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Summary sheet: Methylnaphthidate
Chemical Nomenclature
Common names Methylnaphthidate, HDMP-28
Substitutive name Methylnaphthidate
Systematic name Methyl (naphthalen-2-yl)(piperidin-2-yl)acetate
Class Membership
Psychoactive class Stimulant
Chemical class Phenidate
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Threshold 4 mg
Light 10 - 15 mg
Common 15 - 30 mg
Strong 30 - 50 mg
Heavy 50 mg +
Total 2 - 5 hours
Onset 1 - 10 minutes
Peak 1.5 - 2 hours
Offset 1.5 - 2 hours
After effects 1 - 8 hours

Threshold < 4 mg
Light 4 - 8 mg
Common 8 - 14 mg
Strong 14 - 28 mg
Heavy 28 mg +
Total 90 - 180 minutes
Onset 3 - 6 minutes
Peak 1 - 2 hours
Offset 1 - 2 hours
After effects 1 - 2 hours

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.


Methylnaphthidate (also known as HDMP-28) is a novel synthetic stimulant substance of the substituted phenidate chemical class. It is a structural analog of the commonly prescribed ADHD drug methylphenidate (e.g. Ritalin, Concerta) that produces moderately stimulating effects when administered.

Like members of the phenidate class, methylnaphthidate is believed to act as a monoamine reuptake inhibitor.[citation needed] However, it has been reported to display distinct differences in its subjective effects by not behaving as a traditional dopaminergic stimulant. This has been speculated to owe itself to its appreciable effects on serotonin reuptake inhibition that is not observed in typical methylphenidate analogs.[citation needed]

Very little data exists about the pharmacological properties, metabolism, and toxicity of methylnaphthidate, and it has little history of human usage. It is sometimes commercially distributed as a grey-area research chemical by online vendors alongside other methylphenidate analogs like ethylphenidate, isopropylphenidate, and 4F-MPH. It is highly advised to approach this and poorly understood stimulant substance with the proper amount of precaution and harm reduction practices if choosing to use it.



This chemistry section is incomplete.

You can help by adding to it.

The main structural differences between methylnaphthidate and methylphenidate in chemical substance is the replacement of the core phenyl ring with with a napthalene group.


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.

Subjective effects

This subjective effects section is a stub.

As such, it is still in progress and may contain incomplete or wrong information.

You can help by expanding or correcting it.

Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), an open research literature based on anecdotal user reports and the personal analyses of PsychonautWiki contributors. As a result, they should be viewed with a healthy degree of skepticism.

It is also worth noting that 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. Likewise, adverse effects become increasingly likely with higher doses and may include addiction, severe injury, or death ☠.

Physical effects

After effects
Aftereffects (3).svg

Cognitive effects

Experience reports

There are currently no anecdotal reports which describe the effects of this compound within our experience index. Additional experience reports can be found here:

Toxicity and harm potential

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[1] 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.[2]
  • 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.

Legal status

  • Germany: HDMP-28 is controlled under the NpSG (New Psychoactive Substances Act)[3] as of November 26, 2016.[4] 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.[5]
  • Switzerland: HDMP-28 is a controlled substance specifically named under Verzeichnis E. It was added to the list of controlled substances in December 2015.[6]
  • Turkey: HDMP-28 is illegal in Turkey as of February 2016.[7]
  • 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. [8]
  • 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.

See also

External links


  1. Talaie, H.; Panahandeh, R.; Fayaznouri, M. R.; Asadi, Z.; Abdollahi, M. (2009). "Dose-independent occurrence of seizure with tramadol". Journal of Medical Toxicology. 5 (2): 63–67. doi:10.1007/BF03161089. eISSN 1937-6995. ISSN 1556-9039. OCLC 163567183. 
  2. Gillman, P. K. (2005). "Monoamine oxidase inhibitors, opioid analgesics and serotonin toxicity". British Journal of Anaesthesia. 95 (4): 434–441. doi:10.1093/bja/aei210Freely accessible. eISSN 1471-6771. ISSN 0007-0912. OCLC 01537271. PMID 16051647. 
  3. "Anlage NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 24, 2019. 
  4. "Gesetz zur Bekämpfung der Verbreitung neuer psychoaktiver Stoffe" (PDF) (in German). Bundesanzeiger Verlag. Retrieved December 24, 2019. 
  5. "§ 4 NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 24, 2019. 
  6. "Verordnung des EDI über die Verzeichnisse der Betäubungsmittel, psychotropen Stoffe, Vorläuferstoffe und Hilfschemikalien" (in German). Bundeskanzlei [Federal Chancellery of Switzerland]. Retrieved January 1, 2020. 
  7. "Karar Sayısı : 2016/8548" (PDF) (in Turkish). Resmi Gazete. Retrieved January 15, 2020. 
  8. The Misuse of Drugs Act 1971 (Amendment) Order 2017 ( |