h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

"morphine poisoning may also be achieved through the mixing of morphine with poultice applied over broken skin"

This is the principle of the fentanyl patch, the currently sanctioned way of delivering morphine for pain relief during palliative (terminal) care, where the intention of applying medication is not to cure (the patient is past a cure - the intention is to relive pain in the decline into death)

This is useful to us, as to be honest, having an easily broken-into controlled drugs locker in the building containing lots of easy-to-steal liquid morphine wasn't exactly a comforting thought, security wise! Slow release morphine patches acting via skin absorbtion are less tempting to addicts, as well as making it difficult to administer an overdose to the patient (whether by design or misadventure).
I work in elderly care, btw: this nercesarily overlaps hospice care right at the end, for many patients.