LSD is almost entirely metabolized within a day after ingestion. Since the half-life of LSD is only a few hours, only a very small amount of LSD remains even at the end of the trip, and this is excreted in the urine. All traces are undetectable after several days and are certainly gone entirely within a couple of weeks. As detection technology improves and thresholds drop (it is now possible to detect picograms reliably), the time that incredibly small amounts of it could be detected will extend.
It has long been reported that LSD is fully metabolized almost immediately after ingestion. This was based on research done in the 50's and 60s which used instruments not sensitive enough to detect the extremely small amounts of the chemical.
Occasionally, people claim that LSD has been found in spinal fluid years after the last time LSD was taken. There is no support for this claim. If anyone knows of a research article that has looked at spinal fluid of LSD users for LSD, please let us know.
Although research in the 1960s found the half-life of LSD was around 3 hours, more recent research shows that LSD's metabolism takes several hours and its peak plasma levels occur at around 3-5 hours after ingestion. It is important to note that such research is highly dependent on the individuals who were used for the research, with metabolism of many drugs varying by up to 2-3 times, larger numbers of research subjects reduces the likelihood of having a skewed range.
From "Notes on the Persistence of LSD in Humans" by Jim Ketchum MD, working with Aghajanian:
Half-life found to be around 160 minutes mean across 40 subjects. "It seems logical to conclude that in man also, its duration in the brain is finite -- almost certainly less than 24 hours."
From: "Measurement of lysergic acid diethylamide (LSD) in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry." Papac DL, Folts RL , J.Anal. Toxicol., 14, 189-190 (1990)
In a single volunteer given about 70 ug, the apparent plasma half-life of LSD is 5.1 hr. The peak plasma concentration of 1.9 ng/mL occurred 3 hr after administration.
From: "The determination of LSD in human plasma following oral administration", Upshall DG, Wailling DG. Clinc. chim. Acta, 1972; 36:67-73.
LSD was detectable for up to five hours...
From: "A urine screening test of lysergide" Faed EM, McLeod WR. Journal of Chromatographic Science. 11, 4-6 (1973)
"LSD and its metabolites were still detectable in human urine for as long as 4 days after the ingestion of 0.2 mg of the drug."
From LSD My Problem Child, by Albert Hofmann, 1969
The concentration of LSD in the various organs attains maximum values 10 to 15 minutes after injection, then falls off swiftly. The small intestine, in which the concentration attains the maximum within two hours, constitutes an exception. The elimination of LSD is conducted for the most part (up to 80%) through the instestine via liver and bile. Only 1 to 10 percent of the elimination product exists as unaltered LSD; the remainder is made up of various transformation products.
I wasn't really even closing it to say "I've answered the thread, now we can close it." It was more of a "use the search engine" thing, because I swear we've had threads about this before, but I didn't have time to look one up.
