4F-MPH

# Research Output: 4F-MPH

**Substance:** 4-Fluoromethylphenidate (4F-MPH)  
**PSX ID:** PSX-0073  
**Research Date:** 2026-05-11  
**Provenance ID:** 3e22dd2e-ea57-44b2-8238-7e4ca66c12a5  

---

## Chemical Identity

PubChem lookup (CID 52944002) confirmed all chemical identity data, resolving several gaps in the brief's seed data (SMILES, InChIKey, and PubChem CID were all missing).

- **PubChem CID:** 52944002 [Ref 21 (PubChem)]
- **CAS number:** 1354631-33-6 [Ref 21]
- **Molecular formula:** C14H18FNO2 [Ref 21]
- **Molecular weight (free base):** 251.30 g/mol [Ref 21]
- **Molecular weight (HCl salt):** ~287.8 g/mol [Ref 21]
- **IUPAC name:** methyl (2R)-2-(4-fluorophenyl)-2-[(2R)-piperidin-2-yl]acetate [Ref 21]
- **InChIKey:** XISBAJBPDVRSPG-CHWSQXEVSA-N [Ref 21]
- **Systematic name (from brief):** methyl (2R)-2-(4-fluorophenyl)-2-[(2R)-piperidin-2-yl]acetate — **confirmed identical to PubChem IUPAC** [Ref 21]
- **Boiling point:** 329.4 ± 22.0 °C (predicted) [Ref 21]
- **Density:** 1.130 ± 0.06 g/cm³ (predicted) [Ref 21]
- **pKa:** 9.49 ± 0.10 (predicted) [Ref 21]
- **Melting point (HCl salt):** ~147–148 °C (commercial product; not experimentally peer-reviewed) [Ref 21]
- **Solubility:** Soluble in organic solvents (ethanol, methanol, chloroform); aqueous solubility data not published [Ref 21]
- **Appearance:** White crystalline powder (commercial; not from controlled study)

**Structural note:** 4F-MPH is the para-fluorinated analog of methylphenidate (MPH). The fluorine atom substitution at the 4-position of the phenyl ring yields modest increases in DAT and NET inhibitory potency relative to the parent compound. 4F-MPH exists as two pairs of diastereomers: (±)-threo and (±)-erythro. The (±)-threo form is pharmacologically active; the (±)-erythro form is essentially inactive at monoamine transporters (McLaughlin et al. 2017 [Ref 1]).

**Brief discrepancy noted:** The brief seed data lacked SMILES, InChIKey, and PubChem CID. All three are now confirmed via API lookup and should be updated in the database.

---

## Pharmacology

### Mechanism of Action

4F-MPH acts as a potent, catecholamine-selective monoamine reuptake inhibitor, blocking the dopamine transporter (DAT) and norepinephrine transporter (NET) without releasing activity at any transporter (McLaughlin et al. 2017 [Ref 1]; Luethi et al. 2018 [Ref 2]). It does not act as a substrate-type releasing agent, distinguishing it mechanistically from amphetamine-type stimulants. This is consistent with the pharmacological profile of the parent compound methylphenidate and other phenidate analogs (Luethi & Liechti 2020 [Ref 20]).

### Transporter Binding (In Vitro — Rat Brain Synaptosomes)

The following IC₅₀ values were determined by McLaughlin et al. (2017 [Ref 1]) using rat brain synaptosomes:

| Compound | DAT IC₅₀ | NET IC₅₀ | SERT IC₅₀ |
|---|---|---|---|
| (±)-threo-4F-MPH | **61 nM** | **31 nM** | 8,805 nM |
| (±)-erythro-4F-MPH | 8,528 nM | 3,779 nM | >10,000 nM |
| 4F-MPH mixture | 66 nM | 45 nM | — |
| Methylphenidate (MPH) | 131 nM | 83 nM | >10,000 nM |

(±)-threo-4F-MPH is approximately **2.1× more potent than MPH at DAT** and approximately **2.7× more potent at NET** (McLaughlin et al. 2017 [Ref 1]). Both 4F-MPH and MPH are catecholamine-selective, with negligible SERT activity at pharmacologically relevant concentrations.

**Abuse liability prediction:** The high DAT/SERT selectivity ratio of 4F-MPH (DAT IC₅₀:SERT IC₅₀ ratio ~144:1 for threo form) is associated with high abuse potential, consistent with the class-level prediction framework described by Liechti (2015 [Ref 15]). Luethi et al. (2018 [Ref 2]) confirmed that MPH-based NPS including 4F-MPH did not elicit transporter-mediated efflux of any monoamines in vitro — they are uptake blockers, not releasers — but their predominant DAT activity indicates high abuse liability.

### Additional Receptor Pharmacology

No published data exists for 4F-MPH binding at additional receptor targets (dopamine D1/D2, adrenergic receptors, serotonin receptors). Extrapolation from the MPH class suggests negligible activity at these targets at therapeutic-range concentrations, but no 4F-MPH-specific receptor binding data has been published.

### Pharmacokinetics

**No published human pharmacokinetic studies exist for 4F-MPH.** All available PK inferences are derived from case report biological concentrations and structural analogy to methylphenidate.

- **Observed blood concentrations (non-fatal intoxication):** 32 ng/mL (blood), 827 ng/mL (urine) following insufflation of an unquantified dose (Papa et al. 2019 [Ref 5])
- **Observed blood concentrations (fatal case, polydrug):** 0.012–0.05 mg/L femoral blood (Shoff et al. 2019 [Ref 4])
- **Metabolism:** Manier et al. (2020 [Ref 3]) identified **13 metabolites for 4F-MPH** in rat urine using UHPLC-HRMS/MS: 12 phase I metabolites and 1 phase II metabolite. Primary metabolic pathway is hydrolysis (de-esterification) producing the corresponding carboxy metabolite (analogous to ritalinic acid for MPH). Human S9 fraction incubations confirmed the same hydrolytic pattern. The carboxy metabolites are recommended as additional analytical targets for forensic screening alongside the parent compound (Manier et al. 2020 [Ref 3]).
- **CYP enzymes:** No published data specifically for 4F-MPH. Methylphenidate is primarily metabolized by carboxylesterase 1 (CES1) to ritalinic acid, with minor CYP2D6 involvement; similar enzymatic pathway likely applies to 4F-MPH but not confirmed.
- **Half-life:** Not established in published literature.
- **Bioavailability by route:** Not published. Insufflated onset (~10–30 min) faster than oral (~30–60 min) based on user-report data; quantitative bioavailability data not available.

---

## History

Methylphenidate, the parent compound of 4F-MPH, was first synthesized in 1944. 4F-MPH is a fluorinated structural analog developed as a research chemical with no known legitimate therapeutic history.

4F-MPH first appeared on the online research chemical market in **2015**, following the UK's temporary class drug order banning ethylphenidate in April 2015 (McLaughlin et al. 2017 [Ref 1]). Two powdered products containing 4F-MPH were obtained from an online vendor in 2015 by McLaughlin et al. and formed the basis of the first published analytical and pharmacological characterization. One product consisted exclusively of (±)-threo-4F-MPH; the other was a mixture of threo and erythro diastereomers, suggesting separate synthesis batches with incomplete purification (McLaughlin et al. 2017 [Ref 1]).

The **European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) first notified** 4F-MPH through its Early Warning System in **November 2015** following detection on the recreational market. This was the first formal regulatory recognition of 4F-MPH as a novel psychoactive substance in Europe.

4F-MPH was first detected in drug paraphernalia at the Miami-Dade County Medical Examiner's toxicology laboratory in **2016**, representing its first North American detection, though it was not found in a biological specimen in the US until **2018** (Shoff et al. 2019 [Ref 4]).

The compound is sold online as a "research chemical" and has been variously marketed as a cognitive enhancer, stimulant, and (inaccurately) as an entactogen (Papa et al. 2019 [Ref 5]; Holborn et al. 2023 [Ref 12]).

---

## Subjective Effects

**No controlled human studies of 4F-MPH have been published.** All subjective effect data is derived from case reports and community user reports. The generation agent should frame all effects as user-report level unless otherwise specified.

### Case Report Data (Clinically Documented)

In the Papa et al. (2019 [Ref 5]) non-fatal intoxication case, a 26-year-old female presenting after one week of 4F-MPH insufflation reported and exhibited:
- **Neuropsychiatric symptoms:** Agitation, altered mental status
- **Cardiologic symptoms:** Cardiovascular abnormalities (specific parameters not published in the abstract)
- **Treatment required:** Intravenous diazepam for sedation; discharged with promazine and quetiapine (antipsychotic)

The clinical presentation is consistent with sympathomimetic toxidrome: excessive catecholaminergic stimulation producing CNS excitation and cardiovascular effects.

### Community/User-Report Data

Based on user-report data from Reddit communities (Holborn et al. 2023 [Ref 12]) and community harm reduction wikis [Ref 17], reported effects of 4F-MPH include:

**Cognitive:**
- Focus enhancement, analysis enhancement, motivation enhancement
- Thought acceleration, thought organization
- Memory enhancement (subjective)
- Compulsive redosing urge at higher doses

**Physical:**
- Stimulation, wakefulness
- Appetite suppression
- Vasoconstriction, increased heart rate
- Pupil dilation
- Bruxism, excessive sweating
- Headache, nausea

**Emotional:**
- Euphoria (typically mild at low doses)
- Anxiety at higher doses or with extended use
- Post-use dysphoria, depression, irritability

**Self/social:**
- Sociability enhancement at low doses
- Ego inflation (dose-dependent)

Community data also describes 4F-MPH as a "functional" stimulant used for ADHD self-medication, productivity enhancement, and cognitive tasks (Holborn et al. 2023 [Ref 12]; Napoletano et al. 2020 [Ref 9]).

### Duration Estimates (User-Report Derived)

**Oral:**
- Onset: 30–60 minutes
- Peak: 2–4 hours
- Offset: 1–2 hours
- Aftereffects: 5–10 hours
- Total: 4–8 hours

**Insufflated:**
- Onset: 10–30 minutes
- Peak: 1–2 hours
- Offset: 1–2 hours
- Aftereffects: 4–8 hours
- Total: 3–6 hours

These figures are user-report derived and align with the DB seed data [Ref 17]. No pharmacokinetically validated duration data exists.

---

## Safety & Toxicity

### Published Case Reports

**Case 1 — Non-Fatal (Papa et al. 2019 [Ref 5]):**
- 26-year-old female, Italy
- Route: Insufflation ("sniffed") over approximately 1 week
- Product: Diastereomeric threo/erythro mixture, predominantly threo — purchased online as "entactogen"
- Blood 4F-MPH: 32 ng/mL; Urine 4F-MPH: 827 ng/mL
- Presentation: Neuropsychiatric and cardiologic symptoms
- Treatment: IV diazepam for sedation; discharged after 2 days with promazine and quetiapine prescriptions
- No co-intoxicants detected; comorbidities excluded
- Conclusion: Symptoms directly attributable to 4F-MPH alone

**Case 2 — Fatal (Shoff et al. 2019 [Ref 4]):**
- Miami-Dade County, Florida, USA; death date not precisely specified (specimen collected 2018)
- Route: Unknown
- Blood 4F-MPH: 0.012–0.05 mg/L (femoral vein); variation across tube types
- Additional substances detected: 3-methoxy-PCP, amphetamine, methamphetamine, 6-monoacetylmorphine, morphine, codeine, tetrahydrocannabinol — **severe polydrug context**
- First US case with 4F-MPH listed on death certificate; cause of death officially includes 4F-MPH
- A possible erythro isomer was also detected but could not be confirmed due to absence of certified reference material
- **Caution:** Given the polydrug context, the independent contribution of 4F-MPH to death cannot be isolated from the published data

### LD₅₀ / Lethal Threshold

**No LD₅₀ data has been published for 4F-MPH** in any species. No dose-finding or toxicological challenge studies exist in the peer-reviewed literature. Lethal threshold cannot be established from available evidence.

### Class-Level Cardiovascular Risk

Based on the pharmacological class (MPH-like DAT/NET inhibitor), 4F-MPH is expected to share the cardiovascular risk profile of methylphenidate, which includes (Silczuk et al. 2025 [Ref 16]):
- Increased heart rate
- Elevated blood pressure (systolic and diastolic)
- Risk of arrhythmias (particularly at higher doses or in susceptible individuals)
- Rare but documented: myocardial infarction, sudden cardiac death
- Pre-existing cardiac conditions substantially elevate risk

Given that 4F-MPH is 2–3× more potent than MPH at DAT and NET, cardiovascular effects may be more pronounced at equivalent milligram doses.

### Class-Level Psychiatric Risk

Methylphenidate class psychiatric adverse effects include (Silczuk et al. 2025 [Ref 16]):
- Anxiety, agitation, restlessness
- Psychotic symptoms (rare; risk elevated at high doses)
- Exacerbation of pre-existing mood disorders
- Dependence and reinforcement behaviors

These risks are expected to apply to 4F-MPH and may be amplified by its higher potency.

---

## Harm Reduction

### Product Verification

**Critical:** A sample submitted as 4F-MPH at Australia's CanTEST drug checking service was found to actually be **4-fluoro-α-pyrrolidinoisohexanophenone (4F-α-PiHP)**, a synthetic cathinone with entirely different pharmacology. The misrepresentation was not detectable by on-site testing methods and required NMR and HRMS at a university laboratory (Algar et al. 2024 [Ref 13]). This demonstrates a real and documented adulteration/misrepresentation risk in the 4F-MPH market.

**Recommendation:** All 4F-MPH samples should be verified with a reliable analytical technique before use. Reagent colorimetric tests have limited specificity for phenidate analogs. Fentanyl test strips are recommended as a minimum screen for contamination. Professional drug checking services using LC-MS or NMR are optimal.

### Analytical Considerations for Testing

Phenidate analogs including 4F-MPH undergo thermal decomposition in GC injection ports and on-column, producing artifact peaks (2-aryl-ethyl-acetates and 2,3,4,5-tetrahydropyridines) (Klare et al. 2017 [Ref 8]). This renders GC-EI-MS alone insufficient for unambiguous identification. LC-ESI-MS/MS using sodium adduct fragmentation (Shamai Yamin et al. 2020 [Ref 7]) or NMR are more reliable methods. The thermal instability also renders smoking/vaping of phenidate analogs less effective as a route of administration.

### Clinical Management of Intoxication

From the Papa et al. (2019 [Ref 5]) case, IV diazepam (benzodiazepine) was used successfully to sedate an acutely intoxicated patient. This is consistent with standard sympathomimetic toxidrome management. The patient subsequently required antipsychotic medication (promazine, quetiapine). Emergency management is supportive; no 4F-MPH-specific antidote exists.

### Dosing Caution

Users should be aware that:
1. Dose-response relationship has not been established in controlled studies
2. Products vary in diastereomeric composition (threo/erythro ratios vary between batches)
3. The erythro form is essentially inactive; variable ratios mean variable potency per unit mass
4. 4F-MPH is approximately 2–3× more potent than MPH at DAT/NET — caution with doses extrapolated from MPH experience
5. Insufflated onset is substantially faster than oral, increasing overdose and compulsive redosing risk

---

## Tolerance & Dependence

**No published experimental data on tolerance or dependence for 4F-MPH specifically exists.**

### Class-Level Inference

Methylphenidate-class drugs (DAT-selective reuptake inhibitors) have documented:
- **Tolerance:** Develops with repeated use; sensitization or tolerance depending on dose, context, and individual (Broussard et al. 2019 [Ref for MPH animal study])
- **Dependence liability:** Established via primate self-administration models — MPH maintained robust self-administration comparable to cocaine in rhesus monkeys (Gasior et al. 2005 [Ref 18])
- **Abuse potential:** High, by virtue of strong DAT selectivity; higher than NET-selective compounds (Liechti 2015 [Ref 15])

Given 4F-MPH's ~2× greater DAT potency compared to MPH, its dependence liability is plausibly at least equivalent to MPH. No cross-tolerance or withdrawal characterization data has been published for 4F-MPH.

Community user reports cite compulsive redosing as a recognized risk [Ref 17].

---

## Interactions

### Listed Interactions (from DB Seed Data)

**Tramadol — "lethal"**  
No published case report specifically documents a fatal 4F-MPH + tramadol combination. The "lethal" designation cannot be verified against a published source for this specific combination. Mechanistic basis: tramadol is both a weak opioid agonist and a weak monoamine reuptake inhibitor with serotonergic activity; it markedly lowers the seizure threshold. Combining tramadol with a potent stimulant that independently elevates cardiovascular demand and may lower the seizure threshold creates compounded risk. Class-level pharmacology supports serious concern. **FLAG: This interaction severity is not verified against a published source specifically for 4F-MPH + tramadol.**

**MDMA — "dangerous"**  
No published case report of 4F-MPH + MDMA combination exists. Mechanistic basis: MDMA is a potent serotonin releaser with significant cardiovascular effects; 4F-MPH is a potent DAT/NET inhibitor increasing catecholamines. Combined, the two could produce additive or synergistic tachycardia, hypertension, and hyperthermia. MDMA's serotonergic actions combined with 4F-MPH's noradrenergic effects can create toxicologically complex interactions. **FLAG: "Dangerous" severity is mechanistically supported but not verified by a published 4F-MPH + MDMA case.**

**Alcohol — "unknown"**  
For the parent compound methylphenidate, co-administration with ethanol results in carboxylesterase 1-mediated transesterification producing ethylphenidate, a distinct psychoactive compound with selective DAT activity, along with increased early exposure to d-MPH and potentiated euphoria (Patrick et al. 2014 [Ref 14]). Whether a similar transesterification reaction occurs with 4F-MPH + ethanol is plausible but has not been studied. The "unknown" designation is appropriate given the lack of published data.

### Other Pharmacologically Relevant Interactions (Not in DB)

- **MAOIs:** Contraindicated with all stimulants; risk of hypertensive crisis from combined catecholamine excess. No 4F-MPH specific data; class inference.
- **Other stimulants (amphetamines, cocaine, cathinones):** Additive cardiovascular and CNS stimulant effects; compounded toxicity risk. The fatal US case involved polydrug use including amphetamine and methamphetamine alongside 4F-MPH [Ref 4].
- **Cardiovascular medications:** May antagonize antihypertensive drugs; caution with beta-blockers (may unmask alpha-adrenergic effects).

---

## Legal Status

### By Jurisdiction

| Jurisdiction | Status | Date | Notes |
|---|---|---|---|
| **United Kingdom** | Class B controlled drug | 31 May 2017 | Psychoactive Substances Act-related scheduling [Ref 11, 19] |
| **Canada** | Controlled substance | 5 May 2017 | [Ref 11, 19] |
| **Germany** | Controlled under NpSG (New Psychoactive Substances Act) | November 2016 | Reportedly "re-legalized" by accidental omission September 2022 — **web source only; editorial review needed** [Ref 19] |
| **United States** | Not federally scheduled | — | Federal Analog Act potentially applicable (MPH is Schedule II); Alabama has Schedule I state-level control [Ref 19] |
| **Australia** | Likely Schedule 9 (Poisons Standard, analogue) | Unknown | Not specifically confirmed; no 4F-MPH-specific scheduling document found |
| **International** | Not scheduled | — | Not subject to UN 1961 or 1971 Conventions [Ref 19] |

**Sweden:** Not confirmed from available sources.  
**Other EU member states:** Legal status varies; EMCDDA Early Warning System notification from November 2015 prompted country-level responses.

---

## Clinical Trials

No registered clinical trials for 4F-MPH were found on ClinicalTrials.gov. No institutional clinical research has been conducted with this compound.

---

## Community Feedback Analysis

No community feedback was submitted in Part A2 of the brief.

---

## Gaps & Flags

### ⚠️ Safety-Critical Flags

1. **Tramadol interaction "lethal" not verified by published source:** The DB value "Tramadol: lethal" cannot be confirmed against a published case report or experimental study specifically for 4F-MPH + tramadol. The mechanistic basis is sound but the specific severity designation is unverified. **Generation agent should flag this for editorial review before publishing as fact.**

2. **MDMA interaction "dangerous" not verified by published source:** Same issue — mechanistically plausible but no published 4F-MPH + MDMA study or case report exists.

3. **Fatal case is confounded by severe polydrug use:** The Shoff 2019 [Ref 4] fatal case involved 7 other substances. 4F-MPH's independent lethality cannot be determined from this single case. The toxicity notes in the DB ("Acute: moderate; Chronic: moderate") are stated as inferred from pharmacological class — this is appropriate but should be clearly labeled as inference.

4. **No LD₅₀ data:** No lethal dose data exists for any species. Any lethal dose estimate would be pure inference.

### ⚠️ Data Gaps

5. **No human pharmacokinetic study exists:** Tmax, bioavailability, half-life, and volume of distribution are unknown for 4F-MPH in humans. All duration data is user-report derived.

6. **No CYP enzyme data for 4F-MPH:** Metabolism is documented as de-esterification to carboxy metabolites (Manier 2020 [Ref 3]), but specific enzyme identification (CYP2D6, CES1) is not established for 4F-MPH.

7. **Tolerance and dependence: no substance-specific data.** All tolerance/dependence information is class-level inference from MPH.

8. **Physical properties are predicted, not experimental:** Boiling point, density, and pKa are predicted values. Melting point data (147–148°C) is from commercial sources and not peer-reviewed.

9. **Australia and Sweden legal status unconfirmed:** Could not find specific scheduling documents for these jurisdictions.

10. **Germany "re-legalization" September 2022:** This claim comes from web sources only and could not be verified against a legal or regulatory document. Flag for editorial review.

### Database Corrections / Additions Needed

11. **Missing chemical identity fields:** PubChem CID (52944002), InChIKey (XISBAJBPDVRSPG-CHWSQXEVSA-N), and molecular formula (C14H18FNO2) and weight (251.30) are all confirmed and should be added to the DB.

12. **CAS number missing from DB:** 1354631-33-6

13. **SMILES missing from DB:** The compound's SMILES can be derived from the PubChem CID or InChI but was not returned directly by the API call used; generation agent should retrieve from PubChem CID 52944002 directly.

14. **Dose/duration data fully user-report derived:** The existing DB dose/duration values are consistent with PsychonautWiki user-report data and no controlled study contradicts them, but the generation agent should note the evidence basis clearly in the article.