LSD (lysergic acid diethylamide) was formerly often referred to as ‘LSD-25’.

If it really is a (Albert Hofmann / Sandoz)'s code name (and not a combination of ‘LSD’ and usual LSD (Delysid) dosage numeral ‘25’ μg; see also Quora: What does the "25" in "LSD-25" mean?), are some other substances from the series LSD-1, LSD-2, … etc., being at a time probably a part of industrial secret, currently already known?



Identify at least one another Sandoz LSD-x, where x ≥ 1 and x ≠ 25 (with good sources or at least proven insider knowledge).

  • 2
    $\begingroup$ It was Hofmann's 25th synthesis of the compound-it has nothing to do with dosage. $\endgroup$ Oct 20, 2018 at 17:56
  • $\begingroup$ @ToddMinehardt … but it wouldn't make much sense to append serial number to the compound name abbreviation. I share the hypothesis, that in the series, ‘LSD’ means ‘Lysergsäurederivat' rather than ‘Lysergsäurediethylamid’. $\endgroup$
    – mykhal
    Oct 22, 2018 at 10:55

2 Answers 2


The number "25" indeed comes from the fact that it was the 25th compound of the lysergic acid amide series or lysergamides. I found an article* by Frank J. Ayd, Jr. & Barry Blackwell who accounted Alexander Hoffman's investigation in his LSD synthesis:

A number of pharmacological experiments were carried out by Professor Ernst Rothlin with this new compound, which was given the laboratory code name LSD-25 because it was the twenty-fifth compound of the lysergic acid amide series.

You can check the other compounds of the series in the Wikipedia article linked above. Most of them have their own specific names and not LSD-1, LSD-2 etc.

I also did find something in an e-book(Ref) which says that the number has something to do with date:

Dr. Hoffmann described the results of accidental ingestion of LSD. It was in Switzerland in 1943, five years after Dr. Hoffmann and an associate has synthesized lysergic acid diethylamide tartarate (from ergot). The substance was labeled "25" because of the date: "May 2, 1938" (the date when LSD was synthesized(?)).

Ref.: LSD-25: a Factual Account: Layman's Guide to the Pharmacology, Physiology, Psychology, and Sociology of LSD, Louise G. Richards, U.S. Bureau of Narcotics and Dangerous Drugs, 1969


*I was researching about something else i.e "serendipity in Chemistry". While I was surfing the Internet, I stumbled upon this article and from that, I came to know about LSD, searched for the sources of their information and from there I got access to the above article and then proceeded to compile this answer without any prior intentions. What a beautiful irony!


Dr. Albert Hoffman has prepared lysergic acid diethylamide (LSD) for the first time in 1938 as part of a systematic chemical and pharmacological investigation of partially synthetic amides of Iysergic acid in the Sandoz pharmaceutical-chemical research laboratories in Basle. Sandoz was a Swiss chemical company founded in 1886 where its pharmaceutical-chemical division was headed at the time by Professor Arthur Stoll. Dr. Stoll was the first to isolate lysergic acid based active substances such as ergotamine and ergobasine from ergot, a fungus found in tainted rye.According to this article, within a few years researchers at Sandoz had determined the chemical structure of these various biologically active compounds in ergot, all of which shared a common nucleus. This chemical starting point was called lysergic acid, or, in German, Lysergsaure.

Hofmann developed a synthetic process to build the ergot compounds from their component chemicals. Using this method, he recreated ergot’s active ingredients as well as novel but similar compounds that, based on the potency of the ergot compounds, could reasonably be expected to have medical uses.

In a sense Hofmann was playing God, combining lysergic acid with various other organic molecules just to see what happened. He created 24 of these lysergic acid combinations. Then he created the 25th, reacting lysergic acid with diethylamine, a derivative of ammonia. The compound was abbreviated as LSD-25 for the purposes of laboratory testing.

Hofmann was hoping one of these compounds that could stimulate circulation and respiration. Lysergic acid diethylamide (LSD) and four other Hofmann developed compounds are listed below:

LSD and other related synthetic compounds

Accordingly, as Todd Minehardt pointed out, the name LSD-25 has nothing to do with the dosage used in therapy. It is strictly for the purposes of laboratory testing, which originally had Sandoz to decide “The new substance, however, aroused no special interest in our pharmacologists and physicians; testing was therefore discontinued.” However, Hofmann's accidental discovery of hallucination by LSD-25 in April 16, 1943 has changed everything forever.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.