# Mescaline

Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a naturally occurring psychedelic protoalkaloid of the substituted phenethylamine class, known for its hallucinogenic effects comparable to those of LSD and psilocybin. It binds to and activates certain serotonin receptors in the brain, producing hallucinogenic effects.

## Biological sources

It occurs naturally in several species of cacti. It is also reported to be found in small amounts in certain members of the bean family, Fabaceae, including Senegalia berlandieri (syn. Acacia berlandieri), although these reports have been challenged and have been unsupported in any additional analyses.
| Plant source | Amount of mescaline (% of dry weight) |
| Echinopsis lageniformis (Bolivian torch cactus, syns. Echinopsis scopulicola, Trichocereus bridgesii) | Average 0.56; 0.85 in one cultivar of Echinopsis scopulicola |
| Leucostele terscheckii (syns Echinopsis terscheckii, Trichocereus terscheckii) | 0.005 - 2.375 |
| Peyote cactus (Lophophora williamsii) | 0.01-5.5 |
| Trichocereus macrogonus var. macrogonus (Peruvian torch, syns Echinopsis peruviana, Trichocereus peruvianus) | 0.01-0.05; 0.24-0.81 |
| Trichocereus macrogonus var. pachanoi (San Pedro cactus, syns Echinopsis pachanoi, Echinopsis santaensis, Trichocereus pachanoi) | 0.23-4.7; 0.32 under its synonym Echinopsis santaensis |
| Trichocereus uyupampensis (syn. Echinopsis uyupampensis) | 0.05 |
| Trichocereus tacaquirensis (subsp. taquimbalensis syn. Trichocereus taquimbalensis) | 0.005-2.7 |
As shown in the accompanying table, the concentration of mescaline in different specimens can vary largely within a single species. Moreover, the concentration of mescaline within a single specimen varies as well.

## History and use

Peyote has been used for at least 5,700 years by Indigenous peoples of the Americas in Mexico. Europeans recorded use of peyote in Native American religious ceremonies upon early contact with the Huichol people in Mexico. Other mescaline-containing cacti such as the San Pedro have a long history of use in South America, from Peru to Ecuador. While religious and ceremonial peyote use was widespread in the Aztec Empire and northern Mexico at the time of the Spanish conquest, religious persecution confined it to areas near the Pacific coast and up to southwest Texas. However, by 1880, peyote use began to spread north of South-Central America with "a new kind of peyote ceremony" inaugurated by the Kiowa and Comanche people. These religious practices, incorporated legally in the United States in 1920 as the Native American Church, have since spread as far as Saskatchewan, Canada.
In traditional peyote preparations, the top of the cactus is cut off, leaving the large tap root along with a ring of green photosynthesizing area to grow new heads. These heads are then dried to make disc-shaped buttons. Buttons are chewed to produce the effects or soaked in water to drink. However, the taste of the cactus is bitter, so modern users will often grind it into a powder and pour it into capsules to avoid having to taste it. The typical dosage is 200–400 milligrams of mescaline sulfate or 178–356 milligrams of mescaline hydrochloride. The average 76 mm (3.0 in) peyote button contains about 25 mg mescaline. Some analyses of traditional preparations of San Pedro cactus have found doses ranging from 34 mg to 159 mg of total alkaloids, a relatively low and barely psychoactive amount. It appears that patients who receive traditional treatments with San Pedro ingest sub-psychoactive doses and do not experience psychedelic effects.
Botanical studies of peyote began in the 1840s and the drug was listed in the Mexican pharmacopeia. The first of mescal buttons was published by John Raleigh Briggs in 1887. In 1887, the German pharmacologist Louis Lewin received his first sample of the peyote cactus, found numerous new alkaloids and later published the first methodical analysis of it. Mescaline was first isolated and identified in 1896 or 1897 by the German chemist Arthur Heffter and his colleagues. He showed that mescaline was exclusively responsible for the psychoactive or hallucinogenic effects of peyote. However, other components of peyote, such as hordenine, pellotine, and anhalinine, are also active. Mescaline was first synthesized in 1919 by Ernst Späth.
In 1955, English politician Christopher Mayhew took part in an experiment for BBC's Panorama, in which he ingested 400 mg of mescaline under the supervision of psychiatrist Humphry Osmond. Though the recording was deemed too controversial and ultimately omitted from the show, Mayhew praised the experience, calling it "the most interesting thing I ever did".
Studies of the potential therapeutic effects of mescaline started in the 1950s.
The mechanism of action of mescaline, activation of the serotonin 5-HT$_{2A}$ receptors, became known in the 1990s.

### Potential medical usage

Mescaline has a wide array of suggested medical usage, including treatment of depression, anxiety, PTSD, and alcoholism. However, its status as a Schedule I controlled substance in the Convention on Psychotropic Substances limits availability of the drug to researchers. Because of this, very few studies concerning mescaline's activity and potential therapeutic effects in people have been conducted since the early 1970s.

## Behavioral and non-behavioral effects

Mescaline induces a psychedelic state comparable to those produced by LSD and psilocybin, but with unique characteristics. Subjective effects may include altered thinking processes, an altered sense of time and self-awareness, and closed- and open-eye visual phenomena.
Prominence of color is distinctive, appearing brilliant and intense. Recurring visual patterns observed during the mescaline experience include stripes, checkerboards, angular spikes, multicolor dots, and very simple fractals that turn very complex. The English writer Aldous Huxley described these self-transforming amorphous shapes as like animated stained glass illuminated from light coming through the eyelids in his autobiographical book The Doors of Perception (1954). Like LSD, mescaline induces distortions of form and kaleidoscopic experiences but they manifest more clearly with eyes closed and under low lighting conditions.
Heinrich Klüver coined the term "cobweb figure" in the 1920s to describe one of the four form constant geometric visual hallucinations experienced in the early stage of a mescaline trip: "Colored threads running together in a revolving center, the whole similar to a cobweb". The other three are the chessboard design, tunnel, and spiral. Klüver wrote that "many 'atypical' visions are upon close inspection nothing but variations of these form-constants."
As with LSD, synesthesia can occur especially with the help of music. An unusual but unique characteristic of mescaline use is the "geometrization" of three-dimensional objects. The object can appear flattened and distorted, similar to the presentation of a Cubist painting.
Mescaline elicits a pattern of sympathetic arousal, with the peripheral nervous system being a major target for this substance.
According to a research project in the Netherlands, ceremonial San Pedro use seems to be characterized by relatively strong spiritual experiences, and low incidence of challenging experiences.

## Chemistry

Mescaline, also known as 3,4,5-trimethoxyphenethylamine (3,4,5-TMPEA), is a substituted phenethylamine derivative. It is closely structurally related to the catecholamine neurotransmitters dopamine, norepinephrine, and epinephrine.
The drug is relatively hydrophilic with low fat solubility. Its predicted log P (XLogP3) is 0.7.

### Biosynthesis

Mescaline is biosynthesized from tyrosine, which, in turn, is derived from phenylalanine by the enzyme phenylalanine hydroxylase. In Lophophora williamsii (Peyote), dopamine converts into mescaline in a biosynthetic pathway involving m-O-methylation and aromatic hydroxylation.
Tyrosine and phenylalanine serve as metabolic precursors towards the synthesis of mescaline. Tyrosine can either undergo a decarboxylation via tyrosine decarboxylase to generate tyramine and subsequently undergo an oxidation at carbon 3 by a monophenol hydroxylase or first be hydroxylated by tyrosine hydroxylase to form L-DOPA and decarboxylated by DOPA decarboxylase. These create dopamine, which then experiences methylation by a catechol-O-methyltransferase (COMT) by an S-adenosyl methionine (SAM)-dependent mechanism. The resulting intermediate is then oxidized again by a hydroxylase enzyme, likely monophenol hydroxylase again, at carbon 5, and methylated by COMT. The product, methylated at the two meta positions with respect to the alkyl substituent, experiences a final methylation at the 4 carbon by a guaiacol-O-methyltransferase, which also operates by a SAM-dependent mechanism. This final methylation step results in the production of mescaline.
Phenylalanine serves as a precursor by first being converted to L-tyrosine by L-amino acid hydroxylase. Once converted, it follows the same pathway as described above.
    Biosynthesis of mescaline

### Laboratory synthesis

Mescaline was first synthesized in 1919 by Ernst Späth from 3,4,5-trimethoxy­benzoyl chloride. Several approaches using different starting materials have been developed since, including the following:
* Hofmann rearrangement of 3,4,5-trimethoxy­phenyl­propionamide.
* Cyanohydrin reaction between potassium cyanide and 3,4,5-trimethoxy­benz­aldehyde followed by acetylation and reduction.
* Henry reaction of 3,4,5-trimethoxy­benz­aldehyde with nitromethane followed by nitro compound reduction of ω-nitro­trimethoxy­styrene.
* Ozonolysis of elemicin followed by reductive amination.
* Ester reduction of Eudesmic acid's methyl ester followed by halogenation, Kolbe nitrile synthesis, and nitrile reduction.
* Amide reduction of 3,4,5-trimethoxy­phenyl­acetamide.
* Reduction of 3,4,5-trimethoxy­(2-nitrovinyl)benzene with lithium aluminum hydride.
* Treatment of tricarbonyl-(η6-1,2,3-trimethoxy­benzene) chromium complex with acetonitrile carbanion in THF and iodine, followed by reduction of the nitrile with lithium aluminum hydride.

## Pharmacology
### Pharmacodynamics

Mescaline activities :
| Target | Affinity (K$_i$, nM) |
| 5-HT$_{1A}$ | 1,841–4,600 |
| 5-HT$_{1B}$ | >10,000 |
| 5-HT$_{1D}$ | >10,000 |
| 5-HT$_{1E}$ | 5,205 |
| 5-HT$_{1F}$ | ND |
| 5-HT$_{2A}$ | 550–17,400 (K$_i$) 88–30,200 (EC$_{50}$Tooltip half-maximal effective concentration) 56–107% (E$_{max}$Tooltip maximal efficacy) |
| 5-HT$_{2B}$ | 793–800 (K$_i$) >20,000 (EC$_{50}$) |
| 5-HT$_{2C}$ | 300–17,000 20–19,500 (EC$_{50}$) 22–95% (E$_{max}$) |
| 5-HT$_3$ | >10,000 |
| 5-HT$_4$ | ND |
| 5-HT$_{5A}$ | >10,000 |
| 5-HT$_6$ | >10,000 |
| 5-HT$_7$ | >10,000 |
| α$_{1A}$ | >15,000 |
| α$_{1B}$ | >10,000 |
| α$_{1D}$ | ND |
| α$_{2A}$ | 1,400–8,930 |
| α$_{2B}$ | >10,000 |
| α$_{2C}$ | 745 |
| β$_1$–β$_2$ | >10,000 |
| D$_1$ | >10,000 |
| D$_2$ | >10,000 |
| D$_3$ | >17,000 |
| D$_4$ | >10,000 |
| D$_5$ | >10,000 |
| H$_1$–H$_4$ | >10,000 |
| M$_1$–M$_5$ | >10,000 |
| TAAR$_1$ | 3,300 (K$_i$) (rat) 11,000 (K$_i$) (mouse) 3,700–4,800 (EC$_{50}$) (rodent) >10,000 (EC$_{50}$) (human) |
| I$_1$ | 2,678 |
| σ$_1$–σ$_2$ | >10,000 |
| SERTTooltip Serotonin transporter | >30,000 (K$_i$) 367,000 (IC$_{50}$Tooltip half-maximal inhibitory concentration) |
| NETTooltip Norepinephrine transporter | >30,000 (K$_i$) >900,000 (IC$_{50}$) |
| DATTooltip Dopamine transporter | >30,000 (K$_i$) 841,000 (IC$_{50}$) |
| Notes: The smaller the value, the more avidly the drug binds to the site. All proteins are human unless otherwise specified. Refs: ||
In plants, mescaline may be the end-product of a pathway utilizing catecholamines as a method of stress response, similar to how animals may release such compounds and others such as cortisol when stressed. The in vivo function of catecholamines in plants has not been investigated, but they may function as antioxidants, as developmental signals, and as integral cell wall components that resist degradation from pathogens. The deactivation of catecholamines via methylation produces alkaloids such as mescaline.
In humans, mescaline acts similarly to other psychedelic agents. It acts as an agonist, binding to and activating the serotonin 5-HT$_{2A}$ receptor. Its EC$_{50}$Tooltip half-maximal effective concentration at the serotonin 5-HT$_{2A}$ receptor is approximately 10,000 nM and at the serotonin 5-HT$_{2B}$ receptor is greater than 20,000 nM. How activating the 5-HT$_{2A}$ receptor leads to psychedelic effects is still unknown, but it is likely that somehow it involves excitation of neurons in the prefrontal cortex. In addition to the serotonin 5-HT$_{2A}$ and 5-HT$_{2B}$ receptors, mescaline is also known to bind to the serotonin 5-HT$_{2C}$ receptor and a number of other targets.
Mescaline lacks affinity for the monoamine transporters, including the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT) (K$_i$ > 30,000 nM). However, it has been found to increase levels of the major serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) at high doses in rodents. This finding suggests that mescaline might inhibit the reuptake and/or induce the release of serotonin at such doses. However, this possibility has not yet been further assessed or demonstrated. Besides serotonin, mescaline might also weakly induce the release of dopamine, but this is probably of modest significance, if it occurs. In accordance, there is no evidence of the drug showing addiction or dependence. Other psychedelic phenethylamines, including the closely related 2C, DOx, and TMA drugs, are inactive as monoamine releasing agents and reuptake inhibitors. However, an exception is trimethoxyamphetamine (TMA), the amphetamine analogue of mescaline, which is a very low-potency serotonin releasing agent (EC$_{50}$Tooltip half-maximal effective concentration = 16,000 nM). The possible monoamine-releasing effects of mescaline would likely be related to its structural similarity to substituted amphetamines and related compounds.
Tolerance to mescaline builds with repeated usage, lasting for a few days. The drug causes cross-tolerance with other serotonergic psychedelics such as LSD and psilocybin.
The LD$_{50}$ of mescaline has been measured in various animals: 212–315 mg/kg i.p. (mice), 132–410 mg/kg i.p. (rats), 328 mg/kg i.p. (guinea pigs), 54 mg/kg in dogs, and 130 mg/kg i.v. in rhesus macaques. For humans, the LD$_{50}$ of mescaline has been reported to be approximately 880 mg/kg. It has been said that it would be very difficult to consume enough mescaline to cause death in humans.
Mescaline is a relatively low-potency psychedelic, with active doses in the hundreds of milligrams and micromolar affinities for the serotonin 5-HT$_{2A}$ receptor. For comparison, psilocybin is approximately 20-fold more potent (doses in the tens of milligrams) and lysergic acid diethylamide (LSD) is approximately 2,000-fold more potent (doses in the tens to hundreds of micrograms). There have been efforts to develop more potent analogues of mescaline. Difluoro­mescaline and trifluoro­mescaline are more potent than mescaline, as is its amphetamine homologue TMA. Escaline and proscaline are also both more potent than mescaline, showing the importance of the 4-position substituent with regard to receptor binding.

### Pharmacokinetics

About half the initial dosage is excreted after 6 hours, but some studies suggest that it is not metabolized at all before excretion. Mescaline appears not to be subject to metabolism by CYP2D6 and between 20% and 50% of mescaline is excreted in the urine unchanged, with the rest being excreted as the deaminated-oxidised-carboxylic acid form of mescaline, a likely result of monoamine oxidase (MAO) degradation. However, the enzymes mediating the oxidative deamination of mescaine are controversial. MAO, diamine oxidase (DAO), and/or other enzymes may be involved or responsible.
The previously reported elimination half-life of mescaline was originally reported to be 6 hours, but a new study published in 2023 reported a half-life of 3.6 hours. The higher estimate is believed to be due to small sample numbers and collective measurement of mescaline metabolites.
Mescaline appears to have relatively poor blood–brain barrier permeability due to its low lipophilicity. However, it is still able to cross into the central nervous system and produce psychoactive effects at sufficienty high doses.
Active metabolites of mescaline may contribute to its psychoactive effects.

## Interactions

The serotonin 5-HT$_{2A}$ receptor antagonist ketanserin has been found to block the psychoactive effects of mescaline.

## Legal status
### United States

In the United States, mescaline was made illegal in 1970 by the Comprehensive Drug Abuse Prevention and Control Act, categorized as a Schedule I hallucinogen. The drug is prohibited internationally by the 1971 Convention on Psychotropic Substances. Mescaline is legal only for certain religious groups (such as the Native American Church by the American Indian Religious Freedom Act of 1978) and in scientific and medical research. In 1990, the Supreme Court ruled that the state of Oregon could ban the use of mescaline in Native American religious ceremonies. The Religious Freedom Restoration Act (RFRA) in 1993 allowed the use of peyote in religious ceremony, but in 1997, the Supreme Court ruled that the RFRA is unconstitutional when applied against states. Many states, including the state of Utah, have legalized peyote usage with "sincere religious intent", or within a religious organization, regardless of race. Synthetic mescaline, but not mescaline derived from cacti, was officially decriminalized in the state of Colorado by ballot measure Proposition 122 in November 2022.
While mescaline-containing cacti of the genus Echinopsis are technically controlled substances under the Controlled Substances Act, they are commonly sold publicly as ornamental plants.

### United Kingdom

In the United Kingdom, mescaline in purified powder form is a Class A drug. However, dried cactus can be bought and sold legally.

### Australia

Mescaline is considered a schedule 9 substance in Australia under the Poisons Standard (February 2020). A schedule 9 substance is classified as "Substances with a high potential for causing harm at low exposure and which require special precautions during manufacture, handling or use. These poisons should be available only to specialised or authorised users who have the skills necessary to handle them safely. Special regulations restricting their availability, possession, storage or use may apply."

### Other countries

In Canada, France, The Netherlands and Germany, mescaline in raw form and dried mescaline-containing cacti are considered illegal drugs. However, anyone may grow and use peyote, or Lophophora williamsii, as well as Echinopsis pachanoi and Echinopsis peruviana without restriction, as it is specifically exempt from legislation. In Canada, mescaline is classified as a schedule III drug under the Controlled Drugs and Substances Act, whereas peyote is exempt.
In Russia mescaline, its derivatives and mescaline-containing plants are banned as narcotic drugs (Schedule I).

## Notable users

* Salvador Dalí experimented with mescaline believing it would enable him to use his subconscious to further his art potential.
* Antonin Artaud wrote 1947's The Peyote Dance, where he describes his peyote experiences in Mexico a decade earlier.
* Jerry Garcia took peyote prior to forming The Grateful Dead but later switched to LSD and DMT since they were easier on the stomach.
* Allen Ginsberg took peyote. Part II of his poem "Howl" was inspired by a peyote vision that he had in San Francisco.
* Ken Kesey took peyote prior to writing One Flew Over the Cuckoo's Nest.
* Jean-Paul Sartre took mescaline shortly before the publication of his first book, L'Imaginaire; he had a bad trip during which he imagined that he was menaced by sea creatures. For many years following this, he persistently thought that he was being followed by lobsters, and became a patient of Jacques Lacan in hopes of being rid of them. Lobsters and crabs figure in his novel Nausea.
* Havelock Ellis was the author of one of the first written reports to the public about an experience with mescaline (1898).
* Stanisław Ignacy Witkiewicz, Polish writer, artist and philosopher, experimented with mescaline and described his experience in a 1932 book Nikotyna Alkohol Kokaina Peyotl Morfina Eter.
* Aldous Huxley described his experience with mescaline in the essay "The Doors of Perception" (1954).
* Jim Carroll in The Basketball Diaries described using peyote that a friend smuggled from Mexico.
* Quanah Parker, appointed by the federal government as principal chief of the entire Comanche Nation, advocated the syncretic Native American Church alternative, and fought for the legal use of peyote in the movement's religious practices.
* Hunter S. Thompson wrote an extremely detailed account of his first use of mescaline in "First Visit with Mescalito", and it appeared in his book Songs of the Doomed, as well as featuring heavily in his novel Fear and Loathing in Las Vegas.
* Psychedelic research pioneer Alexander Shulgin said he was first inspired to explore psychedelic compounds by a mescaline experience. In 1974, Shulgin synthesized 2C-B, a psychedelic phenylethylamine derivative, structurally similar to mescaline, and one of Shulgin's self-rated most important phenethylamine compounds together with Mescaline, 2C-E, 2C-T-7, and 2C-T-2.
* Bryan Wynter produced Mars Ascends after trying the substance for the first time.
* George Carlin mentioned mescaline use during his youth while being interviewed in 2008.
* Carlos Santana told about his mescaline use in a 1989 Rolling Stone interview.
* Disney animator Ward Kimball described participating in a study of mescaline and peyote conducted by UCLA in the 1960s.
* Michael Cera used real mescaline for the movie Crystal Fairy & the Magical Cactus, as expressed in an interview.
* Philip K. Dick was inspired to write Flow My Tears, the Policeman Said after taking mescaline.
* Arthur Kleps, a psychologist turned drug legalization advocate and writer whose Neo-American Church defended use of marijuana and hallucinogens such as LSD and peyote for spiritual enlightenment and exploration, bought, in 1960, by mail from Delta Chemical Company in New York 1 g of mescaline sulfate and took 500 mg. He experienced a psychedelic trip that caused profound changes in his life and outlook.