Visine-a Nausea, Half Hour, Alpha Adrenergic Receptors, Blood Vessels in the Eye, Smooth Muscles
The one eye I put the drop in was dilated for several hours as well after a breif bout with nausea. Within a half hour of putting in the drop.
Krusty - The active ingredient pheniramine maleate has antihisitimine and vasoconstrictive properties working on alpha-adrenergic receptors in the eye. So it causes blood vessels in the eye to shrink (e.g. getting the red out), but as a side effect it also 'paralyzes' the smooth muscles of the iris causing the pupil to enlarge for some time.