The San Pedro cactus (Echinopsis pachanoi, also known as Trichocereus pachanoi) is a psychedelic cactus, native to the Andes. One can find it growing in Argentina, Bolivia, Ecuador, and Peru.
Today, its primary use is home decoration: big box stores often sell it as a cultivar for gardening or indoor decoration. It has to be said that San Pedro has much more to offer. Something that the vast majority of indoor plants can’t: centuries of history and psychedelic effects.
San Pedro Historical Roots
The San Pedro cactus has been used for millennia by the indigenous peoples of the Andes for religious and shamanic rituals. Archaeological evidence suggests its use dates back at least 2000 to 2300 years.  Mochica culture ceramics from ancient Peru depict the cactus and its use. 
Indigenous groups have used San Pedro for its psychoactive properties in healing ceremonies and rituals. The primary psychoactive compound in the San Pedro cactus is mescaline.
San Pedro Psychedelic Cactus Today
The cactus gained attention in the wider world largely during the 20th century, as anthropologists, ethnobotanists, and adventurers began to explore and document traditional practices in the Andes.
The active compound, mescaline, was isolated from the related peyote (Lophophora williamsii) cactus in 1897 by German chemist Arthur Heffter. 
In recent decades, there has been a renewed interest in the San Pedro cactus, especially among the younger US population, seeking alternative spiritual or recreational experiences.
This has led to a global spread of San Pedro ceremonies, rivalled only by the more pop-culture-famous Ayahuasca alternative.
San Pedro Cactus and Mescaline
The San Pedro cactus contains mescaline, a psychoactive alkaloid also found in the peyote cactus and some other cacti.
Mescaline belongs to the phenethylamine class of psychoactive compounds.
Mescaline is a naturally occurring psychedelic alkaloid of the phenethylamine class (the same one that includes amphetamines). However, its mode of action is quite different.
Mescaline primarily exerts its psychedelic effects through the activation of certain serotonin receptors, especially the 5-HT2A.  The 5-HT2A receptor is a subtype of the serotonin receptor and has been implicated in the mechanism of action of several other classic psychedelics like LSD and psilocybin. 
Activation of this receptor leads to a cascade of intracellular events, which ultimately modifies the usual patterns of serotonin transmission, leading to altered perception.
There’s also evidence to suggest that mescaline interacts with dopamine, norepinephrine, and adrenaline, though this isn’t fully understood and likely plays a secondary role. 
The Pharmacokinetics of Mescaline
Whether you’re just curious or plan a trip to the native country of San Pedro for a ceremony, it’s always a good idea to understand what’s happening in your body while you experience the effects of a psychoactive substance. Here, step by step, is the mode of action of mescaline:
- Stage 1: Once you ingest the substance, it’s absorbed in the stomach;
- Stage 2: As the result of absorption, mescaline enters the bloodstream;
- Stage 3: It crosses the blood-brain barrier, reaching the central nervous system;
- Stage 4: Mescaline, the absorbed molecules of it, activate the serotonin receptors (you can expect the onset in 45-60 minutes);
- Stage 5: While the dosage of the compound is still being processed by your body, at some point, you will experience the peak of its effects (varies greatly, strictly individual);
- Stage 6: The effect of altered perception will last, depending on the dose, from 6 to 15 hours; 
- Stage 7: By hour 4 to 6, mescaline effects will start to wear off. Your body will start to excrete its metabolites;
- Stage 8: In a maximum of 48 hours, all remaining minor effects of mescaline will disappear.
Psychedelic Effects of Mescaline (from San Pedro Cactus)
It’s important to understand the mechanism of action of psychedelic substances if you ever plan on trying them. But in the moment, you are most likely to be focused on “the trip”: a spiritual experience that the mescaline-altered perception produces.
What can you expect to feel, hear and see?
Before we start, note that these effects are strictly individual. They depend on your mind-set and the setting, your personal response to San Pedro, your unique brain chemistry, your age and your mental health.
In general, however, we can define several important parts:
Many of those who tried San Pedro report a range of visual distortions, including:
- Intensified colours;
- Geometric pattern;
- Visual hallucinations;
- Alterations in the perceived forms of objects;
- Unusual clarity and “high level of detail”.
Altered Perception of Time
It may seem to slow down or speed up, depending on your personal response to the substance. A sense of “eternity in a moment” is the most common way to describe it.
Emotional and Spiritual Effects
These revelations are the primary reasons for San Pedro popularity. Some of the ways to describe it are:
- Unity with nature;
- Being one with the universe (or the universe itself);
- Deep introspection;
- Deep reflection.
Expect feelings of love, compassion, and empathy to be heightened.
These can range from a feeling of lightness, energy, or bodily warmth to nausea (especially during the onset after ingestion). Some people also report a tingling sensation throughout the body.
Most people focus on the positive effects: altered thought processes, so-called “default mode reset”, a major boost in creativity, “deep thinking”, synesthesia (a blending of the senses, described as being able to “see” sounds or “feel” colours).
While a psychedelic “trip” can definitely be a positive experience, if performed with a professional guide in a suitable setting, it’s even more important not to take it lightly. Though rare, the infamous “bad trip” is also a possibility. Paranoia, intensified by the psychedelic cactus effects, can be an unpleasant experience, to say the least.
How to get San Pedro’s Psychedelic effects?
First of all, you should know that eating raw San Pedro is dangerous for your health. It’s nauseating. And it’s not efficient as well, since cacti are succulents, and San Pedro consists of pure, mescaline-free water by approximately 90%.
Today, two primary methods are used to get the effects:
- San Pedro cactus tea;
- And mescaline extracts.
While there are plenty of guides about mescaline tea preparation available on-line, we will focus on the extraction details.
What About Psychedelic Cactus Extraction?
Mescaline extraction from San Pedro cacti, specifically the pachanoi variety, is a complicated process. At its core, it’s about harnessing the desired compound, mescaline, from natural sources, and purifying it for concentrated use through solvent-based extraction.  Mescaline can be relatively easily extracted through an acid-base extraction process.
After an initial acidified aqueous extraction, it is possible to perform the de-fattening of the extract using a non-polar solvent such as xylene. The alkaloids from San Pedro will stay in the acidic water layer, while the other unwanted fat plant compounds will be extracted in the xylene layer and separated from the mixture using a separatory funnel.
The basification of the mixture using NaOH till pH 10 will lead to formation of free base alkaloids that can be further removed from the aqueous layer using a non-polar solvent such as xylene. The repeated washing of the aqueous solvent with xylene will higher the final product yield. Further steps can be performed using acidified water and solvents like ether in order to obtain pure crystals of mescaline. The mescaline concentration in the plant matter can be low so take care of performing each step carefully in order to obtain visible crystals and an adequate amount of final product.
Note of Caution
Since San Pedro extraction requires the use of several chemicals, we do not recommend attempting it in a DIY setting. It’s neither safe nor legal in the United States, unless you perform the extraction in a controlled environment with research purposes in mind.