Alpha-1 Agonists
- E.g. phenylephrine
- Uses: mydriasis (without cycloplegia), decongestant
- Adverse effects:
- Can cause significant increase in blood pressure especially in infants and susceptible adults
- Rebound congestion
- Precipitation of acute angle-closure glaucoma in patients with narrow angles or myocardial infarction with higher concentration
Alpha-2 Agonists
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E.g. brimonidine (Alphagan), apraclonidine (Iopidine)
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Uses: glaucoma treatment, prophylaxis against IOP spiking after glaucoma laser procedures, also in the diagnosis of Horner syndrome
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Mechanism: decrease aqueous production, and increase uveoscleral outflow
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Side effects:
- Local: allergic reaction, mydriasis, lid retraction, conjunctival blanching, dry eye
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- Systemic: oral dryness, headache, fatigue, drowsiness, orthostatic hypotension, vasovagal attacks
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Contraindications: infants (apnea, severe hypotension, somnolence, and seizures)