The Psychotropic San Pedro Cactus, Echinopsis pachanoi

Image of the Psychotropic San Pedro Cacti
Image of the San Pedro Cacti, Echinopsis pachanoi

Central and South America is home to a number of psychotropic cacti, most of which share the active constituent mescaline. An important psychotropic cactus is the San Pedro Cacti, Echinopsis pachanoi, native to the Andes Mountains. The San Pedro cactus, aka, cactus of the Four Winds, is an often spineless, columnar, branched cactus – which, can appear human at a distance. Its stems vary from light to dark green, being up to 15cm across. If spines do occur, they are about 2cm long, appearing from the plants areoles in groups of seven. The spines will be yellow or brown. Each areole appears every 2cm up the ribs of the cactus.  Though looking like a person from a distance, it is much taller, anywhere from 3 – 6 metres.

In the Andes, this species of cacti has been in use for thousands of years, with evidence of use by the Moche civilisation some two thousand years ago. As you might imagine, Catholic authorities tried to ban the use of the San Pedro, but they failed. This ancient psychotropic and medical plant has been used by Andean healers to treat fevers and liver, kidney and bladder issues where there was heat (inflammation). It’s not uncommon to see bitter plants having a traditional use of clearing heat from the body, as ‘bitters’ are cooling to the body. It was considered an entheogen by the Shamans and when taken it produced a dream-like state which allowed individuals to experience great visions and deep thought. The cactus grows across central and southern America and we see it’s ancient use wherever it grows. A carving from Peru, dating back to 1300 BC, depicts a mythical creature holding a San Pedro cactus, leaving no doubt that not only was this plant in use back then, but it also held an important significance to them.

When using the majestic San Pedro cactus for medicinal and psychotropic purposes, they either used the whole plant, or occasionally just the outer layer. This is a more pleasant cactus to harvest, thanks to the lack of bothersome spines. Within the cactus, there is water; up to 93%, but then, of course, there are the alkaloids, with the mescaline being of particular interest. In dried samples of San Pedro, there is about 2% mescaline. Tests of fresh cacti show that for every 100g of cactus, there was between 25 to 120mg of mescaline. Which is an incredible amount of variation in the levels of psychotropic active constituents in plants. It is not possible, nor advised, to presume just how potent a plant will be. However, more mature cacti in the wild will provide greater concentrations of mescaline, while lower dosages are found in young, cultivated cacti.

Mescaline acts on serotonin receptors in the central nervous system and this is how it contributes to the mind-altering effect of San Pedro. Shamans have used a variety of traditional methods in the consumption of the San Pedro cactus. One popular example involved boiling the plant into a decoction. This is preferable to making a tea (infusion), because the boiling required to make a decoction allows for better extraction of the active constituents, due to the plant material of a cactus being tougher than leaves or flowers from other plants.

They have also been known to eat the cactus fresh (apparently this tastes like a bitter cucumber), or dried and then powdered. The powder can be taken in a drink or added to capsules – but this is a more laborious method, involving a substantial number of capsules to achieve a typical dose, as such a dose requires a foot and a half of the cactus! So, you can see why decocting it to extract the constituents seemed like the better option – unless, of course, you would fancy eating a foot and a half of bitter cucumber…

Naturally, the San Pedro isn’t the only psychotropic cactus growing across central and Southern America. Echinopsis peruvian is another mescaline containing cactus which, unlike San Pedro, contains another constituent that acts on the central nervous system – tyramine. Tyramine stimulates adrenergic receptors in the central nervous system, and this is an action that would be potentiated if an individual were also taking monoamine oxidase inhibitors found in medication. For this reason, modern day usage of these cacti can be dangerous and could potentially invoke a rather frightening experience if used concurrently with medication.



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Stewart, A. (2019) Wicked Plants, Timber Press

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About Victoria Protheroe 10 Articles
With a lifelong love of nature and wildlife and a Master’s degree in research, Victoria Protheroe enjoys spending her free time combining these interests to explore new areas of wildlife research and conservation. Her current area of interest is with reptile care, specifically snake husbandry.

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