Brimonidine (Alphagan)

Brimonidine (brand name Alphagan) is a selective alpha-2 adrenergic agonist eye drop used to lower intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. It works through multiple mechanisms to reduce eye pressure and may also have neuroprotective properties.

How It Works

Brimonidine lowers intraocular pressure through two mechanisms:

• Reduces aqueous humor production—decreases the amount of fluid the eye makes
• Increases uveoscleral outflow—enhances fluid drainage through an alternative pathway

Additionally, laboratory studies suggest brimonidine may:

• Protect retinal ganglion cells (neuroprotection)
• Improve blood flow to the optic nerve

Common Uses

• Primary open-angle glaucoma
• Ocular hypertension
• As adjunctive therapy with other glaucoma drops
• Acute angle-closure glaucoma—as part of emergency treatment
• Prevention of IOP spikes after laser procedures
• Available in combination with brinzolamide as Simbrinza

How to Use

• Dosing: One drop in affected eye(s) 2-3 times daily, approximately 8 hours apart
• Shake well if using suspension formulation
• Instillation: Wash hands, tilt head back, pull down lower eyelid, apply drop
• After instillation: Close eyes for 1-2 minutes; press on inner corner of eye to reduce systemic absorption and dry mouth
• Contact lenses: Remove before use; wait 15 minutes before reinserting
• Multiple drops: Wait at least 5 minutes between different eye medications

What to Expect

Pressure Reduction

• Typically lowers IOP by 4-6 mmHg
• Effect begins within 1-2 hours
• Peak effect at approximately 2-3 hours
• Duration approximately 8-12 hours

Initial Experience

• May notice mild eye redness
• Dry mouth is common initially
• Some drowsiness possible
• Effects often improve with continued use

Side Effects

Common

• Eye redness or irritation
• Dry mouth—from systemic absorption
• Drowsiness or fatigue
• Blurred vision (temporary)
• Burning or stinging upon instillation

Less Common

• Allergic reaction—can develop even after months of use
  • Increased redness, itching, swelling
  • Occurs in approximately 10-15% of patients
  • May require discontinuation
• Headache
• Dizziness
• Dry nose
• Taste changes

Important: Allergic Reaction

Brimonidine allergy is relatively common and can develop even after using the drop without problems for months. Signs include:

• Worsening eye redness (not improving)
• Eyelid swelling and itching
• Follicular conjunctivitis

If you develop these symptoms, contact your doctor—the medication may need to be switched.

Precautions

• Children: Use with extreme caution in children under 2—risk of serious CNS depression (drowsiness, lethargy, respiratory depression)
• MAO inhibitors: Do not use concurrently
• Cardiovascular disease: Use with caution
• Raynaud's phenomenon: May worsen symptoms
• Depression: Monitor for mood changes
• Driving/machinery: May cause drowsiness—use caution
• Pregnancy/breastfeeding: Discuss with doctor

Brimonidine vs. Other Glaucoma Medications

Medication	Class	IOP Reduction	Dosing
Brimonidine	Alpha-agonist	4-6 mmHg	2-3x daily
Prostaglandin (latanoprost)	Prostaglandin analog	6-8 mmHg	Once daily
Timolol	Beta-blocker	4-6 mmHg	1-2x daily
Dorzolamide	CAI	3-5 mmHg	2-3x daily
Simbrinza	Brimonidine + brinzolamide	6-8 mmHg	2x daily

Frequently Asked Questions

Why do I get dry mouth from an eye drop?

Eye drops can drain through the tear ducts into the nose and throat, where they're absorbed into the bloodstream. Brimonidine causes dry mouth through this systemic absorption. Pressing on the inner corner of your eye after instillation helps reduce this.

Can I develop an allergy to brimonidine over time?

Yes, this is relatively common. Allergic reactions to brimonidine can develop weeks to months after starting the medication, even if you tolerated it initially. Watch for increasing redness, itching, or eyelid swelling.

Is brimonidine safe for children?

Brimonidine should be used with extreme caution in young children. In children under 2, it can cause serious drowsiness, lethargy, and even respiratory depression. Safer alternatives exist for pediatric glaucoma.

Can I use brimonidine with other glaucoma drops?

Yes, brimonidine is commonly used in combination with other glaucoma medications, including prostaglandins and beta-blockers. Wait at least 5 minutes between different eye drops.

How long will I need to use brimonidine?

Glaucoma is typically a lifelong condition requiring ongoing treatment. If brimonidine is working well and tolerated, it's usually continued indefinitely. Never stop glaucoma medications without consulting your doctor.

What if brimonidine causes too much drowsiness?

Lower-concentration formulations (brimonidine 0.1%) may cause less drowsiness than older formulations (0.2%). Discuss with your doctor—alternative medications or combinations may be available.