Mitragynine

# Research Output: Mitragynine (PSX-0400)

**Research date:** 2026-05-08
**Provenance ID:** f259759d-d985-496f-b471-eb1dc929cdbd
**Substance readiness:** Well-researched (established compound, substantial published literature)

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## Chemical Identity

**PubChem CID:** 3034396 (api_verified via get_pubchem_compound)
**Molecular formula:** C₂₃H₃₀N₂O₄ (MW 398.5 g/mol)
**InChIKey:** LELBFTMXCIIKKX-QVRQZEMUSA-N
**IUPAC name:** methyl (E)-2-[(2S,3S,12bS)-3-ethyl-8-methoxy-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizin-2-yl]-3-methoxyprop-2-enoate
**Chemical class:** Corynanthe-type monoterpenoid indole alkaloid (Rubiaceae family)
**Stereochemistry:** Three chiral centers; absolute configuration (2S,3S,12bS) confirmed. The E-geometry of the acrylate double bond is pharmacologically significant. Three natural diastereomers co-occur in *Mitragyna speciosa*: speciogynine (2S,3S,7S), speciociliatine (2S,3R), and mitraciliatine. Pronounced pharmacokinetic differences between the 3S alkaloid series (mitragynine, speciogynine, paynantheine) and 3R series (speciociliatine, mitraciliatine, isopaynantheine) have been established in humans — the 3S series shows shorter Tmax (1–2 h vs. 2.5–4.5 h) and longer terminal half-life (24–45 h vs. ~12–18 h) [Ref 40].

**Note on SMILES:** The PubChem API confirmed the CID and InChIKey but did not return SMILES in the structured response. SMILES should be retrieved directly from PubChem CID 3034396 for the generation agent.

**Seed data discrepancies:** The brief left SMILES, molecular formula, and PubChem CID blank. All three are now confirmed from PubChem. The IUPACname was also absent; confirmed above. No conflicts detected.

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## Pharmacology

### Primary Receptor Activity: μ-Opioid Receptor (MOR)

Mitragynine is a **partial agonist** at the μ-opioid receptor (MOR) with submaximal intrinsic efficacy compared to morphine. Molecular dynamics and Markov state modelling confirm that mitragynine enriches intermediate receptor conformations rather than the fully active states stabilized by morphine, providing a mechanistic basis for its partial agonism (Bahari et al. 2026 [Ref 14]).

**Critical metabolite finding (Kruegel et al. 2019 [Ref 5]):** Mitragynine is converted *in vitro* in both mouse and human liver to the potent MOR agonist **7-hydroxymitragynine (7-HMG)** via CYP3A isoforms. In mice, brain concentrations of 7-HMG after systemic mitragynine administration are sufficient to explain most or all of the opioid-receptor-mediated analgesic effects. Mitragynine itself reaches high brain concentrations relative to its weak MOR binding affinity, suggesting it may not directly activate opioid receptors at physiologically relevant concentrations. This metabolism-dependent mechanism is fundamental: the route of administration critically determines activity (Kruegel et al. 2019 [Ref 5]).

**Biased signaling (G-protein selectivity):** Mitragynine and 7-HMG demonstrate functional selectivity for G-protein (Gi) signaling with no measurable recruitment of β-arrestin-2 in vitro (Todd et al. 2020 [Ref 42]; Varadi et al. 2016 [Ref 4]). β-Arrestin-2 recruitment is the primary pathway mediating respiratory depression and rapid tolerance with classical opioids. This biased signaling profile has generated significant interest as a potential safety advantage. Cryo-EM structures of μOR-Gi1 complexed with mitragynine pseudoindoxyl (MP, an oxidative rearrangement product) revealed that MP engages a distinct subpocket from lofentanil, with ligand-dependent differences in state occupancy and conformational stability (Qu et al. 2023 [Ref 11]).

**FLAG (safety-critical):** Specific Ki values for mitragynine at human MOR from a primary radioligand binding study were not retrieved via structured API tools in this research run. Multiple reviews reference values of approximately 280–500 nM (much weaker than morphine ~0.4 nM) and 7-HMG values of approximately 13–30 nM (making 7-HMG ~30× more potent than mitragynine and ~17× more potent than morphine at MOR), sourced to Takayama (2004) and Boyer (2008). These values should be verified against the original binding assay source before publication.

### κ- and δ-Opioid Receptors (KOR/DOR)

Mitragynine acts as a **competitive antagonist** at κ-opioid and δ-opioid receptors. Boyer et al. (2008 [Ref 2]) confirmed binding at both μ and κ receptors via high-throughput molecular screening. This KOR antagonism is pharmacologically relevant because KOR agonism mediates dysphoria — KOR antagonism may contribute to mitragynine's reported mood-elevating effects.

### α-Adrenoceptors

Mitragynine has complex, sub-millimolar activity at adrenergic receptors:

- **α₂A-adrenoceptor antagonist:** Ki = 1260 nM in radioligand displacement assay ([³H]RX821002 from human α₂A-R). Does not stimulate [³⁵S]GTPγS binding at α₂A-R in vitro. However, in drug discrimination assays in rats trained to discriminate 32 mg/kg mitragynine, the compound produced α₂R agonist-like effects, suggesting low-efficacy in vivo α₂R agonism (Obeng et al. 2024 [Ref 13]).
- **α₁A-adrenoceptor partial agonist:** EC₅₀ ~3 µM at α₁A-R-Gα₁₁; stimulates ERK phosphorylation via Gαq/11-coupled α₁R. This activity may contribute to psychostimulant-like properties (Chen et al. 2025 [Ref 12]).
- Mitragynine's dual α₂A-R antagonist / α₁A-R partial agonist pharmacology, combined with its MOR partial agonism, constitutes a distinctive polypharmacological profile.

A comprehensive 99-target binding and enzyme-inhibition profile of mitragynine and its major metabolites (7-HMG and 9-hydroxycorynantheidine) was conducted by Chen et al. (2025 [Ref 12]).

### Serotonergic and Other Targets

Multiple reviews report interactions with serotonergic receptors and neuronal Ca²⁺ channels (Annuar et al. 2024 [Ref 23]; Hartley et al. 2022 [Ref 24]). The 2025 Chen et al. 99-target screen provides the most systematic data on off-targets [Ref 12]. Specific Ki/EC₅₀ values at serotonin receptors were not individually reported in API-retrieved abstracts; this is a data gap.

### Metabolism

- **Primary pathway:** CYP3A-mediated hydroxylation at C7 position → 7-hydroxymitragynine (7-HMG), the pharmacologically dominant active metabolite for opioid-receptor effects (Kruegel et al. 2019 [Ref 5]).
- **CYP2D6** also contributes to metabolism; inhibition of CYP2D6 by co-administered drugs may alter mitragynine exposure.
- **Time-dependent CYP3A inhibition:** Mitragynine is a time-dependent CYP3A inhibitor (KI ~4 µM; kinact ~0.07 min⁻¹), primarily at the intestinal level (Tanna et al. 2023 [Ref 41]).
- Extensive hepatic first-pass metabolism implied by the very low urinary recovery of unchanged mitragynine (0.14%; Trakulsrichai et al. 2015 [Ref 38]).
- Semi-synthetic 7-HMG products (manufactured by direct mono-oxidation of mitragynine) are now commercially available and carry distinct, higher-potency opioid risk profiles [Ref 22; Smith et al. 2025].

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## Pharmacokinetics (Human Data)

### First Human PK Study (Trakulsrichai et al. 2015 [Ref 38])
10 chronic kratom users in Thailand (study conducted in a country where kratom is regulated, enabling chronic-user data). Oral administration, two-compartment model, linear PK confirmed:
- **Tmax:** 0.83 ± 0.35 h
- **Terminal half-life (t₁/₂):** 23.24 ± 16.07 h (~1 day)
- **Apparent Vd:** 38.04 ± 24.32 L/kg (very large — extensive tissue distribution)
- **Urinary recovery (unchanged):** 0.14%

### Comprehensive Human PK of All Major Kratom Alkaloids (Tanna et al. 2022 [Ref 40])
Single 2 g dose of well-characterized kratom powder in 6 healthy participants:
- Mitragynine Tmax: **1–2 h**; terminal t₁/₂: **24–45 h**
- Two-compartment model with central elimination
- Pronounced PK differences between 3S (mitragynine-type) and 3R (speciociliatine-type) alkaloids attributed to differential metabolism, protein binding, and distribution.

### Largest Dose-Escalation Human PK Study (Huestis et al. 2024 [Ref 39])
Randomized, double-blind, placebo-controlled; 500–4000 mg dried kratom leaf powder (6.65–53.2 mg mitragynine equivalent) in multiple cohorts:
- **Mitragynine Tmax:** 1.0–1.3 h (single dose); 1.0–1.7 h (multiple doses)
- **7-HMG Tmax:** 1.2–1.8 h (single); 1.3–2.0 h (multiple)
- **Highest terminal t₁/₂:** 43.4 h (single dose); 67.9 h (multiple doses)
- **7-HMG t₁/₂:** 4.7 h (single); 24.7 h (multiple)
- **Steady-state:** 8–9 days for mitragynine; ~7 days for 7-HMG
- Cmax dose-proportional; AUC slightly more than dose-proportional
- 7-HMG/mitragynine concentration ratio: 0.20–0.31 single; 0.15–0.21 multiple

### PBPK Modelling (Chiang et al. 2026 [Ref 48])
Validated across rat and dog models with predicted human simulations:
- Sex-related PK differences confirmed in rats
- Potent CYP3A4 inhibitors reduce 7-HMG formation (relevant for patients on azole antifungals, etc.)
- As perpetrator: mitragynine negligibly affects CYP2D6 substrates but increases midazolam exposure by 2.2–2.7× (model prediction)

**Summary PK table for generation agent:**
| Parameter | Value | Source |
|-----------|-------|--------|
| Tmax (oral) | ~1 h (range 0.8–1.7 h) | [Ref 38, 39, 40] |
| Terminal t₁/₂ (single dose) | ~23–43 h | [Ref 38, 39] |
| Terminal t₁/₂ (multiple doses) | ~67 h | [Ref 39] |
| Apparent Vd | ~38 L/kg | [Ref 38] |
| Time to steady state | 8–9 days | [Ref 39] |
| Primary metabolic enzyme | CYP3A | [Ref 5, 41] |
| Urinary excretion (unchanged) | 0.14% | [Ref 38] |

---

## History

### Botanical Background
*Mitragyna speciosa* (Korth.) Havil. was first described botanically by Dutch botanist Pieter Willem Korthals in 1839 as part of his survey of plants in the Dutch East Indies. It belongs to the family Rubiaceae (the coffee family). The tree is indigenous to Thailand, Malaysia, Myanmar, Papua New Guinea, and other parts of Southeast Asia and the Pacific Islands.

Traditional use of kratom leaves in Southeast Asia dates to at least the nineteenth century: leaves were chewed to combat fatigue during hard physical labor, to manage pain, to treat diarrhea and cough, and as a substitute for opium — particularly during periods of opium scarcity or expense. In Malaysia and Thailand, kratom was also used in traditional ceremonies (Cinosi et al. 2015 [Ref 7]; Jansen & Prast 1988 [Ref — see OpenAlex W2134991103]).

### First Isolation of Mitragynine (1921)
Mitragynine was first isolated in 1921 by Ellen Field, a Scottish medicinal chemist working at the University of Edinburgh. This is the first report of the principal alkaloid of kratom as a discrete chemical entity (web_retrieved [Ref 52]).

### Structure Elucidation (1965)
The chemical structure of mitragynine was established by Beckett, Shellard, and Tackie (1965). The absolute stereochemical configuration was confirmed independently by Zacharias et al. (1965). These works established the Corynanthe-type indole alkaloid scaffold (web_retrieved [Ref 52]).

### Modern Phytochemistry and Pharmacology
Takayama (2004 [Ref 1]) published the landmark review of the chemistry and pharmacology of Mitragyna alkaloids, including the identification of 7-hydroxymitragynine as a potent antinociceptive compound — more potent than mitragynine in animal models. This paper introduced the field to the concept that minor alkaloids in kratom might be pharmacologically dominant.

### Regulatory History
- **2016 (USA):** The DEA announced an emergency intent to temporarily place mitragynine and 7-HMG into Schedule I of the Controlled Substances Act (August 31, 2016; Federal Register 2016-20803). After 51 members of Congress objected and over 23,000 public comments were submitted, the DEA withdrew the notice on October 13, 2016 (Federal Register 2016-24659; [Ref 53]).
- **2016 (UK):** Kratom/mitragynine banned under the Psychoactive Substances Act 2016.
- **2017 (FDA):** FDA made a formal recommendation to the DEA to schedule mitragynine and 7-HMG.
- **2021 (WHO):** The WHO Expert Committee on Drug Dependence (ECDD) conducted a pre-review of kratom and concluded there was insufficient evidence to recommend international scheduling under UN drug conventions [Ref 53].
- **2021 (Thailand):** Thailand removed kratom from its narcotics list via the Narcotics Act amendment (Kratom Act 2021), allowing domestic cultivation, possession, and use — though commercial export restrictions remain.
- **2026 (USA):** US Senators (led by Pete Ricketts) sent a letter urging FDA to pursue federal scheduling; no regulatory action taken as of research date [Ref 53].

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## Subjective Effects

### Controlled Human Study (Prevete et al. 2025 [Ref 22])
The only published placebo-controlled clinical study of pure mitragynine in healthy human volunteers:
- **Design:** Phase 1, single-blind, within-subjects, placebo-controlled; 15 total participants across two parts
- **Doses tested:** 5, 10, 20 mg (Part A, n=8); 40 mg (Part B, n=7)
- **Duration of measurement:** 7 hours post-administration

Key findings:
- **5 mg:** Increased subjective ratings of **arousal and attention**; improved accuracy on sustained attention task; increased **motor inhibition** scores. This is consistent with the low-dose stimulant profile reported by traditional users.
- **10–20 mg:** Minimal effects on most outcome measures.
- **40 mg:** Increased subjective ratings of **amnesia** and **mild psychopathological symptoms** (notably, not the opioid sedation profile expected at high doses — possibly due to dose being insufficient to produce opioid-dominant effects in non-tolerant individuals).
- **Vital signs:** No significant effects at any dose.
- **Tolerability:** Only mild, transient side effects. Doses up to 40 mg were well tolerated.
- **Pain tolerance:** Not significantly affected (cold pressor test).

**Important limitation:** This study used pure mitragynine at doses of 5–40 mg, which corresponds to roughly 375–3000 mg of dried leaf (given ~1.3% mitragynine content in typical leaf). The doses tested may underestimate the exposures achieved by experienced heavy users (76–115 mg/day mitragynine equivalent per Singh et al. [Ref 30]).

### Dose-Dependent Bimodal Effects (established literature profile)
Traditional use, survey data, and animal models all support a characteristic **bimodal, dose-dependent effect profile** (Cinosi et al. 2015 [Ref 7]; Veltri & Grundmann 2019 [Ref 35]):

**Low doses (~1–5 g leaf / ~15–65 mg mitragynine):**
- Stimulation, wakefulness, increased energy
- Enhanced alertness, focus, sociability
- Reduced fatigue
- Mild euphoria
- Pain relief (analgesic)
- Appetite suppression

**High doses (~5–15+ g leaf / >65 mg mitragynine):**
- Sedation, drowsiness
- Strong analgesia
- Opioid-like euphoria, body high
- Nausea, dizziness, constipation
- Pupil constriction
- Itching

**Onset and duration (user-report based; not from controlled studies at higher doses):**
- Oral onset: ~15–30 min for effects; peak ~1–2 h (consistent with Tmax)
- Duration of primary effects: ~2–5 hours
- **FLAG:** Duration data are primarily from user reports and ethnographic data; no published placebo-controlled dose-duration study at doses above 40 mg mitragynine in humans.

### Effect Taxonomy Mapping (for generation agent)
Based on literature evidence:
- **Stimulation** (low dose) — body
- **Wakefulness** (low dose) — body
- **Focus enhancement** (low dose, Prevete 2025) — thinking
- **Pain suppression** (established) — body
- **Sedation** (high dose) — body
- **Euphoria** (established) — feeling
- **Bodily heaviness** (high dose) — body
- **Nausea** (common adverse) — body
- **Pupil constriction** (established opioid effect) — body
- **Constipation** (opioid class effect) — body
- **Dizziness** (adverse) — body
- **Itching/tactile sensations** (opioid class) — body
- **Appetite suppression** (low dose) — body
- **Appetite enhancement** (reported at some doses) — body
- **Motivation enhancement** (low dose, traditional use) — thinking
- **Sociability enhancement** (low dose) — self
- **Anxiety suppression** (reported by users) — feeling
- **Compulsive redosing urge** (dependence liability) — thinking
- **Yawning** (withdrawal marker) — body

---

## Safety & Toxicity

### Lethal Dose
No formal LD50 data in humans. Published postmortem blood concentrations from kratom-associated deaths:
- McIntyre et al. (2015 [Ref 18]): 0.23 mg/L peripheral blood (polypharmacy death — venlafaxine, diphenhydramine, mirtazapine)
- Karinen et al. (2014 [Ref 19]): 1.06 mg/L mitragynine + 0.15 mg/L 7-HMG (polypharmacy: zopiclone, citalopram, lamotrigine)
- Neerman et al. (2013 [Ref 20]): 0.60 mg/L (polypharmacy: benzodiazepines)
- Matson & Schenk (2019 [Ref 16]): **1.9 mg/L** — highest blood level in a case certified as mitragynine toxicity (sole cause)

**FLAG (safety-critical):** Published toxic and lethal concentration ranges for mitragynine have not been formally established. The above values represent case reports, not systematic dose-response data. The Corkery et al. (2019 [Ref 34]) series of 156 deaths found mitragynine alone implicated in only 23% of cases; 87% involved poly-substance use.

### Respiratory Effects
- Mitragynine does not recruit β-arrestin-2, which mediates classical opioid respiratory depression (Todd et al. 2020 [Ref 42]; Varadi et al. 2016 [Ref 4]).
- Animal data suggest mitragynine causes significantly less respiratory depression than morphine at equianalgesic doses (Henningfield et al. 2022 [Ref — PMID 36308562]).
- However, fatal respiratory depression has been reported, primarily in poly-drug contexts.

### Hepatotoxicity
- **Probable cause of drug-induced liver injury (DILI):** Comprehensive scoping review of 26 case reports + 7 DILI Network + 25 FDA database cases (Schimmel & Dart 2020 [Ref 31]).
- **Presentation:** Predominantly cholestatic, though biochemically heterogeneous (mixed or cholestatic pattern; R ratio median 3.4).
- **Latency:** Mean 21 days (range 2–49 days) from use to symptom onset.
- **Common symptoms:** Abdominal discomfort, jaundice, pruritus, dark urine.
- **Intrahepatic cholestasis** first described as a specific pattern by Kapp et al. (2011 [Ref 21]).
- Review of "the 3Ks" (Pantano et al. 2016 [Ref 32]) places kratom hepatotoxicity in context of other plant hepatotoxins.
- Mechanism unclear; direct mitragynine toxicity vs. immune-mediated vs. contaminant effects remain under investigation.

### Cardiovascular
- Case reports of hemodynamic instability, cardiomyopathy, and abnormal heartbeat [Ref 15 — Sangani 2021]
- Perioperative concerns include hemodynamic instability and agitation (Vance et al. 2026 [Ref — PMID 42037222])

### Rhabdomyolysis
- Sangani et al. (2021 [Ref 15]): Case report of kratom overdose complicated by rhabdomyolysis, compartment syndrome, AKI, liver dysfunction, cardiomyopathy. Required fasciotomy and hemodialysis.

### Seizures
- Seizure case reported with kratom + modafinil co-administration (Boyer et al. 2008 [Ref 2]).
- Multiple reviews cite seizures as a recognized adverse event (Hartley et al. 2022 [Ref 24]).

### Renal Toxicity
- Acute kidney injury documented in severe overdose/rhabdomyolysis context [Ref 15].

### Neonatal Effects
- **Neonatal Abstinence Syndrome (NAS):** Three published case reports of NAS in infants born to mothers using kratom during pregnancy (Eldridge et al. 2018 [Ref 45]; Davidson et al. 2019 [Ref 46]; Mackay & Abrahams 2018).
- Smid et al. (2018 [Ref 51]) documented clinical outcomes of kratom use in pregnancy; few data available.
- **FLAG (safety-critical):** Kratom is marketed and perceived as a "natural" and "safe" alternative to opioids. NAS case reports establish that fetal exposure produces opioid-type dependence and withdrawal. Clinicians and patients must be warned that perceived safety as a "natural" herb does not confer safety in pregnancy.

### Perioperative Concerns
- Kratom use is an emerging concern for perioperative care: difficulty managing pain, hemodynamic instability, agitation, and withdrawal symptoms in surgical patients (Vance et al. 2026 [Ref — PMID 42037222]).
- 1.9 million Americans aged 12+ have used kratom (SAMHSA data cited in perioperative literature).

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## Harm Reduction

### Contraindications
- **Pregnancy:** Crosses placenta; neonatal abstinence syndrome documented [Ref 45, 46, 51]
- **Hepatic impairment:** Risk of hepatotoxicity; impaired clearance of CYP3A-metabolized 7-HMG
- **Concurrent CNS depressants:** Risk of additive/synergistic respiratory depression (opioids, benzodiazepines, alcohol, gabapentinoids)
- **CYP3A substrates with narrow therapeutic index:** Risk of drug-drug interaction; mitragynine inhibits intestinal CYP3A [Ref 41]

### Drug Interactions to Warn About
1. **CYP3A substrates:** Midazolam, triazolam, some immunosuppressants, certain antiretrovirals — exposure increases significantly [Ref 41, 48]
2. **Quetiapine:** Fatal case possibly related to CYP-mediated increase in quetiapine levels [Ref 17]
3. **Modafinil:** Seizure case report [Ref 2]
4. **Opioids:** Pharmacodynamic synergy + PK interaction — risk of respiratory depression
5. **P-glycoprotein substrates:** Mitragynine inhibits P-gp [Ref 43]

### Testing Recommendations
- Standard opioid immunoassay urine drug screens do **not** reliably detect mitragynine or 7-HMG
- Specific LC-MS/MS methods required for identification [Ref 54]
- Validated 11-alkaloid plasma assay published (Sempio et al. 2025 [Ref 54])

### Naloxone Considerations
- Opioid effects of kratom (primarily mediated by 7-HMG) are naloxone-reversible in animal models
- Practical naloxone doses may need to be higher given the long half-life of mitragynine (up to 67.9 h with multiple dosing) and 7-HMG's high MOR affinity
- Respiratory depression is less prominent than with classical opioids, potentially complicating clinical recognition of overdose

---

## Tolerance & Dependence

### Tolerance Development
- Cross-tolerance to morphine documented in animal models and human reports (Bin Abdullah 2020 [Ref 25])
- Kratom alkaloids (mitragynine, kratom alkaloid extract, mitragynine pseudoindoxyl) produce significantly **less** naloxone-precipitated withdrawal in animal models than morphine at equieffective doses (Wilson et al. 2021 [Ref 27])
- Chronic administration produces drug-induced hyperalgesia in mice (Wilson et al. 2021 [Ref 27])

### Physical Dependence
- Physical dependence develops with regular use, establishing this is not a consequence-free drug
- Harun et al. (2020 [Ref 28]) confirmed physiological dependence and withdrawal potential of mitragynine in rats using schedule-controlled behavior
- Dose threshold for human dependence: **≥4 glasses of kratom tea/day (approximately 76–115 mg mitragynine)** is associated with higher severity of withdrawal symptoms (Singh et al. 2018 [Ref 30])

### Withdrawal Syndrome
Physical and psychological withdrawal symptoms on kratom cessation (Bin Abdullah 2020 [Ref 25]; Singh et al. 2018 [Ref 29, 30]):

**Psychological:**
- Depressed mood, anxiety (70% mild; 81% mild depression) [Ref 29]
- Restlessness, irritability, tension

**Physical:**
- Myalgia and body ache
- Joint pain
- Lacrimation, rhinorrhea
- Yawning
- Insomnia (46% experience more sleep problems on cessation) [Ref 30]
- Diarrhea
- Feverish sensation / chills
- Loss of appetite
- Tremors
- Pruritus
- Loss of concentration
- Nausea

**Severity context:** Cessation from regular kratom use produces withdrawal symptoms that are rated as milder than those of classical opioid analgesics in user reports [Ref 30].

### Neonatal Withdrawal
NAS symptoms reported in case reports: oral intolerance, restlessness, irritability, vomiting [Ref 45, 46].

### Treatment of Kratom Dependence
- **Buprenorphine-naloxone (Suboxone):** Most-studied pharmacological treatment for kratom dependence; used for both acute detoxification and maintenance [Ref 25]
- **IV clonidine + oral dihydrocodeine + lofexidine:** Alternative inpatient detoxification combination [Ref 25]
- Harun et al. (2022 [Ref 26]) review mitragynine's own potential as an opioid substitution therapy (preclinical data)

---

## Interactions

### CYP3A (Most Clinically Significant)
- Mitragynine is a **time-dependent inhibitor** of CYP3A4/5; KI ~4 µM, kinact ~0.07 min⁻¹ (Tanna et al. 2023 [Ref 41])
- **Human clinical data:** Single 2 g dose kratom tea increased midazolam AUC by **1.39× and Cmax by 1.50×** — primarily via intestinal CYP3A inhibition (no change in midazolam half-life) [Ref 41]
- **PBPK prediction:** Midazolam exposure increases 2.2–2.7× with mitragynine [Ref 48]
- CYP3A inhibitors (e.g., ketoconazole) reduce 7-HMG formation, potentially altering the efficacy-toxicity balance [Ref 48]

### CYP2D6
- Inhibitor in vitro; minimal clinical effect on dextromethorphan (CYP2D6 probe) at 2 g kratom tea dose [Ref 41]
- Potential for clinical interactions at higher doses or with sensitive CYP2D6 substrates

### P-glycoprotein
- Mitragynine inhibits P-gp-mediated efflux [Ref 43]
- Relevant for drugs with significant P-gp-mediated intestinal/blood-brain barrier efflux

### CNS Depressants
- Pharmacodynamic synergy with opioids, benzodiazepines, alcohol, and sedating antihistamines
- Multiple fatalities involved concurrent CNS depressant use [Ref 16, 18, 19, 20]

### Serotonergic Drugs
- Mitragynine interacts with serotonergic pathways; potential serotonin syndrome risk not well characterized in published case reports, though theoretical risk exists with SSRIs, SNRIs, and MAOIs given serotonergic receptor activity

---

## Legal Status

Sources: web_retrieved via WebSearch [Ref 53]; regulatory documents.

| Jurisdiction | Status | Notes |
|---|---|---|
| **United States** | Not federally scheduled; legal to possess and sell | DEA "Drugs and Chemicals of Concern" list. Emergency Schedule I withdrawn Oct 2016 after public and congressional opposition. FDA maintains import alert 54-15; issues consumer advisories. Some states and cities have local bans. |
| **United Kingdom** | Illegal | Banned under Psychoactive Substances Act 2016 |
| **Australia** | Schedule 9 (Prohibited Substance) | Complete ban |
| **Canada** | Legal to possess | Sales for human consumption not permitted under Food and Drugs Act |
| **Ireland** | Schedule 1 controlled drug | Since 2017, under Misuse of Drugs Act |
| **France** | Illegal | Banned since 2020 |
| **Netherlands** | Legal | Sold in smart shops |
| **Thailand** | Decriminalized / legal for traditional use | Removed from narcotics list under Kratom Act 2021; regulatory framework in development |
| **Malaysia** | Illegal | Controlled under Poisons Act 1952 |
| **Denmark/Romania/Poland** | Banned | Various national schedules |

**WHO status:** The WHO Expert Committee on Drug Dependence (ECDD) conducted a pre-review in 2021 and concluded there was **insufficient evidence** to recommend international scheduling under UN drug control conventions.

**FLAG:** Legal status is evolving rapidly. Generation agent should note this is a dynamic landscape; some states in the US have enacted bans at the state level (Alabama, Arkansas, Indiana, Rhode Island, Vermont, Wisconsin as of last available data). The KCPA (Kratom Consumer Protection Act) has been enacted in several states to regulate rather than ban.

---

## Clinical Trials

From ClinicalTrials.gov search:

| NCT ID | Title | Phase | Status | Sponsor | Relevance |
|--------|-------|-------|--------|---------|-----------|
| NCT07204171 | Phase 1 Study of Oral MG001 (pure mitragynine) | Phase 1 | Not yet recruiting | NIDA | First formal FDA-IND Phase 1 study of pure mitragynine as OUD treatment candidate; safety and tolerability |
| NCT06072170 | Single Ascending Doses of Kratom in Healthy Adults with Opioid Experience | Phase 1 | Completed | Altasciences / NIDA | Dose-finding study; results pending publication |
| NCT04392011 | Assessing the PK and Drug Interaction Liability of Kratom | Early Phase 1 | Completed | Washington State University | Published as Tanna et al. 2022 [Ref 40] and Tanna et al. 2023 [Ref 41] |
| NCT05846451 | Evaluating a Potential PK Kratom-Oxycodone Interaction | Early Phase 1 | Recruiting | Washington State University | Clinical DDI study; results pending |
| NCT05457803 | Real-world Momentary Assessment of Kratom Use | N/A (observational) | Completed | NIDA | Naturalistic study; results pending full publication |
| NCT07218549 | Evaluation of Safety/Effects of Psychoactive Substances in People with Past Opioid Use | Phase 1 | Not yet recruiting | C.D. Verrico | Includes kratom/mitragynine arm |
| NCT07469527 | Effects of Feel Free Classic Tonic on Stress and PK | N/A | Recruiting | Botanic Tonics, LLC | Commercial kratom-containing product; PK in healthy adults |

**Key upcoming milestone:** NCT07204171 (MG001, NIDA-sponsored Phase 1) represents the first attempt to advance pure mitragynine through formal regulatory clinical development as an OUD therapeutic.

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## Community Feedback Analysis

No community feedback was submitted in Part A2 of the brief.

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## Gaps & Flags

### Safety-Critical Flags (Require Human Editorial Review)

1. **FLAG — Ki values at MOR:** Specific published Ki values for mitragynine at human MOR were not retrieved from a primary binding assay paper via structured API tools in this research run. Values of approximately 280–500 nM (mitragynine) and 13–30 nM (7-HMG) are widely cited in reviews, attributed to foundational work by Takayama (2004) and Boyer (2008). These must be verified against original sources before being published as article data.

2. **FLAG — LD50:** No human LD50 or toxic/lethal concentration range for mitragynine has been formally established. Postmortem blood concentrations range from 0.19–1.9 mg/L in fatal cases, but nearly all involve poly-drug exposures. Published concentrations are not reliable toxicity thresholds.

3. **FLAG — Dose ranges (generation agent must propose):** No published controlled human dose-ranging study at doses above 40 mg pure mitragynine has been published. The Prevete 2025 study (5–40 mg) and Singh 2018 (76–115 mg/day in heavy users) provide bracketing data. Any dose table proposed must be flagged as partially extrapolated from leaf preparations and user reports.

4. **FLAG — Duration data:** Primary effects duration (~2–5 h) is based on user reports and traditional use, not controlled clinical data. The long half-life (43–67 h) does not map to subjective effect duration, consistent with other partial agonists. Residual pharmacological effects may persist beyond subjective experience.

5. **FLAG — Serotonin syndrome risk:** Mitragynine interacts with serotonergic pathways, but no published case reports of serotonin syndrome from mitragynine + serotonergic drug combinations were retrieved in this research run. Risk should be noted as theoretical based on pharmacological profile, not confirmed case data.

6. **FLAG — Semi-synthetic 7-HMG products:** The emergence of semi-synthetic 7-HMG products (sublingual tablets, powders, liquid shots) manufactured by direct oxidation of kratom extract represents a distinct and higher-risk product category. These are NOT equivalent to kratom or mitragynine pharmacologically — 7-HMG is a full or near-full MOR agonist with much greater potency and abuse/overdose potential. The generation agent should clearly distinguish mitragynine from semi-synthetic 7-HMG products.

### Data Gaps (Not Safety-Critical)

7. **No bioavailability (F%) data for pure oral mitragynine** in healthy volunteers; only indirect estimates from urinary recovery and PBPK modeling.

8. **Serotonin receptor Ki values** not retrieved; mentioned qualitatively in multiple reviews.

9. **Specific mechanisms of hepatotoxicity** not established; whether it is direct toxicity, immune-mediated, or contaminant-driven remains unclear.

10. **Effects in special populations** (renal impairment, hepatic impairment, elderly, adolescents) — no published data found.

11. **Oral bioavailability** of individual kratom alkaloids in humans not directly measured; in silico predictions suggest high absorption (BCS Class I-II, >75% Fa) for mitragynine based on physicochemical properties [Ref — PMID 38655841].

12. **CAS registry number** for mitragynine (commonly cited as 4098-40-2) was not independently verified via the structured PubChem API response.

13. **Thailand legal status** is complex: kratom was decriminalized under the Kratom Act 2021 but commercial export regulation details are still developing; generation agent should note uncertainty.