2A/C

Psychotomimetic (a word I am very sad to see does not have a wikipedia entry)



Hallucinogen (ditto)



Entheogen



Psychedelic

When discussing psychoactive substances, terminology can be an occasionally touchy subject. To pull an example out of a hat, although it is useful to describe a class of drugs by their effect--such as the class of 'stimulants'--it lacks utility in other settings. For instance, if we're sitting down and having a conversation about stimulants, it can make a huge difference which chemical class we're talking about: are we talking about xanthine alkaloids, such as caffeine theophylline , or (my personal favorite) theobromine ? Or are we talking about a phenethylamine such as amphetamine ? Perhaps we wish to limit ourselves to abused stimulants, or to the class of stimulants that act on dopamine transporters : but then we still have to distinguish between the amphetamine-like drugs, which releases DA by opening the transporter, and cocaine , which simply blocks the transporter and thus inhibits DA reuptake.Hopefully, you can see how this might make our conversation confusing were we to fail to be quite specific in our statements. However, to the best of my knowledge, there's no ongoing controversy to classification of stimulants (feel free to correct me if I'm wrong). But theresome disagreement over another group, one which seems as though it should be fairly easy to identify.So, a simple question for the audience: what do psilocybin LSD , and mescaline all have in common? If you answered that they are chemically similar, you'd be wrong. Psilocybin and LSD are both indole alkaloids , whereas peyote is another phenethylamine. The difference between them is clear, hopefully even to the untrained eye:LSDPsilocybinMescalineFortunately, these drugs all have a common pharmacological target which is believed to be responsible for their common effect: they are all agonists of the 5HTsubtype of serotonin receptors. This target is common to most drugs with a similar effect. So we have a class of drugs whose primary effects are decently described in both popular and scientific literature--albeit with an absence of precise characterization of long-term and secondary effects--with a common pharmacological target. So when we want to bring them up in polite conversation, how do we refer to them?One obvious answer would be to call them "serotonergic agonists of the 2A/C receptor subtype," or something similar. This has many drawbacks, just to name a few: I can't expect anyone who isn't a neuroscientist to remember that for more than five minutes. Of course, it could still be usable in the scientific literature: but believe it or not, even scientists generally prefer to have non-clunky, non-confusing terminology to refer to things by when possible. So that's right out, at least for our general purposes.Now, this debate's been going on for something like fifty years, and we have four main terms that still get tossed around (each of which seems to still be used right now by at least a few people):A true psychotomimetic drug would be one which causes a state mimicking psychosis or schizophrenia in an individual. This was one of the first terms applied to LSD when it first appeared, as it was thought that LSD was in fact bringing on a psychosis-like state in the subject. For a short time, researchers attempted to use it as a chemical model until it became apparent that something entirely different was going on. These days, very few people would argue that this term is useful to describe the class of drugs we're talking about; but certainly there are still some out thereHallucinogen is, at this point, the most commonly used term. But there is a dissatisfaction with it, which seems--at least, to me--to have been growing over the years. The problem is that it, too, seems to be an inaccurate description of the effect of these drugs based on a poor understanding of the effects. Despite the archetype of acidheads tripping out and staring at the pretty colors or interacting with things that aren't there, only a small percentage of users seems to actually report hallucinations. Although many do report some form of altered perception, it is far from universal and generally limited to distortions of actually present objects--and the user can generally recognize both what the object really is and that their senses are altering it. A hallucination, on the other hand, is ideally something which literally isn't there. As such, many have suggested that the term is better used to refer to tropane alkaloids such as atropine or scopolamine , which can induce visions that seem to be unrelated to one's actual surroundings. As such, those drugs are often referred to as the "true hallucinogens" to distinguish them from the more common and broader use of the term. Another reason why it might be useful to limit the term is demonstrated by this page on eMedicine , the second site to come up after a google search for "hallucinogen"; here, the category is applied so broadly that it might be more simply referred to as "all non-opiate illegal drugs."Entheogen is a term that was coined in the late 70s specifically to counter the use of hallucinogen--disliked because of its negative connotations with insanity--and psychedelic (which we'll cover next)--disliked because of its association with 1960s drug culture. It translates roughly as "causing the god within." Honestly? As the term's use is currently advocated, it's awful. If reeks of having been developed as an attempt to improve PR for recreational use of a class of drugs (even if that wasn't the intent). The problem is it's a use-based term: any drug someone wishes to take for religious purposes can be viably deemed an entheogen. The problem, of course, is that there are an endless variety of human religious practices: ultimately, in one context or another any drug could be an entheogen. Attend a UDV ceremony, and consume the classic entheogen ayahuasca. Then go over to your local reservation--and depending on where you are, you may be able to sample the entheogen peyote or the entheogen tobacco. Perhaps you feel like starting a new religion dedicated to the Roman gods Pan & Bacchus? If so, then at your bacchanalia you may wish to promote use of your group's own entheogen, Viagra. I hope you can see the dilemma: the term seems to be quite useful in an anthropological or archaeological context, but has little use when trying to refer to a class of drugs based on their pharmacological properties.And finally, we have the last entry: psychedelic. Although the term is still much less frequently used in the literature than hallucinogen (for instance, I just did a PubMed search and got a single result for "psychedelic LSD 2006" vs. 56 for "hallucinogen LSD 2006"), I've seen a number of people--both in and out of the scientific arena--advocating for its use. Consider, for instance, the existence of MAPS : the Multidisciplinary Association for Psychedelic Studies. The Heffter Research Institute also refers to the drugs they study as psychedelics. The only problem with the term that critics usually point to is its negative associations with 1960's & 1970's-era drug culture. To my mind, this isn't a very good argument. Psychedelic also has the advantage of being the most useful description of the state evoked by these drugs: "mind-manifesting."I admit that this debate is in certain respects almost entirely political. Nonetheless, the terms one chooses to use do have a certain power to them, especially the power to guide how the public thinks about them. In that respect, all of these terms have major drawbacks: but nonetheless, research into many of them is starting to pick up some serious momentum. So the scientific community may either be ultimately forced to recover one of these terms in the public eye, or come up with yet another term to describe them--and hope that it's both accurate and that it doesn't immediately become associated with drug culture.