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Last Update August 1994
(with help from Michael from Melbourne)

Thanks to many individuals for help in putting this together!
If you know sources of tryptamines that are not mentioned here please mail the author.

Based on McKenna & Towers 1984

Monoamine oxidase (MAO) is the primary inactivation pathway of most tryptamines. Because of this, inhibitors of the MAO enzyme (MAOIs) can be used to potentiate the effects of tryptamines and to make DMT and 5-MeO-DMT orally active.

MAO inhibitors fall into two classes: Irreversible and reversible MAOIs. Irreversible MAOIs (e.g. the hydrazides iproniazid and phenelzine) bind permanently to the enzyme and cause MAO inhibition lasting 1-2 weeks after ingestion. They are used clinically to treat depression. Reversible MAOIs, such as moclobemide, which is used as an antidepressant, and the beta-carbolines harmine and harmaline, are effective for much shorter time, maybe up to 24 hours. Recreational drug users around the world are using mainly harmine and harmaline despite the lack of scientific studies on their effects on humans.

Natives of the Amazon have traditionally combined Banisteriopsis caapi vine, which contains harmine, harmaline and related beta-carbolines, with DMT-containing plants to make an orally active brew called ayahuasca. Other plants containing harmine and/or harmaline can be substituted for B. caapi. The usual 'North-American ayahuasca' consists of Peganum harmala seeds and Desmanthus illinoensis roots, and in Australian 'acaciahuasca' leaves of Acacia complanata are combined with material from DMT-containing acacias (the effectivity of this mixture hasn't been confirmed). MAOIs have also been used to potentiate the effects of mushrooms containing psilocybin.

Terence McKenna has mentioned chocolate being a weak MAOI, which could be a reason for the popular habit of ingesting mushrooms with cocoa.

Peganum harmala (Syrian rue) seeds are the most concentrated natural source of harmine and harmaline - about 3% of their weight consists of these alkaloids. Banisteriopsis caapi has been found to contain from 0.18% to 1.36% beta-carbolines, with the concentration of harmine being from 0.057% to 0.635% (McKenna et al. 1984). According to anecdotal reports one gram of P. harmala seeds ingested inhibits MAO enough to make DMT orally active.

Harmine and harmaline are hallucinogenic on their own with doses starting from around 300 mg (Naranjo 1967). They have little emotional or 'psychedelic' effects, but produce strong visual hallucinations. Because of this the natives of Amazon often add larger amounts (75-100 cm of stem per dose) of B. caapi to ayahuasca brew than is needed for MAO inhibition (Luna 1984).