Eyedrops & Premeditated Murder
Common over-the-counter eye drops are safe, of course (and I personally use eye drops routinely). The primary ingredient is tetrahydrozoline, C13H16N2, which is also used in nasal spray as a decongestant. Tetrahydrozoline effectively soothes blood-shot, itchy eyes by slightly constricting blood vessels and the saline vehicle lubricates eyelids. (1-2 drop(s) delivers approximately 1 cc).
However, drinking tetrahydrozoline can be fatal. Our metabolic system processes chemicals very differently than topically (like via our eyes or skin), absorbing through the gut and delivering the molecules directly into the bloodstream.
Tetrahydrozoline constricts heart blood vessels as the heartbeat speeds up to countermand, ensuing heart failure in high doses.
So, tetrahydrozoline is now forensically recognized as a murder weapon. Two known cases have occurred, perpetrated by a nurse (North Carolina, 2020) and paramedic (2019), respectively. Innocuous drinks like soda or fruit juice spiked with eye drops can be fatal in high doses.