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Southpaw’s Pharmacology Primer Part II: Stereoisomers of drugs/supplements cont’d.

Southpaw’s Pharmacology Primer Part II: Stereoisomers of drugs/supplements cont’d.

Southpaw’s Pharmacology Primer Part II: Stereoisomers of drugs/supplements cont’d.

(Please see Part I before reading this)

Molecules may contain several of these asymmetrical twist points. As well as the “L” and “D” we discussed in Part I, “Left” and “Right” may also be described as (-) for left and (+) for right, or “s” —(lower case s, or sinister, Latin for left) or “d” (lower case d, for dexter, Latin for right). Thus, L, (-) and s all stand for lefthanded, D, (+) and d all stand for righthanded isomers. Between themselves, they have specific differences, which I will mercifully not inflict upon you here :)

Example: THC is the psychotrope that gives the classic marijuana high. Specifically, it is L(-) delta 1,6, transtetrahydrocannabinol. L (-) means “left-left”, so the L(-) prefix on the front of that word means specifically it is the double lefthanded twist isomer of THC. Right? Right! See how easy organic chemistry is ? :)

When we synthesize organic molecules that contain isomers, they generally yield what is called a racemic product, meaning a random 50:50 mixture of the left and right handed isomers. Racemers are okay if we understand that half the product is probably inactive, but we don’t like “dirty” mixtures. We may tolerate wankers and layabouts in society, but not in our drug bottles, so we want to isolate and discard the useless isomer(s) and keep only the good stuff. If the molecule in question is a double isomer, only 25% of the yield is any good to us (1/2 of 1/2), and a triple isomer, only 1/8 is any good (1/2 of 1/2 of 1/2). Thats why complex isometric molecules can be quite expensive, because the yield of active product is so low. Not much wheat, and a lot of chaff.

How do we determine if an isomer is “left” or “right” to begin with? We do this optically because it rotates polarized light to the left or right of zero, respectively. A pure left handed isomer would rotate light -90 degrees left of zero, and a pure right handed isomer +90 degrees right of zero, so we know how much contamination there is pretty accurately by how much the test sample is pulled off of + or - 90, if at all. A perfectly racemic mixture would therefore have a net polar rotation of dead nuts zero. An almost pure, but not totally pure, L isomer would rotate, say, to about -85.

More relevant examples: Ephedra is discussed a lot here. L-ephedrine, or levoephedrine is very potent as a stimulant and is used/abused frequently for its properties by dieters and truckers. In this case, its D isomer does have some weak activity (not all wrong handed isomers are comletely inactive). D-ephedrine—or pseudoephedrine— as it is called, is a common decongestant in cough and cold medine, sold under the popular brand name of Sudafed. If you can flip D-ephedrine (pseudoephedrine) to L-ephedrine, you convert a mild decongestant into a potent psychostimulant.

Dextromethorphan is a common cough suppressant ingredient in cough syrups. Among other brands, it is in Robitussin-DM, and is the “DM” in other such medications containing D-methorphan. Its opposite isomer, L-methorphan or levomethorphan, is more potent than morphine, powerful enough to perform surgery with, in fact. Similarly, if you can flip the common over the counter D-methorphan found in cough syrups into L-methorphan, you convert a mild cough suppressant into a powerful opiate narcotic. You would be very popular with drug dealers.

Just some tricks of the trade I am sharing with you.

Hope this helps you understand isomers, and what impact they have on the drugs and supplements you take.


--- Southpaw

Thank you for posting this. I always wondered what the deal was with the D’s and L’s.

This is a favorite ripoff technique of less than scrupulous herbal and supplement suppliers, btw. I did’nt want to drone on in my orginal post which was long enough, but they can be dishonestly honest, so to speak. If one of their ingredients is heavily isomeric, it is tempting to throw in the racemer, where half is useless to the consumer. Of 1000mg (which is really there, they aren’t lying), 500mg is the wrong isomer and has no value. the FDA scrupulously polices drugs they license to make sure only the correct isomer is there. Unfortunately, herbal suppliers and supplement mfrs. have no such agency to answer to, and temptations exist. As you know, purity issues are a big deal right now in the herbal/supplement industry. I am sure you have noticed brand A of something works great, but brand B of the exact same thing doesn’t. There is certainly more to the purity game than just isolating the correct isomers—but it just makes you wonder, doen’t it? Caveat emptor.

Regards,


--- Southpaw

Great info, southpaw. Thank you.


_______________

avocet8

Re: Southpaw’s Pharmacology Primer Part II: Stereoisomers of drugs/supplements cont’d.

Quote
Originally posted by Southpaw

Dextromethorphan is a common cough suppressant ingredient in cough syrups. Among other brands, it is in Robitussin-DM, and is the “DM” in other such medications containing D-methorphan. Its opposite isomer, L-methorphan or levomethorphan, is more potent than morphine, powerful enough to perform surgery with, in fact. Similarly, if you can flip the common over the counter D-methorphan found in cough syrups into L-methorphan, you convert a mild cough suppressant into a powerful opiate narcotic. You would be very popular with drug dealers.

I know that some people consume large amounts of cough syrup containing DXM in order to get high. Is this because of a small concentration of the opposite isomer?

Excellent post! I had no idea about DM and levomethorphan….btw, do you know the trade name which L-methorphan is used with in surgery?

—-also, what is your background and occupation? No, I’m not a cop :D


If you procrastinate you choose LAST

Re: Southpaw’s Pharmacology Primer Part II: Stereoisomers of drugs/supplements cont’d.

Quote
Originally posted by Southpaw
Dextromethorphan is a common cough suppressant ingredient in cough syrups. Among other brands, it is in Robitussin-DM, and is the “DM” in other such medications containing D-methorphan. Its opposite isomer, L-methorphan or levomethorphan, is more potent than morphine, powerful enough to perform surgery with, in fact. Similarly, if you can flip the common over the counter D-methorphan found in cough syrups into L-methorphan, you convert a mild cough suppressant into a powerful opiate narcotic. You would be very popular with drug dealers.

Take a look at thislink out of academic curiosity only. You can cook the stuff if you know what you are doing, not that I would ever recommend that…

list of over the counter products.

cooking

check out the rest of erowid for other interesting recipe’s.


Running a Massive Co-Front.

Insane man—Two reasons why people drink DM to get high: (1) DM does have modest opiate qualities, maybe 1% of L-methorphan, but if you consume alot, quantity overcomes quallity (like 40oz malt liquor, I suppose), and (2) some DM is converted to LM when it gets first pass metabolized thru the liver.

Canwood—I am a pharmacist with degrees from 2 pharmacy schools (Univ of Wisconsin, and Ph.D in pharmacology from Mercer Univ, in Atlanta), most of the time give prescribing advice to surgeons, and every once in a while testify as an expert witness in court trials. As a Dr. I work with said about me, “it beats having to make an honest living.”

Levomethorphan, a.k.a. levorphanol, goes under the brand name Levo-Dromoran.

http://opioids.com/levorphanol/structure.html

Regards,


--- Southpaw

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