β-Carbolines

Harmala alkaloids — harmine, harmaline and tetrahydroharmine, with harmalol, harmane and norharmane beside them — are tricyclic β-carbolines and reversible inhibitors of monoamine oxidase A. On their own they are not classical psychedelics; they are filed under Psychedelics for the role they play, which is the ayahuasca half. Oral DMT, a tryptamine filed in that family, is destroyed by MAO in the gut and liver, and inhibiting that enzyme is what makes an oral brew active at all.

That mechanism is also the risk, and it is the largest interaction in this subject. An MAO inhibitor amplifies every other serotonergic drug — SSRIs, SNRIs, tricyclics, entactogens, stimulants and other tryptamines — and the combination can produce serotonin syndrome, or a hypertensive response to tyramine in food. The pharmaceutical MAOIs are filed under Antidepressants; the interaction is the same one. Nausea and vomiting here are characteristic rather than incidental.