Here’s an FDA warning about the drug and related meds: https://www.fda.gov/Drugs/DrugSafety/ucm325257.htm
Severe reactions, including coma, severe respiratory difficulty and cardiovascular collapse have been seen in small children after ingesting only 1 or 2 ml of the eye drop. It’s a potent vasoconstrictor, and while relatively safe when used topically (i.e. on eyes and in noses), taking it orally can produce a whole lot more problems. It stimulates the same receptors that adrenaline does (alpha 1 receptors) and can do so quite potently.
It also interacts with a bunch of other drugs. It’d be especially risky for patients with pre-existing coronary artery disease or pulmonary hypertension and a whole lot of other conditions, and it’d certainly mess with folks who are on anti-arrhythmic and anti-hypertensive or anti-anginal meds.
Oh, and seizures. It lowers the threshold for having them, messes with anti-seizure meds, and does pretty much all the bad things that stimulants can do ( psychosis, sudden cardiac death, etc.)
Yet it’s still pretty safe in eyes, noses, and other mucous tissue. It’s a dandy treatment for hemorrhoids, but don’t shove it too far up there lest too much be absorbed via the rectal mucosa.