You might have heard of a San Pedro psychedelic experience, but what is San Pedro cactus? This columnar, cylindrical cactus grows freely in parts of North and South America. It contains mescaline, a psychoactive substance found in peyote and Peruvian torch cacti.

San Pedro cactus (Echinopsis pachanoi or Trichocereus pachanoi) has a history of use in South American cultures. The earliest documented use is in Peru, dating from 6800–6200 B.C.1 Like Ayahuasca and peyote, Indigenous peoples have used San Pedro cactus for religious and medicinal purposes for thousands of years.

So, what is San Pedro, and how does it differ from other mescaline-containing cacti? By the end of this article, you’ll have a better understanding of what San Pedro cactus is, what it does, and important safety considerations to keep in mind. Let’s dive in.

What Is San Pedro Psychedelic?

San Pedro cactus is a fast-growing cactus native to the Andes region of South America. Its primary psychoactive alkaloid is mescaline (3,4,5-trimethoxy-phenylethylamine), which produces effects such as altered perceptions of time, hallucinations, and synesthesia.

The San Pedro cactus contains higher mescaline concentrations than peyote.2 Mescaline primarily works by altering neurotransmitters that play a role in mood and cognition. It binds to 5-HT2 receptors in the brain, which blocks the uptake of serotonin.3 This activity alters your perception of reality, your environment, and yourself.4

Traditional use of San Pedro cactus

San Pedro’s name comes from its use in colonial Peru. In the Christian religion, Saint Peter (San Pedro) opens the gates of heaven. In ritualistic use, mescaline opens the path to the perception of the spiritual world.2

In Andean curanderism, the San Pedro ceremony is called a mesa. “Mesa” refers to the ritual and the healing altar the master healer uses. San Pedro cactus is a diagnostic tool that both the master healer and patient use; the cactus allows the curandero to see the nature of a person’s illness and helps cleanse the patient. Some ceremonies also involve herbs and substances such as brandy, Florida water, and tobacco.2

San Pedro ceremonies are held for some of the following reasons:5

  • Curing emotional, mental, physical, or spiritual illnesses
  • Divining the future or ensuring success
  • Overcoming sorcery or bad luck
  • Rekindling enthusiasm for life, faith, or love

San Pedro cactus is not used to treat depressive symptoms in traditional use. Mental health symptoms such as anxiety, disordered eating, and insomnia are treated with herbs and seeds during a mesa.2

Identifying San Pedro cactus

Here are a few key features to help identify the San Pedro cactus:

  • Fast-growing and columnar cactus
  • Six to eight rounded ribs (the protrusions that run along the stem)
  • Light-colored areoles, which are small bumps that grow along the ribs
  • Stems are green or blue-green
  • Flowers are large and white
  • Tall and fast-growing

San Pedro cactus looks similar to the Peruvian torch cactus, but these psychoactive cacti are two different species. Peruvian torch cactus is generally shorter, with more spread-out branches.

Other Names of San Pedro

San Pedro cactus is also known by the following names:

  • Achuma
  • Aguacolla
  • Gigantón
  • Huachuma
  • Hahuacollay
  • Wachuma

San Pedro Myths

Peruvian torch cactus has more mescaline than San Pedro cactus

In reality, San Pedro cactus has a higher mescaline content than Peruvian torch cactus. Alkaloid content can vary between plants, so it’s difficult to give an exact measurement of mescaline in San Pedro. However, a 2010 study found that San Pedro cactus (E. pachanoi) contained 4.7 percent mescaline content, while Peruvian torch cactus contained 0.24 percent.6

San Pedro cactus is legal

In the United States, it’s legal to own San Pedro cactus for ornamental purposes only. That means you can own and grow this cactus, but it’s illegal to extract any mescaline from it.

The majority of the mescaline is on the outer skin

Mescaline is indeed concentrated on the outer part of the cactus. However, overall mescaline content is calculated by dry weight, which includes the inner tissue. So, even though the concentration of mescaline is higher on the outer skin, you’d want to consume the inner and outer tissue to get the plant’s full mescaline content.

How to Use San Pedro Psychedelic

There are a few different ways to use San Pedro cactus:

  • Tea: After the cactus is cleaned, the slices can be boiled for several hours in water. In Andean curanderism, this bitter brew is placed on the mesa, among other objects.7
  • Capsules: San Pedro can be dried, powdered, and added to pills.
  • Added to water: Powdered San Pedro cactus can be stirred into water (more convenient than filling individual capsules).

Whether or not you’re familiar with San Pedro cactus psychedelic plant history, it’s essential to approach this cactus with respect for its Indigenous use. This plant medicine holds an integral role in Andean curanderism, and it’s vital to source it sustainably and responsibly.

San Pedro Dosage

An active dose of mescaline is 300 mg, which roughly translates to 250 mg of raw San Pedro cactus. San Pedro causes hallucinations in humans at doses equal to or greater than 5 mg/kg.2

Here’s a snapshot of dosages, according to ICEERS:1

  • Threshold dose: 100 mg
  • Low dose: 100 to 200 mg
  • Average dose: 200 to 300 mg
  • High dose: 300 to 500 mg

It’s important to note that mescaline content can vary widely across San Pedro cacti, and the longer a cactus has been stored, the higher its mescaline content. Some curanderos will keep cut plants for up to a year to increase the mescaline concentration.2

Start with a low dose and wait for at least one to two hours before consuming more.

San Pedro Effects

Like peyote cactus, San Pedro cactus can cause physical, psychological, and cognitive effects that depend on the dose, set, setting, and individual.

Here’s a snapshot of San Pedro cactus’s psychedelic effects.2

Physical effects

  • Anxiety
  • Dilated pupils
  • Increased heart rate
  • Heightened blood pressure
  • Nausea
  • Sweating
  • Tremors
  • Vomiting

Cognitive effects

  • Changes in perception of time and space
  • Changes in mood
  • Feelings of insight
  • Hallucinations (primarily visual)
  • Mystical experiences
  • Synesthesia

Timeline of the San Pedro Cactus Experience

How long does it take to kick in?

You’ll start to feel the effects of mescaline within one to two hours after ingestion.

How long does it last?

San Pedro cactus psychedelic effects can last more than 12 hours, depending on the dose.8

How long does it stay in your system?

The primary psychedelic compound in San Pedro cactus, mescaline, can be detected in urine for up to three days.

What to Expect While on San Pedro Psychedelic

Coming down from a trip

San Pedro cactus psychedelic effects can linger for hours or days.9 Known as a comedown, these effects are attributed to the plant’s mescaline content. As a result, you might feel fatigued, have a headache, or have no symptoms at all.

Can I overdose on San Pedro psychedelic?

It’s possible to overdose on mescaline, but you’d have to consume a considerable dose. The estimated lethal dose in humans is approximately 880 milligrams per kilogram of body weight.

Potential bad trip

As with any psychedelic, it’s possible to have a bad trip on San Pedro cactus. There’s no way to guarantee a good trip, but you can set yourself up for success by being mindful of your set and setting.

  • Set: This term refers to your mindset going into the trip. Some people like to prepare for a psychedelic experience by maintaining a spiritual practice, such as journaling, meditation, or prayer. Your goal is to feel present, centered, and open-minded going into the experience, rather than stressed or fearful.
  • Setting: Your environment plays a prominent role in your psychedelic experience. Consume San Pedro in a safe, secure space that you feel comfortable staying in for most of the day.

It’s good to have a trip sitter (like a friend, loved one, or facilitator) present who can help you stay safe during your experience and keep you grounded if things go haywire.

In addition, if you have an intention for your practice, a trip sitter can help remind you why you want to experience San Pedro in the first place.

Safety Tips

Mescaline, and other hallucinogenic drugs, should not be used by people who have a history of mental disorders, such as schizophrenia or bipolar disorder. Additionally, because mescaline can change your heart rate and blood pressure, people with a history of heart conditions should not consume San Pedro cactus.

Additionally, mescaline may interact with other substances and medications, such as SSRIs, MAOIs, and other psychedelics. Speak with your healthcare provider before making any changes to your medications.

San Pedro Frequently Asked Questions

Is San Pedro addictive?

Mescaline, the primary psychoactive compound in San Pedro cactus, is not considered addictive. It isn’t associated with withdrawal symptoms, although building a tolerance to its effects over time is possible.

Is San Pedro poisonous?

San Pedro cactus is not poisonous, and the risk of mescaline toxicity is low.10

Is San Pedro legal to own?

In the United States, it’s legal to cultivate, possess, and purchase San Pedro cactus for ornamental use only. However, it’s illegal to consume the cactus or extract mescaline from it because mescaline is a Schedule I controlled substance.

How much does a San Pedro cactus cost?

The cost of San Pedro varies anywhere from $25 to over $100, depending on the size of the cactus.

Can I mix San Pedro with alcohol?

It’s not recommended to combine psychedelic cacti with alcohol. Some Andrean curanderos include alcohol in San Pedro mesas, but people should not duplicate this practice without proper experience.

Can I mix San Pedro with other drugs?

Some drugs, including prescription medication and other psychedelics, can interact negatively with the mescaline in San Pedro cactus. Therefore, combining mescaline-containing cacti with other drugs is not recommended.

Can I drive while on San Pedro cactus?

Do not drive while you’re under the influence of any substances, including psychedelics like mescaline-containing cacti.

How to microdose San Pedro

A microdose is approximately 10 to 20 percent of a full dose, which translates to roughly 30 grams of mescaline, 10 grams of fresh cactus, or 3.3 grams of dried cactus. Microdosing involves the consumption of small doses of psychedelics over an extended period, like several weeks.

Final Thoughts

San Pedro psychedelic cactus, also known as huachuma, gains psychoactive effects from a natural alkaloid called mescaline. Indigenous peoples in South America have used San Pedro for centuries for ceremonial and medicinal use. San Pedro cactus psychedelic effects can last more than 12 hours, depending on the dose.


  1. San Pedro: Basic Info | Echynopsis pachanoi | Psycheplants | ICEERS. Accessed June 1, 2022.
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