dorzolamide/timolol
Brand names: Cosopt
Cosopt is an eye drop that lowers pressure inside the eye. It combines two medicines to treat glaucoma and high eye pressure.
What it does
Cosopt is used to lower high pressure in your eyes.
Common side effects
Bitter, sour, or unusual taste, Eye burning or stinging, Redness of the eye
Key warnings
Cosopt contains timolol, which can cause breathing problems like asthma.
How It Works
Cosopt has two medicines. Dorzolamide lowers eye pressure by reducing fluid production in the eye. Timolol lowers eye pressure by blocking certain receptors in the eye.
How to Take It
Use one drop of Cosopt in the affected eye(s) two times a day. Try to use the drops about 12 hours apart. If you use other eye drops, wait at least 5 minutes before using them. This helps each medicine work properly.
Pregnancy & Breastfeeding
It is not known if Cosopt will harm an unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is also not known if Cosopt passes into breast milk. Talk to your doctor about the best way to feed your baby if you use Cosopt.
Missed Dose
If you miss a dose, use it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store Cosopt at room temperature (68° to 77°F) and protect it from light.
Side Effects (from patient reports)
Based on 4,759 FDA adverse event reports.
Serious Warnings
Cosopt contains timolol, which can cause breathing problems like asthma. If you have asthma or severe lung disease, you should not use Cosopt. Cosopt can also cause heart problems, including heart failure. If you have heart problems, talk to your doctor before using Cosopt. Cosopt contains dorzolamide, a sulfonamide. Rarely, severe reactions to sulfonamides, including fatal reactions, have occurred. If you have a sulfonamide allergy, you should not use Cosopt.
Known Drug Interactions
7.8 Clonidine Oral beta-adrenergic blocking agents may exacerbate the rebound hypertension which can follow the withdrawal of clonidine.
Mechanism: The beta-blocker in the eye drops can make blood pressure rise even higher if you suddenly stop taking your clonidine medication.
What to do: Do not stop taking clonidine without talking to your doctor, as they may need to adjust your treatment plan to keep your blood pressure stable.
7.7 CYP2D6 Inhibitors Potentiated systemic beta-blockade (e.g., decreased heart rate, depression) has been reported during combined treatment with CYP2D6 inhibitors (e.g., quinidine, SSRIs) and timolol. There have been no reports of exacerbation of rebound hypertension with ophthalmic timolol maleate.
Mechanism: Using two medications that both contain timolol can lead to an overdose, which may slow your heart rate down too much or cause low blood pressure.
What to do: Tell your doctor about all the eye drops and heart medicines you use to avoid taking too much of the same active ingredient.
7.2 High-Dose Salicylate Therapy Although acid-base and electrolyte disturbances were not reported in the clinical trials with dorzolamide hydrochloride ophthalmic solution, these disturbances have been reported with oral carbonic anhydrase inhibitors and have, in some instances, resulted in drug interactions (e.g., toxicity associated with high-dose salicylate therapy).
Mechanism: Taking two drugs that both contain dorzolamide can cause the medicine to build up in your body and lead to chemical imbalances in your blood.
What to do: Check with your pharmacist to make sure you are not using two different products that contain the same active ingredient at the same time.
Common Questions
Can I use Cosopt with other eye drops?
What if my eye gets irritated after using Cosopt?
Can I wear contact lenses while using Cosopt?
How long does it take for Cosopt to start working?
What should I do if I accidentally swallow Cosopt?
Can Cosopt affect my blood pressure?
Will Cosopt cure my glaucoma?
Can I drive after using Cosopt?
What are the signs of an allergic reaction to Cosopt?
How long can I use Cosopt after opening the bottle?
What are the common side effects of dorzolamide/timolol?
Does dorzolamide/timolol interact with other medications?
What drug class is dorzolamide/timolol?
Is dorzolamide/timolol safe during pregnancy?
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What the FDA Data Shows for dorzolamide/timolol
The FDA label for dorzolamide/timolol (sold under brand names such as Cosopt) classifies it as a prescription-only medication in the CAI / Beta-Blocker Combination (Ophthalmic) class. Cosopt is used to lower high pressure in your eyes. Official labeling lists 6 commonly reported side effects, including Bitter, sour, or unusual taste, Eye burning or stinging, Redness of the eye.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 4,759 voluntary reports. The database also lists 3 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. Acquisition-cost data is surveyed weekly by CMS and updated as manufacturers report changes.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: April 17, 2024
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages