Yopo is made from the seeds of Anadenanthera peregrina, a leguminous tree of the Orinoco basin and the northern South American savannas. The seeds are toasted, ground, and mixed with an alkaline material, commonly the ash of a particular bark or burnt snail shell, to produce a fine grey-green powder.
It is administered nasally, and the classic instrument is a paired tube, a Y-shaped or double-ended pipe through which one person blows the powder forcefully into the nostrils of another. The design means the act is ordinarily shared: someone must administer it, and the giving of yopo is itself a relation between two people. Self-administration through a single tube is also done.
The effect is fast, physically punishing and short, beginning with intense burning and streaming and passing into a brief and forceful visionary state. It is used in curing, in divination, and among some peoples collectively at gatherings rather than only by specialists.
The tryptamines it carries are, like those in chacruna, ordinarily inactive by mouth, which is why the nasal route is not a stylistic preference but a necessity. In some places yopo is combined with a beta carboline plant, which is the same principle that governs the ayahuasca brew arrived at through a different delivery.