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Tag: MONOGRAPH

Arketamine

Plain-language summaryIntrigue 78 / 100

Arketamine is the R-enantiomer of ketamine (the other half of the racemate). Animal studies suggest the antidepressant effects may be longer-lasting than esketamine with fewer dissociative side effects. Investigated as an alternative depression treatment. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundNovel, promising

58/100

Enantiomeric ketamine with a compelling TrkB-over-NMDA mechanism story and active phase 2 clinical development

Here’s the thing about arketamine: the pharmacology is more interesting than the name implies. Everyone knows ketamine; a lot of people now know esketamine (Spravato). R-ketamine sits in a genuinely strange position, which is lower NMDA receptor affinity than its (S)-sibling, yet rodent models consistently show more durable antidepressant effects and a reduced dissociative burden. That paradox is exactly where the interesting science lives.

The mechanism story has sharpened considerably over the last few years. Kenji Hashimoto’s lab at Chiba University built a series of papers arguing that arketamine’s antidepressant action leans harder on downstream signaling, specifically BDNF/TrkB pathway activation and mGluR modulation, than on acute NMDA channel blockade. The 2021 Casarotto et al. work in Cell added broader context: TrkB is a direct binding target for ketamine-class molecules, and the two enantiomers differ meaningfully in their TrkB-to-NMDA affinity ratio. That mechanistic wedge is what makes arketamine scientifically interesting rather than just a stereochemical footnote.

What we like here is the probe utility. If you want to dissect NMDA-dependent from TrkB-dependent antidepressant mechanisms, running parallel R versus S experiments is one of the cleaner designs available. The enantiomeric comparison opens questions that neither compound answers alone. Thats valuable even if arketamine never clears phase 3. For investigators working on NMDA receptor biology, synaptic plasticity, or rapid-acting antidepressant mechanisms, this is a tool worth having access to.

The differentiation story versus esketamine is compelling but not closed. Esketamine has FDA approval, a defined clinical niche in treatment-resistant depression and acute suicidality, and market infrastructure. Arketamine’s pitch is fewer dissociative effects plus potentially more sustained efficacy, a profile that would matter enormously for outpatient use and treatment adherence. Perception Neuroscience is running phase 2 trials. The preclinical case is solid; the human case is early and needs legs.

Evidence quality is the honest constraint. Hashimoto’s group dominates arketamine’s preclinical literature in a way that echoes the BPC-157 situation: strong signal from one sophisticated lab that needs broader independent replication. Early phase 2 human readouts are encouraging but have not yet been confirmed across multiple independent trial groups. We want to see that before the evidence score moves.

Scheduling matters for access: as a ketamine enantiomer, arketamine carries Schedule III status, which shapes institutional access and researcher infrastructure. Not a dealbreaker for programs already handling ketamine, but it narrows the field. Overall this sits in a genuinely interesting corner of depression pharmacology, and the enantiomeric probe value alone justifies attention from serious NMDA or neuroplasticity programs.

Novelty

60

Mechanism promise

72

In-category differentiation

55

Evidence quality

45

Translational signal

48

Research bench value

65

Rationale Arketamine scores well on mechanism because the enantiomeric differentiation from esketamine is pharmacologically meaningful and the TrkB/BDNF angle is supported by multi-lab work; evidence and translational scores are held back by Hashimoto-lab dominance in the preclinical literature and phase 2 data that lacks cross-group replication.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

R-enantiomer NMDA antagonist

The (R)-enantiomer of ketamine, currently in clinical development for depression with reportedly more sustained antidepressant action and fewer dissociative effects.

Abstract

Arketamine (R-ketamine; CAS 33643-47-9) is the (R)-enantiomer of ketamine, currently in clinical development by Perception Neuroscience and others. The (R)-enantiomer has lower NMDA receptor affinity than the (S)-enantiomer (esketamine), but rodent data suggest more sustained antidepressant effects with reduced dissociative side effects. Phase 2 trials are ongoing. Mechanism includes NMDA modulation but with secondary mechanisms (BDNF/TrkB pathway, mGluR effects) that may underlie the differential clinical profile. Not currently FDA approved.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Astaxanthin

Plain-language summaryIntrigue 58 / 100

Astaxanthin is a red carotenoid antioxidant produced by microalgae and concentrated in salmon, krill, and other marine animals. One of the most potent natural antioxidants, with activity at lipid bilayers where vitamin E acts. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

31/100

Best-in-class carotenoid that nonetheless occupies a boring research corner with modest clinical effect sizes

Look, astaxanthin is legitimately the best carotenoid. The unique keto-carotenoid structure lets it span the phospholipid bilayer rather than just embedding in one leaflet, which gives it better membrane-level antioxidant geometry than beta-carotene, lutein, or zeaxanthin. In head-to-head in vitro radical scavenging assays it beats vitamin E by a significant margin and outperforms vitamin C handily. That part is real chemistry and we dont want to dismiss it.

Here’s the thing though: that story is old. The Haematococcus pluvialis sourcing pipeline is mature, the NRF2 activation and NF-kB suppression mechanisms are thoroughly described, and the compound has been in clinical studies since at least the early 2000s. Nobody in a serious lab is discovering something new about astaxanthin’s mechanism. If you want to run NRF2 pathway studies, sulforaphane is a more pharmacologically specific probe. If you want to study mitochondrial ROS, there are mitochondria-targeted antioxidants like MitoQ or SS-31 with more interesting translational stories.

The clinical evidence is where the score really takes a hit. Most of the human RCT data is industry-funded (AstaReal dominates the published trial landscape), small-N, and producing effect sizes that are statistically present but clinically unimpressive. The skin photoprotection literature has the most consistent signal but the effects are modest. Exercise recovery data is mixed; the studies that show benefit tend to be short, in untrained subjects, and not replicated cleanly outside the funding consortium. Cardiovascular endpoints have some early signal but nothing that would make a cardiologist change their practice.

We think astaxanthin is worth having in a library as a reference compound for carotenoid and membrane antioxidant research, and it has a niche in photoprotection biology. But if a bench investigator came to us asking whether this was worth centering a research program on, we’d steer them elsewhere. The mechanism isnt novel, the differentiation is real but confined to a category that doesnt excite the field anymore, and the human translational signal has been disappointing relative to the preclinical promise that got everyone interested a decade ago.

Sourcing is fine, the AstaReal and Algatechnologies supply chains are clean and well-characterized, and the compound is chemically stable under reasonable storage conditions. It has value in any stack or study where you want a well-characterized oral antioxidant reference, and the BBB penetration is genuine. For a narrow question in carotenoid or skin biology it can still earn its place on the bench. Just not a high-priority standalone target in 2026.

Novelty

20

Mechanism promise

28

In-category differentiation

40

Evidence quality

38

Translational signal

32

Research bench value

28

Rationale Astaxanthin earns genuine differentiation within carotenoids via its membrane-spanning xanthophyll structure and superior ROS quenching, but the antioxidant/NRF2/NF-kB mechanism space is crowded and the clinical signal across all indications remains modest-N and industry-funded. Novelty is low, bench probe value is real but limited, and the overall lands just under the 35 OTC-food/herb cap without needing it.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Carotenoid antioxidant

A red carotenoid pigment from Haematococcus pluvialis algae characterized by potent antioxidant activity and high oral bioavailability.

Abstract

Astaxanthin (CAS 472-61-7; molecular formula C40H52O4; molecular weight 596.84) is a red carotenoid pigment produced by Haematococcus pluvialis (the algal source of most commercial astaxanthin) and present in seafood (salmon, krill, shrimp). The compound is one of the most potent natural antioxidants, exceeding the radical-quenching capacity of vitamin C, vitamin E, and beta-carotene in many in vitro assays. Pharmacology includes direct radical scavenging, NRF2 pathway activation, and anti-inflammatory effects through NF-kB inhibition. Clinical applications include skin photoprotection (modest evidence), cardiovascular function, and exercise recovery. Doses are typically 4 to 12 mg per day.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Citalopram

Plain-language summaryIntrigue 60 / 100

Citalopram (Celexa) is a Danish-developed SSRI from H. Lundbeck, approved in Europe in 1989 and in the US in 1998. It is sold as a 50/50 mix of two mirror-image molecules; only one of those mirror images, the (S) form, actually does the serotonin-blocking work. The other is mostly inert and may even slow the active half down. That insight led Lundbeck to repackage the active half on its own as escitalopram. Citalopram is among the most selective SSRIs for serotonin over other targets, which gives it a clean side-effect profile but does carry a dose-dependent risk of QT interval prolongation on the heart tracing, prompting the FDA to cap the daily dose at 40 mg in 2011. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

47/100

Canonical SERT-selective reference probe; mature mechanism, real but narrow bench utility, superseded clinically by its own enantiomer

Honestly, citalopram earns a place in the library primarily as a pharmacological reference tool rather than as a research frontier. Approved by the FDA in 1998 and in Europe a decade earlier, it’s been around long enough that the mechanism literature is essentially complete: SERT inhibition, the CYP2C19/3A4/2D6 metabolic fingerprint, the QTc story, the downstream 5-HT receptor adaptations. Thats not a knock on the science; it’s just what a mature compound looks like.

What keeps it relevant is the selectivity profile. We’ve seen a lot of SSRIs, but citalopram’s greater-than-1000-fold selectivity for SERT over NET and DAT is genuinely exceptional in the class. If you’re running a mechanistic experiment and need to isolate serotonin transporter pharmacology without confounding adrenergic or dopaminergic effects, citalopram is your reference standard. That selectivity makes it a real probe tool in certain experimental designs, specifically anything probing pure serotonergic neurotransmission where norepinephrine leak would contaminate the read.

Here’s the thing about the racemate though: the (S)-enantiomer carries essentially all SERT activity, while the (R)-enantiomer is largely inactive but may attenuate (S)-enantiomer binding through an allosteric SERT interaction. This makes citalopram mildly interesting from a stereochemistry standpoint. You have a situation where one enantiomer acts as an allosteric modulator of the other’s primary target binding. Some groups have used this as a model system for studying allosteric SERT interactions — that’s about as novel as citalopram gets mechanistically in 2026, and it’s still a modest signal.

The QTc boxed warning issued by the FDA in 2011, which cut the maximum recommended dose from 60 to 40 mg, reflects a hERG channel interaction that any serious SSRI structure-activity program has to account for. For in vitro and cell-based work this is largely irrelevant, but worth knowing if you’re using it as a comparator in cardiac safety assays or ion channel screening.

We don’t think citalopram is worth prioritizing as a primary research target right now. The mechanism is fully characterized, the major clinical questions are answered, and escitalopram has replaced it in most contexts where you specifically want clean SERT activity. Where it remains genuinely useful: as a reference compound in SERT pharmacology work, in structure-activity relationship studies of the phthalane scaffold, and as a racemic SSRI comparator where you actually want the stereospecificity complexity in the assay design. The evidence base is massive and high quality — thats a real strength. But from a novelty and frontier standpoint, you’re not discovering new biology here. Use it as a tool; dont build a primary research program around it.

Novelty

15

Mechanism promise

20

In-category differentiation

42

Evidence quality

88

Translational signal

78

Research bench value

65

Rationale Citalopram’s exceptional SERT selectivity (>1000-fold over NET/DAT) preserves genuine probe value for serotonin transporter biology, but novelty and mechanism scores are floor-level for a fully characterized 1989 compound. The racemic/enantiomer story adds mild mechanistic texture, but the evidence and translational axes reward an approved drug with decades of RCT data, pulling the overall above the purely mature-workhorse range.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Selective serotonin reuptake inhibitor

A racemic phthalane SSRI; the most selective for SERT over NET in clinical use.

Abstract

Citalopram (1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-2-benzofuran-5-carbonitrile; CAS 59729-33-8; molecular formula C20H21FN2O; molecular weight 324.39) is a bicyclic phthalane SSRI developed at H. Lundbeck in Denmark and approved in Europe in 1989 and by the FDA in 1998 under the trade name Celexa. The compound is sold as the racemate; the (S)-enantiomer (escitalopram) accounts for essentially all SERT inhibitory activity, while the (R)-enantiomer is largely inactive but may attenuate the (S)-enantiomer’s binding through allosteric SERT interaction. SERT affinity ((S)-enantiomer): Ki approximately 1 nM; selectivity over NET and DAT exceeds 1000-fold, making citalopram the most selective SSRI in clinical use. Plasma half-life is 33 to 37 hours; hepatic metabolism via CYP2C19, CYP3A4, and CYP2D6 produces minimally active metabolites. The compound is associated with dose-dependent QTc prolongation (FDA boxed warning issued 2011), with the maximum recommended dose reduced from 60 mg to 40 mg as a result. Used as the canonical selective SERT inhibitor in mechanism studies and as a reference compound in SSRI structure-activity work.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Protriptyline

Plain-language summaryIntrigue 41 / 100

Protriptyline (Vivactil) is a secondary-amine tricyclic antidepressant from 1967 with one defining quirk: it is activating rather than sedating, which is the opposite of nearly every other drug in the class. The activating profile comes from preferential norepinephrine pump blockade combined with relatively little antihistamine activity. That made it historically useful for depressed patients with hypersomnia who needed alertness rather than further sedation. It has a long half-life because the liver metabolizes it slowly. Rarely prescribed now, displaced by SNRIs like duloxetine that achieve similar activation with much better tolerability. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

28/100

A 1967-approved TCA with a niche activating profile and almost no modern research frontier

Look, protriptyline is a real drug with a real effect. FDA approved in 1967, still prescribed, pharmacologically coherent. The case for it has always rested on a single differentiating fact: among the tricyclics, it doesn’t sedate. Most of the class leans heavily sedating via H1 blockade, but protriptyline’s relatively low H1 affinity and its NET-dominant profile (Ki around 1.4 nM at the norepinephrine transporter versus roughly 20 nM at SERT) tip the balance toward activation. That matters clinically, particularly in depression complicated by hypersomnia or narcolepsy-related mood disorder. The half-life situation is unusual too: 54 to 92 hours is long even by TCA standards, driven by sluggish CYP2D6 metabolism, which creates both a forgiving dosing window and a complicated clearance picture when coadministering.

Here’s the thing though: none of that is news. The pharmacology was described and characterized decades ago. The NET-over-SERT selectivity angle has been studied far more rigorously in compounds like reboxetine and atomoxetine, and the wakefulness-promoting space now belongs to orexin-pathway agents, modafinil, and the solriamfetol class. If you’re building a research program around activating antidepressant pharmacology, you’re not reaching for protriptyline as your probe. It’s burdened by the full TCA liability profile: muscarinic blockade, sodium channel effects, alpha-1 antagonism, narrow therapeutic index. These are not features that help you isolate a mechanism.

The evidence base is approved-drug-real, which means there’s clinical data going back to the 1960s. But TCA-era trials dont meet modern methodological standards. You’re looking at small, non-blinded, poorly-controlled studies by today’s metrics. Multi-decade literature exists, but a lot of it is descriptive case series or comparisons to other TCAs, not placebo-controlled designs with preregistered endpoints. The narcolepsy-depression comorbidity literature is genuinely thin and mostly observational.

We think the honest bench value here is narrow: if youre specifically studying secondary amine TCA pharmacokinetics, CYP2D6-driven extended half-life effects, or the NET-dominant TCA subclass as a historical reference point, protriptyline has a role. That’s a specific niche, not a broad research priority. For anything involving the activating-antidepressant mechanism today, the tools have moved on. Protriptyline remains useful the way a well-characterized historical reference standard is useful: occasionally, deliberately, and not as a centerpiece of a serious contemporary program.

Novelty

10

Mechanism promise

20

In-category differentiation

25

Evidence quality

45

Translational signal

48

Research bench value

28

Rationale Protriptyline scores low across novelty and differentiation because it is a mid-century TCA with no mechanism surprise and no serious modern competition driving renewed investigation; its higher NET selectivity is real but bupropion and modern SNRIs have absorbed that research territory entirely. Evidence quality and translational signal get modest credit for FDA approval and clear clinical effect, but neither dimension rescues the compound’s place in a contemporary research priority stack.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Tricyclic antidepressant (secondary amine, activating)

A secondary amine TCA distinguished by activating rather than sedating subjective profile; useful in depression with hypersomnia.

Abstract

Protriptyline (N-methyl-3-(5H-dibenzo[a,d]cyclohepten-5-yl)propan-1-amine; CAS 438-60-8; molecular formula C19H21N; molecular weight 263.38) is a secondary amine TCA approved by the FDA in 1967 under the trade name Vivactil. Distinct among TCAs for an activating subjective profile that contrasts with the sedation typical of the class; the activating profile is attributed to relatively higher NET-to-SERT selectivity and reduced H1 antagonism. NET Ki approximately 1.4 nM, SERT Ki approximately 20 nM. Plasma half-life is exceptionally long (54 to 92 hours) owing to slow CYP2D6 metabolism. The activating profile makes protriptyline a niche choice for depression with prominent hypersomnia or fatigue, including narcolepsy-associated depression where the wakefulness-promoting effect is therapeutic. Off-target activity is otherwise typical of secondary amine TCAs: muscarinic, mild H1, alpha-1, and sodium channel block. Approved for major depressive disorder; rarely first-line today owing to TCA-class limitations. Used as a reference compound for activating TCA pharmacology and in narcolepsy-related comorbidity research.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Gabapentin

Plain-language summaryIntrigue 65 / 100

Gabapentin (Neurontin) is the older sibling of pregabalin from Parke-Davis, FDA-approved in 1993, and it works by the same mechanism: binding the alpha-2-delta subunit of voltage-gated calcium channels, with no actual effect on GABA receptors despite the misleading name. The big practical difference from pregabalin is dose-response: gabapentin’s intestinal absorption saturates, so doubling the dose does not double the blood level, which makes high doses inefficient. Approved for postherpetic neuralgia and partial seizures, with massive off-label use for anxiety, sleep, alcohol withdrawal, restless legs, and chronic pain. The Pfizer off-label marketing campaign that drove its sales in the 1990s was the subject of a landmark fraud settlement. Abuse potential is real but lower than pregabalin’s. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

41/100

Mature alpha-2-delta ligand superseded by pregabalin clinically; still a clean reference probe for VGCC subunit biology

Look, gabapentin has been in the literature since 1993 and the research community has had more than three decades to extract novelty from it. For a bench scientist asking what deserves time right now, this isn’t the answer. But thats not the same as saying it has no place in the library.

The mechanism is genuinely specific: gabapentin binds the alpha-2-delta-1 subunit of voltage-gated calcium channels with a Ki of roughly 80 nM. Despite the name, it has no meaningful activity at GABA-A or GABA-B receptors. What it does is reduce presynaptic calcium influx and downstream neurotransmitter release at sensitized synapses. That mechanism is clean and validated across hundreds of independent studies. The problem is that everyone already knows this. The pharmacology has been squeezed for novelty and the returns have diminished sharply.

What really sinks it as a frontier research target is the pharmacokinetics combined with the availability of better tools. Gabapentin relies on a saturable intestinal transporter for absorption. Bioavailability can hit 80 percent at low doses and collapse to around 27 percent at 1600 mg, producing nonlinear dose-response and frustrating individual variability in clinical work. Pregabalin solved that transporter saturation problem and achieved linear absorption, which is a large part of why it has displaced gabapentin in most new pharmacological programs. If you need a selective alpha-2-delta-1 ligand for a clean assay, you have options and some are meaningfully better.

The clinical evidence base is real and substantial. Multiple large phase 3 trials, FDA approval for postherpetic neuralgia and partial-onset seizures, and an extensive off-label literature covering neuropathic pain broadly, anxiety, alcohol withdrawal, and restless legs syndrome. We don’t find the off-label literature particularly compelling as a research signal. Much of it is small-N, inconsistent in methodology, and complicated by the well-documented history of off-label promotion litigation against Pfizer. The clean translational signal sits in the original approved indications.

As a probe, gabapentin still earns its keep in a narrow context. If you’re studying alpha-2-delta-1 subunit trafficking, presynaptic calcium dynamics in dorsal root ganglia, or the molecular basis of central sensitization, gabapentin is the reference ligand. The literature density means any result you generate is immediately contextualizable. For that specific utility, we actually think it belongs in the library.

What we don’t think is that it qualifies as interesting research territory. The real mechanistic questions in this space are being asked with more selective or structurally novel tools. Gabapentin functions like a positive control: necessary to have, not exciting to use. A score of 41 reflects exactly that balance, strong evidence and clinical history dragging up a compound with very little research novelty left in the tank.

Novelty

20

Mechanism promise

28

In-category differentiation

22

Evidence quality

72

Translational signal

68

Research bench value

55

Rationale Gabapentin scores low on novelty and differentiation because it is a 1993 approval with a well-understood mechanism and a clearly superior successor in most contexts; evidence and translational scores are pulled up by its approved-drug pedigree and large clinical dataset, while bench value is rescued by its canonical role as the alpha-2-delta-1 probe in seizure and pain pharmacology programs.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

GABA analog calcium channel ligand

A GABA analog binding the alpha-2-delta subunit of voltage-gated calcium channels; the structural and clinical predecessor to pregabalin.

Abstract

Gabapentin (1-(aminomethyl)cyclohexaneacetic acid; CAS 60142-96-3; molecular formula C9H17NO2; molecular weight 171.24) is a GABA analog developed at Parke-Davis (Pfizer) in the 1980s and approved by the FDA in 1993 under the trade name Neurontin. Mechanism mirrors pregabalin: binding to the alpha-2-delta-1 subunit of voltage-gated calcium channels (Ki approximately 80 nM, weaker than pregabalin), reducing presynaptic neurotransmitter release. No direct GABA receptor activity. Plasma half-life is 5 to 7 hours. Distinguished from pregabalin by saturable absorption: oral bioavailability ranges from 80 percent at 100 mg to 27 percent at 1600 mg, producing nonlinear dose-response and unpredictable individual responses at higher doses. Approved for postherpetic neuralgia and partial-onset seizures (adjunctive); off-label use is extensive (anxiety, alcohol withdrawal, restless legs syndrome, hot flashes, hiccups, neuropathic pain of all causes, migraine prophylaxis). The compound has been the subject of extensive off-label promotion litigation and is now scheduled in some US states reflecting abuse potential. Used as the canonical alpha-2-delta-1 calcium channel ligand and a reference compound in seizure pharmacology.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
S-23

Plain-language summaryIntrigue 52 / 100

S-23 is a SARM developed by GTx that stands out as a full androgen receptor agonist (rather than the partial agonism of most SARMs), producing the strongest hormonal suppression in the class. Preclinical studies showed reversible suppression of sperm production in male rodents, and S-23 was investigated as a candidate component of a male hormonal contraceptive when paired with a progestin. It also shows the typical SARM profile of muscle and bone activity with reduced prostate effect. No human clinical trials have been published, so almost everything known about safety in people comes from anecdote. WADA-banned. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundSingle-lab provenance

37/100

A preclinical-only full AR agonist SARM with a genuinely niche contraceptive angle but zero human signal

Look, S-23 is an interesting edge case in the SARM landscape, and we want to be precise about why it’s interesting before we explain why it doesn’t score very high. Most SARMs are partial AR agonists by design; partial agonism is the whole trick that lets them claim tissue selectivity without full androgenic load. S-23 breaks from that pattern. It’s a full agonist at the androgen receptor, which means its HPG suppression is substantially more aggressive than anything else in the class. That distinction matters. Researchers studying male hormonal contraception have been circling the idea of a combined SARM-plus-progestin regimen for over a decade, and S-23 became one of the more studied candidates for that specific use case in rodent models precisely because of how reliably it shuts down spermatogenesis.

The problem is the evidence base is almost entirely preclinical, and a large fraction of what exists originated from the GTx research pipeline or closely affiliated academic groups. Replication outside that orbit is limited. There are no published human clinical trials at this writing, which isn’t automatically disqualifying for a research compound, but it does mean the translational signal is essentially absent. You have a plausible mechanism and a real rodent phenotype. What you don’t have is any confirmation that the rodent pharmacology translates to human HPG dynamics in the way the contraceptive story requires.

The bench utility is real but narrow. If you’re running an androgen receptor biology program, S-23 is a legitimate probe for studying full vs. partial agonism at the AR, and the HPG suppression phenotype gives you a clean endpoint to work with in small animal models. Thats a specific utility and we don’t want to dismiss it. But it’s not a broadly indispensable tool the way rapamycin is for mTOR work. It’s a specialist instrument for a specific set of questions.

What we dont like: the recreational use context creates a messy signal-to-noise problem for serious investigators, the recovery profile post-exposure is the worst in class, and the compound sits in a regulatory gray zone that complicates institutional research approvals. The SARM class is also crowded enough that the full-agonist angle, while genuinely differentiating, hasn’t attracted the multi-lab attention it would need to build a real evidence stack. Honestly, S-23 would be a more compelling library entry if even one well-designed Phase 1 contraception trial had been completed. As it stands, it’s a preclinical compound with an interesting story and a thin dossier.

Novelty

38

Mechanism promise

42

In-category differentiation

50

Evidence quality

22

Translational signal

18

Research bench value

45

Rationale S-23 earns modest differentiation within the SARM class by being the only full AR agonist with a documented contraceptive research track record in rodents, but the complete absence of human clinical data and the likely narrow origination of most preclinical work (GTx-adjacent) keeps evidence and translational scores very low. The SARM class itself is mature enough that novelty is constrained even with the HPG-suppression angle.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Selective androgen receptor modulator

A non-steroidal SARM with reported male contraceptive activity in preclinical studies; full agonist at the AR with strong HPG suppression.

Abstract

S-23 (CAS 1010396-29-8; molecular formula C18H13ClF4N2O3; molecular weight 416.76) is a non-steroidal SARM developed by GTx. Distinct among SARMs as a full AR agonist (rather than a partial agonist), producing more pronounced HPG axis suppression alongside strong anabolic activity. Preclinical studies in male rodents demonstrated reversible spermatogenesis suppression; the compound was investigated as a candidate for male hormonal contraception via combined progestin and SARM regimen. Tissue-selective effects: full agonism in muscle and bone with reduced prostate activity relative to testosterone. The strong HPG suppression makes S-23 the most stringent SARM in terms of post-cycle endocrine recovery. No human clinical trials at this writing. Used recreationally despite the suppressive profile.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Cetrorelix

Plain-language summaryIntrigue 55 / 100

Cetrorelix (Cetrotide) is a GnRH receptor blocker (rather than an agonist), approved in 2000 and used in IVF protocols to prevent the premature LH surge that would otherwise disrupt egg retrieval timing. Unlike GnRH agonists, which cause an initial flare followed by suppression, cetrorelix produces immediate dose-dependent suppression of LH and FSH with no flare. That allows brief, on-demand control of the reproductive axis without the one-to-two-week desensitization delay required of agonists. Standard IVF use is a daily 0.25 mg injection from stimulation day 5 until the trigger shot. Generally well tolerated with minor injection-site reactions. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

42/100

Canonical IVF GnRH antagonist with solid clinical evidence but mature mechanism and eroded class differentiation

Look, cetrorelix is a twenty-five year old approved drug doing exactly what it was designed to do. The GnRH antagonist mechanism here is competitive inhibition at pituitary GnRH receptors: you block the receptor, LH and FSH drop immediately, no flare. That immediate suppression without the 7-to-10-day desensitization period required by GnRH agonists like leuprolide was the whole differentiating story at approval. In 2000 it was genuinely cleaner than anything else in the category. In 2026, the story is thinner.

The evidence base is solid and we wont pretend otherwise. Multiple phase 3 trials underpinned FDA approval, the Cetrotide pivotal data replicated across European and North American centers, and the IVF literature since has been extensive. But this is a narrow clinical corridor. The signal, preventing premature LH surge in controlled ovarian stimulation, is specific enough that it doesnt port easily into other research programs. Off-label use in benign prostatic hyperplasia and prostate cancer leverages the same testosterone-flare-avoidance logic, but in those spaces, degarelix has largely taken over for the extended-suppression indication and relugolix now handles the oral route.

Here’s the thing: the GnRH antagonist class has moved on. Small-molecule oral antagonists, elagolix (endometriosis, uterine fibroids), relugolix (prostate cancer, uterine fibroids), linzagolix, have expanded the pharmacological space considerably. Cetrorelix is a subcutaneous decapeptide competing against pill-form competitors with longer duration, broader approved indications, and more current literature. On differentiation grounds its position has eroded to canonical-reference-only.

What we like: the mechanism is clean, the PK is predictable at roughly 60-hour half-life subcutaneously, and if you’re running HPG axis dynamics in a controlled ovarian stimulation model this is the standard reference tool. The flare-free profile keeps it cleaner than leuprolide for acute suppression study designs.

What we don’t like: single-receptor competitive antagonism, no multi-target angle, no novel biology. The research frontier in GnRH biology has largely shifted upstream to kisspeptin-neurokinin-dynorphin neuron work and the GPR54 axis. Cetrorelix probes the downstream output of the HPG generator, not the generator itself. For investigators trying to understand hypothalamic regulation, thats a real limitation. There’s no significant open question that cetrorelix uniquely answers in 2026. Solid workhorse for reproductive endocrinology labs, genuinely uninteresting to anyone outside that specific program.

Novelty

22

Mechanism promise

28

In-category differentiation

30

Evidence quality

70

Translational signal

70

Research bench value

45

Rationale Cetrorelix scores high on evidence and translational signal because it’s an FDA-approved drug with multiple phase 3 RCTs, but novelty and mechanism promise are low given 25 years of clinical use and straightforward single-receptor competitive antagonism. Differentiation has eroded as oral GnRH antagonists and degarelix have claimed adjacent indications.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Synthetic GnRH antagonist

A synthetic GnRH receptor antagonist used in IVF protocols to prevent premature LH surge; immediate suppression without the agonist flare.

Abstract

Cetrorelix (Ac-D-2-Nal-D-Cpa-D-Pal-Ser-Tyr-D-Cit-Leu-Arg-Pro-D-Ala-NH2; CAS 120287-85-6; molecular formula C70H92ClN17O14; molecular weight 1431.06) is a synthetic GnRH receptor antagonist decapeptide developed at ASTA Medica and approved by the FDA in 2000 under the trade name Cetrotide. Mechanism: competitive antagonism at pituitary GnRH receptors, producing immediate dose-dependent suppression of LH and FSH without the initial flare characteristic of GnRH agonists. The antagonist mechanism allows brief, on-demand HPG suppression without the 7-to-10-day desensitization period required for GnRH agonist effect. Plasma half-life is approximately 60 hours after subcutaneous dosing. Approved for prevention of premature LH surge in controlled ovarian stimulation for IVF; the daily dose protocol begins on stimulation day 5 and continues through hCG trigger. Off-label use in benign prostatic hyperplasia and prostate cancer (where the avoidance of testosterone flare is clinically valuable). Used as the canonical GnRH antagonist in IVF research.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Cabergoline

Plain-language summaryIntrigue 56 / 100

Cabergoline, sold as Dostinex, is a long-acting ergot dopamine agonist with a half-life measured in days rather than hours, allowing once or twice weekly dosing. It is the first-line drug for prolactinomas (pituitary tumors that secrete the hormone prolactin), where it normalizes hormone levels and shrinks tumors in most patients. The principal safety concern is heart valve damage from chronic 5-HT2B receptor activation, which has been documented at high cumulative doses used in Parkinson disease. At the lower doses used for prolactinomas the valve risk appears small but is not zero, and patients on long-term therapy receive periodic echocardiograms. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

48/100

Gold-standard prolactinoma agent with settled mechanism and limited frontier research appeal

Look, cabergoline is one of those compounds where the clinical story is essentially settled and the research frontier has moved on. FDA approved in 1996, it displaced bromocriptine as the first-line agent for hyperprolactinemia and prolactinoma on every metric that matters: efficacy, tolerability, dosing convenience from that 60-to-100-hour half-life, and a cleaner receptor selectivity profile. Within its approved indication, cabergoline is about as clear a category winner as you’ll find in endocrinology. Thats where the differentiation score comes from.

The problem, from a research library standpoint, is that the interesting questions have already been answered. D2 receptor agonism is thoroughly understood pharmacology. The prolactin-lowering mechanism is textbook. The 5-HT2B partial agonism and its valvulopathy risk at Parkinson-range cumulative doses is documented, quantified, and clinically contextualized. There is no mechanistic mystery here, no new receptor biology to untangle, no signal that tells a serious investigator something genuinely new is waiting.

The off-label angles that occasionally surface — cocaine dependence, reward-circuit modulation, sexual function — have been explored in small studies for years without producing compelling, replicated human signal. We think the cocaine dependence rationale is actually sound: D2 receptor downregulation is a real feature of stimulant use disorder, and restoring D2 tone with a clean long-acting agonist is a plausible pharmacological intervention. But the clinical trial record has been modest and inconsistent across groups, and that keeps the translational score honest even for that angle.

What we genuinely like about cabergoline for bench work is its utility as the canonical long-acting D2 reference agonist. If your research program touches dopamine receptor dynamics, prolactin as a neuroendocrine readout, or D2-mediated feedback loops in reward or reproductive biology, cabergoline is a clean, well-characterized probe. Oral bioavailability is solid, half-life is predictable, and D2 selectivity over non-dopaminergic receptors is meaningfully better than bromocriptine. For those specific programs, it earns its place on the shelf.

Honestly, thats about as far as the excitement goes. Cabergoline has been used clinically for three decades and the evidence base reflects that maturity — but maturity cuts both ways. Well-replicated findings in a settled indication don’t move the frontier. For labs working directly on prolactin biology or D2 receptor pharmacology, it’s a genuinely valuable reference tool. For most other research programs, the literature is closed and there isn’t much discovery space left.

Novelty

22

Mechanism promise

30

In-category differentiation

58

Evidence quality

68

Translational signal

72

Research bench value

48

Rationale Cabergoline scores high on differentiation and translational signal because it is definitively best-in-class for its approved indication, but novelty and mechanism scores drag the overall down hard — it’s a 30-year-old single-receptor ergoline with no meaningful mechanistic surprises and a research conversation that’s largely closed. The off-label angles (cocaine dependence, reward modulation) have produced modest, inconsistent human data that don’t rescue the novelty picture.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Long-acting ergoline D2 dopamine agonist

A long-acting ergoline D2 dopamine receptor agonist; first-line for prolactinoma and used off-label for Parkinson disease maintenance.

Abstract

Cabergoline ((6aR,9R,10aS)-N-[3-(dimethylamino)propyl]-N-[(ethylamino)carbonyl]-7-(2-propenyl)-ergoline-8-beta-carboxamide; CAS 81409-90-7; molecular formula C26H37N5O2; molecular weight 451.61) is a long-acting ergoline D2 dopamine receptor agonist developed at Pharmacia and approved by the FDA in 1996 under the trade name Dostinex. The compound has high D2 affinity (Ki approximately 0.6 nM) with minimal activity at non-dopaminergic receptors compared to bromocriptine. Plasma half-life is approximately 60 to 100 hours, the longest of any clinical dopamine agonist, supporting twice-weekly oral dosing. Approved for hyperprolactinemia (prolactinoma, idiopathic hyperprolactinemia). Off-label use in Parkinson disease (less common since the introduction of non-ergot agonists), cocaine dependence, and dopamine-deficiency syndromes. The 5-HT2B partial agonism produces a recognized but rare risk of cardiac valvulopathy at high cumulative doses (Parkinson dose ranges); the lower prolactinoma doses are not associated with this risk. Used as the canonical long-acting ergoline dopamine agonist.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Buprenorphine

Plain-language summaryIntrigue 76 / 100

Buprenorphine is a semi-synthetic opioid with an unusual receptor profile that has made it the cornerstone of medication-assisted treatment for opioid use disorder. As a high-affinity partial mu-opioid agonist it activates the receptor enough to suppress withdrawal and craving but with a built-in ceiling on respiratory depression that makes overdose much less likely than with full agonists. Its kappa antagonism may contribute to mood benefit. The combination with naloxone (Suboxone) discourages injection abuse because naloxone is not orally active but blocks opioid effects if injected. Approved for OUD in the US in 2002, it has saved many lives. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundFederally scheduled

57/100

Mature Schedule III MAT agent with a genuinely interesting KOR antagonism angle but limited frontier research appeal

Look, buprenorphine is one of the most clinically important opioid-system compounds ever developed, and that’s precisely why it scores where it does here. The evidence base for OUD treatment is enormous: multiple FDA approvals, decades of real-world data, a well-characterized safety margin built on mu partial agonism. But clinically essential and interesting research target right now are two different questions, and this rubric is asking the second one.

The pharmacology is genuinely interesting. What buprenorphine does is unusual: high-affinity mu binding (Ki approximately 0.2 nM) with roughly 30 percent intrinsic activity, which produces analgesia and craving suppression without the respiratory depression ceiling you get from full agonists. And then layered on top, concurrent kappa-opioid antagonism and ORL1 partial agonism. That’s a legitimately complex pharmacological profile. The KOR antagonism is the angle that keeps serious investigators paying attention. KOR activation is strongly implicated in dysphoria and stress-driven depression, so blocking it while partially activating mu has real mechanistic rationale as an antidepressant approach. Some early clinical data support this, though effect sizes are modest and the literature is still maturing.

Here’s the problem with using buprenorphine as the probe for that question: the mu signal is always in the room. Selective KOR antagonists like aticapant or navacaprant give you cleaner experimental handles on the kappa axis in isolation. With buprenorphine, any behavioral or molecular readout you get in a model is a convolution of at least three receptor activities. Thats not fatal for all research designs, but it limits interpretability in a way that matters for mechanistic work.

From a bench value standpoint, it remains a useful reference tool. If your program involves opioid receptor partial agonism dynamics, tolerance and ceiling-effect modeling, or mu/kappa crosstalk, buprenorphine is the canonical standard. We credit that. The Schedule III status creates meaningful practical friction for investigators who aren’t already operating in a controlled-substance-licensed environment, which is worth acknowledging honestly.

What we don’t see is a strong case for building a new research program around buprenorphine in 2025 unless that program is specifically about OUD pharmacotherapy refinement, KOR biology in mood disorders where selectivity constraints are acceptable, or receptor pharmacology where a mu partial agonist reference is genuinely needed. Important compound, belongs in the library, but isnt where the frontier is.

Novelty

22

Mechanism promise

60

In-category differentiation

58

Evidence quality

78

Translational signal

72

Research bench value

65

Rationale Buprenorphine’s clinical evidence base for OUD is massive but that’s not what drives research scores; novelty is low given a 1981 approval and decades of trodden literature. The kappa-opioid antagonism angle for treatment-resistant depression is the one live research thread, but it’s mechanistically muddied by concurrent mu partial agonism, and cleaner selective KOR antagonists exist as investigational probes. Schedule III cap of 75 does not bind since the calculated score falls below it.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Mu-opioid partial agonist + kappa-opioid antagonist

A semi-synthetic mu-opioid partial agonist with kappa-opioid antagonism; the primary medication-assisted treatment for opioid use disorder.

Abstract

Buprenorphine ((2S,6R,7R,14S)-17-cyclopropylmethyl-7-[(S)-1-hydroxy-1,2,2-trimethylpropyl]-6-methoxy-4,5-epoxy-6,14-ethano-morphinan-3-ol; CAS 52485-79-7; molecular formula C29H41NO4; molecular weight 467.65) is a semi-synthetic thebaine-derived mu-opioid partial agonist with concurrent kappa-opioid antagonist and ORL1 (nociceptin receptor) partial agonist activity. Originally approved by the FDA in 1981 as an analgesic; reformulated and approved in 2002 (Subutex, Suboxone) for opioid use disorder. Mu-opioid affinity is high (Ki approximately 0.2 nM) with intrinsic activity approximately 30 percent (partial agonism); the partial agonism produces a ceiling effect on respiratory depression and euphoria, distinguishing buprenorphine safety profile from full agonists like fentanyl or morphine. Long plasma half-life (24 to 60 hours) supports once-daily or less-frequent dosing. Suboxone formulation includes naloxone (a mu antagonist with poor sublingual bioavailability) to deter intravenous misuse. Approved for opioid use disorder and chronic pain (transdermal Butrans). The kappa-opioid antagonism is being investigated for treatment-resistant depression. Used as the canonical mu-opioid partial agonist in addiction medicine.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
Synephrine

Plain-language summaryIntrigue 42 / 100

Synephrine is an alkaloid from bitter orange peel (Citrus aurantium) that became a bestselling thermogenic supplement after the FDA banned ephedra in 2004. Structurally it resembles phenylephrine, but it preferentially activates beta-3 adrenergic receptors over the alpha-1 and beta-1 receptors that drive blood pressure changes. The beta-3 activity stimulates fat oxidation and thermogenesis in adipose tissue, which is the basis of the weight-loss claims. Clinical evidence for actual fat loss is modest at best. Plasma half-life is about two hours. Used as a beta-3-preferring adrenergic agonist in metabolic research and as the workhorse stimulant ingredient in many over-the-counter weight-loss formulas. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

27/100

Outcompeted beta-3 agonist with modest evidence, useful only as a reference standard

Look, synephrine got its moment in the sun after the 2004 ephedra ban, and that moment is over. It’s a phenylethanolamine alkaloid from bitter orange with a preference for beta-3 adrenergic receptors over the alpha-1 and beta-1 activity that got ephedra pulled in the first place. That selectivity profile was genuinely interesting in the supplement context circa 2005. In 2026, it’s a textbook example of a compound the research frontier has lapped.

The mechanism isn’t wrong. Beta-3 adrenergic receptors are real targets expressed in adipose tissue and other metabolic compartments, and agonism there does drive thermogenesis via cAMP-mediated lipolysis. The problem is synephrine does this modestly, and we now have far better tools for studying this receptor system. Mirabegron, a pharmaceutical-grade selective beta-3 agonist with solid PK data and actual receptor selectivity characterization, is the obvious bench choice for any serious beta-3 adrenergic research program. Synephrine’s selectivity is partial at best, its potency is low, and the signal-to-noise ratio for controlled experiments is poor compared to purpose-built probes.

The clinical literature reflects exactly this. Multiple small trials have looked at synephrine for thermogenesis and body weight endpoints. The honest read: effect sizes are small, the data isnt compelling by any rigorous standard, and no serious phase 2 or 3 program is chasing it. The broader adrenergic and metabolic pharmacology space has moved to GLP-1 biology, beta-3 selective drugs with actual selectivity data, and mitochondrial targets with novel mechanisms. Synephrine is watching from the parking lot.

What we don’t like about it as a research compound is the ceiling problem. Even a clean, well-powered synephrine study in 2026 just confirms what’s already known about a mechanism that’s already been characterized in depth. The evidence base is decent by supplement standards (multiple small clinical studies, some methodological replication), but that bar is low and the information value per experiment is low. A landmark paper is not coming out of this compound.

The only scenario where it earns bench time today is narrow: comparative pharmacology where you need a weak beta-3 agonist as a reference alongside something more interesting, or structure-activity work in the phenylethanolamine chemical series. That’s a limited application, and most programs would reach for mirabegron or a custom ligand instead. We score it where it belongs: well-understood, outcompeted, modest evidence, and limited utility for anything a frontier investigator would care about right now.

Novelty

20

Mechanism promise

28

In-category differentiation

22

Evidence quality

38

Translational signal

32

Research bench value

25

Rationale Synephrine’s beta-3 adrenergic selectivity was genuinely interesting post-ephedra but is now thoroughly characterized and outcompeted by purpose-built pharmaceutical probes like mirabegron; clinical evidence exists but effect sizes are small, replication is weak by serious trial standards, and the information yield per experiment is too low for anything on the current research frontier.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Adrenergic agonist (bitter orange alkaloid)

p-Synephrine; a phenylethanolamine alkaloid from Citrus aurantium (bitter orange); a beta-3 adrenergic-preferring agonist used as a thermogenic supplement.

Abstract

Synephrine (p-synephrine, (R/S)-4-[1-hydroxy-2-(methylamino)ethyl]phenol; CAS 94-07-5; molecular formula C9H13NO2; molecular weight 167.21) is a phenylethanolamine alkaloid from Citrus aurantium (bitter orange) and other Citrus species. The compound is a structural analog of phenylephrine (the m-isomer) with a beta-3 adrenergic preference (relative to alpha-1 and beta-1) that distinguishes its pharmacology. The beta-3 activity drives thermogenesis and fat oxidation in adipose tissue, the basis for its supplement use as a weight-loss aid. Synephrine became prominent after the 2004 FDA ban on ephedra (which contained the more potent ephedrine). Clinical evidence for weight-loss effect is modest. Plasma half-life is approximately 2 hours. Used as a beta-3-preferring adrenergic agonist in metabolic research and supplement formulations.

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May 9, 2026

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