Stimulant drug
HDMP-28 or methylnaphthidate is a stimulant drug of the piperidine and naphthylaminopropane groups, closely related to methylphenidate (Ritalin), but with the benzene ring replaced by naphthalene. It is a potent dopamine reuptake inhibitor, with several times the potency of methylphenidate and a short duration of action, and is a structural isomer of another potent dopamine reuptake inhibitor, N,O-Dimethyl-4-(2-naphthyl)piperidine-3-carboxylate. It has been sold as a designer drug since around 2015.
Most of the TMP analogs of HDMP-28 have SERT Ki values in the range >10,000 and so are selective for dopamine and noradrenaline reuptake, with little or no effect on serotonin. HDMP-28 has high affinity to SERT, and so behaves as a triple reuptake inhibitor.
D.R. is the discrimination ratio = [3H]DA÷[3H]CFT.
A low D.R. indicates more addictive, whereas a high D.R. indicates low propensity for self-administration.
Safety at a Glance
High Risk- It is strongly recommended that one use harm reduction practices when using this drug.
- MDMA - The neurotoxic effects of MDMA may be increased when combined with other stimulants.
- Toxicity: The toxicity and long-term health effects of recreational methylnaphthidate use do not seem to have been studied in a...
- Dangerous with: 25x-NBOH, 25x-NBOMe, Atropa belladonna, Cocaine (+5 more)
- Overdose risk: Stimulant overdose from Methylnaphthidate is a medical emergency primarily involving cardiovascul...
If someone is in crisis, call 911 or Poison Control: 1-800-222-1222
Dosage
oral
insufflated
Duration
oral
Total: 2 hrs – 5 hrsinsufflated
Total: 1.5 hrs – 3 hrsHow It Feels
Methylnaphthidate introduces itself with the same clinical precision as other members of the phenidate family. Within twenty to forty minutes of oral ingestion, attention sharpens and the ambient noise of unfocused thought begins to quiet. There is no dramatic onset, no rush, no euphoria. Instead, there is a subtle but measurable improvement in the ability to concentrate, prioritize, and follow through on tasks. The world does not change. The mind's capacity to engage with it simply improves.
At the peak, reached around one to two hours in, the experience is one of clean, focused productivity. Working memory functions well. The ability to sustain attention on a single task for extended periods is enhanced. There is a mild increase in motivation, a quiet sense that tasks are worth completing and that the energy to complete them is available. The cognitive enhancement is moderate, falling somewhere between the gentler racetams and the more aggressive amphetamines. Socially, there may be a slight increase in verbal fluency and confidence, but the compound is fundamentally nonsocial in its character.
Physical effects are minimal and predictable. Mild tachycardia, reduced appetite, and slight dryness of the mouth constitute the bulk of the somatic experience. The body remains comfortable and functional throughout. There is no significant jaw tension, no vasoconstriction of note, and no temperature dysregulation. This physical gentleness is part of what makes methylnaphthidate suitable for its intended use as a functional cognitive enhancer.
The duration is moderate, with primary effects lasting three to five hours. The offset is gradual, a slow dimming of the enhanced focus rather than a sudden drop. There is no significant rebound or crash. Appetite returns, fatigue creeps back in at its normal pace, and sleep is achievable within a reasonable timeframe. The morning after is unremarkable. As with other functional phenidates, the experience is defined not by what it adds to consciousness but by what it quietly removes: the friction between intention and execution, the inertia that makes starting difficult, the drift that makes sustaining attention a chore.
Subjective Effects
The effects listed below are based on the Subjective Effect Index (SEI), an open research literature based on anecdotal reports and personal analyses. They should be viewed with a healthy degree of skepticism. These effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects.
Physical Effects
Physical(11)
- Appetite suppression— A distinct decrease in hunger and desire to eat, ranging from reduced interest in food to complete d...
- Dehydration— A state of insufficient bodily hydration manifesting as persistent thirst, dry mouth, and physical d...
- Increased blood pressure— Increased blood pressure (hypertension) is an elevation of arterial pressure above the normal 120/80...
- Increased heart rate— A noticeable acceleration of heartbeat that can range from a subtle awareness of one's pulse to a fo...
- Respiratory depression— A dangerous slowing and shallowing of breathing that can progress from barely noticeable reductions ...
- Seizure— Uncontrolled brain electrical activity causing convulsions and loss of consciousness -- a life-threa...
- Serotonin syndrome— Serotonin syndrome is a potentially fatal medical emergency caused by excessive serotonergic activit...
- Stimulation— A state of heightened physical and mental energy characterized by increased wakefulness, elevated mo...
- Teeth grinding— An involuntary clenching and rhythmic grinding of the jaw muscles, known clinically as bruxism, that...
- Temperature regulation disruption— Impaired thermoregulation causing unpredictable fluctuations between feeling hot and cold, with risk...
- Vasoconstriction— A narrowing of blood vessels throughout the body that produces sensations of cold extremities, tingl...
Cognitive & Perceptual Effects
Cognitive(18)
- Amnesia— A complete or partial inability to form new memories or recall existing ones during and after substa...
- Analysis enhancement— A perceived improvement in one's ability to logically deconstruct concepts, recognize patterns, and ...
- Anxiety— Intense feelings of apprehension, worry, and dread that can range from a subtle background unease to...
- Cognitive fatigue— Mental exhaustion and difficulty sustaining thought after intense cognitive experiences, common duri...
- Delusion— A delusion is a fixed, false belief that is held with unshakeable certainty and is impervious to con...
- Depression— A persistent state of low mood, emotional numbness, hopelessness, and diminished interest or pleasur...
- Focus enhancement— An enhanced ability to direct and sustain attention on a single task or stimulus with unusual clarit...
- Irritability— Irritability is a sustained state of emotional reactivity in which the threshold for annoyance, frus...
- Mania— Abnormally elevated mood, energy, and activity with impulsive behavior and grandiosity, associated w...
- Motivation enhancement— A heightened sense of drive, ambition, and willingness to accomplish tasks, making productive effort...
- Motivation suppression— Motivation suppression is a state of diminished drive and willingness to engage in goal-directed beh...
- Panic attack— A panic attack is a discrete episode of acute, overwhelming fear or terror that arises suddenly and ...
- Psychosis— Psychosis is a serious psychiatric state involving a fundamental break from consensus reality — char...
- Thought acceleration— The experience of thoughts occurring at a dramatically increased rate, as if the mind has been shift...
- Thought deceleration— The experience of thoughts occurring at a markedly reduced pace, as if the mind has been placed into...
- Thought loops— Becoming trapped in a repeating cycle of thoughts, actions, and emotions that loops every few second...
- Time distortion— Subjective perception of time becomes dramatically altered — minutes may feel like hours, or hours p...
- Wakefulness— An increased ability to stay awake and alert without the desire to sleep. Distinct from stimulation ...
Pharmacology
Methylnaphthidate is thought to act primarily as a monoamine triple reuptake inhibitor, meaning it effectively elevates the levels of dopamine, noradrenaline and serotonin neurotransmitters throughout the brain and CNS by binding to and partially blocking the transporter proteins that normally clear out these monoamines from the synaptic cleft. This allows these molecules to accumulate throughout the brain, particularly within the reward pathways in the brain, resulting in stimulating and euphoric effects.
The toxicity and long-term health effects of recreational methylnaphthidate use do not seem to have been studied in any scientific context and the exact toxic and lethal dosages are unknown. This is because methylnaphthidate is a research chemical with very little history of human usage. Anecdotal evidence from people who have tried methylnaphthidate suggests that there are no negative health effects attributed to simply trying the drug by itself at low to moderate doses and using it very sparingly (but nothing can be completely guaranteed). Independent researchshould always be done to ensure that a combination of two or more substances is safe before consumption.
It is strongly recommended that one use harm reduction practices when using this drug.
In terms of its tolerance, methylnaphthidate can be used multiple days in a row for extended periods of time, but acute tolerance does exist and builds up gradually over repeated extended use. This results in the user requiring an increase in dosage to achieve the same effects.
While generally considered less recreational, methylnaphthidate has potential for abuse on par with that of amphetamine, cocaine or methylphenidate due to its lack of significant tolerance, euphoric effects and action upon dopamine and serotonin transporters. -MDMA** - The neurotoxic effects of MDMA may be increased when combined with other stimulants. -Cocaine** - This combination may synergistically increase strain on the heart to dangerous degrees.
Germany: HDMP-28 is controlled under the NpSG (New Psychoactive Substances Act) as of November 26, 2016. Production and import with the aim to place it on the market, administration to another person and trading is punishable. Possession is illegal but not penalized.
Switzerland: HDMP-28 is a controlled substance specifically named under Verzeichnis E. It was added to the list of controlled substances in December 2015.
Turkey: HDMP-28 is illegal in Turkey as of February 2016.
United Kingdom: HDMP-28 is a class B drug in the UK as of 31st May 2017 and is illegal to possess, produce or supply.
United States: HDMP-28 is not explicitly controlled in the US, but it could possibly be considered an analog of a Schedule II substance (methylphenidate) under the Federal Analog Act.
Responsible use
Research chemical
Stimulant
Methylphenidate
HDMP-28 (Wikipedia)
HDMP-28 (Isomer Design)
HDMP-28 (Bluelight)
Detection Methods
Standard Drug Panel Inclusion
Methylnaphthidate is a phenidate-class stimulant that is not detected on standard 5-panel, 10-panel, or 12-panel immunoassay drug screens. Phenidates are structurally distinct from amphetamines and do not cross-react with amphetamine or methamphetamine antibodies used in commercial immunoassays. There is no dedicated phenidate channel on any standard workplace or clinical drug panel.
Urine Detection
Methylnaphthidate and its primary metabolite ritalinic acid (or the corresponding deesterified acid analogue) can be detected in urine for approximately 1 to 3 days after a single oral dose. The ester bond in phenidate compounds is rapidly hydrolyzed by plasma and hepatic esterases, producing the corresponding acid metabolite which is the dominant species found in urine. Higher doses or repeated administration may extend the detection window modestly.
Blood and Saliva Detection
Blood concentrations of Methylnaphthidate decline rapidly due to ester hydrolysis, with a detection window of approximately 6 to 24 hours for the parent compound. The acid metabolite persists longer in plasma, detectable for up to 48 hours. Oral fluid testing can detect the parent compound for approximately 12 to 36 hours, though this route of detection is rarely employed for phenidates in practice.
Hair Follicle Detection
Hair follicle analysis may detect Methylnaphthidate or its metabolites for up to 90 days. However, incorporation of phenidate-class compounds into hair has not been extensively studied, and commercial laboratories do not routinely test for these substances. Specialized forensic laboratories with LC-MS/MS capability and appropriate reference standards would be required.
Confirmatory Testing
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the gold standard for confirming the presence of Methylnaphthidate and its metabolites. The ester bond in phenidates makes them somewhat labile under GC-MS conditions, so LC-MS/MS is preferred. Both parent compound and the deesterified acid metabolite should be targeted for comprehensive analysis.
Reagent Testing
Marquis reagent typically shows no reaction or a very faint color change with Methylnaphthidate, which helps distinguish it from amphetamines (orange-brown) and MDMA (purple-black). Mecke reagent generally shows no reaction. Mandelin reagent may produce a faint yellow or no change. The absence of strong reagent reactions is characteristic of the phenidate class and is itself a useful piece of information when combined with other reagent results.
Interactions
| Substance | Status | Note |
|---|---|---|
| 25x-NBOH | Dangerous | — |
| 25x-NBOMe | Dangerous | — |
| Atropa belladonna | Dangerous | Extreme cardiovascular strain from anticholinergic and stimulant effects combined |
| Cocaine | Dangerous | — |
| Datura | Dangerous | Extreme cardiovascular strain from anticholinergic and stimulant effects combined |
| Diphenhydramine | Dangerous | Extreme cardiovascular strain from anticholinergic and stimulant effects combined |
| Harmala alkaloid | Dangerous | Risk of hypertensive crisis and serotonin syndrome; potentially fatal combination |
| MDMA | Dangerous | — |
| Peganum harmala | Dangerous | Risk of hypertensive crisis and serotonin syndrome; potentially fatal combination |
| 1,3-Butanediol | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 25E-NBOH | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 2C-T | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 2C-T-2 | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 2C-T-21 | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| Alcohol | Uncertain | — |
| Dissociatives | Uncertain | — |
History
Methylnaphthidate is part of the stimulant class of psychoactive substances, which has a long and complex history spanning medical, military, occupational, and recreational use.
The modern history of stimulants begins with the isolation of ephedrine from traditional Chinese medicine in the 1880s, followed by the synthesis of amphetamine in 1887 and methamphetamine in 1893. Throughout the 20th century, stimulants were widely prescribed for conditions ranging from nasal congestion to depression, and were extensively used by militaries during World War II and the Korean War.
The recognition of abuse potential and adverse health effects led to increasing regulation from the 1960s onward, though stimulant medications remain among the most commonly prescribed treatments for ADHD and narcolepsy.
Methylnaphthidate exists within this broader context of stimulant pharmacology, with its specific history shaped by its date of development, clinical applications (if any), legal status, and pattern of use within different communities.
Harm Reduction
It is strongly recommended that one use harm reduction practices when using this drug.
In terms of its tolerance, methylnaphthidate can be used multiple days in a row for extended periods of time, but acute tolerance does exist and builds up gradually over repeated extended use. This results in the user requiring an increase in dosage to achieve the same effects.
While generally considered less recreational, methylnaphthidate has potential for abuse on par with that of amphetamine, cocaine or methylphenidate due to its lack of significant tolerance, euphoric effects and action upon dopamine and serotonin transporters. -MDMA** - The neurotoxic effects of MDMA may be increased when combined with other stimulants. -Cocaine** - This combination may synergistically increase strain on the heart to dangerous degrees.
Germany: HDMP-28 is controlled under the NpSG (New Psychoactive Substances Act) as of November 26, 2016. Production and import with the aim to place it on the market, administration to another person and trading is punishable. Possession is illegal but not penalized.
Switzerland: HDMP-28 is a controlled substance specifically named under Verzeichnis E. It was added to the list of controlled substances in December 2015.
Turkey: HDMP-28 is illegal in Turkey as of February 2016.
United Kingdom: HDMP-28 is a class B drug in the UK as of 31st May 2017 and is illegal to possess, produce or supply.
United States: HDMP-28 is not explicitly controlled in the US, but it could possibly be considered an analog of a Schedule II substance (methylphenidate) under the Federal Analog Act.
Responsible use
Research chemical
Stimulant
Methylphenidate
HDMP-28 (Wikipedia)
HDMP-28 (Isomer Design)
HDMP-28 (Bluelight)
Toxicity & Safety
The toxicity and long-term health effects of recreational methylnaphthidate use do not seem to have been studied in any scientific context and the exact toxic and lethal dosages are unknown. This is because methylnaphthidate is a research chemical with very little history of human usage. Anecdotal evidence from people who have tried methylnaphthidate suggests that there are no negative health effects attributed to simply trying the drug by itself at low to moderate doses and using it very sparingly (but nothing can be completely guaranteed). Independent researchshould always be done to ensure that a combination of two or more substances is safe before consumption.
It is strongly recommended that one use harm reduction practices when using this drug.
Tolerance and addiction potential
In terms of its tolerance, methylnaphthidate can be used multiple days in a row for extended periods of time, but acute tolerance does exist and builds up gradually over repeated extended use. This results in the user requiring an increase in dosage to achieve the same effects.
While generally considered less recreational, methylnaphthidate has potential for abuse on par with that of amphetamine, cocaine or methylphenidate due to its lack of significant tolerance, euphoric effects and action upon dopamine and serotonin transporters.
Dangerous interactions
Warning: Many psychoactive substances that are reasonably safe to use on their own can suddenly become dangerous and even life-threatening when combined with certain other substances. The following list provides some known dangerous interactions (although it is not guaranteed to include all of them).
Always conduct independent research (e.g. Google, DuckDuckGo, PubMed) to ensure that a combination of two or more substances is safe to consume. Some of the listed interactions have been sourced from TripSit.
25x-NBOMe & 25x-NBOH - 25x compounds are highly stimulating and physically straining. Combinations with Methylnaphthidate should be strictly avoided due to the risk of excessive stimulation and heart strain. This can result in increased blood pressure, vasoconstriction, panic attacks, thought loops, seizures, and heart failure in extreme cases.
Alcohol - Combining alcohol with stimulants can be dangerous due to the risk of accidental over-intoxication. Stimulants mask alcohol's depressant effects, which is what most people use to assess their degree of intoxication. Once the stimulant wears off, the depressant effects will be left unopposed, which can result in blackouts and severe respiratory depression. If mixing, the user should strictly limit themselves to only drinking a certain amount of alcohol per hour.
DXM - Combinations with DXM should be avoided due to its inhibiting effects on serotonin and norepinephrine reuptake. There is an increased risk of panic attacks and hypertensive crisis, or serotonin syndrome with serotonin releasers (MDMA, methylone, mephedrone, etc.). Monitor blood pressure carefully and avoid strenuous physical activity.
MDMA - Any neurotoxic effects of MDMA are likely to be increased when other stimulants are present. There is also a risk of excessive blood pressure and heart strain (cardiotoxicity).
MXE - Some reports suggest combinations with MXE may dangerously increase blood pressure and increase the risk of mania and psychosis.
Dissociatives - Both classes carry a risk of delusions, mania and psychosis, and these risk may be multiplied when combined.
Stimulants - Methylnaphthidate may be dangerous to combine with other stimulants like cocaine as they can increase one's heart rate and blood pressure to dangerous levels.
Tramadol - Tramadol is known to lower the seizure threshold and combinations with stimulants may further increase this risk.
MAOIs - This combination may increase the amount of neurotransmitters such as serotonin to dangerous or even fatal levels. Examples include syrian rue, banisteriopsis caapi, and some antidepressants.
MDMA - The neurotoxic effects of MDMA may be increased when combined with other stimulants.
Cocaine - This combination may synergistically increase strain on the heart to dangerous degrees.
Overdose Information
Stimulant overdose from Methylnaphthidate is a medical emergency primarily involving cardiovascular and neurological toxicity.
Signs of overdose: Extremely rapid or irregular heartbeat, chest pain, severe headache, dangerously elevated body temperature, seizures, agitation progressing to psychosis, confusion, and loss of consciousness.
Emergency response:
- Call emergency services immediately
- Keep the person cool (remove excess clothing, apply cool water)
- If seizures occur, protect the head and clear the area of hard objects
- If the person loses consciousness, place in recovery position
- Do not give the person more stimulants, caffeine, or depressants unless directed by medical professionals
Prevention: Pre-measure doses. Avoid redosing. Stay hydrated (but don't overhydrate). Take breaks from physical activity. Monitor heart rate if possible. Have someone present who can recognize warning signs.
Dangerous Interactions
The combinations listed below may be life-threatening. Independent research should always be conducted to ensure safety when combining substances.
Extreme cardiovascular strain from anticholinergic and stimulant effects combined
Extreme cardiovascular strain from anticholinergic and stimulant effects combined
Extreme cardiovascular strain from anticholinergic and stimulant effects combined
Risk of hypertensive crisis and serotonin syndrome; potentially fatal combination
Risk of hypertensive crisis and serotonin syndrome; potentially fatal combination
Tolerance
| Full | Develops with prolonged use |
| Half | 3 - 7 days |
| Zero | 1 - 2 weeks |
Cross-tolerances
Legal Status
Germany: HDMP-28 is controlled under the NpSG (New Psychoactive Substances Act) as of November 26, 2016. Production and import with the aim to place it on the market, administration to another person and trading is punishable. Possession is illegal but not penalized.
Switzerland: HDMP-28 is a controlled substance specifically named under Verzeichnis E. It was added to the list of controlled substances in December 2015.
Turkey: HDMP-28 is illegal in Turkey as of February 2016.
United Kingdom: HDMP-28 is a class B drug in the UK as of 31st May 2017 and is illegal to possess, produce or supply.
United States: HDMP-28 is not explicitly controlled in the US, but it could possibly be considered an analog of a Schedule II substance (methylphenidate) under the Federal Analog Act.
Responsible use
Research chemical
Stimulant
Methylphenidate
HDMP-28 (Wikipedia)
HDMP-28 (Isomer Design)
HDMP-28 (Bluelight)
Tips (4)
Have a landing plan for the Methylnaphthidate comedown. Prepare food, melatonin or magnesium, and a comfortable environment in advance. Avoid using depressants to manage the comedown as this creates polydrug dependency patterns.
Test Methylnaphthidate with appropriate reagent kits and fentanyl test strips. Stimulant supplies have increasingly been found contaminated with fentanyl, which has caused a surge in overdose deaths among stimulant users.
Avoid binge patterns with Methylnaphthidate. Sleep deprivation combined with stimulant use dramatically increases psychosis risk after 48+ hours awake. If you find yourself redosing to avoid the comedown, that is a major warning sign.
Weigh your dose of Methylnaphthidate with a milligram scale. Street stimulants vary wildly in purity and potency. What looks like a normal amount could be significantly stronger than expected, especially with a new batch.
See Also
References (4)
- Amphetamine: new content for an old topic — Heal et al. Neuropsychopharmacology Reviews (2013)paper
- PubChem: Methylnaphthidate
PubChem compound page for Methylnaphthidate (CID: 9817261)
pubchem - Methylnaphthidate - TripSit Factsheet
TripSit factsheet for Methylnaphthidate
tripsit - Methylnaphthidate - Wikipedia
Wikipedia article on Methylnaphthidate
wikipedia