Petco Text Logo
Petco Pet Logo
  • Two Easy Ways to Start Earning Rewards!

    rewards header
    Become a member today!
    Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
    Petco Pay LogoBecome a credit card member today!

    Earn 2X Pals Rewards points at Petco
    when you use Petco Pay!

    APPLY NOW
    Learn More About Petco Pay Benefits

Timolol Ophthalmic for Dogs & Cats: Treat & Prevent Glaucoma

Published on September 10, 2024
Updated on November 5, 2025
Reviewed by Petco's Veterinarian Team

Beta blocker used to treat glaucoma in dogs and cats as well as to prevent glaucoma in the normal eye in patients with glaucoma in only one eye.

Summary

Used For:

Used to treat glaucoma and prevent glaucoma in the normal eye in patients with glaucoma in one eye.

Brands:

Betimol, Cosopt, Istalol, Timoptic

Species:

Dogs and cats

Other names:

Timolol maleate, timolol hemihydrate, (S)-timolol, timololum

Drug type:

Ocular

Prescription required:

Yes

Pregnancy and lactation:

Likely safe in pregnancy, timolol is excreted in the milk.

Side effects:

Rare

General description

Timolol ophthalmic preparation is a beta blocker used to treat or prevent glaucoma in dogs and cats.

Uses

Glaucoma, prevention of glaucoma in normal eye in patients with glaucoma in only one eye, reducing the pressure within the treated eye.

How it works

Timolol reduces the pressure within the treated eye by causing a reduction in the amount of aqueous humor (the fluid within the eye) that is produced.

Dosage

Dogs and Cats: One drop in affected eye(s) every 12 hours.

The medication dosages listed represent the variation in dosing for all underlying medical conditions.

Medications should only be administered to pets under the direct guidance of a veterinarian.

Forms

Timolol ophthalmic preparation is available as 0.25 and 0.5 percent solutions for use in the eyes.

Storage information & handling

Timolol should be stored at room temperature and protected from light and freezing temperatures.

What results can I expect?

Timolol should decrease the pressure within treated eyes by 25-30 percent. Pet parents should see improvement in their pet’s signs of glaucoma.

Missed Dosage

If a dose is missed, continue with the next dosage at the scheduled time.

Overdose / acute toxicity

Overdosage is rare but signs would include drowsiness, low blood pressure, slow heart rate and vertigo.

If you believe your pet has received an overdose of timolol, contact your veterinarian immediately for appropriate treatment.

Side effects

Rare, but may include the following:

  • Slow heart rate
  • Abnormal heart rhythm
  • Low or high blood pressure
  • Heart failure
  • Dizziness
  • Behavioral changes
  • Anxiety
  • Coughing
  • Breathing problems
  • Hives
  • Skin rashes
  • Gastrointestinal upset (nausea, diarrhea, decreased or absent appetite)

Contraindications

Do not use in pets with:

  • Previous sensitivity
  • Bronchial asthma
  • Severe chronic obstructive pulmonary disease
  • Certain heart conditions (2nd or 3rd degree atrioventricular block, cardiogenic shock, overt heart failure)

Drug interactions

The following drugs may have increased effect when used in conjunction with timolol to lower the pressure within the eye:

  • Dorzolamide
  • Topical miotics
  • Topical dipivefrin
  • Topical epinephrine
  • Carbonic anhydrase inhibitors

Timolol ophthalmic preparation given with systemic beta blockers may lower blood pressure.

If timolol ophthalmic preparation is given with calcium channel blockers, it may have additive effects upon the heart.

Precaution

When applying timolol ophthalmic preparation, do not allow the tip of the container to touch the eye or surrounding tissues.

Sources

Plumb’s Veterinary Drug Handbook

Disclaimer
The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.

Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Share

Styled arrow button