Telepathine is an old name for harmine, a beta-carboline found in plants like Banisteriopsis caapi. Pharmacologically it is a reversible, selective MAO-A inhibitor. Related alkaloids include harmaline (also MAO-A inhibiting) and tetrahydroharmine, which mainly affects serotonin reuptake.
With DMT, harmine’s MAO-A inhibition makes oral DMT active and longer-lasting, which is why ayahuasca works. Without MAO-A inhibition, DMT is rapidly broken down and has little oral effect.
With psilocybin or psilocin, harmine is not needed for oral activity. Psilocin is mainly cleared by glucuronidation, so MAO-A plays a smaller role. Harmine may still intensify or prolong effects and can make the experience more bodily or emotional, but evidence in humans is limited and responses vary.
Because MAO-A inhibition adds interaction risks, combinations with serotonergic or stimulant drugs can be unsafe, and nausea or unpredictability may increase. For a practical overview of interactions and contraindications, see this guide: interactions and contraindications of caapi. Stay cautious with mixes and dosing.