Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Cosopt. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking Cosopt. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• bitter taste after putting in your eye drops
• burning, stinging, or discomfort in the eye(s) when the drops are used
• crusting on eyelid or corner of the eye
• Dry Mouth
• headache
• itching of the eye
• nausea
• nosebleeds
• redness of the eye
• tearing (eye produces excess tears)

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain
• blurred vision
• irregular heartbeat and slowing of heart rate
• muscle pain
• skin rash
• symptoms of Kidney Stones (e.g., blood in urine, nausea or vomiting, pain in side, back, or abdomen)
• unusual tiredness or weakness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• coughing, shortness of breath, troubled breathing, tightness in the chest, or wheezing
• symptoms of a Anaphylaxis (severe allergic reaction) (e.g., difficulty breathing, Hives, itchy raised skin rash, or swelling of the mouth and throat)
• symptoms of severe skin reaction (e.g., skin blisters, severe red or purple rash or itching, skin lesions and sores, Fever, sore throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Cosopt.

Cosopt

Each mL of clear, colourless-to-nearly-colourless ophthalmic solution contains 20 mg of dorzolamide (as 22.3 mg of dorzolamide hydrochloride) and 5.0 mg of timolol (as 6.83 mg of timolol maleate). Nonmedicinal ingredients: benzalkonium chloride (0.0075%), sodium citrate, hydroxyethyl cellulose, sodium hydroxide, mannitol, and water for injection.

Cosopt, Preservative-Free

Each mL of clear, colourless-to-nearly-colourless ophthalmic solution contains 20 mg of dorzolamide (as 22.3 mg of dorzolamide hydrochloride) and 5.0 mg of timolol (6.83 mg of timolol maleate). Nonmedicinal ingredients: sodium citrate, hydroxyethyl cellulose, sodium hydroxide, mannitol, and water for injection.

Do not use dorzolamide - timolol eye drops if you:

• are allergic to dorzolamide, timolol, or any ingredients of the medication
• have bronchospasm, including bronchial Asthma, or a history of bronchial asthma or COPD (Chronic Obstructive Pulmonary Disease) (e.g., chronic Bronchitis, emphysema)
• have heart problems that include an extremely low heart rate, second or third degree heart block, overt heart failure or cardiogenic shock (shock due to heart-related causes)
• have severely reduced kidney function
• take carbonic anhydrase inhibitors (e.g., Acetazolamide, Topiramate) by mouth

There may be an interaction between dorzolamide - timolol (eye drops) and any of the following:

• Abiraterone
• acetylcholine
• alpha agonists (e.g., Clonidine, methyldopa)
• alpha blockers (e.g., Alfuzosin, Doxazosin, Tamsulosin)
• Aminophylline
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, lisdexamphetamine)
• angiotensin converting enzyme inhibitors (ACEIs; Captopril, Enalapril, Ramipril)
• angiotensin receptor blockers (ARBs; e.g., candasartan, Irbesartan, Losartan)
• antipsychotics (e.g., Chlorpromazine, Clozapine, Haloperidol, Olanzapine, Quetiapine, Risperidone)
• barbiturates (e.g., butalbital, pentobarbital Phenobarbital)
• beta-2 agonists (e.g., salbutamol, formoterol, terbutaline)
• brimonidine
• Bupropion
• calcium channel blockers (e.g., Diltiazem, Verapamil, Nifedipine, Amlodipine)
• carbachol
• Celecoxib
• chloroquine
• Cinacalcet
• Clobazam
• clonidine
• darunavir
• Desipramine
• diazoxide
• Digoxin
• Diphenhydramine
• Dipyridamole
• Disopyramide
• diuretics (water pills; e.g., Furosemide, Hydrochlorothiazide, triamterene)
• Donepezil
• Dronedarone
• Duloxetine
• Epinephrine
• ergot alkaloids (e.g., Dihydroergotamine, ergonovine, ergotamine, methylergonovine)
• Fentanyl
• Galantamine
• Guanfacine
• high doses of acetylsalicylic acid (Asa)
• hydroxychloroquine
• imatinib
• Imipramine
• insulin
• isoniazid
• ketoconazole
• lidocaine
• lopinavir
• lumefantrine
• Methadone
• Methylphenidate
• Midodrine
• Mirabegron
• monoamine oxidase inhibitors (M.O.S. e.g., Moclobemide, Phenelzine, Rasagiline, Selegiline, Tranylcypromine)
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, duloxetine, Fluoxetine, Paroxetine, Sertraline)
• Nilotinib
• nonsteroidal anti-inflammatory medications (e.g., Diclofenac, Ibuprofen, Ketoprofen, Naproxen)
• other beta-blockers (e.g., propranolol, Atenolol, metoprolol)
• other carbonic anhydrase inhibitors (e.g., acetazolamide)
• Pentoxifylline
• phosphodiesterase-5 inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil)
• Pilocarpine
• Primaquine
• Propafenone
• quinidine
• quinine
• rifampin
• ritonavir
• sulfonamide diabetes medications (e.g., chlorpropamide, Gliclazide, Glyburide)
• terbinafine
• Theophylline
• Ticlopidine
• Yohimbine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Cosopt. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use Cosopt.

Allergies: Some people who are allergic to sulfonamide (or "sulfa") medications may experience a similar allergic reaction to dorzolamide. Before you use dorzolamide - timolol eye drops, inform your doctor about any previous adverse reactions you have had to medications, especially sulfonamide antibiotics or Diabetes medications. Contact your doctor if you experience a skin rash while using Cosopt. Stop using Cosopt and get medical attention if you experience hives; shortness of breath; peeling or blistering skin; or swelling of the mouth, lips, tongue, or throat.

Blurry vision: Side effects such as blurred vision may affect the ability to drive and operate machinery. Avoid driving, operating machinery, or performing other tasks which require you to see clearly until your vision has cleared.

Choroidal detachment: Anyone with chronic or recurrent choroidal detachment should talk to their doctor about further use of the eye drop.

Contact lenses: The preservative used in the eye drops (benzalkonium chloride) may be absorbed by soft contact lenses. Contact lenses should be removed before using the eye drops and not reinserted for at least 15 minutes. The preservative-free eye drops have not been studied for use by people who wear contact lenses.

Eye surgery, eye (corneal) defect, infections, trauma: Anyone using Cosopt who has had eye surgery, preexisting long-term eye (corneal) defect, trauma to the eye, or who has symptoms of an eye infection (e.g., eye redness, itchiness, discharge, crusts on the eyelids, or the feeling of something in the eye) should contact their doctor concerning further use of the eye drop.

General: As with other topically applied eye drops, Cosopt may be absorbed into the bloodstream. The same side effects reported with oral medications from the families known as beta-blockers (e.g., timolol, Propranolol, Metoprolol) or sulfonamides (e.g., sulfamethoxazole) may occur with the eye drops. These side effects may include, but are not limited to, shortness of breath, dizziness, lightheadedness, rash, or slow heartbeat. Refer to the section, "What side effects are possible with Cosopt?" for more information.

Liver function: Cosopt has not been studied in people with liver function impairment. If you have liver problems, discuss with your doctor how Cosopt may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Cosopt, and whether any special monitoring is needed.

Low blood sugar: People who are prone to low blood sugar and people with diabetes should closely monitor their blood sugar while using Cosopt as it may mask the signs of low blood sugar.

Medical conditions: Timolol belongs to the family of medications known as beta-blockers. Although timolol is given as an eye drop, small amounts may be absorbed into the bloodstream. For this reason, it should not be used by anyone who must avoid internal use of beta-blockers. This includes those with abnormally low heart rate, certain abnormal heart rhythms, uncontrolled Congestive Heart Failure, asthma, or severe chronic obstructive pulmonary disease.

Muscle weakness: Beta-blockers such as timolol have been reported to increase muscle weakness associated with certain symptoms, such as double vision or generalized weakness. If you experience these symptoms, contact your doctor.

Overactive Thyroid: Timolol may mask the signs of overactive thyroid. If you have an overactive thyroid gland (Hyperthyroidism), discuss with your doctor how Cosopt may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Cosopt, and whether any special monitoring is needed. People who have this condition or are prone to developing it should be carefully monitored by their doctors.

Pregnancy: Cosopt should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while using Cosopt, contact your doctor immediately.

Breast-feeding: It is not known if dorzolamide passes into breast milk. Timolol does pass into breast milk. If you are a breast-feeding mother and are using Cosopt, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.