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Cosopt Side Effects

Generic name: dorzolamide / timolol ophthalmic

Medically reviewed by Last updated on Oct 31, 2023.

Note: This document contains side effect information about dorzolamide / timolol ophthalmic. Some dosage forms listed on this page may not apply to the brand name Cosopt.

Applies to dorzolamide/timolol ophthalmic: ophthalmic solution.

Serious side effects of Cosopt

Along with its needed effects, dorzolamide/timolol ophthalmic may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking dorzolamide / timolol ophthalmic:

More common

  • Blurred vision
  • burning or stinging of the eye (when medicine is applied)
  • feeling of something in the eye
  • itching of the eye
  • redness of the eye and lining of the eyelid
  • sensitivity of the eyes to light

Less common

  • Back, abdominal, or stomach pain
  • change in vision
  • coughing, shortness of breath, troubled breathing, tightness in the chest, or wheezing
  • discharge from the eye
  • dizziness
  • eye or eyelid pain, swelling, discomfort, or irritation
  • increased blood pressure
  • increased frequency of urination or painful urination
  • itching of the eyelid
  • seeing flashes or sparks of light
  • seeing floating spots before the eyes
  • swelling of lining of the eyelid
  • tiny bumps on lining of the eyelid


  • Blistering, peeling, or loosening of the skin
  • blood in the urine
  • blue lips, fingernails, or skin
  • chest pain or discomfort
  • chills
  • cough
  • diarrhea
  • difficult or troubled breathing
  • fainting
  • headache or weakness, severe and sudden
  • irregular, fast or slow, or shallow breathing
  • itching
  • joint or muscle pain
  • lightheadedness
  • mental depression
  • nausea or vomiting
  • pain, numbness, tingling, or burning feeling in the hands or feet
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • shortness of breath
  • skin rash
  • slow or irregular heartbeat
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips
  • sweating
  • unusual tiredness or weakness

Get emergency help immediately if any of the following symptoms of overdose occur while taking dorzolamide / timolol ophthalmic:

Symptoms of overdose

  • Confusion
  • muscle cramps or pain
  • numbness, tingling, pain, or weakness in the hands or feet
  • seizures
  • trembling
  • weakness and heaviness of the legs

Other side effects of Cosopt

Some side effects of dorzolamide / timolol ophthalmic may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Bitter, sour, or unusual taste

Less common

  • Cold- or flu-like symptoms
  • crusting or scales on eyelid
  • dryness of the eyes
  • indigestion or upset stomach
  • sore throat
  • stuffy or runny nose
  • tearing of the eye


  • Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • depression
  • dry mouth
  • stuffy nose

For Healthcare Professionals

Applies to dorzolamide / timolol ophthalmic: ophthalmic solution.


The most common side effects have included taste perversion and ocular burning and stinging (up to 30%). Topically applied timolol ophthalmic drops may be absorbed systemically and side effects similar to systemically administered timolol or other beta-blockers such as severe respiratory or cardiac reactions may be experienced.[Ref]


Very common (10% or more): Burning/stinging

Common (1% to 10%): Conjunctival infection, blurred vision, corneal erosion, ocular itching, tearing

Frequency not reported: Choroidal detachment following filtration surgery, iridocyclitis, eyelid crusting, signs and symptoms of ocular allergic reaction, transient myopia, photophobia


-Common (1% to 10%): Eyelid inflammation, eyelid irritation

-Uncommon (0.1% to 1%): Iridocyclitis

-Rare (less than 0.1%): Irritation (including redness, pain, eyelid crusting, transient myopia), corneal edema, ocular hypotony, choroidal detachment (following filtration surgery)


-Common (1% to 10%): Signs and symptoms of ocular irritation (including blepharitis, keratitis, decreased corneal sensitivity, dry eyes)

-Uncommon (0.1% to 1%): Visual disturbances (including refractive changes)

-Rare (less than 0.1%): Ptosis, diplopia, choroidal detachment following filtration surgery

-Frequency not reported: Itching, tearing, redness, blurred vision, corneal erosion[Ref]


Respiratory side effects have included bronchitis, sinusitis, pharyngitis, cough, and upper respiratory tract infection in 1% to 5% of patients. Dyspnea, nasal congestion, and respiratory failure have been reported in less than 1% of patients.

Respiratory side effects associated with timolol ocular have included pulmonary edema, respiratory failure, dyspnea, nasal congestion, cough, and upper respiratory infections.

Respiratory side effects associated with timolol, as with other beta-antagonists, have included bronchial constriction in susceptible patients. Alternative therapy should be considered in patients with reactive airways disease. Cases of fatal respiratory arrest have been reported in patients with asthma, even after topically-administered timolol.

Respiratory side effects associated with oral timolol or other oral beta-blockers have included laryngospasm with respiratory distress, rales and bronchial obstruction.[Ref]


Frequency not reported: Bradycardia, cardiac failure, chest pain, heart block, hypotension, myocardial infarction


-Uncommon (0.1% to 1%): Bradycardia

-Rare (less than 0.1%): Chest pain, palpitation, arrhythmia, congestive heart failure, cardiac arrest, heart block, hypotension, claudication, Raynaud's phenomenon, cold hands/feet

-Frequency not reported: Atrioventricular block, cardiac failure[Ref]

Nervous system

Very common (10% or more): Dysgeusia

Rare (less than 0.1%): Tinnitus

Frequency not reported: Cerebral vascular accident, paresthesia


-Common (1% to 10%): Headache

-Rare (less than 0.1%): Dizziness, paresthesia


-Common (1% to 10%): Headache

-Uncommon (0.1% to 1%): Dizziness, syncope

-Rare (less than 0.1%): Paresthesia, increase in signs and symptoms of myasthenia gravis, cerebrovascular accident, cerebral ischemia[Ref]


Rare (less than 0.1%): Contact dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis


-Rare (less than 0.1%): Rash


-Rare (less than 0.1%): Alopecia, psoriasiform rash or exacerbation of psoriasis

-Frequency not reported: Skin rash[Ref]


Frequency not reported: Depression


-Uncommon (0.1% to 1%): Depression

-Rare (less than 0.1%): Insomnia, nightmares, memory loss

-Frequency not reported: Hallucinations, anxiety[Ref]


Frequency not reported: Diarrhea, dry mouth


-Common (1% to 10%): Nausea

-Rare (less than 0.1%): Throat irritation, dry mouth


-Uncommon (0.1% to 1%): Nausea, dyspepsia

-Rare (less than 0.1%): Diarrhea, dry mouth

-Frequency not reported: Dysgeusia, abdominal pain, vomiting[Ref]



-Rare (less than 0.1%): Decreased libido, Peyronie's disease

-Frequency not reported: Sexual dysfunction, retroperitoneal fibrosis, impotence[Ref]


Rare (less than 0.1%): Signs and symptoms of systemic allergic reactions, (including angioedema, urticaria, pruritus, rash, anaphylaxis)


-Rare (less than 0.1%): Signs and symptoms of systemic allergic reactions, (including angioedema, urticaria, pruritus, localized and generalized rash, anaphylaxis), systemic lupus erythematosus[Ref]



-Common (1% to 10%): Asthenia, fatigue


-Uncommon (0.1% to 1%): Edema, asthenia, fatigue[Ref]



-Frequency not reported: Hypoglycemia[Ref]



-Frequency not reported: Myalgia[Ref]


Uncommon (0.1% to 1%): Urolithiasis[Ref]


1. Product Information. Cosopt (dorzolamide-timolol ophthalmic). Merck & Co., Inc. 2022.

2. Cerner Multum, Inc. UK Summary of Product Characteristics.

3. Cerner Multum, Inc. Australian Product Information.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.