Dorzolamide / timolol eye drops (Cosopt and others)

How Medicare covers it

Part D (eye drops used at home taken/used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

Lowers high pressure inside the eye (elevated intraocular pressure) in people with open-angle glaucoma or ocular hypertension who did not reach their target pressure on a beta-blocker alone. It is a combination eye drop used only in the eye.

What it is for, in depth

Dorzolamide-timolol is a fixed-combination eye drop for people with open-angle glaucoma or ocular hypertension whose eye pressure stayed too high on a beta-blocker alone — the label defines this as failing to reach the target pressure after repeated measurements over time. It puts a carbonic anhydrase inhibitor and a beta-blocker in one bottle, taken twice a day, instead of using dorzolamide three times a day plus timolol twice a day separately; the label notes the combined drop lowers pressure slightly less than that separate, more frequent schedule. It lowers pressure but does not cure glaucoma, so it is a long-term control treatment. It comes as a 2%/0.5% ophthalmic solution.

How it works

It combines two drugs that each lower eye pressure by making less fluid (aqueous humor) in the eye. Dorzolamide blocks carbonic anhydrase, an enzyme in the eye that helps make that fluid. Timolol is a non-selective beta-blocker that also reduces fluid production. Together they lower pressure more than either one alone.

How it is taken

An eye drop solution (dorzolamide 2% / timolol 0.5%). The dose is 1 drop in the affected eye or eyes twice a day. If you use another eye drop, wait at least 5 minutes between drugs. Remove soft contact lenses before use — the preservative benzalkonium chloride can be absorbed by lenses — and wait 15 minutes before putting lenses back in.

Common side effects

The most common side effects, in up to 30% of patients, were a bitter, sour, or unusual taste and eye burning or stinging. Effects in 5% to 15% were redness of the eye (conjunctival hyperemia), blurred vision, surface irritation of the cornea (superficial punctate keratitis), and eye itching. About 5% of patients stopped treatment because of side effects.

Serious warnings

Even as an eye drop, timolol is absorbed into the body and can cause the same serious effects as beta-blockers taken by mouth, including severe worsening of asthma and, rarely, death from bronchospasm or heart failure. Dorzolamide is a sulfonamide and can cause severe allergic and skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, which have rarely been fatal. Stop the drops and seek care for serious or unusual reactions. It can also mask signs of low blood sugar and of an overactive thyroid, and worsen muscle weakness in myasthenia gravis.

Who should be careful

Do not use it if you have bronchial asthma or a history of asthma, severe COPD, a slow heart rate (sinus bradycardia), second- or third-degree heart block, clear heart failure, cardiogenic shock, or an allergy to any ingredient. It is not recommended in severe kidney impairment (creatinine clearance under 30 mL/min), because dorzolamide has not been studied there and it leaves the body through the kidneys. Use with caution in liver impairment, diabetes, lung disease, or myasthenia gravis. Safety and effectiveness are established for the single drugs in children 2 years and older, but not under age 2.

Major interactions

Do not combine it with an oral carbonic anhydrase inhibitor — the effects add up and use together is not recommended. Using it with a beta-blocker taken by mouth can add to beta-blockade in the body and in the eye, and two topical beta-blockers should not be used together. Calcium channel blockers and digitalis can add to slow heart conduction and low blood pressure. Drugs that lower catecholamines, such as reserpine, can add to low blood pressure and slow heart rate. CYP2D6 inhibitors such as quinidine and some SSRIs can strengthen timolol's body-wide beta-blocking effects. High-dose salicylate (aspirin-type) therapy can interact through acid-base changes.

Why it is in its tier

Dorzolamide-timolol is most often placed on Tier 1 in 2027 Medicare Part D formularies — the modal tier, used by 56.09% of listing plans — and every plan in the data lists it (100%). Tier 1 is the preferred generic tier, with the lowest copays, which fits its status as a generic eye drop. The CMS Part D dashboard put average program spending for Dorzolamide-Timolol at $70.97 per beneficiary for 2024, a low cost level. That dashboard figure is a program average, not your copay. The tier shown is the most common one; individual plans vary, so check your own plan's formulary.

Sources

• DORZOLAMIDE HYDROCHLORIDE AND TIMOLOL MALEATE SOLUTION [SANDOZ INC] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Dorzolamide and Timolol Ophthalmic

What official patient guides say

Dorzolamide and timolol comes as a solution (liquid) to put in the eye, and you place it in the affected eye or eyes twice a day at around the same times every day. If you miss a dose, put it in as soon as you remember it, but if it is almost time for the next dose, skip the missed dose and go back to your regular schedule — do not put in a double dose to make up for a missed one. Keep the medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture, not in the bathroom.

Source: MedlinePlus — Dorzolamide and Timolol Ophthalmic

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is $1.0113 per unit (DORZOLAMIDE-TIMOLOL 2-0.5%(PF)) — about $30.34 for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-07

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 5,495 list Dorzolamide / timolol eye drops (Cosopt and others) — 100% of plans. Most of those plans put it on Tier 1: 3,082 plans, 56.1% of the plans that list it. Other plans place it on Tier 2 (2,128 plans) or Tier 3 (285 plans). For example: Aetna Medicare Dual Extra (HMO D-SNP) puts it on Tier 1; Aetna Medicare Dual Extra Care (PPO D-SNP) puts it on Tier 1; Aetna Medicare Value Plus (PPO) puts it on Tier 1. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan's deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.