This is a combination medication that contains two ingredients: dorzolamide and timolol. Dorzolamide is a member of the family of medications known as carbonic anhydrase inhibitors. Timolol is a member of the family of medications known as beta-blockers. Together, these medications are used to reduce the pressure inside the eye for people with open-angle glaucoma or ocular hypertension (increased pressure in the eye). These medications work by reducing the production of fluid in the eye, thereby lowering the pressure in the eye.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

The recommended adult dose of dorzolamide - timolol eye drops is one drop in the affected eye(s) twice daily.

Dorzolamide - timolol eye drops should be used at least 10 minutes before or after other eye drops that are being used.

Wash your hands thoroughly before using eye drops. To prevent contamination of the eye drops with bacteria, do not allow the tip of the container to touch the eye, fingers, or other surfaces. Serious damage to the eye may result if you use eye drop solutions that have become contaminated.

If you are using the preservative-free solution, also avoid touching the eye area with the fins (plastic pieces at the sides of the unit dose eye dropper), as the fins can scratch or cut your eye, causing serious eye injury. To avoid scratching or cutting your eye, line up the "fins" of the container with the inside and outside corners of your eye. If possible, ask a caregiver to put the drops in for you.

When using the preservative-free solution, the container and remaining solution must be discarded after each treatment. Refer to the package insert for instructions on how to administer these eye drops properly.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

It is important that this medication be used exactly as prescribed by your doctor. If you miss a dose, instill it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not instill a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Each mL of sterile, isotonic, buffered, slightly viscous, aqueous solution contains 20 mg of dorzolamide (as 22.3 mg of dorzolamide hydrochloride) and 5 mg of timolol (as 6.83 mg of timolol maleate). Nonmedicinal ingredients: benzalkonium chloride (0.0075%) added as preservative, dehydrate sodium citrate, hydroxyethyl cellulose, mannitol, sodium hydroxide 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 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

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 this medication. 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 this medication. 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 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 this medication.

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 this medication.

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 this medication. Stop using this medication 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 this medication who has had eye surgery, pre-existing 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, this medication 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 this medication?" for more information.

Liver function: This medication has not been studied in people with liver function impairment. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, 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 this medication 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 this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, 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: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while using this medication, 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 this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of this medication have not been established for children.

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

• acetylcholine
• alpha agonists (e.g., clonidine, methyldopa)
• alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• amiodarone
• anti-Parkinson's medications (e.g., amantadine, apomorphine, bromocriptine, levodopa, pramipexole, ropinirole, rotigotine)
• beta-2 agonists (e.g., salbutamol, formoterol, terbutaline)
• beta-blockers (e.g., propranolol, atenolol, metoprolol)
• brimonidine
• bupropion
• calcium channel blockers (e.g., diltiazem, verapamil, nifedipine, amlodipine)
• cannabis
• ceritinib
• crizotinib
• decongestant cold medications (e.g., phenylephrine, pseudoephedrine)
• decongestant eye drops and nose sprays (e.g., naphazoline, oxymetazoline, xylometazoline)
• diabetes medications (e.g., acarbose, canagliflozin, glyburide, insulin, lixisenatide, metformin, rosiglitazone, sitagliptin)
• digoxin
• dipyridamole
• disopyramide
• donepezil
• dronedarone
• epinephrine
• ergot alkaloids (e.g., dihydroergotamine, ergonovine, ergotamine, methylergonovine)
• fentanyl
• flecainide
• galantamine
• grass pollen allergen extract
• guanfacine
• ivabradine
• lidocaine
• mefloquine
• selective serotonin reuptake inhibitors (SSRIs; e.g., fluoxetine, paroxetine, sertraline)
• nonsteroidal anti-inflammatory medications (e.g., diclofenac, ibuprofen, ketoprofen, naproxen)
• other carbonic anhydrase inhibitors (e.g., acetazolamide, brinzolamide, topiramate)
• pilocarpine
• propafenone
• quinidine
• rivastigmine
• somatostatin analogues (e.g., lanreotide, octreotide, pasireotide)
• sphingosine 1-phosphate receptor (S1P) receptor inhibitors (e.g., fingolimod, ponesimod, siponimod)
• theophylline
• tipranavir
• tofacitinib

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 this medication. 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.