you should let your doctor know, as your doses may need adjusting.

There may be an increased risk of a slowed heart rate or drop in blood pressure if these eye drops are used in combination with any of the following medicines:

  • medicines for an abnormal heartbeat (antiarrhythmics), eg amiodarone, quinidine
  • beta-blocker medicines taken by mouth, eg atenolol, propranolol
  • calcium channel blockers such as diltiazem, nifedipine or verapamil
  • digoxin.

If this medicine is used with clonidine, there is a risk of a rebound increase in blood pressure if the clonidine is stopped suddenly. If the clonidine needs to be stopped, this medicine should be stopped several days before slowly stopping the clonidine.

In people with diabetes, timolol can prolong the lowering of blood sugar (hypoglycaemia) caused by insulin or other antidiabetic medicines. People with diabetes should monitor their blood sugar, as timolol can also mask the signs of hypoglycaemia.



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