Oxidative metabolism of mescaline in the central nervous system--V. In vitro deamination of mescaline to 3,4,5-trimethoxy-benzoic acid

Pharmacokinetic and Pharmacodynamic Aspects of Peyote and Mescaline: Clinical and Forensic Repercussions

BACKGROUND

Mescaline (3,4,5-trimethoxyphenethylamine), mainly found in the Peyote cactus (Lophophora williamsii), is one of the oldest known hallucinogenic agents that influence human and animal behavior, but its psychoactive mechanisms remain poorly understood.

OBJECTIVES

This article aims to fully review pharmacokinetics and pharmacodynamics of mescaline, focusing on the in vivo and in vitro metabolic profile of the drug and its implications for the variability of response.

METHODS

Mescaline pharmacokinetic and pharmacodynamic aspects were searched in books and in PubMed (U.S. National Library of Medicine) without a limiting period. Biological effects of other compounds found in peyote were also reviewed.

RESULTS

Although its illicit administration is less common, in comparison with cocaine and Cannabis, it has been extensively described in adolescents and young adults, and licit consumption often occurs in religious and therapeutic rituals practiced by the Native American Church. Its pharmacodynamic mechanisms of action are primarily attributed to the interaction with the serotonergic 5-HT2A-C receptors, and therefore clinical effects are similar to those elicited by other psychoactive substances, such as lysergic acid diethylamide (LSD) and psilocybin, which include euphoria, hallucinations, depersonalization and psychoses. Moreover, as a phenethylamine derivative, signs and symptoms are consistent with a sympathomimetic effect. Mescaline is mainly metabolized into trimethoxyphenylacetic acid by oxidative deamination but several minor metabolites with possible clinical and forensic repercussions have also been reported.

CONCLUSION

Most reports concerning mescaline were presented in a complete absence of exposure confirmation, since toxicological analysis is not widely available. Addiction and dependence are practically absent and it is clear that most intoxications appear to be mild and are unlikely to produce lifethreatening symptoms, which favors the contemporary interest in the therapeutic potential of the drugs of the class.

Metabolic pathways of 4-bromo-2,5-dimethoxyphenethylamine (2C-B): analysis of phase I metabolism with hepatocytes of six species including human

4-Bromo-2,5-dimethoxyphenethylamine (2C-B) is a psychoactive designer drug of abuse that is sold under the street names "Venus", "Bromo", "Erox", "XTC" or "Nexus". Concern has been raised because only little is known about its toxicity and metabolism in humans. In the present study we incubated 2C-B with human, monkey, dog, rabbit, rat and mouse hepatocytes to identify the metabolites formed and to determine possible toxic effects as evidenced by an ATP assay. Our data allow construction of the main metabolic pathways of 2C-B. Oxidative deamination results in the 2-(4-bromo-2,5-dimethoxyphenyl)-ethanol (BDMPE) and 4-bromo-2,5-dimethoxyphenylacetic acid (BDMPAA) metabolites. Additionally, 4-bromo-2,5-dimethoxybenzoic acid (BDMBA) can be produced also by oxidative deamination. Further metabolism of BDMPE and BDMPAA may occur by demethylation. Alternatively, the later metabolites can be generated by demethylation of 2C-B followed by oxidative deamination. Two remarkable interspecies differences in metabolism of 2C-B were observed (i) a hitherto unknown metabolite, 4-bromo-2,5-dimethoxy-phenol (BDMP), was identified after incubation only with mouse hepatocytes; (ii) 2-(4-bromo-2-hydroxy-5-methoxyphenyl)-ethanol (B-2-HMPE) was produced by hepatocytes from human, monkey and rabbit but not by dog, rat and mouse. Comparing the toxic effects of 2C-B between hepatocytes of the six examined species we observed only minor interspecies differences. However, large inter-individual differences in susceptibility of hepatocytes from three human donors were observed.

Stereochemical aspects of para-chloroamphetamine metabolism. Rabbit liver microsomal metabolism of RS-, R(-)-. and S(+)-para-chloroamphetamine

With the aid of a chiral derivatizing reagent and a sensitive and specific nitrogen-phosphorus gas chromatographic assay, metabolism of para-chloroamphetamine (PCA) enantiomers has been studied following incubation of racemic (RS)-, R(-)- and S(+)-PCA with rabbit liver microsomal preparations. Significant metabolism of racemic PCA and the individual enantiomers was observed following incubation in rabbit liver microsomal preparations. Metabolism required viable microsomes, NADPH and Molecular oxygen, and the rate of metabolism increased following pretreatment with phenobarbital. Incubation of racemic PCA resulted in more rapid metabolism of the S(+) enantiomer than of the R(-) enantiomer. When the enantiomers were incubated individually, each enantiomer was metabolized more rapidly than when incubated as part of a racemic mixture, and the R(-) enantiomer was metabolized more rapidly than the S(+) enantiomer.