Semi-synthetic 7-hydroxymitragynine and raw kratom plant material (or unmodified kratom extract) aren't the same thing in my mind. 7-hydroxymitragynine in its pure or near pure state is more drug-like than kratom. I've taken 90mg of 7-hydroxymitragynine at once and it produced an effect that kratom couldn't. At 90mg I felt none of the typical intense nausea and vertigo that one feels from very high doses of plant material or plant extracts. Instead I felt a strong fairly typical opioid high with relatively few side-effects.
That said, 7-hydroxymitragynine seems tianeptine-like in the sense that it produces a strong degree of narcosis while producing relatively little respiratory depression. For example 600mg of high quality tianeptine sodium can produce a degree of narcosis roughly equivalent to 80mg of oxycodone, but with markedly less respiratory depression. This is the reason consumer level products containing tianeptine (like Tianna, Zaza etx) haven't caused a federal ban of tianeptine. Tianeptine, as addictive as it may be, simply doesnt kill enough people to cause a federal ban, and this in turn is due to the low level of respiratory depression that tianeptine produces. Tianeptine has even been studied as treatment for asthma.
In any event, If one were accustomed to the effects of both 7-hydroxymitragynine and GHB, it shouldn't be a big issue. In fact I've combined the two (although in my case it was BDO not GHB). But i would be particularly cautious with the GHB dose. GHB is a sneaky drug, especially upon redosing, and can produce overdose on its own right. This can present a particular danger when combined with any opioid, because very high doses of GHB produce a extreme amount of nausea combined with extreme sedation, and opioids only compound the problem. The bigger risk in combining the two is vomiting in one's sleep (aspiration) rather than death via pure respiratory depression. The nausea from extreme doses of GHB or BDO is horrible, akin to chewing a tin of chewing tobacco with zero nicotine tolerance. It's the kind of nausea that makes you wish you were dead. This is of course accompanied by temporary loss of consciousness (you sort of wake up, pass out, wake up, pass out, etc repeatedly]. BDO overdose is worse than GHB overdose, but they both feel horrible. The dosing is tricky too, .5ml of BDO or.5g of GHB sodium salt can be all that separates you from a good time, and pure misery.
But I'd say overall, 7-hydroxymitragynine appears to be more dangerous than raw kratom leaf, since 7-hydroxymitragynine has me nodding uncontrollably at high doses (aka that forward head tilt and brief lapse into sleep) whereas no dose of kratom would do that (without me simultaneously projectile vomiting since I'd probably need 50 grams of raw kratom to mimick 90mg of 7-hydroxymitragynine). Anything that has one uncontrollably nodding (especially in an experienced opioid user like me) immediately makes it appear more dangerous than something like plain leaf kratom.
