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[Ketamine Subthread] Isomers: R and S Ketamine

fairnymph

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S (+) Ketamine -- The More Potent Stereoisomer

Most ketamine is racemic, i.e. it is composed of equal parts S/(+) and R/(-) ketamine. The (+) isomer of ketamine is more potent than the (-) isomer. It also seems that (+) ketamine would be superior as a psychedelic tool, for a number of reasons.
Some facts/differences worth noting:
In a study which used male adults, the amount of ketamine needed for total anaesthesia was ~271 mg (+) ketamine vs ~409 mg racemic ketamine. [1]
(+) ketamine is generally considered to be approx. 2-3 times more potent than (-) ketamine.[3]
(+) ketamine is cleared from the body in HALF the time it takes for racemic ketamine. The clearance of (-) ketamine takes only slightly longer than racemic ketamine.[1]
(-) ketamine significantly inhibits the clearance of (+) ketamine. This means that if you have pure (+) ketamine, after you come out of a k-hole, the aftereffects of the k will wear off more quickly than they would if you had done racemic ketamine.[1]
(+) ketamine inhibits the dopamine transporter 8 times more potently than (-) ketamine.[2]
However, application of S(+)-ketamine was associated with a remarkably smoother emergence period, a profound postoperative analgesia, a more rapid recovery of cerebral functions, and a greater preference by the study persons. The incidence of psychotomimetic phenomena appeared to be negligibly less after S(+)-ketamine in comparison to racemic ketamine, but their quality was described as far less unpleasant. Clinical use of S(+)-ketamine administered at one-half of the usual dose is thus not only associated with a reduction of undesirable adverse effects without altering ketamine's anaesthetic and analgesic potency, but also offers distinctive improvements due to the reduced drug load. Moreover, increasing experimental evidence supports a remarkable neuroprotective effect of S(+)-ketamine, which may become a promising drug for new therapeutic approaches to neuroprotection.[3]
It was found that (S)-ketamine binds with a 3-4 time higher affinity to the PCP binding site of the NMDA receptor than (R)-ketamine, and that at these concentrations (R)-ketamine interacts also weakly with the sigma receptor sites, where (S)-ketamine binds only negligibly....R)-ketamine did not produce psychotic symptoms, but a state of relaxation. The (S)-ketamine-induced metabolic hyperfrontality appears to parallel similar metabolic findings in acute psychotic schizophrenic patients and encourages further investigations of glutamatergic disturbances in schizophrenia.
This leads me to believe that the psychedelic effects of racemic ketamine are being produced by the (+) isomer. This would further lead me to conclude that pure (+) ketamine would be more psychedelic in its subjective effects -- as well as less sedating (as noted in the study). [4]
With sub-anaesthetic doses of ketamine in humans, 50% of the test subjects who took racemic ketamine experienced anterograde amnesia (could not remember portions of the k-experience) , while only 8% of those who took (+) ketamine experienced amnesia. This means that your ability to recall a ketamine trip would be greatly improved if you were taking pure (+) ketamine. [5]
Subjective mood was judged by the volunteers to be significantly better after S-(+)-ketamine, and volunteers found S-(+)-ketamine to be more acceptable than racemic ketamine. The frequency of dreams was the same after both drugs. No unpleasant dreams were reported after S-(+)-ketamine, but one of the volunteers who received racemic ketamine had uncomfortable dreams. It seems that (+) ketamine has a distinct positive vibe to it, unlike racemic ketamine which is more neutral (or even negative) in its psychological effects. [6]
[1] Ihmsen H, Geisslinger G, Schuttler J.
Stereoselective pharmacokinetics of ketamine: R(-)-ketamine inhibits the elimination of S(+)-ketamine. Clin Pharmacol Ther. 2001 Nov;70(5):431-8.
[2] Nishimura M, Sato K. Ketamine stereoselectively inhibits rat dopamine transporter. Neurosci Lett. 1999 Oct 22;274(2):131-4.
[3] Himmelseher S, Pfenninger E.The clinical use of S-(+)-ketamine--a determination of its place Anasthesiol Intensivmed Notfallmed Schmerzther. 1998 Dec;33(12):764-70.
[4] Vollenweider FX, Leenders KL, Oye I, Hell D, Angst J. Differential psychopathology and patterns of cerebral glucose utilisation produced by (S)- and (R)-ketamine in healthy volunteers using positron emission tomography (PET). Eur Neuropsychopharmacol. 1997 Feb;7(1):25-38.
[5] Pfenninger E, Baier C, Claus S, Hege G. Psychometric changes as well as analgesic action and cardiovascular adverse effects of ketamine racemate versus s-(+)-ketamine in subanesthetic doses Anaesthesist. 1994 Nov;43 Suppl 2:S68-75.
[6]Doenicke A, Kugler J, Mayer M, Angster R, Hoffmann P.[Ketamine racemate or S-(+)-ketamine and midazolam. The effect on vigilance, efficacy and subjective findings]
Anaesthesist. 1992 Oct;41(10):610-8
 

Pander Bear

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Wow, thats very cool. Would there be any way to cull the (+) isomer from normal racemic ketamine through kitchen chemistry? I would venture a guess of "no", but still, Wow.
It's a shame that the study doesn't deal with non-anaesthetic doses.
cool article fairnymph
 

PlurredChemistry

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can be done pretty easily, but its not kitchen chemistry unfortunately...
interesting side note (or question, i'm not 100% sure if this is true) - after the whole thalidimide thing (one enantiomer cured morning sickness, the other caused birth defects) - any drug in the US that has enantiomeric forms, both enantiomers, must be tested for toxicity. Even if only one is to be used (or synthesized), both are tested. Apparently if one enantiomer is toxic and the other is not they can't sell the good enantiomer anyways...
interesting
 

fractal

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Yeah isomers are like that with many drugs, for example a type of methamphetamine is found in most vicks inhalers but of course its not the type of meth you want.
 

antEater

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Originally posted by fractal:
Yeah isomers are like that with many drugs, for example a type of methamphetamine is found in most vicks inhalers but of course its not the type of meth you want.
Silly Fractal, all types of methamphetamine are the kinds you want :)
 

PlurredChemistry

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wow antEater - that was painful (or really funny, i'm not sure which)
have you been doing your assigned readings? i don't thing so...
pop quiz soon
muahhahahaha
 

NESSxix

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with the vicks inhaler though, why is it spelled differently sometimes. on one label i think it was spelled as "L-metamfetamine" something like that
 

antEater

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Originally posted by fairnymph:
Actually, fractal is correct...the l-methamphetamine found in vicks inhaler's have ZERO recreational value, unlike street methamphetamine which is almost always pure d-meth.
Gosh, you try and be funny and everyone jumps on your back. Sheesh...
Well, of course it's not recreational, or else there would be a shortage of these inhalers at the store, just like Whipped Cream. :)
I think the methamphetamine vs. metamfetamine is some sort of British/Queen's English thing. They're always trying to add a little colour to their vocabulary :)
 

Jimmy the Gun

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Juwwee, you so smart ;) Seriously though, that is a very well research post, mad pr0ps yo :)
peace
 

TheTripDoctor

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Sorry fairnymph, + ketamine is the anesthetic one, as you have shown, however it retains little to no psychedelic effect and as such it has been used clinically in europe, specifically spain. - ketamine is the psychedelic one, and as you will note, subjects under racemic ketamine report delusions and hallucinations, while + subjects do not.
 

Xorkoth

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Although, there is a report on Erowid of a person who took a trip on the S isomer of ketamine alone, and reported that it was tremendously psychedelic, clearer, easier to remember, and easier on the body to come down. He preferred it over "normal" ketamine.

http://www.erowid.org/experiences/exp.php?ID=43590

If you read it, the identitiy of the chemical is assured, although we can only rely on the author's word.
 

TheTripDoctor

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yea i just read it, its possible that most of the research done on (+)ketamine was for the purpose of anesthesia.

In that case, the real concern to THEM would be the after effects, since it goes like this:


An anesthetist administers enough ketamine to literally anesthetise someone, which is FAR FAR past a recreational dose, past 4th plateau in fact, but its INSTANT, so you dont dwell in each stage. The person after surgery would come down, and THEN have psychedelic effects. We have no idea what the person would have felt or said while under anesthesia. So in THAT case...

Research done on ketamine for this purpose would focus on the after effects of the drug used in anesthetic doses, i think the main idea put forth is that (+)ketamine didnt cause NDE phenomena AFTER the person came out of it, while racemic ketamine DID. My theory would be that by the time the person is brought out of it or wakes up (so to speak), the psych effects are over from (+), while the psych effects of (+-) would still be occuring due to a prologned duration.

That means that (+)ketamine, if taken in lower doses, can probably do the exact same thing racemic ketamine does

The + isomer is more potent by weight, for sure, but its likely that the isomers have different effects, what the difference is i dont know, ive had racemic vial ketamine as well as ketamine obtained from a chem house USP grade (technically BP since it wasnt in the US). But I have never had ketamine that had been resolved or separated to just one isomer.

What seems to be the case is that little research was done on the effects of (+)ketamine at sub anesthetic doses, only the passing notice of absence of psychedelic effects in patients given (+)ketamine for surgery, during the emergence phase.
 

Limpet_Chicken

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Problem with thalidomide, is it is metabolised to its toxic isomer in the liver so ANY thalidomide will end up teratogenic.
 

anhalonium9

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hey tripd0ct0r.... um, it took four years to post a response and come up with sources.

WTF!
that is some funny shit.....
 
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