How Do Ophthalmic Alpha Agonists Work?

Ophthalmic alpha agonists are a class of drugs used in ophthalmic solutions, to constrict blood vessels (vasoconstriction) in the eyes. Alpha agonist drugs stimulate the activity of protein molecules known as alpha-adrenergic receptors, found on the smooth muscles of blood vessels.

Alpha-adrenergic receptors make muscle around blood vessels contract in response to hormones (catecholamines) epinephrine and norepinephrine released by the adrenal gland. Alpha agonist drugs are known as sympathomimetic drugs, which mimic the effect of catecholamines on the alpha-adrenergic receptors, enabling vasoconstriction.

Alpha agonist eye drops help reduce redness and irritation of the eyes by vasoconstriction of swollen blood vessels in the eye. Some ophthalmic alpha agonists used by ophthalmologists target the contraction of specific eye muscles to dilate the pupils for examination, or to treat droopy eyelids.

Ophthalmic alpha agonists are used in the following situations:

• To treat:
  • Irritation or burning caused by dry eyes
  • Redness of the eye from irritation
  • Drooping eyelids (blepharoptosis)
• To dilate the pupils for examination of the eye or surgery
• Prevent the iris to adhere to the lens
  • Because of inflammation (uveitis)
  • After eye surgery to remove a portion of the iris (iridectomy)

Side effects of ophthalmic alpha agonists include:

• Transient stinging or irritation in the eye
• Blurred vision
• Mydriasis (dilation of pupils)
• Change in intraocular pressure
• Headache
• Punctate keratitis (inflammation in the cornea)
• Conjunctival hyperemia (dilation of blood vessels in the whites of the eyes)
• Dry eyes
• Rebound myosis (constriction of the pupils)
• Reactive hyperemia
• Hypersensitivity reactions such as allergic conjunctivitis or dermatitis
• Sensitivity to light

Rare severe side effects include:

• Arrhythmia (irregular heartbeat)
• Myocardial infarction (heart attack)
• Subarachnoid hemorrhage (bleeding within the subarachnoid space- the area between your brain and the tissues that cover it)

Some Ophthalmic Alpha Agonist Drugs Include:

• Naphazoline hydrochloride (All Clear, Clear Eyes, Naphcon)
• Phenylephrine hydrochloride (Altafrin, Neofrin, Refresh Redness Relief)
• Oxymetazoline hydrochloride (Upneeq)