Adrenergic antiglaucoma drugs are sympathomimetic agents used in the management of glaucoma, primarily by reducing intraocular pressure (IOP). These drugs act by influencing alpha-adrenergic receptors in the eye, leading to decreased aqueous humor production and, in some cases, increased outflow.
The most clinically relevant drugs in this group include Brimonidine, Apraclonidine, Dipivefrin, and Epinephrine. While newer agents are preferred today, understanding these drugs is essential for pharmacology, ophthalmology, and nursing examinations.
Therapeutic and Pharmacologic Class
These drugs are classified as:
1. Antiglaucoma agentsThey act mainly on α-adrenergic receptors in the ciliary body and ocular vasculature.
Mechanism of Action (Core Concept)
Adrenergic antiglaucoma drugs lower intraocular pressure primarily by:
1. Decreasing aqueous humor formation from the ciliary bodyAlpha-2 selective agonists (like brimonidine and apraclonidine) reduce cyclic AMP levels in the ciliary epithelium, leading to reduced aqueous humor production.
Brimonidine
Brimonidine is a selective alpha-2 adrenergic agonist and is one of the most commonly used drugs in this class today.
Mechanism of Action
Brimonidine:
- Decreases aqueous humor production
- Increases uveoscleral outflow
Therapeutic Uses
Brimonidine is used in:
- Chronic open-angle glaucoma
- Ocular hypertension
- Adjunct therapy with other antiglaucoma drugs
Adverse Effects
Common side effects include:
- Dry mouth
- Drowsiness and fatigue
- Headache
- Allergic conjunctivitis
Because it can cross the blood–brain barrier, CNS depression may occur, especially in children and elderly patients.
Apraclonidine
Apraclonidine is also an alpha-2 adrenergic agonist, but it is less selective than brimonidine.
Mechanism of Action
Apraclonidine reduces:
Aqueous humor productionTherapeutic Uses
Apraclonidine is mainly used:
- For short-term control of intraocular pressure
- To prevent IOP spikes after laser eye surgery
It is not preferred for long-term therapy due to rapid tolerance (tachyphylaxis).
Adverse Effects
Side effects include:
- Eye irritation
- Allergic reactions
- Dry mouth
- Fatigue
Dipivefrin
Dipivefrin is a prodrug of epinephrine designed to improve ocular penetration and reduce systemic side effects.
Mechanism of Action
After conversion to epinephrine in the eye, dipivefrin:
- Decreases aqueous humor production
- Increases aqueous outflow
Therapeutic Uses
Dipivefrin was historically used in:
Open-angle glaucomaHowever, it is now rarely used due to better alternatives.
Adverse Effects
Dipivefrin may cause:
- Mydriasis
- Eye irritation
- Increased sensitivity to light
- Systemic cardiovascular effects if absorbed
Epinephrine
Epinephrine is a non-selective adrenergic agonist with both alpha and beta activity.
Mechanism of Action
Epinephrine:
- Reduces aqueous humor production
- Increases outflow through trabecular meshwork
Therapeutic Uses
Epinephrine was used in:
Chronic open-angle glaucomaToday, its use is limited due to significant side effects.
Adverse Effects
Epinephrine can cause:
- Palpitations
- Arrhythmias
- Hypertension
- Mydriasis and photophobia
Adverse Reactions and Side Effects (Class Effects)
Central Nervous System
- Headache
- Nervousness
- Drowsiness
Cardiovascular System
- Palpitations
- Arrhythmias
- Hypertension (especially with systemic absorption)
Eye, Ear, Nose, Throat (EENT)
- Burning or stinging sensation
- Eye pain
- Sensitivity to light (photophobia)
Important Nursing and Patient-Care Considerations
Patients should be advised to:
- Avoid activities requiring good visual acuity if mydriasis occurs
- Expect possible light sensitivity
- Report palpitations or dizziness immediately
To reduce systemic absorption:
- Instill drops into the conjunctival sac, not directly onto the eyeball
- Apply nasolacrimal duct pressure for at least 1 minute after instillation
Monitoring and Safety (“Make the Connection”)
Healthcare providers should:
- Monitor intraocular pressure regularly (tonometry)
- Monitor blood pressure, pulse, and heart rhythm when therapy begins
- Avoid concurrent use with MAO inhibitors, due to interaction risk
Contraindications and Precautions
Use with caution in patients with:
- Cardiovascular disease
- Hypertension
- Arrhythmias
- Depression or CNS disorders
Alpha-2 agonists should be used carefully in children, as CNS depression can occur.
Nursing Diagnosis (Exam-Relevant)
Common nursing diagnoses include:
- Disturbed sensory perception (visual)
- Risk for injury related to visual disturbances and photophobia
High-Yield Exam Pearls
- Brimonidine is the preferred alpha-2 agonist for long-term glaucoma therapy.
- Apraclonidine is mainly for short-term use and post-laser IOP spikes.
- Dipivefrin is a prodrug of epinephrine.
- All adrenergic antiglaucoma drugs primarily decrease aqueous humor production.
Simple Mnemonic for Recall
“B-A-D-E” for Adrenergic Glaucoma Drugs
B – Brimonidine (most common)
A – Apraclonidine (short-term)
D – Dipivefrin (epinephrine prodrug)
E – Epinephrine (older drug)
FAQs on Adrenergic Antiglaucoma Drugs
Which adrenergic drug is most commonly used today?
Brimonidine is the most commonly used adrenergic antiglaucoma drug.
Why is apraclonidine not used long-term?
Because tolerance (tachyphylaxis) develops quickly.
How do these drugs reduce intraocular pressure?
By decreasing aqueous humor production and sometimes increasing outflow.
Why apply pressure on the lacrimal duct after eye drops?
To prevent systemic absorption and reduce side effects.
Why are epinephrine and dipivefrin rarely used now?
Due to cardiovascular side effects and availability of safer alternatives.
