|Summary sheet: Methylnaphthidate|
|Common names||Methylnaphthidate, HDMP-28|
|Systematic name||Methyl (naphthalen-2-yl)(piperidin-2-yl)acetate|
|Chemical class||Naphthidate / Piperidine|
|Routes of Administration|
Methylnaphthidate (also known as HDMP-28) is a novel synthetic stimulant substance of the substituted naphthidate and piperidine chemical classes. 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. 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.
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.
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.
|This subjective effects section is a stub.|
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Disclaimer: The effects listed below are cited from the subjective effect index, which is based on anecdotal reports and the personal experiences of PsychonautWiki contributors. As a result, they should be treated with a healthy degree of skepticism. It is worth noting that these effects will rarely (if ever) occur all at once, although higher doses will increase the chances of inducing a full range of effects. Likewise, adverse effects become much more likely on higher doses and may include serious injury or death.
- Appetite suppression
- 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.
- 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:
- Thought acceleration
- Analysis enhancement
- Increased music appreciation
- Focus enhancement - This component is most effective at low to moderate dosages as anything higher will usually impair concentration.
- Motivation enhancement
- Euphoria - The euphoric rush associated with methylnaphthidate use (as result of dopamine reuptake 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.
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.
Although many psychoactive substances are reasonably safe to use on their own, they can quickly become dangerous or even life-threatening when taken with other substances. The following lists some known dangerous combinations, but cannot be guaranteed to include all of them. Independent research should always be conducted to ensure that a combination of two or more substances is safe to consume. Some interactions listed have been sourced from TripSit.
- MDMA - The neurotoxic effects of MDMA may be increased when combined with other amphetamines.
- Cocaine - This combination may increase strain on the heart.
- Stimulants - Methylnaphthidate can be potentially dangerous in combination with other stimulants as it can increase one's heart rate and blood pressure to dangerous levels.
- 25x-NBOMe & 25x-NBOH - Members of the 25x family are highly stimulating and physically straining. Combinations with stimulants should be avoided due to the risk of excessive stimulation. This can result in panic attacks, thought loops, seizures, increased blood pressure, vasoconstriction, and heart failure in extreme cases.
- Alcohol - Alcohol can be dangerous to combine with stimulants due to the risk of accidental over-intoxication. Stimulants mask the sedative effects of alcohol, which is the main factor people use to assess their degree of intoxication. Once the stimulant wears off, the depressant effects of alcohol are left unopposed, which can result in blackouts and respiratory depression. If combined, one should strictly limit themselves to only drinking a certain amount of alcohol per hour.
- DXM - Combinations with DXM should be strictly avoided due to DXM's effects on serotonin and dopamine reuptake. This can lead to panic attacks, hypertensive crisis, or serotonin syndrome.
- MXE - Combinations with MXE may dangerously elevate blood pressure and increase the risk of psychosis.
- Tramadol - Tramadol lowers the seizure threshold. 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, 2C-T-2, 2C-T-7, αMT, 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.
- 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 illegal in Switzerland as of December 2015.
- 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.
- 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. https://doi.org/10.1007/BF03161089
- Gillman, P. K. (2005). Monoamine oxidase inhibitors, opioid analgesics and serotonin toxicity. British Journal of Anaesthesia, 95(4), 434-441. https://doi.org/10.1093/bja/aei210
- "Anlage NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 24, 2019.
- "Gesetz zur Bekämpfung der Verbreitung neuer psychoaktiver Stoffe" (PDF) (in German). Bundesanzeiger Verlag. Retrieved December 24, 2019.
- "§ 4 NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 24, 2019.
- "Verordnung des EDI über die Verzeichnisse der Betäubungsmittel, psychotropen Stoffe, Vorläuferstoffe und Hilfschemikalien" (in German). Der Bundesrat. Archived from the original on March 29, 2017. Retrieved December 24, 2019.
- The Misuse of Drugs Act 1971 (Amendment) Order 2017 (Legislation.gov.uk) | http://www.legislation.gov.uk/uksi/2017/634/made