One rainy day, long ago, I took 100mg of Zembrin, a patented kanna extract that is probably just mesembrine + some filler. About five and a half hours later, I smoked some leaf enhanced with DMT and a full spectrum harmala alkaloidal extract. The comeup was unusually slow, then I had the sudden realization that something was not right. This was well before the DMT took hold in earnest. Something was hard, something was off. There was a barrier to the experience that I had never experienced before, a wall of some sort. Eventually, I became enfolded in the DMT space, and it became a positive experience. The experience was much, much longer than a typical enhanced leaf experience--almost 45 minutes. At first (well, after I came to) I thought that the extract was unevenly laid on the leaf and that I had hit a concentrated pocket of harmala alkaloids. It was only several hours later while musing about my still foggy, slightly-tripped out headspace, that I remembered that I had taken a LOT of kanna extract in the morning. I counted my blessings, glad to be alive after making such a foolish polydrug mistake.
The short answer: they definitely do interact, I didn't die, and it's probably very fortunate for me that the dose of harmala was low and pyrolized rather than large and oral.
