You're not a chemist, but you have a PhD in chemistry? John, have you been lying to us, you naughty boy?
Your claim that all opiates have a high rectal bioavailability is not entirely correct. Oxymorphone in particular has very poor bioavailability by the oral and rectal routes, but a much higher bioavailability when insufflated. When I had Opanas, I could plug 20 mg and get a nice buzz, or snort 2-3 mg for the same effect. 5 mg snorted had me totally on my arse.
I don't have a lot of experience with hydromorphone, but its biavailability is definitely somewhat higher when snorted than plugged. The effects wear off really quickly, though.
I love plugging opiates, but it's not always the best ROA. There are individual differences too, depending on P-glycoprotein expression in the GI tract, as well as a host of other factors.
