LSD

LSD, or lysergic acid diethylamide, is a semisynthetic compound belonging to the ergoline class and is classed pharmacologically as a serotonergic psychedelic or hallucinogen ^[1][2]. It is made from lysergic acid, which is obtained from the alkaloids of ergot, a fungus that grows on rye and related grains, and it is extraordinarily potent, active at doses far smaller than those of almost any other psychoactive drug ^[1][2].

The Swiss chemist Albert Hofmann first synthesized LSD in 1938 while working at Sandoz Laboratories, and he discovered its psychological effects in 1943 after accidentally absorbing a small amount, an episode remembered in psychedelic lore as the prelude to the first deliberate self-experiment with the drug ^[1]. During the 1950s and 1960s it was studied by psychiatrists as a possible aid in treating alcoholism and other conditions, and was infamously used in secret government experiments, before it became a symbol of 1960s counterculture and was subsequently outlawed ^[1].

The subjective experience, often called a trip, can include vivid visual imagery, distortions of time and space, shifts in emotion, and a sense of altered meaning; experiences may be pleasurable or frightening, and outcomes are strongly shaped by the setting and the person's state of mind ^[1][2]. LSD is not considered addictive and does not produce a physical withdrawal syndrome, and it has a wide margin between active and toxic doses, although it can provoke acute anxiety or, rarely, lasting perceptual disturbances ^[1][2]. After decades of restriction, interest in its therapeutic potential has revived, with modern research examining psychedelic-assisted approaches to anxiety, depression, and cluster headache; a regulatory breakthrough-therapy designation has been granted to a standardized form for generalized anxiety disorder ^[1].

Legally, LSD is tightly controlled almost everywhere; it is listed in Schedule I under United States law and placed in the strictest category of the international convention on psychotropic substances, meaning it is treated as having a high potential for misuse and, until recently, no accepted medical use ^[1].

Physically, LSD is remarkably non-toxic; there is no established lethal dose in humans from the drug itself, it does not produce physical dependence, and in supervised studies serious medical events are rare. The real risks are psychological and situational. A bad trip can mean intense anxiety, panic, paranoia, or confusion, and because judgment and coordination are impaired for hours, accidents and reckless decisions are a genuine danger. A minority of people develop HPPD (hallucinogen persisting perception disorder), where visual disturbances linger long after the drug is gone.

LSD can also unmask or worsen serious mental illness; anyone with a personal or family history of psychosis or schizophrenia should steer well clear. Tolerance builds fast, so taking it on back-to-back days does almost nothing, and there is cross-tolerance with other psychedelics. Interactions matter too; lithium and tricyclic antidepressants have been tied to severe reactions including seizures when combined with LSD, while SSRIs tend to blunt the effect. Legally it is a Schedule I substance in the United States and tightly controlled almost everywhere, so possession carries heavy penalties despite the drug's low addiction potential.

LSD interacts mainly at the receptor rather than the liver. Chronic SSRI treatment blunts the response; in a 1996 survey, 28 of 32 people taking fluoxetine, paroxetine, sertraline or trazodone for more than three weeks reported the subjective effects were reduced or almost gone. The same investigators found the opposite with tricyclics and lithium, where responses were amplified, and lithium carries the worst signal of the set: naturalistic reports link it to seizures and severe dissociative reactions alongside classic psychedelics. Antipsychotics with 5-HT2A antagonism, risperidone and quetiapine among them, cut the experience short by blocking the receptor LSD acts on.

Clearance is spread across CYP2D6, CYP1A2, CYP2C9, CYP2E1 and CYP3A4. That redundancy limits how much any single inhibitor matters, but CYP2D6 is the standout: in a pooled analysis of 81 healthy volunteers, poor metabolizers had roughly 75% higher exposure, a longer half-life and longer, stronger effects. Strong CYP2D6 inhibitors including paroxetine, fluoxetine, bupropion and ritonavir would be expected to shift exposure the same way.

Checking a whole stack? Run it through interactions + stacks.

Lysergic acid diethylamide was first synthesized on November 16, 1938 by the Swiss chemist Albert Hofmann at the Sandoz laboratories in Basel, as the twenty-fifth compound in a series of ergot-derived lysergic acid amides, hence the internal designation LSD-25. Its psychoactive properties went unnoticed until April 16, 1943, when Hofmann absorbed a trace amount and experienced its effects; three days later, on April 19, 1943, he deliberately ingested 0.25 mg in the self-experiment later commemorated as "Bicycle Day."

Sandoz brought the drug to market by 1947 under the trade name Delysid, distributing it to psychiatrists and researchers as an experimental tool for psychotherapy and for inducing model psychoses. Through the 1950s and 1960s LSD was studied extensively, including by the CIA's covert MKUltra program, before spilling into 1960s counterculture and prompting its prohibition and placement in Schedule I in the United States. Interest revived in the 2010s, with LSD candidates such as MM120 entering modern clinical trials for anxiety.