Great for clinical use as it has no cross tolerance with common morphine based opiates. IMO no recreational value.
Are you talking about levorphanol? AFAIK it is still a mu/delta/kappa opioid agonist just like all the "classic" ones, and will therefore have
some cross tolerance, but it is also a SNRI/dissociative to some extent like DXO.
I personally think it would be rather interesting to try & don't see any reason it wouldn't be non-euphoric @ the right dose. (then again, if you're on levorphanol I would expect you'd have a tolerance...) As you said though, its long duration makes it more useful for chronic pain (c.f. abusing methadone)
On principle though, you're right, it's best to avoid "recreational" opioid use. The reason I think levorphanol should be used more is due to its multimodal painkilling abilities as well as extended duration compared to morphine/etc. (I remember reading that levorphanol and methadone are the two "longest acting" opioids in practice.
I know you can still get levorphanol prescribed, but I bet it's pretty hard to find. The few people I have talked to who had the possibility of recieving a levo Rx couldn't find any pharmacies that actually stocked it. (tehn again I am not really searching very hard)
Comparable to desomorphine? I'd say this is one to avoid...
How is deso/levo any "less safe" than other strong mu agonists in use like hydromorphone, oxymorphone, diamorphine, if dosed properly? It's not like desomorphine etc have intrinsically "bad" effects that other opioids do not have.
....
On the topic of butorphanol, that's one of the wacky partial agonists developed under the thought that it would produce less dependence than full agonists, while still killing pain. A related drug, nalbuphine, was retracted from the market because it actually increased subjective ratings of pain in men (not women, strangely). It's got funky kappa agonism, and ia probably closer in activity to drugs like buprenorphine, pentazocine, nalbuphine than levorphanol. The N-cyclobuthylmethyl group does not bode well for "good" effects at mu opioid receptors.
Butorphanol is still used as a veterinary painkiller though, because humans find it shitty. (kappa agonism can get dysphoric)