I'm not sure that's the case though, there are several diseases (both physical and mental) that simply can't be healed or rehabilitated and they are most certainly patients if they are in a doctors care. Now doctors administering the lethal cocktail, I would argue, *should* consider them patients since they are under their direct care (if only for that brief, if it goes correctly, interaction). The random experimenting of 'new' and untested (for this purpose) on inmates is a bit troubling. In the case of Joseph Wood, they used a combination of midazolam & hydromorphone (injecting him at least 15 times). As someone who has been on opiates (that exact one even) for 10+ years (10 knee surgeries + spine/back issues), I can relate my experience on dosage. It can vary widely from person to person and that seems to be a bit genetic and then tolerance over time. My first experience involved me taking several times the lethal dosage (was trying to make the pain go away, not just tolerable). That translated to 7200mg of OxyContin (back when you could chew them), 1200mg of Percocet and about 39,000mg of acetaminophen; in about 25-28 hours. I didn't die, wasn't high and was still in pain (my liver is amazing).
My ramble is trying to make the point that just rolling the dice while trying to kill someone seems a little too much like torture and a hell of a lot like ignoring the oaths doctors take. The nitrogen options mentioned in these threads seems far more humane with a far less chance of it randomly fucking it up (except for that whole wrongful conviction, forced deals and the like).