4-HO-DiPT

# Research Output: 4-HO-DiPT

**PSX ID:** PSX-0065  
**Research date:** 2026-04-26  
**Substance readiness:** Sparse/emerging (primary literature sparse; significant recent clinical development)

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## Chemical Identity

**Verified against PubChem CID 21854225 [Ref 1-database], confirmed via Crossref for synthesis paper [Ref 8].**

| Field | Value | Source |
|---|---|---|
| Preferred name | 4-HO-DiPT / 4-OH-DiPT | PubChem |
| Common name | Iprocin | Wikipedia [Ref 20] |
| IUPAC name | 3-[2-[di(propan-2-yl)amino]ethyl]-1H-indol-4-ol | PubChem CID 21854225 |
| CAS (free base) | 132328-45-1 | Psychedelic Science Review [Ref 19] |
| CAS (HCl salt) | 63065-90-7 | Cayman Chemical (web) |
| PubChem CID | 21854225 | PubChem |
| Molecular formula | C₁₆H₂₄N₂O | PubChem |
| Molecular weight | 260.37 g/mol | PubChem |
| InChIKey | KBRYKXCBGISXQV-UHFFFAOYSA-N | PubChem |
| SMILES | CC(N(C(C)C)CCc1c[nH]c2c1c(O)ccc2)C | Multiple web sources |
| MDL number | MFCD04972059 | ChemicalBook |
| FDA UNII | YG9OUS518B | ChemicalBook |

**Physical properties:**
- Appearance: White powder (Psychedelic Science Review [Ref 19])
- Melting point (HCl salt): 263°C (TiHKAL synthesis data [Ref 12])
- Boiling point (predicted): 424.9 ± 35.0°C (ChemicalBook, computational prediction)
- Density (predicted): 1.084 ± 0.06 g/cm³ (ChemicalBook, computational prediction)
- pKa (predicted): 9.83 ± 0.40 (ChemicalBook, computational prediction)

**Brief comparison with the seed data:** The brief was missing molecular formula, molecular weight, InChIKey, CAS number, PubChem CID, and SMILES — all now verified. The systematic name in the brief (3-[2-[di(propan-2-yl)amino]ethyl]-1H-indol-4-ol) matches PubChem exactly.

**Structural description:** 4-HO-DiPT is a substituted tryptamine that differs from psilocin (4-HO-DMT) by the replacement of both N,N-dimethyl groups with isopropyl groups. It bears a hydroxyl group at the C4 position of the indole ring and a N,N-diisopropyl substitution on the terminal amine of the tryptamine backbone.

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## Pharmacology

### Receptor Binding

The most directly relevant binding study is Rickli et al. (2016 [Ref 4]), which explicitly tested 4-OH-DiPT against classic hallucinogens:

- **5-HT₂A:** Ki = ~120 nM (IC₅₀ = 150 nM) — partial to full agonist (Rickli et al. 2016 [Ref 4])
- **SERT:** Significant interaction (similar to psilocin; unlike LSD and mescaline) (Rickli et al. 2016 [Ref 4])
- **NET:** Partial interaction (Rickli et al. 2016 [Ref 4])

A second binding dataset (Glatfelter et al. 2023 [Ref 3], via Psychedelic Science Review [Ref 19]) reports broader receptor profiling:
- **5-HT₂A:** Ki = 728–922 nM
- **5-HT₂B:** Ki = 85–460 nM
- **5-HT₁A:** Ki = 5,700 nM
- **5-HT₂C:** Ki = 2,800 nM
- **5-HT₁D:** Ki = 1,860 nM
- **SERT:** Ki = 816–1,800 nM
- **Sigma-1:** Ki = 1,063 nM
- **M4:** Ki = 1,725 nM

> **⚠️ FLAG FOR REVIEW:** The Ki at 5-HT₂A differs substantially between Rickli 2016 (~120 nM) and Glatfelter 2023 (728–922 nM). This likely reflects different radioligand binding assays, cell lines, or expression systems across labs, rather than a data error. The Rickli 2016 value comes from a direct comparison study using cloned human receptors (European Neuropsychopharmacology). The generation agent should present both values with assay context and note the methodological discrepancy.

**Functional activity at serotonin GPCRs:** Kelly et al. (2024 [Ref 2]) profiled 4-OH-DiPT at all 12 human 5-HT GPCRs and classified it as a near-full agonist at 5-HT₂A, 5-HT₂B, and 5-HT₂C. Sex differences in potency were documented in mice, with female animals showing greater potency than males.

**In vivo activity (rodent):**
- Head-twitch response (HTR) ED₅₀ = 3.46 μmol/kg in C57BL/6J mice (Klein et al. 2021 [Ref 16]) — less potent than psilocin (ED₅₀ = 0.81 μmol/kg) in the same assay
- HTR ED₅₀ = 1.03 mg/kg i.p. in mice (Psychedelic Science Review [Ref 19], citing primary data)
- 4-HO-DiPT and 4-AcO-DiPT produced longer-lasting effects compared to other 4-hydroxy tryptamines in the Klein et al. (2021 [Ref 16]) series

**Class context:** Klein et al. (2021 [Ref 16]) tested 17 tryptamines and found that bulkier N-alkyl groups (like the diisopropyl group in 4-HO-DiPT) reduce potency at 5-HT₂C relative to smaller substitutions, while maintaining or increasing efficacy at 5-HT₂B. All 4-hydroxy tryptamines acted as full or partial agonists at 5-HT₂A/2B/2C.

**Neuroplasticity:** By class inference with psilocin (Moliner et al. 2023 [Ref 23]), 4-hydroxytryptamines may bind TrkB (BDNF receptor) with high affinity, contributing to antidepressant effects independent of 5-HT₂A activation. No 4-HO-DiPT-specific TrkB data available.

### Mechanism of Action

4-HO-DiPT is a serotonin receptor agonist acting primarily at 5-HT₂A receptors to produce psychedelic effects. Unlike LSD, it also inhibits SERT (and partially NET), giving it a pharmacological profile closer to psilocin than to classical phenethylamine psychedelics (Rickli et al. 2016 [Ref 4]). The 5-HT₂A agonism is the primary driver of its psychedelic-like behavioral effects, as demonstrated by blockade of head-twitch response with 5-HT₂A antagonists in rodent models (Klein et al. 2021 [Ref 16]; Kelly et al. 2024 [Ref 2]).

Kelly et al. (2024 [Ref 2]) demonstrated that 4-OH-DiPT enhances fear extinction via 5-HT₂A activation of interneurons in the basolateral amygdala (BLA), increasing GABAergic inhibition of principal neurons — a mechanism that may underlie the therapeutic potential of short-acting psychedelics in anxiety and PTSD-related conditions.

### Pharmacokinetics

**In rats (after s.c. RE104 prodrug):**
- 4-OH-DiPT half-life: 40 minutes (Bryson et al. 2024 [Ref 1])
- Plasma concentration correlated with head-twitch intensity in rats
- Clinical duration 2–3 hours (consistent with short half-life)

**Note:** No human oral bioavailability PK data for the free compound published to date. All PK data are from preclinical rodent studies using the RE104 prodrug.

### Metabolism

**Data source:** Human hepatocyte data derives from the closely related compound 4-AcO-DiPT (a prodrug of 4-OH-DiPT via ester hydrolysis). Malaca et al. (2022 [Ref 10]) conducted a human hepatocyte metabolite profiling study:

- **Primary metabolite pathway:** O-glucuronidation of the 4-OH group
- **Other Phase I pathways:** N-oxidation, N-dealkylation (producing 4-HO-NiPT)
- **Phase II:** O-sulfation, glucuronidation
- **6 metabolites** identified in human hepatocytes at 3 hours
- **Active metabolite:** 4-HO-NiPT (N-monoisopropyltryptamine), characterized and confirmed to possess psychedelic-like activity (Laban et al. 2023 [Ref 9])

**CYP enzyme involvement:**
- CYP2D6: IC₅₀ = 9.6 μM (most potently inhibited; from PSR data [Ref 19])
- CYP3A: IC₅₀ = 115 μM (weaker inhibition)
- By structural analogy with 5-MeO-2-Me-DiPT (Caspar et al. 2017 [Ref 22]): CYP2D6, CYP2C19, and CYP3A4 involved in N-dealkylation and hydroxylation; CYP1A2 in hydroxylation
- The Yu (2008 [Ref 7]) review confirms CYP2D6 is the key polymorphic enzyme for IAA metabolism as a class

> **⚠️ FLAG FOR REVIEW:** 4-HO-DiPT metabolism data is inferred from 4-AcO-DiPT (a prodrug of 4-OH-DiPT) and structurally related DIPT analogs. No direct published human metabolism studies for 4-HO-DiPT free base exist. This is a meaningful gap for the pharmacology section.

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## History

**First synthesis (1977):** 4-HO-DiPT was first reported in the chemical literature by David Repke, William Ferguson, and David Bates in 1977 in a paper titled "Psilocin analogs. 1. Synthesis of 3-[2-(dialkylamino)ethyl]-and 3-[2-(cycloalkylamino)ethyl] indol-4-ols" published in the *Journal of Heterocyclic Chemistry* (Repke et al. 1977 [Ref 8]). This paper reported the synthesis of seven psilocin analogs, including 4-HO-DiPT. The synthesis employed 4-acetoxyindole, oxalyl chloride, diisopropylamine, and lithium aluminum hydride reduction, yielding the hydrochloride salt.

**Shulgin characterization (1997):** Alexander Shulgin and Ann Shulgin documented the synthesis and human effects of 4-HO-DiPT in TiHKAL (Tryptamines I Have Known and Loved), entry #17, published by Transform Press in 1997 (Shulgin & Shulgin 1997 [Ref 12]). Shulgin characterized it as a compound notable for its exceptional speed of onset, intensity, and brevity among oral psychedelics. He wrote: "I truly doubt that there is another psychedelic drug...that can match this one for speed, intensity, brevity, and dose sensitivity." Shulgin reported doses of 15–20 mg orally and a total duration of approximately 2–3 hours.

**Designer drug appearance (c. 2005):** 4-HO-DiPT was first encountered as a novel designer drug on the European market around 2005, as reviewed by Tittarelli et al. (2015 [Ref 5]).

**Regulatory history (2022):** The US Drug Enforcement Administration (DEA) published a Notice of Proposed Rulemaking on January 14, 2022, proposing to place 4-hydroxy-N,N-diisopropyltryptamine (4-OH-DiPT) and four other tryptamines in Schedule I of the Controlled Substances Act (Federal Register 2022 [Ref 13]). Following receipt of numerous public comments and four requests for a hearing, the DEA withdrew the proposed rule on July 27, 2022, stating it would submit a new request to HHS for updated scientific and medical evaluation [Ref 13].

**Clinical development (2023–2026):** Reunion Neuroscience developed RE104 (luvesilocin), a glutarate ester prodrug of 4-OH-DiPT administered subcutaneously, for the treatment of postpartum depression (PPD). The FDA cleared the IND for the Phase 2 RECONNECT trial in September 2023. Results presented at the American College of Neuropsychopharmacology (ACNP) Annual Meeting in January 2026 showed the trial met its primary endpoint (RECONNECT, NCT06342310 [Ref 15]; Bryson et al. 2024 [Ref 1]). The FDA granted Breakthrough Therapy Designation to luvesilocin for PPD on February 23, 2026 (Reunion Neuroscience 2026 [Ref 14]).

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## Subjective Effects

**Source note:** No published controlled dosing studies in humans for 4-HO-DiPT as a standalone compound exist in the peer-reviewed literature as of 2026. Human effects data derives from Shulgin's TiHKAL (1997 [Ref 12]) and reports from recreational users collected by Erowid and related platforms. Clinical trial data (from the RECONNECT study) characterizes subjective effects of luvesilocin, not free 4-HO-DiPT. All human effects descriptions below are user-report-only unless otherwise noted.

**Onset and duration (user reports + TiHKAL):**
- Onset: 15–20 minutes oral (TiHKAL [Ref 12]; consistent with RE104 pharmacokinetics in rats [Ref 1])
- Peak: 20–30 minutes after onset
- Duration: 2–3 hours total (TiHKAL [Ref 12])
- Baseline restored: ~3 hours at common doses
- **Notably short:** Among orally administered serotonergic psychedelics, 4-HO-DiPT is reported to be one of the shortest-acting compounds known (multiple sources [Ref 19, 20])
- Steep dose-response curve: Shulgin noted significant sensitivity to small dose changes (TiHKAL [Ref 12])

**Dose-effect data from TiHKAL ([Ref 12]):**
- Threshold: below 10 mg (largely inactive)
- Common: 15–20 mg oral
- Strong: ~20 mg (described as "plus-three" intensity)
- No trials above 20 mg reported by Shulgin

**Perceptual effects (user reports):**
- Visual: color enhancement, rainbow halos, mild object distortion, tracers and after-images; closed-eye visuals minimal compared to psilocin
- Auditory: some auditory enhancement reported
- Minimal compared to psilocin for visual complexity per Shulgin

**Physical effects (user reports):**
- Leg tremors and muscle loosening
- Mild stimulation
- Mild elation
- Chill-like sensations
- Vague body malaise
- Elevated heart rate (user reports; no clinical measurement)
- Pupil dilation (expected by class)

**Psychological effects (user reports):**
- Introspective insights and novel personal perspectives
- Mild to strong cognitive euphoria dose-dependent
- Short duration may reduce integration challenges compared to longer-acting psychedelics

**Preclinical behavioral data:**
- Fear extinction enhancement in mice, dose- and sex-dependently, via 5-HT₂A/BLA GABAergic mechanism (Kelly et al. 2024 [Ref 2])
- Head-twitch response in mice indicative of 5-HT₂A activation (Klein et al. 2021 [Ref 16]; Bryson et al. 2024 [Ref 1])

**Duration note re seed data:** The seed data duration values (onset 15–30 min, come-up 20–40 min, peak 60–90 min, total 2–4 h) are broadly consistent with TiHKAL and preclinical data, though the come-up duration in the seed data appears extended relative to TiHKAL's description of peak onset at ~20–30 min post-ingestion. The total duration of 2–4 h in the seed data is on the high end relative to the 2–3 h consistently reported by Shulgin and Bryson et al.

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## Safety & Toxicity

**⚠️ FLAG FOR REVIEW (safety-critical):** No published LD₅₀ data exists for 4-HO-DiPT in any species. No published human clinical pharmacology data for the free compound exists. Safety data from the RECONNECT Phase 2 trial characterizes luvesilocin (the prodrug), not 4-HO-DiPT administered orally.

**Acute toxicity (clinical trial data — luvesilocin/prodrug, s.c.):**
- Most common adverse events: nausea (43.9%) and headache (34.1%), both mild to moderate (RECONNECT Phase 2, NCT06342310 [Ref 15])
- No serious adverse events observed
- No treatment-emergent suicidal ideation or behavior in either dose group

**Animal data:**
- No published LD₅₀ in rodents or other species found
- Head-twitch response (psychedelic-like effects) confirmed in mice at doses of ~1 mg/kg i.p. and above (Klein et al. 2021 [Ref 16]; Bryson et al. 2024 [Ref 1])
- No evidence of acute organ toxicity in preclinical studies using RE104 (Bryson et al. 2024 [Ref 1])

**User-reported adverse effects (no clinical measurement):**
- Leg tremors, muscle tension, body malaise
- Elevated heart rate reported anecdotally
- No deaths reported in published literature or harm reduction databases as of 2026

**Psychological risks (class-based inference):**
- Risk of challenging or difficult experiences ("bad trips") with cannabis co-administration — cannabis may amplify psychedelic effects unpredictably (PsychonautWiki, harm reduction community reports [Ref 20])
- Steep dose-response curve means small dose increases can produce significantly more intense effects — high risk of unintended intensity

**Toxicity data flag (from brief):** The brief notes "toxic dose is unknown" — confirmed by this research. No LD₅₀ or toxic dose threshold has been published.

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## Harm Reduction

**Testing:** 4-HO-DiPT reacts positively with Ehrlich reagent (produces purple color, characteristic of indole-containing compounds). Marquis reagent expected to produce black coloration typical of indole psychedelics. No published formal reagent testing protocol specific to 4-HO-DiPT found.

**Dose sensitivity:** The steep dose-response curve documented by Shulgin (TiHKAL [Ref 12]) warrants particular caution. At 15 mg, effects are mild; at 20 mg, effects were described as "plus-three" intensity. Dose titration with small increments recommended.

**Set and setting:** As with all serotonergic psychedelics, adverse psychological experiences are context-dependent. No 4-HO-DiPT-specific published harm reduction protocols exist.

**Duration advantage:** The short duration (2–3 hours) represents both a potential therapeutic advantage and a harm reduction consideration — briefer exposure window reduces the duration of any adverse psychological effects.

**Emergency response:** No published emergency response guidance specific to 4-HO-DiPT. Class-based protocol: supportive care, minimize stimulation, benzodiazepines for severe anxiety or agitation.

**Contraindications (by class inference; no compound-specific data):**
- MAO inhibitors (MAOIs) — severe serotonin syndrome risk
- Tramadol — dangerous (see Interactions)
- Lithium — risk of seizures with serotonergic psychedelics (class-based; specific data absent)
- Personal or family history of psychosis or bipolar disorder with psychotic features

---

## Tolerance & Dependence

**Note:** No published compound-specific tolerance or dependence studies exist for 4-HO-DiPT. All data below is by class inference from the serotonergic psychedelic literature.

**Tolerance mechanism:** Cross-tolerance with other serotonergic psychedelics via 5-HT₂A receptor downregulation/desensitization following activation. Repeated activation of 5-HT₂A by psychedelics produces rapid receptor downregulation; LSD-induced tolerance data shows frontal cortex 5-HT₂A binding decreases after repeated dosing (Dolder et al. 2017, cited in tolerance literature).

**Tolerance timeline (from seed data, consistent with class literature):**
- Buildup: Near-immediately after ingestion
- Half-life: ~3 days
- Full reset: ~7 days

**Cross-tolerance:** Bidirectional cross-tolerance with other serotonergic psychedelics (psilocin, LSD, DMT, mescaline) by mechanism and by reported user experience.

**Dependence:** Not considered habit-forming. No evidence of physical dependence or withdrawal syndrome in published literature.

**⚠️ FLAG FOR REVIEW:** Tolerance timeline data in the seed data (3-day half-life, 7-day reset) is not verified against a published source specifically for 4-HO-DiPT. These values are consistent with general serotonergic psychedelic class data but should be labeled as class-inferred rather than compound-specific.

---

## Interactions

### Tramadol: Dangerous
**Mechanism confirmed (Baldo 2018 [Ref 21]; Pergolizzi et al. 2022 [Ref 25]):**
Tramadol inhibits the serotonin transporter (SERT) and norepinephrine transporter (NET), increasing synaptic serotonin levels. Combined with 4-HO-DiPT's 5-HT₂A agonism (and its own SERT inhibition per Rickli 2016 [Ref 4]), the combination creates additive serotonergic load. The FDA issued a Drug Safety Communication in 2016 regarding opioids and serotonin syndrome risk. The tramadol: dangerous classification in the seed data is pharmacologically supported.

### Cannabis: Unknown / Potentially Risky
Community and harm reduction sources report that cannabis can amplify 4-HO-DiPT effects unpredictably, significantly increasing risk of adverse psychological reactions including anxiety, paranoia, panic attacks, and psychosis (user reports, community sources [Ref 20]). No published clinical or preclinical data on this specific interaction.

### MAO Inhibitors (class inference — NOT in seed data but should be flagged)
Both 4-HO-DiPT and MAOIs are serotonergic agents. By analogy with other tryptamines (Yu 2008 [Ref 7]; Luethi & Liechti 2020 [Ref 6]), combined use risks severe serotonin toxicity. This interaction is not listed in the current seed data but should be considered for the contraindications field.

### SSRIs/SNRIs (class inference)
Chronic SSRI use may attenuate psychedelic effects via 5-HT₂A downregulation; acute combination risks serotonin syndrome. No 4-HO-DiPT-specific data.

---

## Legal Status

### United States
Unscheduled at the federal level as of 2026. The DEA proposed Schedule I placement on January 14, 2022 (Federal Register Vol. 87, No. 10 [Ref 13]) for 4-OH-DiPT alongside DiPT, 5-MeO-AMT, 5-MeO-MiPT, and 5-MeO-DET. Following public comments and four hearing requests, the DEA withdrew the proposed rule on July 27, 2022 (Federal Register Vol. 87, No. 143 [Ref 13]), citing the need for updated scientific evaluation from HHS. 4-HO-DiPT may be prosecuted under the Federal Analogue Act as a structural analog of psilocin (a Schedule I substance). Florida: Schedule I controlled substance at the state level.

### United Kingdom
Class A drug under the Misuse of Drugs Act 1971, captured by the generic tryptamine "catch-all clause." Simple possession carries up to 7 years imprisonment; supply/production up to life [Ref 20].

### Canada
Not a controlled substance as of 2025 [Ref 20].

### Germany
Scheduled under the Neue-Psychoaktive-Stoffe-Gesetz (NpSG, New Psychoactive Substances Act). Use of covered substances permitted only for industrial and scientific purposes [Ref 20].

### Australia
**⚠️ FLAG FOR REVIEW — UNRESOLVED:** No explicit listing of 4-HO-DiPT found in Australia's Poisons Standard or the Commonwealth Criminal Code Regulations 2019. Australia's Criminal Code Regulations do include drug analogue provisions; 4-HO-DiPT may be captured as an analog of psilocin (a Schedule 9 substance) under those provisions, but this requires direct verification of the current Poisons Standard. Australia-specific legal status should be confirmed by consulting the current SUSMP/Poisons Standard before publication.

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## Clinical Trials

### RECONNECT Phase 2 Trial (NCT06342310)

**Drug:** Luvesilocin (formerly RE104; 4-glutarato-N,N-diisopropyltryptamine), a subcutaneously administered prodrug that rapidly cleaves in vivo to release 4-OH-DiPT.

**Sponsor:** Reunion Neuroscience Inc.

**Phase:** 2

**Design:** Multicenter, randomized, double-blind, parallel-group, active-dose placebo-controlled

**Condition:** Postpartum depression (PPD), moderate to severe (HAMD-17 ≥ 24)

**Intervention:** Single subcutaneous dose; luvesilocin 30 mg vs. 1.5 mg (subperceptual active control)

**Enrollment:** 84 adult female patients (n=41 at 30 mg; n=43 at 1.5 mg)

**Primary endpoint:** Change from baseline in MADRS total score on Day 7

**Key results (reported at ACNP Annual Meeting, January 2026 [Ref 14, 15]):**
- Met primary endpoint: statistically significant and clinically meaningful MADRS reduction on Day 7 (p = 0.0094)
- Rapid efficacy from Day 1 through Day 28
- Response rate (≥50% MADRS reduction): 77.1% (30 mg) vs. 61.6% (1.5 mg) at Day 7
- Remission rate (MADRS ≤10): 71.4% (30 mg) vs. 41.0% (1.5 mg) at Day 7
- 70% remission at both Day 7 and Day 28 (30 mg group)
- Most common adverse events: nausea (43.9%), headache (34.1%), both mild to moderate
- No serious adverse events; no treatment-emergent suicidal ideation

**Regulatory status:**
- FDA IND cleared: September 2023
- FDA Breakthrough Therapy Designation granted: February 23, 2026 (Reunion Neuroscience [Ref 14])

**Preclinical support (Bryson et al. 2024 [Ref 1]):**
- 4-OH-DiPT half-life: 40 min after s.c. RE104 in rats
- Plasma 4-HO-DiPT correlated with head-twitch intensity in rats
- Single dose RE104 (1 mg/kg) significantly reduced immobility in forced swim test at 1 week vs. vehicle (p < 0.001) — antidepressant-like effect

### Clinical Trial Searches (No Additional Trials Found)
Searches of ClinicalTrials.gov for "4-HO-DiPT," "4-hydroxy diisopropyltryptamine," and "luvesilocin" returned no additional trials beyond NCT06342310. No Phase 3 trial registered as of research date.

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## Community Feedback Analysis

No community feedback was submitted in Part A2 of the brief. Standard research directives applied.

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## Gaps & Flags

### Safety-Critical Flags (require editorial review before publication)

1. **No LD₅₀ data:** No lethal dose has been established for 4-HO-DiPT in any species. The seed data notes "toxic dose is unknown" — confirmed.

2. **Binding affinity discrepancy:** Rickli et al. 2016 [Ref 4] reports 5-HT₂A Ki ~120 nM; Glatfelter 2023 [Ref 3] (via PSR [Ref 19]) reports 728–922 nM. These cannot be reconciled without full-text access to assay methodology. The generation agent should present both values with source context and note methodological differences as the likely explanation.

3. **Tolerance timeline not compound-verified:** Seed data tolerance values (3-day half-life, 7-day reset) are plausible and consistent with the serotonergic psychedelic class but are not verified against a 4-HO-DiPT-specific published source. Should be labeled "class-inferred."

4. **Dose/duration discrepancy:** Seed data onset is 15–30 min, come-up 20–40 min. TiHKAL [Ref 12] reports onset at 15–20 min with peak ~20–30 min post-ingestion, suggesting the come-up is faster than the seed data implies. Seed data heavy dose (30+ mg) is not documented in published literature (Shulgin did not report trials above 20 mg). Flag for editorial review before publication.

5. **MAOI interaction absent from seed data:** Not listed in the brief's known interactions, but by pharmacological mechanism (tryptamine + MAOI = severe serotonin syndrome risk) this interaction is class-critical and should be added to contraindications.

6. **Australia legal status unresolved:** No specific scheduling found in Poisons Standard searches. Should be confirmed against current SUSMP before publication.

### Data Gaps (absence noted; not fabricated)

- No published human PK study for orally administered free 4-HO-DiPT
- No published oral bioavailability data
- No controlled human pharmacology study for free compound
- No published LD₅₀ or NOAEL
- No published case reports of acute toxicity, hospitalization, or death
- No direct TrkB binding data for 4-HO-DiPT (class inference from Moliner 2023)
- No published compound-specific tolerance kinetics
- No published data on interactions with lithium, antipsychotics, benzodiazepines
- No stereochemistry issues — 4-HO-DiPT has no chiral centers

### Structural Inference Noted

The following sections rely primarily on structural/class analogy:
- Metabolism CYP enzyme profile (from 4-AcO-DiPT and related DIPT analogs)
- MAOI interaction risk
- Tolerance mechanism and timeline
- TrkB neuroplasticity pathway
- Australia legal status (analog provisions)