7-Hydroxymitragynine
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7-Hydroxymitragynine (7-HMG) — 7-OH — is a semi-synthetic opioid of the monoterpenoid indole alkaloid class. It is the primary active metabolite of mitragynine — kratom's dominant alkaloid — and far more potent than morphine as a painkiller.[1] It activates opioid receptors in the brain, producing pain suppression, sedation, and euphoria.
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First isolated in 1994 from Thai kratom leaf,[2] 7-HMG was identified as a trace alkaloid with extraordinary painkilling potency.[1] In 2019, researchers showed it is the compound responsible for most of kratom's pain relief — forming in the liver after kratom consumption.[3] Since 2023, concentrated semi-synthetic products have flooded gas stations; the FDA recommended DEA scheduling in July 2025.[4]
Subjective effects include pain relief, sedation, euphoria, and anxiolysis. The experience is defined by what it removes: discomfort recedes, and body and mind settle into heavy calm. Nausea, constipation, and slowed breathing are characteristic unwanted effects; no psychedelic or hallucinogenic features appear at any dose.
7-HMG produces physical dependence and opioid withdrawal; respiratory depression 4.5 times more potent than morphine[5] makes breathing failure the primary lethal risk. Tolerance is shared bidirectionally with morphine,[6] and combining with any other depressant sharply amplifies the risk of fatal breathing failure. No controlled human trials of isolated 7-HMG exist — the safe dose range is unknown.
History[edit]
Discovery
7-Hydroxymitragynine was first isolated in 1994 from Thai kratom leaf by Ponglux and colleagues.[2] In 2002, Takayama's group showed this trace alkaloid was 13 times more potent than morphine in pain tests.[1] By 2005, animal studies confirmed it produces tolerance, cross-tolerance with morphine, and withdrawal — a classical opioid dependence profile.[6]
Scientific Reframing
In 2016, Kruegel and colleagues showed 7-HMG activates pain-suppression pathways at opioid receptors without triggering a secondary signaling branch thought to cause adverse effects.[7] Then in 2019, the same group established that mitragynine is converted to 7-HMG in the liver — making 7-HMG the compound actually responsible for most of kratom's pain relief.[3] A further complication: 7-HMG is unstable in human blood, converting to the even more potent mitragynine pseudoindoxyl.[8]
Market Emergence and Regulatory Response
Between 2023 and 2025, concentrated semi-synthetic 7-HMG products proliferated in gas stations and online shops.[9][10] The FDA issued warning letters to seven companies in June 2025 and formally recommended DEA scheduling on July 29, 2025.[4] As of May 2026, DEA rulemaking is pending.
The name "7-OH" — from 7-hydroxymitragynine — became dominant in consumer markets as semi-synthetic products entered smoke shops from 2023 onward. The branding is significant: "7-OH" frames the product as a novel compound rather than a concentrated derivative of a traditional plant. Early commercial kratom products had already been found with artificially elevated 7-HMG concentrations,[11] but the explicit branding of isolated 7-HMG as its own product category marked a pharmacological break from the kratom tradition.
Chemistry[edit]
Structural Class
7-Hydroxymitragynine belongs to the monoterpenoid indole alkaloid family, built on a Corynanthe-type scaffold.[12] It is derived from mitragynine by adding a single hydroxyl group at the C-7 position — a small change that creates a partial opioid agonist more than 13 times more potent than morphine.[1] Its molecular formula is C₂₃H₃₀N₂O₅ (414.5 g/mol).
7-HMG is a trace constituent of kratom leaf — less than 2% of total alkaloid content.[13] The liver converts Mitragynine into 7-HMG after kratom consumption.[3] In human blood, 7-HMG is itself unstable, converting to an even more potent compound — a transformation that happens far faster in human plasma than in other species, meaning animal studies likely underestimate its strength in people.[8]
Pharmacology[edit]
Mechanism of Action
7-HMG partially activates µ-opioid receptors — those responsible for pain suppression — while blocking the other two main opioid receptor types.[7][14] It triggers one downstream signaling pathway without activating a second one thought to drive adverse effects like respiratory depression.[15][7] Animal data undercut that prediction: 7-HMG slows breathing 4.5 times more potently than morphine, and naloxone fully reverses it.[5]
Pharmacokinetics
When kratom is taken orally, liver enzymes (CYP3A) convert mitragynine into 7-HMG.[3] A single dose peaks in blood at roughly 1.8 hours and is mostly cleared in about 4.7 hours.[16][17] With repeated use, clearance time extends to 24.7 hours — the compound accumulates, reaching stable levels after about 7 days.[17]
In human blood, 7-HMG converts to mitragynine pseudoindoxyl, a compound even more potent at opioid receptors.[8] This conversion is far faster in humans than in other species, so animal studies likely underestimate 7-HMG's potency in people.[8] Sublingual and nasal products bypass liver metabolism, delivering more compound to the bloodstream faster than oral routes.[9]
Neuroscience[edit]
Where It Acts
7-HMG activates opioid receptors along the pain-control pathway running from the brainstem to the spinal cord, suppressing pain signals at multiple levels.[18] It also suppresses the brain's breathing centers with 4.5 times the potency of morphine.[5]
In the brain's reward circuit, low doses increase dopamine release while high doses decrease it.[19] Classical opioids like morphine increase dopamine across the dose range — 7-HMG's opposite pattern at high doses remains unexplained.
Why It Matters
The prediction that 7-HMG's selective signaling would reduce adverse effects has not held up for breathing.[5] The discovery that kratom's analgesic effects are mainly mediated by 7-HMG[3] — which then converts to a more potent compound in human blood[8] — means results from animal studies translate unreliably to humans.
The therapeutic index in humans — the gap between an effective analgesic dose and a dangerous one — has not been measured. The relative contribution of 7-HMG versus its downstream metabolite to human effects is unknown, because the plasma conversion rate differs dramatically between species.[8] The mechanism behind the biphasic dopamine response[19] — increased release at low doses, decreased at high — remains unexplained.
Subjective Effects[edit]
The 7-HMG experience is opioid in character: a spreading warmth that blunts physical pain, quiets emotional tension, and slows both body and mind. Nothing is amplified or brightened — everything quiets. The experience is defined by what it removes.
Compared to morphine, the analgesia and euphoria are qualitatively similar, arising from the same receptor activation. Concentrated semi-synthetic 7-HMG products produce a faster and more intense version of the same state than traditional kratom preparations. No psychedelic or hallucinogenic features have been documented at any dose.
Effect Grid
Common doses produce the characteristic opioid experience: substantial pain suppression, pronounced euphoria and cognitive euphoria, and marked anxiety suppression. A warm body high and tactile euphoria dominate the physical experience. Sedation becomes prominent, with a heavy, comfortable bodily heaviness and strong muscle relaxation.
Nausea is common, particularly on the come-up. Constipation, pupil constriction, and respiratory depression are pharmacologically expected at this level. Spontaneous body sensations including itching may occur. Dry mouth and appetite suppression are typical. Motor control impairment and thought deceleration are functionally significant.
Compulsive redosing urge may emerge. Duration of effects is expected to last several hours. Emotional suppression and dreaming suppression are likely with evening dosing.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Muscle relaxation · Pain suppression · Bodily heaviness · Constipation · Nausea · Spontaneous body sensations · Tactile euphoria · Breathing alteration · Dizziness · Physical fatigue · Appetite suppression · Dry mouth · Sexual arousal suppression · Vomiting · Yawning · Excessive sweating · Temperature dysregulation · Bodily dissociation
Constipation · Nausea · Spontaneous body sensations · Tactile euphoria · Breathing alteration · Dizziness · Physical fatigue · Appetite suppression · Dry mouth · Sexual arousal suppression · Vomiting · Yawning · Excessive sweating · Bodily dissociation
Cognitive impairment · Focus suppression · Information processing suppression · Thought deceleration · Memory suppression · Motivation suppression · Confusion
Memory suppression · Motivation suppression · Confusion
Timeline
Gradual emergence of first effects as mitragynine undergoes hepatic CYP3A oxidation to 7-HMG. Subtle warmth and mild anxiolysis may be the earliest perceptible shifts.
Opioid-typical warmth, analgesia, and sedation reach maximum intensity. Euphoria, muscle relaxation, and pupil constriction are prominent. Nausea most likely during early peak.
Gradual decline of analgesic and euphoric effects consistent with single-dose elimination half-life of 4. 7 hours. Sedation and bodily heaviness may persist longer than mood effects.
Subclinical residual effects including mild sedation, reduced anxiety, and possible rebound irritability. With chronic dosing, the elimination half-life extends to 24. 7 hours, significantly prolonging aftereffects.
Safety[edit]
- Acute toxicity
- High
- Chronic toxicity
- Moderate
- Withdrawal
- Severe
- Tolerance buildup
- moderate
- Tolerance reset
- —
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- High
- Cross-tol.
- morphine · mu-opioid agonists (class)
Toxicity
Acute Toxicity
The primary lethal risk from 7-HMG is suppressed breathing — respiratory depression 4.5 times more potent than morphine in animal models.[5] This is fully reversed by naloxone. No lethal dose has been established, and no controlled human toxicity data exist.safety citation needed
Fatalities
Most published fatality data report mitragynine rather than 7-HMG blood concentrations. An analysis of 156 kratom-associated deaths found 80% were male (mean age 32.3 years), with polysubstance use in 87% of cases.[20] A case-control study identified 38 single-substance kratom fatalities with autopsy findings including fluid in the lungs, enlarged liver, and enlarged heart.[21]
safety citation needed The role of 7-HMG versus its downstream metabolite in fatal toxicity is unknown. Postmortem 7-HMG concentrations are rarely measured separately.
Liver Injury
Kratom use has been associated with liver injury in case reports, including bile duct obstruction[22] and severe liver damage resembling autoimmune patterns.[23][24] Whether 7-HMG or other alkaloids are responsible has not been determined.
Muscle Breakdown
Severe muscle breakdown requiring surgical intervention has been reported after kratom overdose, though other substances were also present.[25]
Neonatal Risk
No published data exist on neonatal withdrawal from gestational 7-HMG exposure. Risk is expected given its opioid receptor activity.safety citation needed
Psychological Risks
No psychedelic, dissociative, or hallucinogenic effects have been documented. Psychological risks are opioid-class: compulsive redosing,[9][26] opioid use disorder meeting DSM-5 criteria,[27] and progressive dose escalation toward more potent compounds.[28]
Tolerance and Dependence
Tolerance develops with chronic use, following morphine's pattern.[6] It is bidirectional with morphine — tolerance to one produces tolerance to the other.[6] Rapid escalation is documented clinically, including one case with progression to mitragynine pseudoindoxyl at 9 × 20 mg daily including nocturnal dosing.[28]
Physical dependence produces classical opioid withdrawal: muscle aches, insomnia, anxiety, nausea, and sweating. Animal models show this resembles morphine withdrawal,[6] and human cases confirm it requires medical management.[26][28] Prior 7-HMG exposure sensitizes reward pathways — animal studies show subsequent morphine intake increases.[29]
Treatment approaches include buprenorphine[27][30] and methadone.[31] A systematic review found consistent animal abuse liability but clinical evidence remains limited.[32]
Drug Interactions
CYP3A4 inhibitors — itraconazole, ketoconazole, grapefruit, ritonavir — alter both 7-HMG formation and clearance. In humans, itraconazole cut 7-HMG peak levels by 56%;[16] in rats, ketoconazole increased potency 9.7-fold.[33] The net effect with preformed 7-HMG products is unpredictable.safety citation needed
CNS depressants — opioids, benzodiazepines, alcohol, sleeping pills — add to 7-HMG's breathing suppression. Polysubstance use was present in 87% of kratom-associated fatalities.[20][21]
Cannabidiol (CBD): Co-administration increased mitragynine exposure 2.8-fold in rats via enzyme inhibition.[34]
CYP3A substrates — benzodiazepines, statins, calcium channel blockers — kratom alkaloids can slow the enzyme that clears these drugs, increasing their blood levels.[35]
CYP2D6 and P-glycoprotein substrates: Kratom alkaloids inhibit both pathways, potentially increasing exposure to many other drugs.[36]
Serotonergic drugs: Serotonergic activity has been noted for kratom alkaloids,[37] but no cases of a dangerous overheating response have been reported with 7-HMG.safety citation needed
Contraindications
Absolute contraindications:
- Concurrent CNS depressant use — opioids, benzodiazepines, barbiturates, alcohol, sleeping pills — additive respiratory depression with established fatality risk[20][21]
- Severe liver disease — 7-HMG depends on liver enzymes for clearance; impaired function may cause unpredictable accumulation; liver injury has been reported with kratom use[22][23]
- Severe respiratory disease — baseline breathing impairment increases vulnerability to opioid-mediated respiratory depression[5]
Relative contraindications:
- CYP3A4 inhibitor use — altered drug levels with unpredictable net effect[16][33]
- Pregnancy — no data on gestational exposure; neonatal withdrawal expected based on opioid receptor activitysafety citation needed
- Active substance use disorder — 7-HMG maintains self-administration and increases subsequent morphine intake in animal models[29]
- Moderate liver disease — enzyme-dependent metabolism may be altered
Harm Reduction[edit]
Forms & Identification
7-HMG products come in several formats: sublingual films, pressed tablets, liquid tonics, and nasal sprays. Sublingual and nasal routes bypass liver metabolism, delivering more compound to the bloodstream faster than oral routes.[9] Two products with the same milligram amount can produce very different effects depending on the delivery format.
Product labeling is unreliable in this market. Early kratom products were found with artificially elevated 7-HMG concentrations,[11] and the current semi-synthetic market has no standardized testing or manufacturing oversight.[38] Stated doses on packaging should not be assumed accurate.
Guidelines
- Start with the lowest available dose and wait for full onset before considering redosing — onset varies by route (sublingual and nasal are faster than oral)
- Never combine with other depressants — alcohol, benzodiazepines, other opioids, and sleeping pills produce additive respiratory depression
- Have naloxone available and ensure someone present knows how to administer it
- Avoid using alone, particularly with sublingual or nasal products that produce rapid-onset effects
- Do not drive or operate machinery — sedation and impaired reaction time are core effects
- Be aware of accumulation — 7-HMG's half-life extends from approximately 4.7 hours (single dose) to 24.7 hours with repeated use,[17] meaning effects can stack unexpectedly with daily dosing
- Avoid CYP3A4 inhibitors including grapefruit, which can unpredictably alter 7-HMG levels
Set & Setting
The opioid experience is less sensitive to set and setting than psychedelics, but environment still matters. A safe location with a sober companion present reduces risk during initial exposures. Because 7-HMG suppresses breathing — the primary lethal mechanism — falling asleep alone after use is a specific danger, which escalates sharply with any co-ingested depressant.
Aftercare & integration. 7-HMG's extended half-life with repeated dosing[17] means residual effects can persist longer than expected. Allow a full recovery period before driving, working, or making significant decisions. Hydration, light food, and rest support physical recovery.
The opioid warmth and emotional quieting produced by 7-HMG can create a strong pull toward re-use, particularly for those managing chronic pain or emotional distress. Honest self-assessment of the desire to redose — especially if the interval between uses is shortening — is the single most important aftercare practice.
Recovery & Support
7-HMG produces classical opioid dependence. Daily use, withdrawal symptoms between doses, or escalating doses are signals that medical support is warranted. Treatment approaches include buprenorphine[27] and methadone[31] — established medications for opioid use disorder.
Withdrawal resembles opioid withdrawal broadly: muscle aches, insomnia, anxiety, nausea, sweating, and restlessness. Medical management substantially reduces discomfort.[26] Abrupt cessation after heavy chronic use carries risk of severe withdrawal[28] — consultation with a healthcare provider experienced in opioid tapering is the safer path.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency:
7-HMG is an opioid — the emergency signs are opioid overdose signs. Watch for: breathing that slows, becomes irregular, or stops; blue or gray lips and fingertips; pinpoint pupils; unresponsiveness to loud voice or sternal rub; gurgling or snoring sounds in an unconscious person.
Immediate steps:
- 1. Call emergency services immediately if breathing is slow, irregular, or absent
- 2. Administer naloxone if available — intranasal or intramuscular, per packaging instructions
- 3. Place the person in the recovery position (on their side) if unconscious but breathing
- 4. Stay with them — naloxone wears off faster than 7-HMG, and breathing may stop again
- 5. Do NOT induce vomiting in an unconscious person
- 6. Do NOT leave them alone to "sleep it off"
What to tell the dispatcher:
Name the substance (7-hydroxymitragynine or "7-OH" — a kratom-derived opioid), the amount if known, the time of ingestion, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Reversal agent: Naloxone fully reverses 7-HMG respiratory depression.[5] A second dose may be required because naloxone's duration of action is shorter than 7-HMG's.
Legal Status[edit]
The regulatory landscape for 7-hydroxymitragynine is actively evolving, driven by the emergence of concentrated semi-synthetic products since 2023.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States (federal) | Not scheduled (as of May 2026) | FDA recommended DEA scheduling of concentrated 7-OH products on July 29, 2025; DEA rulemaking pending. Warning letters issued to seven companies in June 2025[4] |
| United States (state) | Varies by state | Arizona, Oklahoma, Texas, and Utah restrict 7-HMG content to less than 2% of total alkaloid content in commercial products[39] |
| Australia | Schedule 9 (prohibited substance) | 7-HMG is listed as a prohibited substance[39] |
| United Kingdom | Not scheduled | Kratom and alkaloids not currently controlled under the Misuse of Drugs Act; concentrated 7-HMG products generating regulatory scrutinycitation needed |
| Canada | Not explicitly scheduled | Health Canada prohibited marketing of kratom for oral use in 2020; 7-HMG as isolated compound not specifically listed under the Controlled Drugs and Substances Actcitation needed |
| Thailand | Decriminalized (personal use) | Kratom decriminalized for personal use in 2021; regulatory nuances may apply to isolated alkaloidscitation needed |
| Malaysia | Controlled | Kratom possession and sale prohibited under the Poisons Actcitation needed |
| European Union | Not scheduled at EU level | Regulation varies by member state; no EU-wide scheduling of kratom alkaloidscitation needed |
references
- [1] ^abcdTakayama H, Ishikawa H, Kurihara M, Kitajima M, Aimi N, Ponglux D, Koyama F, Matsumoto K, Moriyama T, Yamamoto L, Watanabe K, Murayama T, Horie S (2002) Studies on the Synthesis and Opioid Agonistic Activities of Mitragynine-Related Indole Alkaloids: Discovery of Opioid Agonists Structurally Different from Other Opioid Ligands. — Journal of Medicinal Chemistry doi:10.1021/jm010576e
- [2]
- [3]
- [4]
- [5]
- [6]