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San Pedro Potency FAQ
by Steve Barton
v 1.1 - Sep 1994
Erowid Note: This FAQ was not authored by Erowid. It may include out-of-date and/or incorrect information. Please check the version date to see when it was most recently revised. It appears on Erowid as part of our historical archives. For current information, see Erowid's summary pages in the substance's main vault.


This FAQ is presented for informational purposes only. We do not advocate illegal activities. We do believe in the right of the individual to have free access to information and ideas. We strongly recommend that the reader learn about applicable local and federal laws regarding possession, production, and sale of these and related cacti.

Ver 1.1 of a FAQ on this persistent topic. co-author credit is due to RBrennan for his indespensable research & tireless intellectual exchanges with me as we gather data and clarify our thinking on "the San Pedro Question." - Steve Barton

What is the name of the legal mescaline-containing cactus?
Most commonly, you are referring to Trichocereus pachanoi, aka "San Pedro". Various other Trichocerei have been shown to contain mescaline, however, and there have been been informal reports of usage of T. peruvianus and what we suspect is T. macrogonus as well. T. pachanoi is employed as a grafting stock, landscape plant, ornamental accent, and (in South America) as hedging and fencing. It has wonderful 9" night-blooming flowers, in season. It is amenable to pot-culture (i.e., growing it in a clay pot on your patio). It is legal to own, but illegal to consume or process into mescaline.

How strong is it?
That depends on "which pachanoi". It is highly variable.

Isn't T. pachanoi weaker than peyote?
That depends on "which pachanoi" you are talking about. Reports published in scholarly journals have shown pachanoi to sometimes be twice as strong as peyote. In addition, T. pachanoi grows a few orders of magnitude faster than peyote; pachanoi can double in mass every year, while peyote takes about a decade to grow to flowering size. T. pachanoi branches can grow to 18' by 4" dia, while natural peyote tops out at about 2" high by 4" dia. T. pachanoi is certainly a formidable mescaline producer and has three millenia of human usage. "Weak" is really an unfair word to apply to either plant.

In addition, peyote is illegal to posess (lacking religious exemption) and is becoming endangered in nature; hence it is harder to find, while T. pachanoi often turns up at the local nursery, etc. How strong *is* the cactus you can't get?

I thought that it was some other Trichocereus that is as strong as peyote.
There is a UL that peruvianus is "10x as strong as pachanoi". Again, the response to this is "which pachanoi?" Here is a table of some of the primary citations on Trichocereus potency that should make it clearer:

species%age fresh%age drycitation
peyote?1-6% (rarely >1%)XXX
pachanoi 0.02%*0.331%C&M

* estimated, calculated assuming constant 94% water in fresh material. Provided simply for convenience in comparing different studies. *most* give figures only based on dry material, while Ag gives only fresh.

Agurell, S. 1969 "Cactaceae Alkaloids. I." Lloydia 32:206-216 Found no detectable mescaline at all in T. peruvianus.
Friedberg, Claudine. 1959 "Rapport sur une mission au Perou..." Travaux de l'Institut Francais d'Etudes Andines AFAIK, this is the earliest measurement of M content in pachanoi.
Crosby & McLaughin 1973 "Cactus Alkaloids XIX. Crystallization of mescaline HCl and 3-MEOtyramine HCl from T. pachanoi" Lloydia 36:416
Helmlin HJ & Brenneisen R, J Chromatogr 1992 Feb 28; 593 (1-2): 87-94 Samples of T. pachanoi were taken from private collections, shopping malls & florist's shops.
Pardanani & McLaughlin. 1977. "Cactus Alkaloids. XXVI. Mescaline and Related Compounds from Trichocereus peruvianus" Lloydia Vol 40 #6. This seems to be the sole primary cite on which all claims of peruvianus potency is based.
Turner & Heyman 1960 (cite by C&M) "the presence of mescaline in Opuntia cylindrica (sic)" J. Org. Chem. 25: 2250
cited by C&M, these figures are widely quoted but I have not examined C&M's primary sources for them.

As you can see, pachanoi varies by 20X. This is not likely to be experimental error; H&B using consistent methodology came up with figures that nicely bracket all other citations. The strongest pachanoi measured is 3X the strongest peruvianus measured, and while it is less than half the strength of the strongest peyote on record it is more than twice the strength of peyote you are likely to get your hands on. The strongest T. peruvianus reported is not quite as powerful as the "usual" peyote.

But maybe there was an even more powerful T. peruvianus that was never tested?
Likely, studies of other trichos similar to H&B would also show a variance. How great a variance, and what its top value would be is unknown to the scientific literature. It is possible that the failure to find mescaline in peruvianus reported in Ag is nothing more than the lower-bound.

There is reason to think that other trichos than pachanoi have at times been identified by anthropological informants as "San Pedro", but whether this means that they are pharmacologically as-or-more active is not known at this time.

If you have such a T. peruvianus and can do respectable quantitative chemistry, why not send a note to Lloydia? TIA.

What makes one pachanoi stronger than another?
This is an open question. There is lore within the entheogenic cactophile community that there is both seasonal variation and variance due to plant culture, but no proper scientific studies have been done. There is also a legend of a "purple pachanoi" that was reputed to be very powerful. Turning purple is also a symptom of phototoxicity (over-exposure to sun). Shoots from old clumps are held to be stronger by some, as are branches with 4 ridges (rare to non-existent in pachanoi), and those grown in mineral-rich soil in the Andes. It is possible that different genetic strains of pachanoi have different potential. Much of the pachanoi available is thought to be clonally propagated from one or a very few genetic lines and probably selected for its utility as a grafting stock, although "different individuals" do turn up from time-to-time.

If the cactophile community showed the same dilligence and resourcefulness as have the cannabis-cultivators we would be able to answer your question with certainty (although I certainly do not envy the degree of legal and illegal attention the multi-$G cannabis industry has attracted).

How do I know if I the San Pedro I have is strong or weak?
Ok, so this dude sold you some San Pedro. Do you have the strong kind or the weak kind? Neither you nor I have any idea. Probably neither does the dude. There are some suppliers with a track-record of selling "effective" San Pedro. If you are risk-averse, see if you can find someone who has been in business for some time and ask their other customers.

So how do I know how much to take?
Now you're sitting there with a cactus cutting in your hand, intending to commit felonious cactophagy, and are about to add aggravated weenie-cide unless I can give you a straight answer on how much of that cactus in your hand you should eat. The "maximum safe dose" of mescaline, according to Ott, is 1000 mg. Assume the worst (best) about your cactus, that it is H&B's 2.375% (dry), the most powerful pachanoi known to science. You would therefore not want to take more than 714 gms (fresh), or about 1 1/2 lbs. The threshold dose is about 150 mg, so you'd need at least 107 gms (nearly 4 oz.) to get any effect in the best (worst) case. If you got the wimpy stuff you will need to eat at least 2.5 kg to get the least effect. To get the maximum safe dose from the wimpy stuff you need to eat ~17 kg; probably about one-fifth your own body weight.

I got the wimpy stuff, now what do I do?
Let the rest of it callous off, root it out, plant it, and join the rest of us in discovering what this organism wants from life. It may or may not be weak because of lack of genetic potential; nobody really knows. This is not Safeway, this is a living organism we are approaching and attempting to enlist. Negotiations may be in order. If nothing else, the flowers are gorgeous. Join your local cactus society, or a net mailing-list and expand your horizons.

I've yet to try the wimpy stuff, BTW, although as a plant- collector I buy many more specimens than will ever make it into my kitchen; there might be some wimpy ones in my back-yard unbeknownst to me. But perhaps it is not very common; only representing very unhappy plants that have been living in a shopping-mall or similar unnatural locale. 400 gms of any I've tried seems like an "entheogenic all-day lollipop" to me.

If I could get 1000 pachanoi branches blooming in my garden I'd be a *very* happy gardener, regardless of their alkaloidal content.