Tetrahydropalmatine

Tetrahydropalmatine at a Glance

Tetrahydropalmatine (THP), best known as its active levo enantiomer l-THP (Chinese drug name rotundine, also gindarin), is an isoquinoline alkaloid of the tetrahydroprotoberberine (THPB) class — the same ring-reduced family as canadine and l-stepholidine. It is the signature alkaloid of corydalis (Corydalis yanhusuo) tuber and of several Stephania species, and the compound that carries most of corydalis’s traditional reputation as a pain- and sleep-herb ^{2,12Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

What sets THP apart from the flat, quaternary protoberberines it is related to — berberine, palmatine, coptisine, jatrorrhizine — is a single structural fact with large consequences: its central ring is fully reduced, converting a permanently charged, gut-confined cation into a lipophilic tertiary amine that crosses the blood–brain barrier and blocks dopamine receptors ^{9,12Reference 9Jin GZ et al. · 1986Tetrahydroprotoberberine — a new chemical type of antagonist of dopamine receptors — animal studyView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. THP is, in effect, a naturally occurring dopamine antagonist, and that is the axis around which its sedative, analgesic, anxiolytic and anti-addiction pharmacology turns.

The evidence posture is unusually strong for a plant alkaloid at the human end. l-THP has been a State-approved over-the-counter sedative and analgesic in China for decades, and — rare for a phytochemical — it has been carried into controlled human trials in heroin abstinence, cocaine-use safety and schizophrenia ^{3,4,13Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →Reference 13Ponomareva OY et al. · 2020RCTL-tetrahydropalmatine, a novel dopamine antagonist, fails to improve psychiatric symptoms as adjunctive treatment for schizophrenia — randomized, double-blind, placebo-controlled trialView study →}. But most of the mechanistic work is still isolated l-THP in rodents, and the human trials are small and mixed. The headline safety point is that THP is not inert: as a brain-penetrant dopamine antagonist it lowers blood pressure and heart rate in animals, and it is the neuroactive alkaloid behind the hepatitis and pediatric-overdose reports of the “Jin Bu Huan” product ^{6,7Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}.

Tetrahydropalmatine as a Dopamine Antagonist

This is the defining property of the molecule and the reason it does not behave like the protoberberines it is chemically derived from.

The protoberberine alkaloids (berberine, palmatine, coptisine, jatrorrhizine) are quaternary — flat, aromatic, permanently positively charged, poorly absorbed, and dominated by gut and metabolic activity. Tetrahydropalmatine is that skeleton with the central ring reduced (hence tetrahydro): the permanent charge is gone, the molecule is a lipophilic tertiary amine, and it readily enters the brain. Ring reduction is what turns a metabolic gut compound into a central dopamine-receptor antagonist — the trait that unites the whole tetrahydroprotoberberine class and that the parent quaternary alkaloids essentially lack ^{9,12Reference 9Jin GZ et al. · 1986Tetrahydroprotoberberine — a new chemical type of antagonist of dopamine receptors — animal studyView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

THP’s receptor profile is not a flat pan-antagonism but a mixed, differentiated one. In the definitive pharmacology, l-THP is a higher-affinity antagonist at D1 receptors, a low-affinity antagonist at D2 receptors, and additionally interacts with D3 receptors ^{1Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →}. This D1-leaning, D3-touching profile is precisely what made it interesting for addiction — reward and relapse circuitry runs heavily through D1 and D3 signalling — and it distinguishes THP from classical D2-dominant neuroleptics like haloperidol ^{1Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →}. The tetrahydroprotoberberine scaffold as a class also shows measurable sigma-receptor affinity in medicinal-chemistry SAR work ^{10Reference 10Gadhiya S et al. · 2016Tetrahydroprotoberberine alkaloids with dopamine and σ receptor affinity — medicinal chemistry / SARView study →}.

The practical reading is the same caution that applies to canadine: do not transfer berberine’s metabolic clinical data to THP, and do not read THP’s CNS pharmacology onto berberine. They sit next to each other on a biosynthetic pathway but hit entirely different targets.

The l- vs dl- Enantiomer Distinction

THP is chiral, and the distinction is load-bearing — it decides both potency and which literature you are reading.

l-THP — the levo, (S)-, or levo-tetrahydropalmatine form — is the pharmacologically active dopamine antagonist. It is the enantiomer sold in China as rotundine and the one used in essentially all the modern addiction and psychiatric trials ^{1,3,4,13Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →Reference 13Ponomareva OY et al. · 2020RCTL-tetrahydropalmatine, a novel dopamine antagonist, fails to improve psychiatric symptoms as adjunctive treatment for schizophrenia — randomized, double-blind, placebo-controlled trialView study →}. The names rotundine (from Stephania rotunda) and gindarin refer to this levo compound.

dl-THP — the racemate (an equal mix of the levo and dextro forms) — is what several older cardiovascular studies dosed, and it is a weaker preparation because half of it is the less-active dextro enantiomer ^{6,7,11Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →Reference 11Chang CK et al. · 1999AnimalThe neuroprotective effect of DL-tetrahydropalmatine in rat heatstroke — animal studyView study →}. When a paper reports “DL-THP,” its effect sizes are not directly comparable to a pure l-THP result.

Layered on top of the enantiomer story is an OTC-medicine history that few plant alkaloids have. In China, l-THP has long been a State Drug Administration–approved over-the-counter drug for its analgesic, sedative and hypnotic properties, sold both as rotundine tablets (on the order of 30–60 mg l-THP) and inside compound sleep formulas ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. That regulatory history is why the human “dose” of this molecule is far better defined than for most phytochemicals — and why its safety profile, including the overdose reports below, is comparatively well described.

Analgesic & Anti-Addiction Research

These are THP’s two standout applications and the ones with the most human-relevant data, so they carry their own section.

Analgesia. Corydalis’s traditional use is pain, and THP is the alkaloid most responsible. Modern mechanism work locates a large part of that analgesia not in opioid receptors but in voltage-gated sodium channels: of four Corydalis yanhusuo alkaloids tested, tetrahydropalmatine gave “the best analgesic effect and the lowest cardiac risk,” inhibiting peak Nav1.7 currents and promoting channel inactivation ^{2Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →}. A sodium-channel, non-opioid analgesic mechanism is a meaningful point of difference from the poppy alkaloids and fits THP’s long OTC use for pain in China ^{2,12Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

Anti-addiction — the human signal. This is where THP is genuinely unusual. Because it is a mixed D1/D3 dopamine antagonist, it blunts drug reward and relapse in animal models across several drug classes: l-THP shifts the cocaine self-administration dose–response curve down and attenuates cocaine-primed reinstatement in rats at doses that spare food responding ^{1Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →}, and it inhibits methamphetamine self-administration and methamphetamine-induced reinstatement at doses that do not impair locomotion ^{5,14Reference 5Liu L et al. · 2021ReviewLevo-tetrahydropalmatine — a new potential medication for methamphetamine addiction and neurotoxicity — reviewView study →Reference 14Gong X et al. · 2016Levo-tetrahydropalmatine, a natural mixed dopamine receptor antagonist, inhibits methamphetamine self-administration and methamphetamine-induced reinstatement — animal studyView study →}. The compound has then been carried into people. A pilot randomised trial in heroin users found l-THP roughly tripled the three-month abstinence rate (47.8% vs 15.2% on placebo) while reducing craving ^{3Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →}, and a randomised, double-blind, placebo-controlled study in cocaine users established that a short course of oral l-THP (30 mg twice daily) was safe, well tolerated, and did not interfere with cocaine’s pharmacokinetics or acute cardiovascular effects ^{4Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →} — the safety groundwork for developing it as a cocaine-use-disorder treatment. These are small trials, but a plant alkaloid with any controlled human relapse data is rare.

The honest counterweight sits in psychiatry: a 4-week randomised, double-blind, placebo-controlled trial of l-THP 60 mg/day added to antipsychotics in schizophrenia found no benefit on any psychiatric measure — though it did reduce extrapyramidal side-effects and, unexpectedly, raised inflammatory markers ^{13Reference 13Ponomareva OY et al. · 2020RCTL-tetrahydropalmatine, a novel dopamine antagonist, fails to improve psychiatric symptoms as adjunctive treatment for schizophrenia — randomized, double-blind, placebo-controlled trialView study →}.

What It's Used For

The through-line is the mixed dopamine antagonism above; the load-bearing caveat is that most of the mechanistic evidence is isolated l-THP in rodents, with the human data confined to the small addiction and psychiatry trials.

Evidence by IndicationStrength of support · Beta

Support is an experimental score I’m building — a composite weighted by study type (human > animal > in vitro > review) and study volume, tempered for isolate-vs-plant match. It’s a beta: a fast way to rank strength of evidence at a glance, not a validated metric. Each application links down to its write-up. THP scores comparatively high because — unusually for a plant alkaloid — some applications reach small human trials.

01Substance-Use / Anti-AddictionPromising62%Rat cocaine & meth self-admin/reinstatement ^{1,14Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →Reference 14Gong X et al. · 2016Levo-tetrahydropalmatine, a natural mixed dopamine receptor antagonist, inhibits methamphetamine self-administration and methamphetamine-induced reinstatement — animal studyView study →} + small human RCTs (heroin abstinence, cocaine safety/PK) ^{3,4Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →}

02AnalgesiaPromising56%Mechanism (Nav1.7) in isolated alkaloids ^{2Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →} + decades of OTC analgesic use in China ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}

03Sedative / Hypnotic & AnxiolyticPromising48%OTC sedative-hypnotic use ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →} + dopamine-antagonist rationale; thin controlled human efficacy data

04Cardiovascular DepressionShaky40%Consistent rat hypotension/bradycardia via central DA/5-HT2 (dl-THP) ^{6,7Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}

05Hepatoprotection (NAFLD)Shaky32%Rodent hepatic-steatosis model via AMPK-SREBP-1c-Sirt1 ^{8Reference 8Yin X et al. · 2023In vitroTetrahydropalmatine ameliorates hepatic steatosis in nonalcoholic fatty liver disease by switching lipid metabolism via the AMPK-SREBP-1c-Sirt1 signaling axis — animal / in vitroView study →}

06NeuroprotectionShaky28%Rat heatstroke neuroprotection model (dl-THP) ^{11Reference 11Chang CK et al. · 1999AnimalThe neuroprotective effect of DL-tetrahydropalmatine in rat heatstroke — animal studyView study →}

Mechanisms

Pharmacokinetics

The property that makes THP pharmacologically interesting is the one berberine lacks: as a lipophilic tertiary amine it crosses the blood–brain barrier, which is why it reaches central dopamine receptors at all ^{9,12Reference 9Jin GZ et al. · 1986Tetrahydroprotoberberine — a new chemical type of antagonist of dopamine receptors — animal studyView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. Against that, its systemic exposure is poor — THP is inadequately absorbed in the intestine, rapidly cleared, and has low oral bioavailability, which is why much formulation work (self-microemulsifying and solid-dispersion systems) exists specifically to raise its absorption ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. Human plasma pharmacokinetics have been measured (the cocaine safety RCT reported Cmax, Tmax, half-life and clearance after oral l-THP) ^{4Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →}, but a clean, agreed human oral-bioavailability percentage for the isolate is not established here. Metabolism is hepatic, and the two enantiomers show measurably different pharmacokinetic fates — one more reason l- and dl- data should not be pooled ^{11,12Reference 11Chang CK et al. · 1999AnimalThe neuroprotective effect of DL-tetrahydropalmatine in rat heatstroke — animal studyView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

Clinical Trials

Uncommonly for a plant alkaloid, THP has reached several small controlled human trials — chiefly in addiction and psychiatry, using the isolated l-THP.

Last checked: July 2026.

Isolate vs. Plant Studies

THP’s evidence base is overwhelmingly the isolated molecule — nearly every result above is purified l-THP (or, in the older cardiovascular work, dl-THP) given at a defined oral or injected dose, not a corydalis decoction ^{1,3,4,6,14Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →Reference 14Gong X et al. · 2016Levo-tetrahydropalmatine, a natural mixed dopamine receptor antagonist, inhibits methamphetamine self-administration and methamphetamine-induced reinstatement — animal studyView study →}. That is a genuine strength at the human end: the heroin, cocaine and schizophrenia trials all dosed a defined quantity of the pure alkaloid, so their results speak to this molecule, not to an undefined botanical ^{3,4,13Reference 3Yang Z et al. · 2008RCTMedication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trialView study →Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →Reference 13Ponomareva OY et al. · 2020RCTL-tetrahydropalmatine, a novel dopamine antagonist, fails to improve psychiatric symptoms as adjunctive treatment for schizophrenia — randomized, double-blind, placebo-controlled trialView study →}. The mechanism studies likewise test the isolate or, for the class-level dopamine and sigma pharmacology, its tetrahydroprotoberberine relatives ^{1,9,10Reference 1Mantsch JR et al. · 2007AnimalLevo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal studyView study →Reference 9Jin GZ et al. · 1986Tetrahydroprotoberberine — a new chemical type of antagonist of dopamine receptors — animal studyView study →Reference 10Gadhiya S et al. · 2016Tetrahydroprotoberberine alkaloids with dopamine and σ receptor affinity — medicinal chemistry / SARView study →}.

The transferability caveat therefore runs the other direction from most compound pages: do not read an l-THP trial as evidence for whole corydalis tuber. Commercial C. yanhusuo preparations vary enormously in alkaloid content, and traditional vinegar-processing alters alkaloid solubility, so the amount of THP actually delivered by a given corydalis product is not fixed — and the tuber also contains dehydrocorydaline, dehydrocorybulbine, corydaline, protopine and other actives that a purified-THP study excludes.

Its Role in Plants

Tetrahydropalmatine is a benzylisoquinoline alkaloid built, like the rest of its family, from the branch-point intermediate (S)-reticuline and elaborated through the tetrahydroprotoberberine pathway shared with canadine and the protoberberines. Structurally it is the fully reduced (tetrahydro) counterpart of palmatine: where the plant oxidises the tetrahydroprotoberberine skeleton it yields the flat quaternary palmatine, and where reduction persists it accumulates the tertiary-amine THP. In the tuber these alkaloids co-occur as a defensive alkaloid complex; THP is one of the more abundant members in Corydalis yanhusuo and the Stephania species that make it a named drug source ^{2,12Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

Prevalence in Nature

THP occurs chiefly in the tubers and rhizomes of two alkaloid-rich lineages: the Papaveraceae — above all corydalis (Corydalis yanhusuo), where it is a signature tuber alkaloid — and the Menispermaceae, especially Stephania species (S. rotunda, S. epigaea), the source of the drug name rotundine ^{2,12Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. It is also reported from Phellodendron (P. chinense) and scattered across other genera of the same two families ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}. As with the related protoberberines, it concentrates in underground storage organs rather than leaves.

Quantified content is genuinely unreliable to state as a single figure: THP levels vary widely with species, plant part, growing conditions, traditional vinegar-processing, and — for commercial supplements — considerable batch-to-batch variation. Where a clean, comparable percentage-of-dry-weight figure per source is needed, it is a documented gap rather than a settled number.

Major Natural Sources

Source	Botanical	Part	Notes
Corydalis	Corydalis yanhusuo	Tuber / rhizome	Signature alkaloid; the classic pain-herb source 2,12Reference 2Xu Y et al. · 2021In vitroAnalgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloidsView study →Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →
Stephania	Stephania rotunda, S. epigaea	Tuber / root	Source of the name rotundine; drug-grade l-THP 12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →
Phellodendron	Phellodendron chinense	Bark	Reported minor source 12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →

Discovery & Synthesis

Tetrahydropalmatine was isolated from Corydalis and Stephania tubers, the two lineages that also gave it its common names: rotundine from Stephania rotunda, and gindarin as an older synonym for the same levo compound. Its systematic identity is straightforward — it is the tetrahydro (fully ring-reduced) form of the protoberberine palmatine, and a member of the tetrahydroprotoberberine class alongside canadine. Structure–activity work on the broader THPB scaffold, aimed at its dopamine and sigma receptor affinity, has produced synthetic analogues, confirming the skeleton is chemically tractable ^{10Reference 10Gadhiya S et al. · 2016Tetrahydroprotoberberine alkaloids with dopamine and σ receptor affinity — medicinal chemistry / SARView study →}. Commercially, l-THP is obtained by extraction from corydalis/Stephania tubers (and can be prepared by resolution or reduction routes for research); its scale is driven by its status as an approved OTC drug substance in China rather than by Western supplement demand ^{12Reference 12Du Q et al. · 2022ReviewComprehensive review of tetrahydropalmatine — plant sources, pharmacology, pharmacokinetics and toxicology — reviewView study →}.

Patents: not yet researched.

Toxicity & Safety

THP earns a moderate rating, not a low one — the honest headline is that it is a pharmacologically active, brain-penetrant dopamine antagonist with documented overdose and hepatotoxicity reports, not a benign botanical.

Hepatotoxicity. l-THP is the neuroactive alkaloid in the notorious herbal product “Jin Bu Huan,” and long-term use of that product was associated with acute hepatitis in adults; the compound was described in that clinical spectrum as “a potent neuroactive substance” ^{7Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}. This is the single most important safety signal, and it sits in tension with the experimental anti-steatosis finding ^{8Reference 8Yin X et al. · 2023In vitroTetrahydropalmatine ameliorates hepatic steatosis in nonalcoholic fatty liver disease by switching lipid metabolism via the AMPK-SREBP-1c-Sirt1 signaling axis — animal / in vitroView study →} — dose and chronic exposure evidently matter.

Pediatric overdose and CNS/cardiovascular depression. In the same clinical series, accidental ingestion by children produced life-threatening neurological and cardiovascular manifestations ^{7Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}. This fits the pharmacology: as a central dopamine antagonist THP produces dose-dependent hypotension and bradycardia in animals ^{6,7Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}, and sedation/CNS depression at higher doses.

Extrapyramidal and psychiatric effects. As a dopamine antagonist, THP can affect movement and dopaminergic signalling; the schizophrenia add-on trial actually recorded reduced extrapyramidal symptoms but also an unexpected rise in inflammatory markers (sICAM-1, CRP) ^{13Reference 13Ponomareva OY et al. · 2020RCTL-tetrahydropalmatine, a novel dopamine antagonist, fails to improve psychiatric symptoms as adjunctive treatment for schizophrenia — randomized, double-blind, placebo-controlled trialView study →}. The dopamine-blocking mechanism means interactions with antipsychotics, other dopaminergic drugs, and additive CNS depression with alcohol and sedatives are plausible and were not formally characterised here.

Reproductive and developmental safety of isolated THP is not established here, and given its brain penetration and dopamine activity it should be treated as unknown rather than assumed safe. Drug-interaction and pregnancy/lactation decisions belong to the whole-herb corydalis monograph, where intake is actually decided.

Safety at a Glance

⚠️ Moderate toxicity

• A genuinely studied molecule with human safety data. A short oral course (30 mg twice daily) was safe and well tolerated in a controlled cocaine-user RCT, with no acute cardiovascular problem ^{4Reference 4Hassan HE et al. · 2017RCTPharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled studyView study →}.
• Documented hepatotoxicity. l-THP is the active alkaloid behind the “Jin Bu Huan” hepatitis reports with prolonged use — not a benign botanical ^{7Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}.
• Overdose is dangerous, including in children. Accidental pediatric ingestion caused life-threatening neurological and cardiovascular effects ^{7Reference 7Horowitz RS et al. · 1996Case reportThe clinical spectrum of Jin Bu Huan toxicity — case series (l-tetrahydropalmatine)View study →}; the compound lowers blood pressure and heart rate ^{6Reference 6Lin MT et al. · 1996Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal studyView study →}.
• Active dopamine antagonist. Plausible additive sedation with alcohol/CNS depressants and interactions with dopaminergic/antipsychotic drugs; not formally characterised here.
• Reproductive safety unknown. No isolate-specific developmental data; treat silence as unknown, not safe — pregnancy/lactation is decided on the corydalis monograph.

Dosage

There is no universally established dietary-supplement dose for tetrahydropalmatine, and the figures below are research and regulated-drug references, not a recommendation.

Two practical caveats. First, l- and dl- are not interchangeable — a racemic (dl-THP) figure delivers roughly half the active levo compound of an equal l-THP dose. Second, whole corydalis products are not standardised to a THP amount and vary enormously by batch and processing, so a tuber preparation does not deliver a predictable THP dose. These are doses studied in research or used as a regulated drug and are not a personal recommendation.

References

1. Mantsch JR, Li SJ, Risinger R, Awad S, Katz E, Baker DA, Yang Z. (2007). Levo-tetrahydropalmatine attenuates cocaine self-administration and cocaine-induced reinstatement in rats — animal study. Psychopharmacology (Berl), 192(4), 581–591. https://pubmed.ncbi.nlm.nih.gov/17361394/
2. Xu Y, Sun J, Li W, Zhang S, Yang L, Teng Y, et al. (2021). Analgesic effect of the main components of Corydalis yanhusuo is caused by inhibition of voltage-gated sodium channels — in vitro / isolated alkaloids. Journal of Ethnopharmacology, 280, 114457. https://pubmed.ncbi.nlm.nih.gov/34329712/
3. Yang Z, Shao YC, Li SJ, Qi JL, Zhang MJ, Hao W, Jin GZ. (2008). Medication of l-tetrahydropalmatine significantly ameliorates opiate craving and increases the abstinence rate in heroin users — pilot randomized trial. Acta Pharmacologica Sinica, 29(7), 781–788. https://pubmed.ncbi.nlm.nih.gov/18565275/
4. Hassan HE, Kelly D, Honick M, Shukla S, Ibrahim A, Gorelick DA, et al. (2017). Pharmacokinetics and safety assessment of l-tetrahydropalmatine in cocaine users — a randomized, double-blind, placebo-controlled study. Journal of Clinical Pharmacology, 57(2), 151–160. https://pubmed.ncbi.nlm.nih.gov/27363313/
5. Liu L, Liu M, Zhao W, Zhao YL, Wang Y. (2021). Levo-tetrahydropalmatine — a new potential medication for methamphetamine addiction and neurotoxicity — review. Experimental Neurology, 344, 113809. https://pubmed.ncbi.nlm.nih.gov/34256045/
6. Lin MT, Chueh FY, Hsieh MT, Chen CF. (1996). Antihypertensive effects of DL-tetrahydropalmatine — an active principle isolated from Corydalis — animal study. Clinical and Experimental Pharmacology & Physiology, 23(8), 738–742. https://pubmed.ncbi.nlm.nih.gov/8886500/
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