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Fundamental #10: Decide how much to use and measure dosages carefully.
Myth Debunking
A Look at the Mescaline Content of T. peruvianus and T. pachanoi
by Fire Erowid
Dec 2001
Citation:   Erowid, Fire. "A Look at the Mescaline Content of T. peruvianus and T. pachanoi". Erowid Extracts. Dec 2001;2:20-21.
Rumors persist among those interested in mescaline containing cacti that Trichocereus peruvianus (Peruvian Torch) is "10x stronger" than Trichocereus pachanoi (San Pedro). As usual, there appear to be a number of reasons for this confusion.

The Sources
The earliest reference supporting the myth seem to be Peyote and Other Psychoactive Cacti, by Adam Gottlieb. In 1977 Gottlieb wrote, "T. peruvianus is purported to contain ten times the mescaline content of San Pedro." He makes no mention of where this rumor came from and cites no sources to support it, but the claim remains in the 1997 reprint.

Second is a note in Ott's Pharmacotheon (1993) where he states that "Mescaline has been found in 12 species of Trichocereus, the highest concentration in T. peruvianus." To support this, Ott cites the only published reference on the isolation of mescaline from T. peruvianus which showed .817% mescaline by dry weight.1 Unfortunately, he appears to have ignored the data found by Poisson who, in 1960, found 2.0% mescaline by dry weight in T. pachanoi.2

The Data
The published data does not support a claim of 10x potency. A look at the original sources shows that the potencies of the two species are quite similar, with the difference from one specimen to the next outweighing the difference between species. Mescaline contents (by dry weight) in pachanoi have been found ranging from .33% - 2.375%, while peruvianus has been found with .817% and 0%.3,4,5

The only way we reach anything like 10x potency for peruvianus is if we compare the single published isolation of peruvianus against the lowest recorded mescaline content for T. pachanoi. Obviously this is a faulty analysis.

Published Mescaline Content
T. pachanoi (dry)
2.375%Helmlin & Brenneisen 1992
2%Poisson 1960
0.67%Agurell 1969a
0.33%Crosby & McLaughlin 1973
T. peruvianus (dry)
0.817%Pardanani 1977
0%Agurell 1969b
Diameter
Length is a traditional method of measuring a dose of columnar cacti. "A piece the length of your forearm, from elbow to knuckle" (12-15 inches or 30 - 40 cm) is a common recommendation, which unfortunately doesn't take diameter into consideration. Due to the relative unavailability of accurate scales, many amateur cacti enthusiasts continue to measure dosages by length rather than weight. It is important to remember that it is the volume of the cactus that determines total mescaline content, not length, and volume increases non-linearly with diameter.

T. peruvianus tends to grow to a larger diameter than T. pachanoi [RS, KTrout], meaning that at equal potency, less length is required of peruvianus for the same dose. Even after standardizing all other factors (assuming an equal average of 90% water by weight and 1% mescaline by dry weight of these two types of cacti),7 the difference between the mescaline content of a 9 cm diameter and a 6 cm diameter cactus is significant. An 8 cm long section of a 9 cm diameter cactus would yield approximately 400 mg of mescaline--a good solid dose-- while an equal length section of a 6 cm diameter cactus would yield only 180 mg, just above a threshold dose.

[Erowid Note: This note was added after readers were confused that we seemed to be saying a dose of cactus is 30 - 40 cm but then the next paragraph talks about 8cm long pieces.

The calculation is done as if the cactus is a cylinder of water, then taking off around 20% for the fact that these cacti are not perfect cylinders. Because the volume is based on pi * r^2 (radius squared), increases in diameter cause a multiplication in total volume and thus total mescaline content. This is an oversimplifcation because mescaline tends to be concentrated toward the outside of the column and is not distributed evenly in the plant, but it is importan to keep in mind that diameter is as important a factor as potency of cactus when thinking about how much cactus constitutes a dose. Further complicating matters, mass does not always work because recently watered cactus are heavier than cactus that has been water starved. Take two identical cactus with the exact same concentration of mescaline per gram of raw plant material that have been water starved. Then one is watered thoroughly and the other is not. The one that receives water will weigh more after a couple days of watering and the concentration of mescaline per gram of raw plant material will be lower in the wet cactus than in the drier cactus. The main take away is not to assume too much about potency of a given cactus. ]

Summary
It is important to note that both T. pachanoi and T. peruvianus vary significantly in mescaline content from one specimen to the next, based on factors such as soil condition, altitude, amount of sun and age. Additionally, there is great confusion taxonomically concerning T. peruvianus. Most experts agree it's likely there are many distinct species being circulated as T. peruvianus.

Unfortunately, without more testing of T. peruvianus samples, it's difficult to know how the average peruvianus compares to the average pachanoi. Common wisdom and bioassay data still put T. peruvianus as the more potent of the two, but only about 2-2.5 times stronger at best, and without scientific data to back up the claim. What this all suggests to the average consumer is that when looking for potent cacti, the reliability of the source is likely more important than the species.