Pharmahuasca is a lab-prepared combination of DMT with a monoamine oxidase A inhibitor, typically harmine or harmaline, designed to mimic the core pharmacology of ayahuasca using purified, measured compounds.
DMT is normally broken down quickly by the enzyme MAO-A. When paired with an MAO-A inhibitor like harmine, that breakdown is reduced, so DMT remains active for hours rather than minutes. Reported effects can last several hours, depending on dose, route, and individual factors.
Unlike traditional ayahuasca, which is a complex plant brew, pharmahuasca uses isolated molecules for more controlled dosing and fewer plant-to-plant variations. It may be taken orally or via sublingual or buccal routes.
Researchers have tested DMT combined with MAO-A inhibitors in controlled settings; for an example of related work, see this PubMed record.
Hope this helps clarify what pharmahuasca is.