^ not to say that tripping off of DXM is "good" for you, but the claims of brain damage have been found in very specific cases where large doses have been taken consistently for a long long time. It doesn't "cause brain damage easily." There's many other issues that go along with DXM (btw, it metabolizes into DXO that's really not like PCP at all; DXO is a very stoning feeling that doesn't share a lot of the trippy, schizophrenic qualities that DXM/PCP does), but overstating the largely-disproven claims of brain damage (citations upon request; am on a phone right now) could cause more harm than good.
To the OP: I would advise against it. Dosing DXM after opiates/opioids (even comparatively weaker ones like kratom) typically makes people feel sick and/or unpleasant. I've experienced terrible headaches dosing this way that sometimes lead to puking sessions and take several hours to go away. If you combine these two substances, I'd suggest taking DXM first and, several several hours after the fact (at least six to be safe) take your opioid at a heavily-reduced dose. A DXM trip can feel like it resets opiate tolerance, and even small doses taken closer or with the opiate/opioid (doses in range of 15 - 75 mg, depending on your tolerance and affinity toward DXM) can cause heavily-increased effects.
Be very careful with this combo, and don't take 300 mg of DXM a couple hours after kratom, unless you like puking and skull-fucking headaches. It might not happen, but from personal and anecdotal experience there's a good chance it will.
