This is an unofficial archive of PsychonautWiki as of 2025-08-08T03:33:20Z. Content on this page may be outdated, incomplete, or inaccurate. Please refer to the original page for the most up-to-date information.
WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.
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 monoaminereuptake inhibitor.[citation needed] However, it has been reported to display distinct differences in its subjective effects by not behaving as a traditional dopaminergicstimulant. 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.
The main structural differences between methylnaphthidate and methylphenidate in chemical substance is the replacement of the core phenyl ring with with a napthalene group.
Pharmacology
Methylnaphthidate is thought to act primarily as a monoamine triple reuptake inhibitor, meaning it effectively elevates the levels of dopamine, noradrenaline and serotoninneurotransmitters 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.
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 PsychonautWikicontributors. 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 ☠.
Increased heart rate - This component has been reported by some as being uniquely pronounced in the -phenidate family. These effects might owe themselves to increased free-circulating serotonin in the blood, which would lead to sustained agonism at Serotonin-2B receptors on the heart.
Teeth grinding - This component can be considered to be present, but less intense when compared with that of MDMA.
After effects
The effects which occur during the offset of a stimulant experience generally feel negative and uncomfortable in comparison to the effects which occurred during its peak. This is often referred to as a "comedown" and occurs because of neurotransmitter depletion. Its effects commonly include:
Euphoria - The euphoric rush associated with methylnaphthidate use (as result of dopaminereuptake inhibition) is very short-lived and compulsive, similar to that of cocaine.
Cognitive fatigue - This component can occur during the offset of this compound as a rebound effect which is usually equal in its intensity to the enhancements which occurred before it.
Time distortion - This can be described as the experience of time speeding up and passing much quicker than it usually would when sober.
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:
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.
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.
"[[DangerousInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] & "[[DangerousInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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.
"[[UncertainInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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.
"[[UnsafeInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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.
"[[UnsafeInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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).
"[[UncertainInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - Some reports suggest combinations with MXE may dangerously increase blood pressure and increase the risk of mania and psychosis.
"[[UncertainInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - Both classes carry a risk of delusions, mania and psychosis, and these risk may be multiplied when combined.
"[[UnsafeInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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.
"[[DangerousInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - Tramadol is known to lower the seizure threshold[1] and combinations with stimulants may further increase this risk.
"[[DangerousInteraction" contains a listed "[" character as part of the property label and has therefore been classified as invalid.]] - 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.
↑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. eISSN1937-6995. ISSN1556-9039. OCLC163567183.
. eISSN 1471-6771. ISSN 0007-0912. OCLC 01537271. PMID 16051647.