38.4 Antiglaucoma Drugs

Glaucoma meds work in different ways to lower eye pressure and save your vision. Some increase fluid outflow, while others decrease fluid production. It's crucial to understand how these drugs work to manage glaucoma effectively.

Each type of glaucoma med has its own pros and cons. From prostaglandin analogs that can change your eye color to beta blockers that might slow your heart rate, knowing the side effects helps you use these drugs safely and effectively.

Types and Mechanisms of Antiglaucoma Drugs

Prostaglandin analogs

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• Increase uveoscleral outflow of aqueous humor by relaxing the ciliary muscle and widening the spaces between muscle bundles, allowing more fluid to drain (latanoprost, travoprost, bimatoprost)

Beta blockers

• Decrease production of aqueous humor by blocking beta receptors in the ciliary body, reducing blood flow and slowing fluid formation (timolol, betaxolol, carteolol)

Alpha agonists

• Decrease production of aqueous humor by constricting blood vessels in the ciliary body and increase uveoscleral outflow by widening drainage channels (brimonidine, apraclonidine)

Carbonic anhydrase inhibitors

• Decrease production of aqueous humor by inhibiting carbonic anhydrase enzyme, which is essential for fluid formation
  • Oral (acetazolamide, methazolamide)
  • Topical (dorzolamide, brinzolamide)

Cholinergic agonists

• Increase outflow of aqueous humor through the trabecular meshwork by contracting the ciliary muscle and opening drainage channels (pilocarpine, carbachol)

Rho kinase inhibitors

• Increase outflow of aqueous humor through the trabecular meshwork by relaxing the trabecular meshwork and increasing fluid drainage (netarsudil)

Indications, Side Effects, and Drug Interactions

Indications

• Primary open-angle glaucoma, most common form of glaucoma
• Ocular hypertension, elevated eye pressure without optic nerve damage
• Angle-closure glaucoma, less common form caused by blocked drainage channels (cholinergic agonists and carbonic anhydrase inhibitors)

Side effects

• Prostaglandin analogs cause eye color changes (darkening of the iris), eyelash growth, and eye irritation
• Beta blockers lead to bradycardia (slow heart rate), bronchospasm (airway constriction), fatigue, and depression
• Alpha agonists result in dry mouth, fatigue, drowsiness, and allergic reactions
• Carbonic anhydrase inhibitors cause bitter taste, paresthesia (tingling sensation), fatigue, and kidney stones (oral)
• Cholinergic agonists lead to eye pain, blurred vision, headache, and bronchospasm
• Rho kinase inhibitors cause conjunctival hyperemia (eye redness), eye irritation, and headache

Drug interactions

• Beta blockers increase the risk of bradycardia when combined with calcium channel blockers (diltiazem) and digoxin
• Carbonic anhydrase inhibitors increase the risk of hypokalemia (low potassium) when used with thiazide and loop diuretics (furosemide)
• Cholinergic agonists increase the risk of bradycardia when combined with beta blockers

Nursing Considerations

Monitoring and assessment

• Assess intraocular pressure (IOP) using tonometry before and during treatment to evaluate medication effectiveness
• Monitor for side effects and adverse reactions, such as eye irritation, vision changes, or systemic symptoms
• Assess patient's adherence to medication regimen through patient interviews and medication reconciliation

Collaboration and education

• Educate patients on proper administration technique for eye drops to ensure optimal drug delivery and minimize contamination risk
• Collaborate with healthcare providers (ophthalmologists, optometrists) to adjust medication therapy based on patient response and tolerability
• Encourage regular follow-up appointments with eye care professionals to monitor disease progression and treatment efficacy

Patient Education

Medication adherence

• Teach patients the importance of adhering to prescribed medication regimen to maintain optimal intraocular pressure control and prevent vision loss
• Instruct patients on proper eye drop administration technique
  1. Wash hands thoroughly with soap and water before use to prevent eye infection
  2. Tilt head back and gently pull lower eyelid to form a pocket for the eye drop
  3. Squeeze one drop into the pocket without touching the eye or eyelashes with the dropper tip to avoid contamination
  4. Close eye gently and apply pressure to the inner corner (punctal occlusion) for 1-2 minutes to maximize drug absorption and minimize systemic absorption
  5. Wait at least 5 minutes before administering a second medication to prevent washout of the first drug
• Advise patients to report side effects (eye redness, irritation) or vision changes (blurred vision, halos) to their healthcare provider promptly

Lifestyle modifications

• Emphasize the importance of regular eye exams and follow-up appointments to monitor glaucoma progression and adjust treatment as needed
• Encourage patients to wear sunglasses and wide-brimmed hats for eye protection from UV radiation, which may contribute to glaucoma risk
• Discuss the importance of a healthy lifestyle, including a balanced diet rich in fruits and vegetables (kale, spinach) and regular exercise (brisk walking), for overall eye health and glaucoma prevention