Generic Name

Dorzolamide Hydrochloride; Timolol Maleate

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Classification

FDA Approved Indications

• Open-angle glaucoma
• Ocular hypertension

Mechanism of Action

Dorzolamide inhibits carbonic anhydrase in the ciliary processes of the eye, reducing aqueous humor production, while Timolol is a non-selective beta-adrenergic receptor blocker that decreases aqueous humor formation, leading to lowered intraocular pressure.

Dosage and Administration

Adult: One drop in affected eye(s) twice daily.

Pediatric: Use not established; consult a pediatric ophthalmologist.

Geriatric: No specific dosage adjustment, but consider renal and hepatic function.

Renal Impairment: Use with caution; monitor intraocular pressure.

Hepatic Impairment: Use with caution; no specific dose adjustment.

Pharmacokinetics

Absorption: Absorbed through the eye tissues after topical administration.

Distribution: Minimal systemic absorption; some may enter systemic circulation.

Metabolism: Dorzolamide undergoes partial systemic hydrolysis; timolol undergoes hepatic metabolism.

Excretion: Renal and hepatic routes, depending on the component.

Half Life: Approximately 4-9 hours for timolol; not well-defined for dorzolamide, but generally in a similar range.

Contraindications

• Hypersensitivity to any component
• Reactive airway disease (asthma)
• Sinus bradycardia
• Second- or third-degree AV block
• Cardiac failure

Precautions

• Use with caution in patients with COPD, bronchospasm, or hypotension.
• Monitor intraocular pressure regularly.
• Use during pregnancy only if clearly needed.

Adverse Reactions - Common

• Ocular burning, stinging, or discomfort (Common)
• Blurred vision (Common)
• bitter taste in the mouth (Common)

Adverse Reactions - Serious

• Systemic effects of timolol (e.g., bradycardia, hypotension, bronchospasm) (Serious but less common)
• Allergic conjunctivitis or keratitis (Rare)

Drug-Drug Interactions

• Systemic beta-blockers (additive effects)
• Calcium channel blockers (bradycardia, hypotension)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Wash hands before and after use.
• Avoid touching the dropper tip to the eye or other surfaces.
• Report any signs of allergic reactions, eye irritation, or systemic side effects.
• Carry medical ID indicating use of beta-blocker if appropriate.

Special Considerations

Black Box Warnings:

• No known black box warnings.
• Systemic absorption of timolol may cause systemic adverse effects, especially in patients with cardiovascular or respiratory diseases.

Genetic Factors: No specific genetic factors impacting use.

Lab Test Interference: May interfere with serum potassium and blood glucose readings due to systemic absorption.

Overdose Management

Signs/Symptoms: Systemic absorption may cause bradycardia, hypotension, bronchospasm, hypoglycemia.

Treatment: Supportive care; monitor vital signs; administer atropine or vasoconstrictors if indicated; hemodialysis not effective for timolol.

Storage and Handling

Storage: Store at room temperature, 59°F to 86°F (15°C to 30°C).

Stability: Stable until expiration date if unopened; once opened, use within 6 weeks.