What are the risks?

The use of ayahuasca, like the use of any psychoactive substance, has its risks that may be different for different people. This is because the effects of a substance depend on three things:

•    The substance (type and quantity)

•    The user (what physiological and mental state s/he is in)

•    The environment that surrounds the users (is it safe enough or does it carry risks)

•    Several cases of serious injury or death have been associated with the use of ayahuasca.

At the same time, there is the possibility of serious adverse reactions from the use of the brew, especially if it is taken along with illegal drugs and/or controlled foods or medications. The reason for this is the monoamine oxidase inhibitors, which disable a key enzyme in the body responsible for the degradation of various chemicals. Without this enzyme, these chemicals are toxic to the body.

People who use ayahuasca need to be well informed about the foods, medicines and drugs that are contraindicated for concomitant use with substances containing MAOIs (monoamine oxidase inhibitors).

A very large number of medicines sold with or without a prescription, or illegal drugs, can lead to very unpleasant or fatal effects when combined with substances that act as MAOIs .

Also, as any strong hallucinogen, ayahuasca can cause short- or long-term personality changes. It is possible to trigger psychotic episodes.

Source:
http://www.erowid.org/chemicals/ayahuasca/ayahuasca.shtml