====== Sympathomimetic eyedrops and their mechanism of action on the Iris ======

==== Alpha-1 Adrenergic Agonists ===

  * cause vasoconstriction, mydriasis and uterine contractions
    * Phenylepherine (neoynepherine): Alpha-1 receptor agonist
    * Other similar drugs: Dipivefrin, naphazoline

==== Alpha-2 adrenergic agonists ====
  * have more effects on CNS
    * Apraclonadine: weakly binds to Alpha-1 receptors
      * Will cause dilation in Horner syndrome pupil due to this binding effect and upregulation of the receptor that occurs 2-5 days after sympathetic block 
    * Bromonidine (Alphagan P) is similar with less Alpha-1 effect on pupil

==== Indirect Acting Agents ====
  * Cocaine: blocks reuptake of norepinephrine 
    * causes dilation in normal pupil but not in a Horner syndrome pupil
  * Amphetamine: causes release of and blocks reuptake of norepinepherine
    * causes dilation in normal pupil but not in a Horner syndrome pupil. 

{{tag>drugs}}