Cosdor eye drops - Precautions | How to apply

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Cosdor eye drops contain two active substances (dorzolamide and timolol). Dorzolamide belongs to the group of carbohydrase inhibitors while timolol belongs to beta-blockers. Both substances decrease the secretion of the aqueous humor, but with different mechanisms, so, the combined use of these two substances exhibits an additive effect. Decreased secretion of aqueous humor causes reduction of intraocular pressure, which is why Cosdor is used to treat open angle glaucoma and pseudoexfoliative glaucoma.


Due to possible absorption into the systemic circulation, this drug may exhibit some systemic side effects. Therefore, its use is contraindicated in following conditions:

  • Asthma and chronic obstructive pulmonary disease. Timolol is a beta blocker and may cause bronchoconstriction, and therefore should not be used (even when given in the form of eye drops) in patients with respiratory disorders.
  • Sinus bradycardia, cardiogenic shock or atrioventricular block II or III degree. Timolol can block beta-2 receptors in heart (even when given in the form of eye drops) and should not be used in patients who have cardiac diseases.
  • Hyperchloremic acidosis
  • Severe kidney damage

It is very important that you use this medicine properly to reduce the risk of systemic absorption. Therefore, after putting the drop in your conjunctival fornix, press on the inside corner for two minutes. This will reduce the risk of systemic absorption and systemic adverse effects.


Cosdor should be used cautiously in patients with Raynaud's disease (peripheral circulation disease) due to possible worsening of the symptoms.

Beta blockers (timolol) may mask the symptoms of hypoglycaemia, and this medicine should be used with extreme caution in diabetics.

Application in patients suffering from myasthenia gravis should be avoided, because this drug may exacerbate the symptoms.

Cosdor may mask the symptoms of excessive thyroid activity (hyperthyroidism) and symptoms of this disease may worsen if you abruptly stop using Cosdor. For this reason, Cosdor eye drops should be applied cautiously in patients with thyroid disease.

Serious forms of allergic reactions (toxic epidermal necrolysis or Stevens-Johnson syndrome) have been rarely reported.

Cosdor, pregnancy and breastfeeding

US FDA and AU TGA classify this drug in group C as animal studies have demonstrated the teratogenic effects of this drug on the fetus. Since Cosdor contains timolol, which is a beta-blocker, newborns may develop symptoms, such as: difficulty breathing, low blood pressure, slow heart rate and low blood sugar levels. If use of these eye drops during pregnancy is necessary, then it is important to regularly monitor the intrauterine development of the fetus.

There is not enough data on the use of this medicine during breastfeeding, which is why it is advised to avoid breastfeeding while using this medicine. Studies on rats have shown that dorzolamide can cause weight loss in infants.

If administered in therapeutic doses, timolol cannot be excreted in breast milk in amounts that would be harmful to infants.

How to apply

The recommended dose is one drop two times a day. The drug should be applied directly to the conjunctival sac of the affected eye.

Instructions for use:

  • Wash your hands with soap before use.
  • Unscrew the bottle cap.
  • Tilt your head back and pull down the lower eyelid, so that the sac between the eye and the lower eyelid is formed.
  • Gently press the bottle and put one drop into the conjunction sac.
  • Make sure the dropper tip does not touch the eye, as this increases the risk of eye infections.
  • After you have dropped one drop, close the eye and press the inner corner of the eye (corner closer to the nose) with fingers for two minutes. This reduces the risk of systemic absorption and systemic adverse effects.
  • Close the bottle well and return it to the cardboard box.

If you use other ophthalmic preparations (eye drops, ointment or cream) then do not use them one hour before or after using Cosdor.


Cosdor should not be administered concurrently with the following medicines:

  • Calcium antagonists (e.g. amlodipine, nifedipine, verapamil, diltiazem, etc.), used in the treatment of numerous heart diseases. Cosdor can increase the effects of these drugs, which increases the risk of side effects.
  • Beta-blockers (e.g. bisoprolol, carvedilol, metoprolol, nebivolol, propranolol, atenolol and others). Cosdor may affect the efficacy of these drugs.
  • Antiarrhythmic drugs (e.g. amiodarone, sotalol, quinidine and others).
  • Cardiac glycosides used in the treatment of cardiac insufficiency (e.g. digoxin).
  • Mono amino oxidase inhibitors (e.g. linezolid, isocarboxazide, selegiline and others).
  • Selective serotonin uptake inhibitors (e.g. fluoxetine and paroxetine).
  • Drugs used to treat diabetes.

Side effects

Cosdor can cause the following side effects:

  • Low blood sugar level
  • Depression
  • Nightmares
  • Headache
  • Dry eyes
  • Blurred vision
  • Paresthesia
  • Slow heart rate
  • Low blood pressure
  • Pain in the chest
  • Difficulty breathing
  • Impaired taste
  • Impotence
  • Alopecia
  • Nausea
  • Dyspepsia
  • Allergic reactions


  1. NCBI link
  2. PIL

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