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PIHKAL and TIHKAL

PIHKAL and TIHKAL are the two landmark books by the chemist Alexander "Sasha" Shulgin and his wife Ann Shulgin that document, compound by compound, a large family of psychoactive molecules Shulgin first synthesized and evaluated. They are foundational references for modern psychedelic science and harm reduction. This article is the Library's map of them — what they are, how they're organized, and where to read them — following the same approach the Library's Hierophant uses for Sacred-Texts and Theoi: we do not reproduce the copyrighted text; we index it and link out to where it lives legally.

PIHKAL (1991) — "Phenethylamines I Have Known And Loved." Covers the phenethylamine family (the 2C-x series, the DOx series, the mescaline and MDMA relatives, and many others).
TIHKAL (1997) — "Tryptamines I Have Known And Loved." Covers the tryptamine family (DMT and its relatives, the psilocin/psilocybin group, and others).

How the books are built

Each book has two parts:

Part One — an autobiographical and philosophical narrative (in PIHKAL, a lightly fictionalized memoir of "Shura" and "Alice"; in TIHKAL, essays spanning chemistry, law, and spirituality). This half is fully copyrighted and is not freely distributable.
Part Two — the systematic chemistry: one entry per compound. This is the part researchers cite. The Shulgins placed this second half under terms that permit free non-commercial reproduction, which is why it is mirrored online.

The Shulgin Rating Scale

Shulgin recorded the subjective intensity of each experience on a simple qualitative scale (described here in our own words):

minus (−) — no effect detected.
plus/minus (±) — a threshold: something is felt, but it could be imagination.
plus (+) — a real but light effect; the compound is clearly active, its character not yet obvious.
two plus (++) — clearly and unmistakably active; the full character shows, and the person can still choose to engage with the world or the experience.
three plus (+++) — maximal intensity for that compound; fully absorbing.
four plus (++++) — a rare, separate category: a peak / transcendent state, not simply "more" than +++.

The scale also tracks dose (an active range in milligrams) and duration (onset and total length) — the factual harm-reduction data the Library does surface.

How the Library treats this material

Following the Hierophant / link-out model:

We map and cite; we do not paste. Reproducing the books' text verbatim would be a copyright violation. Our contribution is the index, the context, and our own glossary written in our own words.
Harm-reduction reference, not a manufacturing manual. The Library serves dose ranges, duration, effects, interactions, contraindications, testing, and set/setting/aftercare — the information that keeps people safer. Consistent with its scope, it does not host synthesis or extraction routes; for the full chemistry entries we point to the licensed mirror.
Un-gated. This is reference and education for adults, presented plainly and without gatekeeping.

Pharmacological frameworks originating in the books

Beyond individual compound monographs, Shulgin's research established foundational principles across organic psychopharmacology:

The Ten Essential Amphetamines: The structural mapping of ten natural plant essential oils (allylbenzenes and propenylbenzenes from nutmeg, sassafras, calamus, and parsley) to ten psychoactive phenethylamines. While Shulgin hypothesized in vivo amination, subsequent biochemistry disproved hepatic amination in favor of targeted Cytochrome P450 epoxidation and 1'-hydroxylation (see Shulgin Ten Essential Amphetamines and Metabolic Chemistry).
Tryptamine Prodrug Architecture (4-OH vs. 4-AcO): Documented in TIHKAL, capping the vulnerable 4-position hydroxyl group of psilocin and related indoles with an acetyl ester protects against auto-oxidation and forms stable crystalline prodrugs (like 4-AcO-DMT) cleaved cleanly by plasma esterases in vivo (see Cannabinoid and Tryptamine Prodrugs).
Stereocenters and Enantiomeric Potency: The α-methyl chiral center in phenethylamines fundamentally divides activity: the (R)-isomer drives 5-HT2A psychedelic agonism, while the (S)-isomer drives monoamine release and central stimulation (see Stereochemistry in Cannabinoid and Psychedelic Synthesis).
Structure-Activity Relationships and the α,N,O-TMS Rule: In TIHKAL Entry #55 (α,N,O-TMS), Shulgin documented his "holy grail" 2-position indole rule: adding a 2-methyl group to an unsubstituted tryptamine (DMT, DET) abolishes activity, but adding it to 4- or 5-substituted tryptamines (Psilocin, 5-MeO-DMT) preserves potency. The entry also bridges analytical N,O-bis-TMS silylation with the structural shifts governing serotonin, melatonin, dopamine, and hypothalamic oxytocin release; see Structure-Activity Relationships in Psychopharmacology.
The Analogue Act and the Salt Shaker Critique (aMT, TIHKAL #48): In his entry on aMT (alpha-methyltryptamine), Shulgin presented his famous critique of the 1986 Federal Analogue Act, arguing that "substantial similarity" is an arbitrary legal net with a variable mesh size. He used his famous "salt shaker" metaphor (is a shaker with 6 holes substantially similar to one with 5?) to demonstrate that while an isomer is an objective chemical fact, an analogue is a subjective legal fiction; see Isomers, the Analogue Act, and Forensic Chemistry.
Sacramental Entheogens and the Temple of True Inner Light (DPT, TIHKAL #9): In his commentary on DPT (dipropyltryptamine), Shulgin explored the Manhattan-based Temple of True Inner Light, which openly used DPT as its central Eucharistic sacrament ("the True Flesh of God"). Shulgin marveled at why the DEA avoided scheduling DPT or prosecuting the congregation for decades, contemplating whether federal authorities feared a landmark First Amendment and RFRA showdown over synthetic religious sacraments; see Religious Sacraments, RFRA, and the Temple of True Inner Light.

Where to read the full entries

The Part-Two chemistry entries are hosted, with the Shulgins' permission, at Erowid:

PIHKAL: erowid.org/library/books_online/pihkal
TIHKAL: erowid.org/library/books_online/tihkal
Erowid's compound vaults also carry dose/duration/effect/interaction summaries and experience reports: erowid.org

The complete books (both parts) are published by Transform Press.

Filed under Substances and pharmacology