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  • Timolol is a topical drug used in the treatment of glaucoma.
  • Glaucoma is a potentially devastating eye disease, caused by the build up of abnormally high pressure in the eye. A normal eye produces and drains watery fluid (called aqueous humor). Pressure within the eye builds up if this fluid does not drain properly. This pressure can damage the optic nerve, leading to vision loss.
  • Timolol belongs to a class of drugs known as beta-blockers, which affect beta-adrenergic receptors. Beta-blockers are most often used systemically to reduce the workload of the heart and lower blood pressure.
  • Timolol is absorbed across the cornea into the front chamber of the eye (the anterior segment). The drug decreases the amount of aqueous humor the eye produces, thereby lowering pressure. How exactly the drugs work, however, is not fully understood.
  • Topical timolol is also absorbed into the systemic circulation, with potential effects on both the cardiac and respiratory systems. Timolol applied to one eye may exert an effect on the opposite eye, through its systemic absorption.
  • Timolol may be combined with other topical anti-glaucoma drugs in an effort to control intraocular pressure. One commercially available product (Cosopt®) combines timolol maleate with dorzolamide, a topical carbonic-anhydrase inhibitor.
  • Timolol is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • Timolol is not approved for use in animals by the Food and Drug Administration (FDA), but it is prescribed legally by veterinarians as an extra-label drug.

    Brand Names and Other Names

  • This drug is registered for use in humans only.
  • Human formulations: Timolol maleate: Timoptic® (Merck), Timoptic-XE® (Merck), Timoptic in OCUDOSE® (Merck), Timolol maleate ophthalmic solution® (Bausch & Lomb), Timolol maleate sterile ophthalmic solution® (Akorn), Cosopt ® (Merck), and various generic preparations; Timolol hemihydrate: Betimol ® (Santen)
  • Veterinary formulations: None

    Uses of Timolol

  • Timolol is used in cases of glaucoma in dogs and cats.

    Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, timolol can potentially cause side effects in some animals.
  • Timolol should not be used in animals with known hypersensitivity or allergy to the drug.
  • Because timolol is a non-selective beta-blocker it must be used with caution, or avoided in animals with congestive heart failure and certain respiratory conditions, such as allergic bronchitis, asthma and obstructive pulmonary diseases.
  • Timolol may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with timolol. Such drugs include oral beta-blocking agents.

    How Timolol Is Supplied

  • Timolol is commercially available in two forms, timolol maleate and timolol hemihydrate.
  • Timolol maleate is available as 0.25% and 0.5% solutions in 2.5 ml, 5 ml, 10 ml and 15 ml bottles.
  • Timolol maleate is also available in an extended release gel (Timoptic-XE®) in 2.5% and 5% concentrations (2.5 and 5 ml sizes).
  • The Timoptic in OCUDOSE® formulation is preservative-free, and is available as 2.5% and 5% solutions in individual containers that supply a dose of 0.2 ml.
  • In the product Cosopt®, 0.5% timolol maleate is combined with 2% dorzolamide in one solution.
  • Timolol hemihydrate is available as 0.25% and 0.5% solutions in 2.5 ml, 5 ml, 10 ml and 15 ml sized bottles.

    Dosing Information

  • Medications should never be administered without first consulting your veterinarian.
  • The usual dose of timolol is one drop twice daily. Although three times daily administration may be considered in refractory cases, the potential for side effects is also increased.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Glaucoma medications must be giving consistently and on a reliable time schedule. Even if your pet feels better, glaucoma medications should not be stopped unless your veterinarian specifically instructs you to do so.

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