DMT is a very powerful substance that deserves respect. Two things are problematic here, first of all the mixing with a dissociative anesthetic and second, whether IV/IMing DMT is in general something that deserves to be considered for the common psychonaut/kitchen chemist and discussed in this forum.
For the first part, you have to understand that we dont want a false moralism here and a 'my drugs are better than yours' kind of thing, but it feels awkward to read a post of someone that wants to mix something so special and highly-existentially-challenging as dmt, with a synthethic dissociative anesthetic that has very little history of human use, and sounds possibly like a 'I want to get as high as possible', instead of a 'I respect these substances and trully feel with this combination I can gain insight and become a more conscious person'.
There is also the fact that very little is known of this combination, of dosages, of possible dangerous somatic effects and synergies, and that ketamine in general is not as safe as the classic serotoninergic psychedelics. Do you feel like you are not getting enough out of dmt? Then we at the nexus would say for you to rather change smoking method, increase dosage, or try with some harmalas (like sublingual thh), or with mushrooms as there seems to be plenty of good reports in this sense, and way safer (considering usual set and setting cares are taken). The other thing is that ketamine is not really a focus on this forum. This doesnt mean it its evil, that nobody has/can ever benefit from it, but its just not really a desired subject in this forum, just like other synthetics/RC/Opiates/Stimulants are also not.. Its not an absolutely forbidden thing here or something, but we'd rather stay with the classic psychedelics and specially dmt, of course... There's plenty of forums out there for this other kind of substances
Secondly As for the IV/IM issue, this ingestion method in general brings several more complicated aspects.. What if one takes some impure product with solvent/acid/whatever remains or other unknown impurities? What if one rips a vein/breaks needle in arm while suddenly transported to hyperspace? What if what if what if? And then there is the issue that there may be immature impulsive people that read an IV/IM-use dmt discussion and decide to do it 'for the kicks', and badly screw up one way or another, become newspaper headlines, etc... ?
So its not that objectively IV/IMing is a wrong thing, but we feel that one can use these substances in much safer ways and we would rather people here did NOT consider this kind of administration method.. In the event that people decide to do it in any case, what we can do is say that there is one research that was done with IV DMT use by Rick Strassman, they had VERY pure dmt (synthesized and over 99.9% pure) in fumarate formed dissolved in sterile solution, and that the highest dose was 0.4mg/kg, and this was already considered too much for some, so if one does it, should start much lower than that, at 0.1 or max 0.2 mg/kg, and gradually go up in subsequent sessions.
If one really decides to do it, please have someone experienced do the injection, do not do it alone as you may hurt yourself BADLY and be tripping and incapacitated to do anything. Also special care of set and setting is needed!
Once again: We do NOT recommend injecting dmt, even less in some combination with something else!!! If someone will do it anyways, please reconsider, and if still so, read guideliness above and be VERY prudent, making SURE all the chemicals used are TOTALLY pure, adding several steps of recrystalization/washing/cleaning, etc etc..