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methylphenidate, ethylphenidate, isopropylphenidate +1 moremethylphenidate, ethylphenidate, isopropylphenidate, cocaine show less
Methylnaphthidate
HDMP-28 (methylnaphthidate) is a synthetic stimulant of the substituted phenidate class. It is a structural analog of methylphenidate, several times more potent at the DAT and with added SERT activity.[1] It blocks the recycling of dopamine, norepinephrine, and serotonin in the brain, amplifying all three signals simultaneously.[2]
Methylnaphthidate (HDMP-28) is a synthetic stimulant of the substituted phenidate class. It is a structural analog of methylphenidate, distinguished by several-fold greater potency at the DAT and the addition of meaningful serotonin reuptake activity.[1] Methylnaphthidate is a triple monoamine reuptake inhibitor, producing its effects by blocking the recapture of dopamine, norepinephrine, and serotonin at their respective transporters.[2]
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methylphenidate, ethylphenidate, isopropylphenidate +1 moremethylphenidate, ethylphenidate, isopropylphenidate, cocaine show less
Synthesized in 2001 by Deutsch et al. as a research tool for studying cocaine abuse treatment, methylnaphthidate was never developed for medical use.[3] It appeared on research chemical markets around 2014–2015, following earlier phenidate derivatives such as ethylphenidate.[1] It is now explicitly controlled in the United Kingdom, Canada, Germany, and Switzerland, while remaining unscheduled at the federal level in the United States.
Subjective effects include stimulation, wakefulness, appetite suppression, and mood elevation. The experience resembles Methylphenidate but may carry a warmer emotional tone — attributed to serotonin activity, though this has not been confirmed in controlled study.[4] Anxiety, restlessness, and low mood in the hours after use are characteristic unwanted effects.
Psychological dependence potential is high — animal studies show reinforcement equal to cocaine[5] — and the cardiovascular system bears the main acute toxicity burden. Serotonin activity adds interaction risks absent from Methylphenidate; combining with serotonin-raising drugs or MAOIs can trigger a life-threatening overheating and seizure response.[2] No human studies exist — all safety knowledge comes from animal data, transporter binding studies, and analogy to related phenidates.[6][7]
History[edit]
Discovery
Deutsch et al. first synthesized methylnaphthidate in 2001 as part of a series of methylphenidate analogs designed to study cocaine abuse treatment.[3] The naphthyl substitution proved several times more potent than the parent compound at the DAT. The compound was never pursued for therapeutic development — it existed purely as a pharmacological research tool.
Research chemical emergence
Despite appearing in the scientific literature since 2001, HDMP-28 did not surface on research chemical markets until approximately 2014–2015[1][4] — following earlier phenidate derivatives like ethylphenidate, which had appeared circa 2011–2013.
Regulatory and forensic attention
Several countries moved to control methylnaphthidate following its appearance on NPS markets — the United Kingdom scheduled it as Class B in 2017, and Germany listed it under its Novel Psychoactive Substances Act in 2016.[2]
The designation HDMP-28 comes from the compound's position in the Deutsch et al. synthesis series — the 28th in a line of high-dopamine-transporter-affinity methylphenidate analogs. The most consequential early behavioral study — Lile et al.'s 2003 rhesus monkey work — established that HDMP-28 was reinforced as readily as cocaine,[5] a finding that shaped its reputation as a compound warranting particular caution.
Chemistry[edit]
Structural class
Methylnaphthidate belongs to the substituted phenidate class — a family of piperidine-based compounds structurally derived from methylphenidate.[3] The key modification is replacement of a phenyl ring with a larger naphthyl (two-ring aromatic) group. This expands the aromatic surface, increases lipophilicity, and introduces SERT affinity absent in the parent compound.
Molecular identity
| Molecular formula | C₁₈H₂₁NO₂ |
| Molecular weight | 283.4 g/mol |
Methylnaphthidate is broken down primarily by ester hydrolysis — the same metabolic process that converts Methylphenidate to an inactive form.[1] The larger naphthyl ring is expected to slow this breakdown, giving methylnaphthidate a longer duration than the parent compound.[6]
Pharmacology[edit]
Mechanism of action
Methylnaphthidate blocks the recycling of dopamine, norepinephrine, and serotonin at their respective transporters — keeping all three neurotransmitters active in the synapse longer than they would otherwise be.[2][1]
The naphthyl ring changes the compound's transporter selectivity. Where methylphenidate acts mainly on dopamine and norepinephrine transporters, methylnaphthidate also binds the SERT at comparable strength — placing it pharmacologically closer to cocaine.[2][8] Norepinephrine transporter activity is inferred from class membership, not directly confirmed for this compound.safety citation needed
Pharmacokinetics
No pharmacokinetic studies have been conducted in humans. Community reports suggest oral onset within 1–10 minutes, with effects lasting 2–5 hours; insufflation produces faster onset and shorter duration.[4] The compound is longer-acting than Methylphenidate, attributed to slower ester hydrolysis driven by the naphthyl substitution.[6]
Neuroscience[edit]
Where it acts
As a potent DAT inhibitor, methylnaphthidate raises dopamine in the brain's reward circuit — the pathway running from the brainstem to the nucleus accumbens that drives motivation and reinforcement.[3] Animal studies show it maintained self-administration behavior as readily as cocaine, a direct measure of reinforcing potency.[5]
Why it matters
Dopamine drives compulsive wanting — the motivation to seek a substance — more than it drives pleasure. Methylnaphthidate's strong dopamine blockade amplifies this wanting, consistent with the compulsive redosing tendency reported for phenidate-class stimulants. Elevated serotonin may add a mood-modulating dimension, though whether this produces perceptible effects at typical doses remains untested.
Key unanswered questions include: how quickly methylnaphthidate occupies the dopamine transporter in the human brain — a kinetic property strongly predictive of abuse liability; whether SERT activity produces detectable subjective effects at typical doses; and whether repeated exposure causes lasting changes in dopamine receptor density, as occurs with other stimulants.
Subjective Effects[edit]
Methylnaphthidate brings sharp focus, elevated mood, and driven energy — the kind of stimulation that narrows attention to a task and makes fatigue disappear. There may be a quality of warmth absent from other phenidates, though whether that reflects genuine serotonin activity or observer variability isn't settled.[4]
It sits pharmacologically between methylphenidate and cocaine — more potent than the former, with a serotonin component that makes it unusual among phenidates. Reports describe the experience as qualitatively similar to methylphenidate, with possible differences in hedonic warmth.[4]
Synthesized in 2001 by Deutsch et al. as a pharmacological probe for cocaine abuse treatment research, methylnaphthidate was never pursued for therapeutic development.[3] It appeared on novel psychoactive substance markets around 2014–2015, following earlier phenidate derivatives such as ethylphenidate.[1] It is explicitly controlled in several countries including the United Kingdom, Canada, and Germany, while remaining unscheduled at the US federal level.
Subjective effects include stimulation, wakefulness, appetite suppression, and mood elevation. The experience is reported as qualitatively similar to methylphenidate but with a possible warmer hedonic character — a difference attributed to its SERT activity, though this remains unconfirmed by controlled study.[4] Anxiety, restlessness, and post-stimulation dysphoria are anticipated unsought effects.
Psychological dependence potential is high — non-human primate studies show reinforcing efficacy equal to cocaine — while physical dependence appears low by class analogy.[5] The primary acute risk is cardiovascular, driven by potent catecholaminergic activity, and the compound's serotonin activity introduces interaction dangers absent from methylphenidate.[2] No human studies of any kind have been conducted; all safety assessments derive from transporter binding data, a single non-human primate behavioral study, and structural analogy.[6][7]
History[edit]
Discovery
Deutsch, Ye, Shi, Liu, and Schweri first synthesized methylnaphthidate in 2001 as part of a systematic series of methylphenidate analogs designed to probe structure-activity relationships relevant to cocaine abuse treatment.[3] The naphthyl substitution proved considerably more potent than the parent compound at the DAT, establishing the foundational pharmacological interest. Davies, Panmand, and Bhatt independently synthesized naphthyl methylphenidate analogs in 2004 using a different synthetic approach, further characterizing the stereochemistry-dependent transporter selectivity of the series.[8]
Research chemical emergence
Despite its presence in pharmacological literature since 2001, HDMP-28 did not appear on research chemical markets until approximately 2014–2015.[1][4] Its emergence followed the earlier market introduction of related phenidate derivatives — ethylphenidate and isopropylphenidate — which had appeared circa 2011–2013. No therapeutic or clinical development program has ever been initiated; the compound was synthesized exclusively as a pharmacological tool.
Regulatory and forensic attention
Several jurisdictions moved to control methylnaphthidate following its appearance on NPS markets — the United Kingdom scheduled it as Class B in 2017, and Germany listed it under its Novel Psychoactive Substances Act in 2016.[2] The compound attracted forensic interest when Ajeebsanu et al. conducted a comprehensive metabolic investigation in 2024, focused on doping detection in equestrian sports rather than human pharmacology.[6]
The designation HDMP-28 originates from the compound's position in the Deutsch et al. synthesis series — it is the 28th compound in the HDMP (high dopamine transporter affinity methylphenidate analog) numbering. On research chemical markets, the compound circulates under both "HDMP-28" and "methylnaphthidate," with the latter name describing its structural relationship to methylphenidate more transparently. The most consequential early behavioral study — Lile et al.'s 2003 rhesus monkey self-administration work — established that HDMP-28 was reinforced as readily as cocaine, a finding that would later inform its reputation among research chemical users as a compound warranting particular caution.[5]
Chemistry[edit]
Structural class
Methylnaphthidate belongs to the substituted phenidate class — a family of piperidine-based monoamine reuptake inhibitors derived from the methylphenidate scaffold. The defining structural modification is replacement of the phenyl ring at the α-carbon with a 2-naphthyl (β-naphthalene) group, expanding the aromatic surface area and increasing lipophilicity.[3] This larger aromatic system confers measurable SERT affinity absent in the parent compound.
A published characterization of the compound as belonging to "the phenyltropane class"[6] is incorrect — methylnaphthidate does not share the tropane ring system of cocaine or the phenyltropane series.
Molecular identity
| Molecular formula | C₁₈H₂₁NO₂ |
| Molecular weight | 283.4 g/mol |
The core scaffold consists of a piperidine ring bearing a methyl ester at the α-carbon, with the 2-naphthyl aromatic system extending from the same position. The methyl ester is the site of metabolic hydrolysis, analogous to the ester cleavage that converts methylphenidate to ritalinic acid.[1]
Stereochemistry
Methylnaphthidate possesses two stereocenters — the α-carbon bearing the naphthyl group and the C-2 position of the piperidine ring — producing four stereoisomers grouped into threo and erythro diastereomeric pairs. HDMP-28 refers specifically to the (αR,2R)-threo enantiomer, the pharmacologically active form with preferential DAT affinity.[3]
The erythro diastereomers display a markedly different profile, binding the serotonin transporter with high selectivity rather than the dopamine transporter.[8] This stereochemical dependence of transporter selectivity parallels the well-characterized threo/erythro pharmacology of methylphenidate itself. A related pyrrolidine-ring variant (HDMP-29) produces no reinforcement in non-human primate self-administration, demonstrating the critical role of both ring size and stereochemistry in the behavioral pharmacology of this series.[5]
Physical properties
No published data on melting point, solubility, partition coefficient, or solid-state stability of methylnaphthidate have been identified in the peer-reviewed literature. The increased aromatic surface area of the naphthyl ring predicts higher lipophilicity than methylphenidate, consistent with the enhanced transporter binding potency, but no experimental measurement has been reported.
Pharmacology[edit]
Mechanism of action
Methylnaphthidate acts as a reuptake inhibitor at all three major monoamine transporters — dopamine (DAT), norepinephrine (NET), and serotonin (SERT).[2][1] By blocking these transporters, the compound prevents the recycling of dopamine, norepinephrine, and serotonin from the synapse, increasing the concentration and signaling duration of all three neurotransmitters.
The naphthyl ring substitution fundamentally alters the transporter selectivity profile relative to methylphenidate. Where methylphenidate is highly selective for dopamine and norepinephrine transporters with negligible serotonin activity, methylnaphthidate binds both DAT and SERT at comparable potencies — positioning it pharmacologically closer to cocaine in its monoamine transporter profile.[2] Jones et al. confirmed that the naphthyl methylphenidate counterpart acts at both human DAT and human SERT "rather uniquely relative to other members" of the phenidate series.[9]
Norepinephrine transporter inhibition is inferred from the compound's membership in the phenidate class, where NET activity is a consistent pharmacological feature.[10] No published binding data confirm this directly for methylnaphthidate.safety citation needed
The NCATS Inxight Drugs database describes methylnaphthidate as "a potent dopamine reuptake inhibitor, with several times the potency of methylphenidate and a short duration of action",[1] while Ajeebsanu et al. characterize it as surpassing methylphenidate "in both dopamine reuptake inhibition and half-life".[6]
Pharmacokinetics
No controlled pharmacokinetic studies of methylnaphthidate have been conducted in humans. All pharmacokinetic parameters — peak plasma concentration, bioavailability, distribution, and elimination half-life — remain uncharacterized in humans.
The compound's half-life is described as longer than that of methylphenidate.[6] The naphthyl substitution is expected to slow the rate of ester hydrolysis — the dominant metabolic pathway for methylphenidate — thereby extending the elimination half-life.
Ajeebsanu et al. identified 31 metabolites using equine liver microsomes and a fungal model: 22 Phase I metabolites (produced via ring hydroxylation, hydrogenation, and ester hydrolysis to a ritalinic acid structural analog) and 9 Phase II metabolites (glucuronic acid conjugates).[6] Human enzyme involvement has not been characterized; methylphenidate is predominantly metabolized by carboxylesterase CES1, and HDMP-28 likely follows a similar but not identical pathway.inferred
Community-reported onset times suggest 1–10 minutes orally and 3–6 minutes via insufflation, with total duration of 2–5 hours oral and 90–180 minutes insufflated. One early self-report described 5–7 hours oral duration at 34.8 mg,[4] suggesting the upper bound of community-reported oral ranges may underestimate actual duration at higher doses.
Neuroscience[edit]
Where it acts
As a potent DAT inhibitor, methylnaphthidate elevates synaptic dopamine in the mesolimbic pathway — the circuit running from the ventral tegmental area to the nucleus accumbens that mediates reward, motivation, and reinforcement.[3] This dopaminergic potentiation underlies the reinforcing efficacy demonstrated in non-human primates, where HDMP-28 maintained self-administration behavior equivalent to cocaine.[5] The compound's SERT activity introduces a second pharmacological dimension: elevated synaptic serotonin may modulate mood regulation and prefrontal cortical function in ways that differentiate the subjective character of methylnaphthidate from purely catecholaminergic stimulants.
Why it matters
The Robinson and Berridge incentive salience model distinguishes dopaminergic "wanting" (motivational drive) from "liking" (hedonic pleasure). Methylnaphthidate's potent dopamine transporter inhibition predicts strong enhancement of wanting — consistent with the compulsive redosing tendency reported for phenidate-class stimulants. Whether the serotonin component partially modulates hedonic valence, introducing a warmer emotional tone absent from methylphenidate, remains untested. Repeated stimulant exposure can produce behavioral sensitization — enhanced locomotor and reinforcing effects — through mesolimbic dopamine pathways, a phenomenon that may underlie escalating patterns of use.
Key unanswered questions include: how rapidly methylnaphthidate occupies the dopamine transporter in the human brain — a kinetic property strongly predictive of abuse liability; whether the serotonin transporter activity produces detectable subjective effects (mood elevation, prosocial warmth) at typical doses or remains pharmacologically silent; and whether repeated exposure produces lasting changes in dopamine receptor density or neuroplasticity markers, as occurs with other stimulants.
Subjective Effects[edit]
The experience of methylnaphthidate is shaped by its triple monoamine reuptake inhibitor profile — predominantly dopaminergic and noradrenergic stimulation layered with a serotonergic dimension absent from most phenidate-class compounds. Route of administration substantially alters the experience: insufflation compresses the temporal course and intensifies onset, while oral administration produces more gradual, extended stimulation. Whether the compound's SERT activity introduces entactogen-adjacent mood qualities distinguishable from the clean functional stimulation of purely catecholaminergic phenidates remains unestablished.
Pharmacologically, methylnaphthidate sits between methylphenidate and cocaine in its transporter selectivity profile. Limited anecdotal reports suggest qualitative similarity to methylphenidate with possible differences in hedonic warmth, though the evidence base is insufficient to characterize these distinctions with confidence.[4]
Effect Grid
Clear stimulant effects dominate — sustained focus enhancement, motivation enhancement, and thought acceleration are pronounced. Appetite suppression becomes significant. The SERT component may contribute mild mood elevation with possible entactogen-adjacent warmth not typical of purely catecholaminergic phenidates. Time alteration — typically perceived acceleration — may be noticed. Oral doses range 15–30 mg; insufflated 8–14 mg.
Cardiovascular effects become noticeable: elevated heart rate, mild abnormal heartbeat awareness, and vasoconstriction. Bruxism, dry mouth, and dehydration sensation emerge. Pupil dilation is likely. Excessive sweating may occur with physical activity.
Insomnia is expected if dosed within 6–8 hours of intended sleep. The offset phase brings cognitive fatigue, mild irritability, and reduced motivation as dopaminergic rebound begins.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Visual acuity enhancement · Auditory enhancement
Dry mouth · Insomnia · Muscle tension · Body high · Heart rate perception changes · Physical fatigue · Restlessness · Dehydration sensation · Excessive sweating · Nausea · Bruxism · Headache · Respiratory stimulation · Sexual arousal enhancement · Spontaneous body sensations · Tactile euphoria · Motor control enhancement · Dizziness · Tingling / electric sensations · Trembling · Vomiting
Heart rate perception changes · Physical fatigue · Restlessness · Dehydration sensation · Excessive sweating · Nausea · Bruxism · Headache · Respiratory stimulation · Sexual arousal enhancement · Spontaneous body sensations · Tactile euphoria · Motor control enhancement · Dizziness · Tingling / electric sensations · Trembling · Vomiting
Analysis enhancement · Information processing enhancement · Motivation enhancement · Cognitive fatigue · Immersion enhancement · Pattern recognition enhancement · Thought organization · Memory enhancement · Aesthetic enhancement · Cognitive dysphoria · Cognitive flexibility · Motivation suppression · Novelty enhancement · Creativity enhancement · Language enhancement · Cognitive impairment · Confusion · Thought connectivity · Thought disorganization · Thought loops
Immersion enhancement · Pattern recognition enhancement · Thought organization · Memory enhancement · Aesthetic enhancement · Cognitive dysphoria · Cognitive flexibility · Motivation suppression · Novelty enhancement · Creativity enhancement · Language enhancement · Cognitive impairment · Confusion · Thought connectivity · Thought disorganization · Thought loops
Irritability · Dysphoria · Emotional enhancement · Emotional lability · Emotional suppression · Mania
Emotional lability · Emotional suppression
Flow state · Sociability enhancement · Social connection · Self-control enhancement · Disinhibition · Emotional susceptibility
Disinhibition · Emotional susceptibility
Timeline
Initial awareness of mild alertness shift; subtle stimulation emerging below threshold of clear identification.
Building stimulation with focus sharpening and appetite suppression beginning. Cardiovascular activation becomes perceptible.
Full stimulant effects — sustained focus, motivation enhancement, wakefulness, and possible mood elevation from SERT activity. Cardiovascular effects at maximum.
Gradual diminution of stimulation. Residual wakefulness and appetite suppression persist. Cognitive fatigue begins emerging.
Residual fatigue, mild dysphoria, and appetite returning. Difficulty sleeping may persist for several hours.
⚠ Do not drive or operate machinery until fully rested — cognitive fatigue and residual stimulant effects may impair reaction time.
Safety[edit]
- Acute toxicity
- Moderate
- Chronic toxicity
- Moderate
- Withdrawal
- Mild
- Tolerance buildup
- moderate
- Tolerance reset
- 10 days
- Physical
- Negligible
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- Moderate
- Cross-tol.
- methylphenidate · ethylphenidate · isopropylphenidate
Toxicity
Acute toxicity
No human fatalities or lethal dose data exist for methylnaphthidate.[7] By pharmacological class, high doses carry risk of dangerous blood pressure elevation, rapid heart rate, irregular heart rhythm, and overheating — particularly with physical exertion or in combination with serotonergic drugs.[9][10]
Chronic toxicity
No chronic toxicity data exist for methylnaphthidate. For the phenidate class broadly, chronic harms include cardiovascular strain, psychological dependence, and cognitive disruption.[11] All assessments for this compound specifically are inferred from class analogy.safety citation needed
Psychological risks
Compulsive redosing is the primary behavioral risk — animal models place reinforcing efficacy equal to cocaine.[5] At high doses, anxiety, paranoia, and restlessness are expected; prolonged heavy use can produce hallucinations and disordered thinking, though no such cases have been reported for this compound.
A low-mood rebound effect typically follows use — fatigue, depression, irritability, and cognitive fatigue as dopamine levels recover over hours.
Tolerance and dependence
Tolerance develops through dopamine receptor adaptation and is expected to follow a moderate time course, consistent with the phenidate class.inferred Physical dependence is low — no phenidate derivative has produced a withdrawal requiring medical management.inferred
Psychological dependence potential is moderate to high, based on animal reinforcement data showing efficacy equivalent to cocaine.[5] Withdrawal may bring low mood, excess sleep, appetite enhancement, and thought deceleration.
Drug Interactions
The triple monoamine reuptake inhibitor profile creates interaction risks across three neurotransmitter systems. Serotonin transporter activity adds dangers not present with methylphenidate.
Serotonergic interactions
MAOIs block serotonin breakdown entirely; adding methylnaphthidate's serotonin reuptake blockade on top can cause a life-threatening overheating and seizure response.safety citation needed MDMA and tramadol are similarly hazardous — both raise serotonin through separate mechanisms, and the combined burden risks extreme serotonergic overload, dangerous overheating, and cardiovascular crisis.[9][10]
Dopaminergic and sympathomimetic interactions
Cocaine combined with methylnaphthidate produces additive monoamine elevation and extreme cardiovascular strain — dangerous blood pressure elevation, vessel constriction, and irregular heart rhythm.safety citation needed
Alcohol
Co-administration with alcohol may convert the methyl ester to an ethyl ester through an enzymatic interaction, by analogy with the well-characterized methylphenidate-ethanol reaction.[12][13][14] This conversion has not been confirmed for methylnaphthidate.inferred
All interaction severity ratings for methylnaphthidate are inferred from pharmacological mechanism and class-level evidence. No substance-specific adverse event case reports confirm any interaction. The tramadol, MDMA, and cocaine interactions are classified as potentially lethal based on mechanistic analysis, not clinical observation.
Contraindications
5 knownAll contraindications are inferred from pharmacological class. No methylnaphthidate-specific data exist.
- MAOI use: Absolute contraindication. Risk of dangerous blood pressure crisis and serotonin syndrome.safety citation needed
- Pre-existing heart conditions: Absolute contraindication. Blood pressure elevation, rapid heart rate, and vessel constriction pose acute risk of cardiac events and stroke.safety citation needed
- History of psychosis or bipolar disorder: Relative contraindication. Potent dopaminergic stimulation can trigger or worsen psychotic and manic episodes.inferred
- Concurrent serotonergic medication: Relative contraindication. SSRIs, SNRIs, triptans, and similar drugs combined with serotonin reuptake blockade increase serotonin toxicity risk.safety citation needed
- Seizure disorders: Relative contraindication. Stimulant-class seizure threshold lowering is expected.inferred
Harm Reduction[edit]
Forms & Identification
Methylnaphthidate circulates exclusively through research chemical vendors as a powder or crystalline solid. No pharmaceutical formulations exist. Batch purity and identity cannot be assumed — test every acquisition with appropriate reagent kits, and note that a positive result confirms only the compound class, not purity or dose accuracy.
Volumetric dosing — dissolving a weighed quantity in a measured volume of liquid and dosing by volume — is strongly preferred over weighing individual powder doses. The active dose range is narrow enough that milligram-scale imprecision meaningfully affects both the experience and the risk.
Guidelines
- Test every batch with appropriate reagent kits before use
- Use volumetric dosing rather than weighing individual doses of powder
- Start with a low dose and wait for full onset before considering redosing — oral onset may take up to 10 minutes
- Set a firm limit on total dose and number of redoses before the session begins
- Keep the compound out of arm's reach during the session to reduce impulsive redosing
- Avoid insufflation if possible — the compressed, intensified onset increases reinforcing potential and cardiovascular strain
- Ensure access to water and a cool environment
- Do not use on consecutive days; allow at least 48 hours between sessions
- Do not combine with other stimulants, serotonergic substances, or alcohol
Set & Setting
With reinforcing efficacy comparable to cocaine in animal models, methylnaphthidate warrants careful attention to the psychological context of use. A clear intention and a predetermined endpoint reduce the risk of compulsive redosing — the primary behavioral hazard of potent dopamine reuptake inhibitors.
Avoid hot environments, sustained physical exertion, and dehydration. All amplify cardiovascular strain from catecholaminergic stimulation.
Aftercare & integration. The post-stimulation period typically brings low mood, fatigue, irritability, and difficulty concentrating — a predictable dopamine rebound effect, not a sign of lasting damage.
Prioritize sleep, hydration, and regular meals in the 24–48 hours following use. Avoid caffeine and other stimulants during the comedown. If low mood persists beyond 72 hours, or cravings feel difficult to manage, speak with a healthcare provider or counselor.
Recovery & Support
The reinforcing efficacy data suggest regular use carries meaningful risk of developing a compulsive pattern. If use has escalated in frequency or dose, or attempts to stop have been unsuccessful, structured support is appropriate.
Resources include SAMHSA's National Helpline (1-800-662-4357, US), SMART Recovery, and local addiction services. Stimulant use disorders respond to cognitive-behavioral therapy and contingency management; no pharmacological treatment is established, making behavioral approaches the primary recovery pathway.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: chest pain, severe headache, seizure, loss of consciousness, extreme agitation with confusion, or body temperature hot to the touch through clothing all indicate a medical emergency rather than ordinary discomfort.
- 1. Call emergency services immediately if any of the above signs are present
- 2. Place the person in a cool, quiet environment while waiting for help
- 3. If unconscious but breathing, place in the recovery position (on their side, airway clear)
- 4. Do not restrain an agitated person unless they are at immediate risk of self-harm
- 5. Do not induce vomiting
- 6. Monitor breathing continuously until help arrives
Tell the dispatcher: the substance name (methylnaphthidate or HDMP-28), the approximate amount taken, the time of last dose, the route of administration, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
No reversal agent exists for stimulant overdose.
Legal Status[edit]
As of May 2026, methylnaphthidate is not uniformly scheduled internationally — its legal status varies significantly by jurisdiction.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Not federally scheduled | Not listed under DEA Schedule II (which covers methylphenidate). Federal Analogue Act (21 U.S.C. § 813) may apply when intended for human consumption. New Mexico schedules it at state level[2] |
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Scheduled 31 May 2017 under broad phenidate NPS scheduling[2] |
| Canada | Schedule III (Controlled Drugs and Substances Act) | Controlled substance[2] |
| Germany | Controlled (NpSG) | Listed under Neue-psychoaktive-Stoffe-Gesetz since 26 November 2016[2] |
| Switzerland | Illegal (Verzeichnis E) | Listed since December 2015[2] |
| Turkey | Illegal | Controlled since February 2016[2] |
| Australia | Unconfirmed | Requires verification against TGA ARTG databasecitation needed |
| New Zealand | Unconfirmed | Requires verification against Misuse of Drugs Actcitation needed |
Analog act considerations
In the United States, methylnaphthidate's structural similarity to the Schedule II substance methylphenidate may bring it under the Federal Analogue Act (21 U.S.C. § 813) when intended for human consumption. No such prosecution has been publicly reported.
Legal status changes frequently and varies significantly by jurisdiction. This information reflects known status as of May 2026 and is not legal advice.
Safety[edit]
- Acute toxicity
- Moderate
- Chronic toxicity
- Moderate
- Withdrawal
- Mild
- Tolerance buildup
- moderate
- Tolerance reset
- 10 days
- Physical
- Negligible
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- Moderate
- Cross-tol.
- methylphenidate · ethylphenidate · isopropylphenidate
Toxicity
Acute toxicity
No lethal dose data for methylnaphthidate exist in any species, and no human fatalities attributed to the compound have been identified in the peer-reviewed literature or NPS adverse event databases.[7]
By pharmacological class, the acute risks of a potent triple monoamine reuptake inhibitor include dangerous blood pressure elevation, rapid heart rate, irregular heart rhythm, and vasoconstriction.[11][12] Overheating is a risk, particularly with physical exertion or serotonergic co-exposure. The SERT activity adds a risk dimension absent from methylphenidate, including potential serotonin syndrome at high doses or in combination with other serotonergic agents.safety citation needed
Chronic toxicity
No chronic toxicity data exist for methylnaphthidate. Carlier et al. noted that chronic harms of methylphenidate analogs broadly include cardiovascular strain, potential for psychological dependence, and cognitive dysregulation.[13] Whether HDMP-28's greater DAT potency or serotonin activity modifies chronic risk relative to the parent compound is unknown.
All toxicity assessments for this compound are inferred from pharmacological class and structural analogy with methylphenidate. No primary source confirms any specific toxicity value.safety citation needed
Psychological risks
No controlled studies have assessed the psychological risk profile of methylnaphthidate. By class analogy with other potent dopamine reuptake inhibitors, the following risks are anticipated:
- Acute psychological distress: anxiety, agitation, paranoia, and restlessness at high doses, consistent with excessive stimulation.
- Stimulant psychosis: Prolonged high-dose use of dopamine reuptake inhibitors can precipitate psychotic episodes characterized by paranoid thinking, hallucinations, and disorganized behavior. No such cases have been reported for methylnaphthidate, likely reflecting low prevalence of use rather than absence of risk.
- Post-acute dysphoria: Dopaminergic rebound effect following cessation produces depressed mood, depression, irritability, fatigue, and cognitive fatigue.
- Compulsive redosing: The reinforcing efficacy equal to cocaine in non-human primate models[5] predicts significant compulsive redosing risk.
Tolerance and dependence
No tolerance or dependence data specific to methylnaphthidate exist. All assessments below are based on structural analogy with methylphenidate and pharmacological class.
Tolerance to euphoric and stimulant effects develops through dopamine downregulation and compensatory transporter upregulation. The rate has not been characterized but is expected to follow a moderate time course consistent with the phenidate class.inferred
Physical dependence is low to negligible for the phenidate class. No withdrawal requiring medical management has been described for any phenidate derivative.inferred
Psychological dependence potential is moderate to high, inferred directly from non-human primate data showing reinforcing efficacy equivalent to cocaine.[5] This is the strongest available predictor of abuse liability.
Withdrawal has not been characterized. By class analogy, stimulant withdrawal — low mood, excessive sleep, appetite enhancement, thought deceleration — would be expected following sustained use.
Drug Interactions
The compound's triple monoamine reuptake inhibitor profile creates interaction risk across three neurotransmitter systems. The serotonin transporter activity adds interaction dimensions not present with Methylphenidate.
Serotonergic interactions
Tramadol represents a particularly dangerous combination — its own serotonin and norepinephrine reuptake inhibition, combined with methylnaphthidate's serotonin transporter blockade, produces additive serotonergic stimulation compounded by seizure threshold reduction from both agents.[11][12]
MDMA, a potent serotonin releaser, combined with serotonin reuptake blockade from methylnaphthidate, produces extreme serotonergic stimulation with risk of serotonin syndrome, dangerous overheating, and cardiovascular crisis.[11]
Monoamine oxidase inhibitors (MAOIs) present the most extreme serotonergic interaction risk — complete blockade of serotonin breakdown combined with reuptake inhibition can produce fatal serotonin syndrome.safety citation needed
Dopaminergic and sympathomimetic interactions
Cocaine combined with methylnaphthidate produces additive monoamine elevation and extreme cardiovascular strain — blood vessel constriction, dangerous blood pressure elevation, rapid heart rate, and irregular heart rhythm.safety citation needed
Alcohol
Co-administration with ethanol may produce conversion of the methyl ester to an ethyl ester (ethylnaphthidate) through enzyme interaction, by analogy with the well-characterized methylphenidate-ethanol interaction.[14][15][16] This conversion has not been confirmed for methylnaphthidate.inferred
All interaction severity ratings for methylnaphthidate are inferred from pharmacological mechanism and class-level evidence. No substance-specific adverse event case reports confirm any interaction. The tramadol, MDMA, and cocaine interactions are classified as potentially lethal based on mechanistic analysis, not clinical observation.
Contraindications
5 knownAll contraindications are inferred from pharmacological class. No methylnaphthidate-specific contraindication data exist.
- Monoamine oxidase inhibitor (MAOI) use: Absolute contraindication. Risk of dangerous blood pressure crisis and serotonin syndrome.safety citation needed
- Pre-existing heart conditions: Absolute contraindication. Blood pressure elevation, rapid heart rate, and blood vessel constriction pose acute risk of cardiac events and stroke in individuals with compromised cardiovascular function.safety citation needed
- History of psychosis or bipolar disorder: Relative contraindication. Potent dopaminergic stimulation can precipitate or worsen psychotic episodes and manic states.inferred
- Concurrent serotonergic medication: Relative contraindication. SSRIs, SNRIs, triptans, and other serotonergic agents combined with serotonin reuptake inhibition from methylnaphthidate increase serotonin toxicity risk.safety citation needed
- Seizure disorders: Relative contraindication. Stimulant-class seizure threshold reduction is expected.inferred
Harm Reduction[edit]
Forms & Identification
Methylnaphthidate circulates exclusively through research chemical vendors, typically as a powder or crystalline solid. No pharmaceutical formulations exist. Because the compound has never been manufactured under any quality standard, batch purity and identity cannot be assumed — reagent testing is essential for every acquisition, and even positive reagent results confirm only the presence of a compound class, not purity or dose accuracy.
Volumetric dosing from a prepared solution is strongly recommended over attempting to weigh individual doses of powder. The active dose range is low enough that imprecision from a milligram scale can meaningfully alter the experience and risk profile.
Guidelines
- Test every batch with appropriate reagent kits before use
- Use volumetric dosing rather than weighing individual doses of powder
- Start with a low dose and wait for full onset before considering redosing — oral onset may take up to 10 minutes
- Set a firm limit on total dose and number of redoses before the session begins
- Keep the compound out of arm's reach during the session to reduce impulsive redosing
- Avoid insufflation if possible — the compressed, intensified onset increases reinforcing potential and cardiovascular strain
- Ensure access to water and a cool environment
- Do not use on consecutive days; allow at least 48 hours between sessions
- Do not combine with other stimulants, serotonergic substances, or alcohol
Set & Setting
As a stimulant with reinforcing efficacy comparable to cocaine in animal models, methylnaphthidate warrants particular attention to the psychological context of use. A clear intention for the session — whether functional or recreational — and a predetermined endpoint reduce the risk of compulsive redosing, which is the primary behavioral hazard of potent dopamine reuptake inhibitors.
Physical environment matters for cardiovascular safety: avoid hot environments, sustained physical exertion, and dehydration, all of which amplify the cardiovascular strain from catecholaminergic stimulation.
Aftercare & integration. The post-stimulation period following methylnaphthidate use typically involves a rebound effect phase — low mood, fatigue, irritability, and difficulty concentrating — driven by temporary dopamine depletion. This is a predictable pharmacological consequence, not a sign of lasting damage.
Prioritize sleep, hydration, and regular meals in the 24–48 hours following use. Avoid caffeine and other stimulants during the comedown, as they mask fatigue without addressing the underlying neurochemical rebound. If low mood persists beyond 72 hours, or if cravings to redose feel difficult to manage, consider speaking with a healthcare provider or counselor.
Recovery & Support
The reinforcing efficacy data for methylnaphthidate suggest that regular use carries meaningful risk of developing a compulsive pattern. If use has escalated in frequency or dose, or if attempts to stop have been unsuccessful, structured support is appropriate.
Resources include SAMHSA's National Helpline (1-800-662-4357, US), SMART Recovery, and local addiction services. Stimulant use disorders respond to cognitive-behavioral therapy and contingency management; no pharmacological treatment for stimulant dependence is established, making behavioral approaches the primary recovery pathway.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: chest pain, severe headache, seizure, loss of consciousness, extreme agitation with confusion, or body temperature hot to the touch through clothing all indicate a medical emergency rather than ordinary discomfort.
- 1. Call emergency services immediately if any of the above signs are present
- 2. Place the person in a cool, quiet environment while waiting for help
- 3. If unconscious but breathing, place in the recovery position (on their side, airway clear)
- 4. Do not restrain an agitated person unless they are at immediate risk of self-harm
- 5. Do not induce vomiting
- 6. Monitor breathing continuously until help arrives
Tell the dispatcher: the substance name (methylnaphthidate or HDMP-28), the approximate amount taken, the time of last dose, the route of administration, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
No reversal agent exists for stimulant overdose.
Legal Status[edit]
As of May 2026, methylnaphthidate is not uniformly scheduled under international drug control conventions and occupies a fragmented regulatory landscape. It is explicitly controlled in the United Kingdom, Canada, Germany, Switzerland, and Turkey, while remaining unscheduled at the federal level in the United States.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Not federally scheduled | Not listed under DEA Schedule II (which covers methylphenidate). Federal Analogue Act (21 U.S.C. § 813) may apply when intended for human consumption. New Mexico schedules it at state level[2] |
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Scheduled 31 May 2017 under broad phenidate NPS scheduling[2] |
| Canada | Schedule III (Controlled Drugs and Substances Act) | Controlled substance[2] |
| Germany | Controlled (NpSG) | Listed under Neue-psychoaktive-Stoffe-Gesetz since 26 November 2016[2] |
| Switzerland | Illegal (Verzeichnis E) | Listed since December 2015[2] |
| Turkey | Illegal | Controlled since February 2016[2] |
| Australia | Unconfirmed | Requires verification against TGA ARTG databasecitation needed |
| New Zealand | Unconfirmed | Requires verification against Misuse of Drugs Actcitation needed |
Analog act considerations
In the United States, methylnaphthidate's structural relationship to the Schedule II substance methylphenidate renders it potentially subject to prosecution under the Federal Analogue Act (21 U.S.C. § 813), which treats substantially similar compounds as controlled substance analogs when intended for human consumption. The compound's pharmacological similarity to methylphenidate — acting on the same transporter targets with greater potency — strengthens the basis for analog prosecution, though no such case has been publicly reported.
Frequently asked questions
What is Methylnaphthidate?
Methylnaphthidate is a substituted phenidate stimulant and triple monoamine reuptake inhibitor derived from methylphenidate. First synthesized in 2001 as a pharmacological probe, it emerged on research-chemical markets circa 2014–2015 with no therapeutic development.
How long does Methylnaphthidate last?
Total duration by route of administration — Oral: 2 – 5 hours; Insufflated: 90 – 180 min. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for Methylnaphthidate?
Psychedex publishes a dosage table for Methylnaphthidate on this page covering these routes of administration: oral, insufflated. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with Methylnaphthidate?
The highest-severity documented interactions for Methylnaphthidate: Ibogaine (Lethal), Alpha-2 adrenergic receptor antagonist (Dangerous), Amphetamines (Dangerous), Anticholinergics (Dangerous), Antipsychotics (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is Methylnaphthidate addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for Methylnaphthidate: tolerance builds moderate; full reset takes 10 days; cross-tolerance develops with methylphenidate, ethylphenidate, isopropylphenidate, cocaine. See the article's dependence and safety sections for recorded dependence data.
experience reports
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First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
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- [3] ^abcdDeutsch HM, Ye X, Shi Q, Liu Z, Schweri MM (2001) Synthesis and pharmacology of site specific cocaine abuse treatment agents: a new synthetic methodology for methylphenidate analogs based on the Blaise reaction — European Journal of Medicinal Chemistry PMID:11461755
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- [6] ^abcMuhammed Ajeebsanu M, Subhahar MB, Karakka Kal AK, Philip M, Perwad Z, Karatt TK, Graiban FM, Joseph M, Jose SV (2024) Comprehensive metabolic investigation of dopamine reuptake inhibitor HDMP-28 in equine liver microsomes and Cunninghamella elegans for doping control — Drug Testing and Analysis doi:10.1002/dta.3642
references
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- [6] ^abcdefMuhammed Ajeebsanu M, Subhahar MB, Karakka Kal AK, Philip M, Perwad Z, Karatt TK, Graiban FM, Joseph M, Jose SV (2024) Comprehensive metabolic investigation of dopamine reuptake inhibitor HDMP-28 in equine liver microsomes and Cunninghamella elegans for doping control — Drug Testing and Analysis doi:10.1002/dta.3642