Amphetamine

# Research Output: Amphetamine

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## Chemical Identity

**PubChem CID:** 3007 (api_verified via PubChem lookup)
**Molecular formula:** C9H13N [Ref 1 — PubChem CID 3007]
**Molecular weight:** 135.21 g/mol [Ref 1]
**IUPAC name:** 1-phenylpropan-2-amine [Ref 1] (matches brief seed data)
**InChIKey:** KWTSXDURSIMDCE-UHFFFAOYSA-N [Ref 1] (racemic; was absent from brief — now confirmed)
**Canonical SMILES:** CC(N)Cc1ccccc1 [Ref 1 — derived from PubChem CID 3007 structure]
**CAS number:** 300-62-9 (well-established; not directly returned by API — flag for editorial verification)

**Brief discrepancies resolved:**
- Brief listed no molecular formula, MW, InChIKey, SMILES, or PubChem CID — all are now populated above from api_verified PubChem data.
- IUPAC name "1-phenylpropan-2-amine" in the brief matches the PubChem entry. The brief also listed this as the "systematic name," which is correct.

**Stereochemistry:** Amphetamine exists as two enantiomers. d-Amphetamine has the (S)-configuration and is the more pharmacologically active CNS enantiomer. l-Amphetamine has the (R)-configuration and exerts relatively greater peripheral (cardiovascular/adrenergic) activity. Clinical formulations include: enantiopure d-amphetamine (dextroamphetamine); racemic dl-amphetamine (reapproved 2014); mixed amphetamine salts (3:1 d:l mixture); and lisdexamfetamine, a lysine-conjugated prodrug of d-amphetamine Markowitz & Patrick (2017 [Ref 1]).

**Physical properties:**
- pKa: ~9.9 (weak base) de la Torre et al. (2004 [Ref 2])
- Highly lipophilic; readily crosses blood-brain barrier and cell membranes
- Volume of distribution: ~4 L/kg de la Torre et al. (2004 [Ref 2])
- Melting point and solubility data not retrieved via API (not in PubChem return); flag as gap

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## Pharmacology

### Mechanism of Action

Amphetamine is a substrate-type releasing agent at three monoamine transporters — the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT) — and a TAAR1 agonist. These mechanisms combine to produce massive increases in synaptic monoamine concentrations Fleckenstein et al. (2007 [Ref 27]).

**Substrate-type release mechanism** (via DAT/NET/SERT):
Amphetamine enters presynaptic terminals as a transporter substrate, carried inward in exchange for a monoamine molecule — a process termed "exchange diffusion" Fleckenstein et al. (2007 [Ref 27]). Once intracellular, amphetamine: (1) disrupts VMAT2 function through its weak-base properties, raising vesicular pH and collapsing the proton gradient that drives vesicular storage, thereby redistributing dopamine from vesicles into the cytoplasm; (2) reverses the direction of plasmalemmal transporters (DAT, NET, SERT), driving monoamine efflux into the synapse via carrier-mediated reverse transport; and (3) may also induce channel-like transporter behavior. This is mechanistically distinct from cocaine-type reuptake blockers, which block the transporter without reversing it Sonders et al. (1997 [Ref 15]). The critical role of DAT in amphetamine-induced extracellular dopamine elevation was definitively demonstrated in DAT-knockout mice: AMPH produced a 10-fold increase in extracellular DA in wild-type mice but no increase in DAT-knockout mice, despite similar vesicular depletion in both genotypes Jones et al. (1998 [Ref 6]).

**Relative monoamine selectivity:**
Amphetamine-type stimulants release norepinephrine more potently than dopamine, and both far more potently than serotonin Rothman et al. (2001 [Ref 13]). The NE/DA selectivity ratio for (+)-amphetamine is approximately 3.5 (in vitro), indicating roughly 3.5-fold greater potency at NE release vs DA release Alexander et al. (2005 [Ref 7]). Serotonin release is orders of magnitude weaker than for MDMA. This NE-preferential profile underlies amphetamine's marked peripheral sympathomimetic, anorectic, and wakefulness-promoting effects alongside its dopamine-mediated euphoric and reinforcing properties Rothman & Baumann (2006 [Ref 14]).

**TAAR1 agonism:**
Amphetamine is an agonist at the trace amine-associated receptor 1 (TAAR1), a Gαs-coupled GPCR. Amphetamines showed EC50 <5 µM at rat and mouse TAAR1 in functional cAMP assays; human TAAR1 activation was weaker, with prominent species differences (rank: rat > mouse > human) Simmler et al. (2016 [Ref 4]). Stereoselective binding at TAAR1 is determined primarily by residues Asp102 and Met268 within the receptor; these were confirmed as key determinants of AMPH binding in mutagenesis and homology modeling studies Reese et al. (2014 [Ref 5]). TAAR1 activation is thought to provide a partial autoinhibitory brake on dopaminergic output, modulating (but not overriding) the reinforcing effects at recreational doses.

**Adrenergic receptor effects:**
Alpha-adrenergic stimulation via released NE causes vasoconstriction, increased total peripheral resistance, and elevated blood pressure. Beta-adrenergic stimulation causes increased heart rate, stroke volume, and cardiac output Fitzgerald & Bronstein (2013 [Ref below — toxicology section]).

**Dopamine sensitization:**
Repeated intermittent amphetamine exposure produces behavioral sensitization — a progressive, enduring enhancement of AMPH-induced behavioral and neurochemical responses — via enhanced mesotelencephalic DA release upon re-exposure Robinson & Becker (1986 [Ref 16]). This sensitization underlies the "wanting without liking" pattern central to stimulant dependence: sensitized DA/incentive-salience circuits drive compulsive drug-seeking ("wanting") while hedonic capacity remains blunted or tolerant ("liking") Berridge & Robinson (2016 [Ref 17]).

### Binding Affinity Data

**Flag:** Specific Ki/EC50 values in nM for amphetamine at individual transporter proteins were not fully retrievable via PubMed API for this run (Rothman et al. 2001 abstract was partially available only). The following represents published data from the literature as crossreferenced from Rothman et al. 2001 [Ref 13] and Alexander et al. 2005 [Ref 7], but should be treated as requiring primary source verification before populating structured data:
- d-Amphetamine NE release EC50: ~7 nM (rat synaptosomes, Rothman et al. 2001)
- d-Amphetamine DA release EC50: ~25 nM (rat synaptosomes, Rothman et al. 2001)
- d-Amphetamine 5-HT release EC50: ~1765 nM (rat synaptosomes, Rothman et al. 2001)
- These values reflect the published literature; editorial should verify against Rothman et al. 2001 primary source (PMID 11071707; no DOI resolved via Crossref).

### Pharmacokinetics

**Oral bioavailability:** Good (high) — amphetamine is well-absorbed after oral administration de la Torre et al. (2004 [Ref 2]). Precise percentage bioavailability data not retrieved via API; see flag.
**Tmax (oral, immediate-release):** 2–3 hours Markowitz & Patrick (2017 [Ref 1])
**Half-life:** Adults ~10–12 hours; children ~7 hours (replicated finding) Markowitz & Patrick (2017 [Ref 1]); range 6–12 hours across formulations and pH conditions de la Torre et al. (2004 [Ref 2])
**Volume of distribution:** ~4 L/kg de la Torre et al. (2004 [Ref 2])
**Plasma protein binding:** <20% de la Torre et al. (2004 [Ref 2])
**pKa:** ~9.9 (weak base) de la Torre et al. (2004 [Ref 2])
**Renal clearance:** Urinary pH-dependent. Amphetamine, as a weak base (pKa 9.9), is ionized and trapped in acidic urine. Acidification of urine markedly accelerates elimination (relevant for overdose management and drug interactions); alkaline urine significantly prolongs half-life. This is the primary pharmacokinetic drug interaction mechanism of clinical significance Markowitz & Patrick (2017 [Ref 1]).
**Metabolism:** Hepatic metabolism is extensive, involving multiple CYP enzymes with stereoselective biotransformations that favor the l-isomer substrate Markowitz & Patrick (2017 [Ref 1]). Drug exposure exhibits dose-proportional kinetics. Both hepatic and renal clearance contribute. Specific CYP isoforms (likely CYP2D6 and others) are involved but precise enzyme identities were not confirmed via API retrieval for amphetamine specifically (see Gaps & Flags). Metabolites include 4-hydroxyamphetamine (via aromatic hydroxylation), norephedrine (via beta-hydroxylation), and benzoic acid derivatives.

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## History

Amphetamine was first synthesized in 1887 by the Romanian chemist Lazăr Edeleanu working in Germany, who named the compound phenylisopropylamine [Ref 26]. The pharmacological properties of the substance were unknown for four decades. In 1927, pharmacologist Gordon Alles independently resynthesized amphetamine while searching for a synthetic substitute for ephedrine; he tested it on himself and documented its sympathomimetic and CNS-stimulant properties [Ref 26].

Commercial development began in 1933 when Smith, Kline and French began marketing amphetamine as the over-the-counter inhaler Benzedrine, initially promoted as a decongestant/nasal inhaler [Ref 26]. Throughout the 1930s and 1940s, amphetamine's appetite-suppressant, wakefulness-promoting, and mood-elevating properties were recognized, and it was prescribed for obesity, narcolepsy, and depression.

During World War II, Benzedrine sulfate pills were routinely distributed to military personnel — particularly pilots flying long missions — to combat fatigue and sustain performance [Ref 25]. This wartime use established patterns of widespread amphetamine use that carried into peacetime.

The foundational pharmacological demonstration that amphetamine's behavioral effects were dopamine-mediated came from Randrup & Munkvad (1967 [Ref 22]), who showed that brain dopamine mediates amphetamine-induced stereotyped behavior — a discovery that underpinned the dopamine hypothesis of schizophrenia and decades of subsequent pharmacological research.

In the United States, amphetamine was placed in Schedule II under the Controlled Substances Act in 1970 [Ref 26], reflecting its accepted medical uses alongside high abuse potential. Amphetamine's clinical use has continued in ADHD (children and adults), narcolepsy, and historically obesity. Mixed amphetamine salts (Adderall) and lisdexamfetamine (Vyvanse) represent the principal current clinical formulations.

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## Subjective Effects

Controlled human studies confirm the following subjective effect profile from amphetamine administration:

**Positive/desired effects:** euphoria (labeled "High," "Like Drug" on VAS scales), increased energy, enhanced motivation, mood elevation, increased confidence Wardle & de Wit (2012 [Ref 12]). Amphetamine also enhances cognitive performance in some domains, including attention and executive function, in both ADHD and non-clinical populations.

**Cognitive effects:** d-Amphetamine affects post-error slowing (a measure of error monitoring) in healthy volunteers Wardle et al. (2012 [Ref 11]). Emotional reactivity is altered — amphetamine may reduce sensitivity to negative emotional stimuli independently of its direct mood effects Wardle & de Wit (2012 [Ref 12]).

**Stimulant effects:** Increased wakefulness, reduced appetite, reduced fatigue; enhanced alertness and focus consistent with NET-mediated noradrenergic effects.

**Perceptual/psychotic effects at high doses:** At high doses or with chronic use, amphetamine can produce paranoid psychosis clinically indistinguishable from paranoid schizophrenia. This amphetamine psychosis model has been extensively studied Robinson & Becker (1986 [Ref 16]). PET imaging in humans shows that amphetamine-induced striatal dopamine release is greater in patients with first-episode psychosis than controls, and that sensitization with repeated amphetamine exposure brings healthy controls' DA release to patient levels Weidenauer et al. (2020 [Ref 32 — from psychosis search]).

**Duration data from controlled studies:** Consistent with the brief's dose data: oral onset ~15–30 min, peak 2–4h, total duration 4–8h for standard doses. These figures derive from PK parameters (Tmax 2–3h, T1/2 10–12h) and align with clinical experience.

**Effects taxonomy notes:** The effects taxonomy in the brief (body, thinking, time, perception, feeling, self categories) aligns with the published subjective effect profile. The presence of "tracers," "geometry," and "sleep-transition hallucinations" in the taxonomy is consistent with high-dose or chronically sensitized use; these are not typical of low–moderate controlled doses. Sexual arousal suppression is a recognized NE-mediated effect at recreational/higher doses; Sexual arousal enhancement may occur at lower doses via increased dopamine.

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## Safety & Toxicity

### Acute Toxicity
**Overdose symptoms:** Hyperthermia, tachycardia, hypertension, mydriasis, tremors, agitation, tachypnea, and in severe cases: seizures, cardiac arrhythmias, intracranial hemorrhage, and death Fitzgerald & Bronstein (2013 [Ref below]). The primary mechanism is excessive catecholamine release causing alpha- and beta-adrenergic overstimulation.

**Management:** Benzodiazepines are first-line for CNS excitation and seizures. Beta-blockers (e.g., propranolol) for tachyarrhythmias. Cooling for hyperthermia. Acidification of urine enhances elimination. Antipsychotics are controversial (may lower seizure threshold, prolong QT, impair thermoregulation) Connors et al. (2019 [Ref 33]).

**Human LD50:** Not established. No confirmed human LD50 exists in the published literature (confirmed; consistent with brief seed data).

### Cardiovascular Toxicity
Acute: Tachycardia, hypertension, vasospasm, increased cardiac output via catecholamine excess.
Chronic: Cardiomyopathy (both ischemic and non-ischemic), accelerated atherosclerosis, pulmonary hypertension, arrhythmias O'Connor et al. (2005 [Ref 9]), Frishman et al. (2003 [Ref 10]).

Case report (Bagheri et al. 2025 [Ref 8]): A 43-year-old with 5 years of high-dose dextroamphetamine use (45–65 mg/day) presented with severely reduced LVEF (10–15%), dilated cardiomyopathy, and severe 3-vessel CAD requiring CABG. This case illustrates the potential for irreversible ischemic cardiomyopathy with chronic high-dose use — a more severe outcome than the reversible non-ischemic cardiomyopathy reported in most prior cases.

Long-term cardiovascular monitoring of mixed amphetamine salts (MAS XR) in adults with ADHD showed modest but meaningful increases in heart rate and blood pressure Weisler et al. (2005 [Ref 29]).

**Flag:** Chronic cardiovascular and neurotoxicity evidence derives primarily from methamphetamine cohort studies; amphetamine-specific human data remain sparse as noted in the brief. The generalizability is biologically plausible but should be stated as methamphetamine-cohort-derived in the article.

### Cerebrovascular Toxicity
Amphetamine abuse is associated with cerebral infarction and intracranial hemorrhage, mediated primarily by acute hypertension, vasospasm, and thrombosis O'Connor et al. (2005 [Ref 9]).

### Neurotoxicity
At high doses, amphetamine-type stimulants can damage dopaminergic terminals via a mechanism involving cytosolic DA oxidation, reactive oxygen species, and autophagy — demonstrated in VMAT2-heterozygous mice where reduced vesicular storage amplified METH-induced neurodegeneration Larsen et al. (2002 [Ref 30], Sulzer lab). The rate-limiting step is VMAT2-mediated protection of cytosolic DA from oxidation. For amphetamine specifically (vs methamphetamine), neurotoxic doses are higher and human data are limited.

### Pregnancy
Amphetamine use in pregnancy is associated with congenital anomalies and poor obstetric outcomes; use during pregnancy is contraindicated Ornoy (2018 [Ref 24]), Keegan et al. (2010 [Ref below]).

### Psychological Risks
- High-dose use and/or prolonged use can precipitate paranoid psychosis
- Pre-existing cardiovascular disease, hypertension, hyperthyroidism, and glaucoma represent contraindications based on mechanism (catecholamine excess)

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## Harm Reduction

**Testing:** Amphetamine can be identified with Marquis reagent (orange reaction), Simon's reagent (identifies secondary amines; negative for primary amines like amphetamine), and Robadope reagent (distinguishes primary from secondary amines). Fentanyl test strips are recommended for illicit supply.

**Cardiovascular monitoring:** Users with pre-existing cardiovascular conditions (hypertension, arrhythmia, structural heart disease) are at elevated risk. Blood pressure and heart rate monitoring is recommended during use.

**Hyperthermia:** In hot environments (clubs, exercise), heat dissipation is impaired by vasoconstriction. Cooling, hydration, and rest are critical harm reduction measures.

**Redosing:** Compulsive redosing (noted in the brief's effect taxonomy) is a well-recognized harm pattern driven by rapid euphoric tolerance and dopaminergic sensitization. Extended binge use markedly increases cardiovascular and psychiatric risk.

**Contraindications (from mechanism and published guidelines):**
- MAO inhibitors (hypertensive crisis, serotonin syndrome)
- Pre-existing cardiovascular disease, structural heart disease, hypertension
- Hyperthyroidism (potentiates catecholamine effects)
- Glaucoma (mydriasis increases intraocular pressure)
- History of psychosis or bipolar disorder (can exacerbate)
- Pregnancy

**Emergency response:** For suspected amphetamine overdose: call emergency services; manage seizures with benzodiazepines; cool hyperthermia; monitor cardiac function; do NOT delay seeking care.

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## Tolerance & Dependence

### Tolerance
Tolerance to euphoric and subjective effects develops rapidly (within days of repeated use) through downregulation of postsynaptic dopamine receptor sensitivity. Functional effects (appetite suppression, cognitive performance, wakefulness) show slower or absent tolerance development — the basis for sustained ADHD treatment efficacy with chronic dosing. This circuit-specific adaptation pattern (hedonic tolerance without functional tolerance) is consistent with the brief's seed data.

Cross-tolerance established with: methamphetamine, cocaine, other dopaminergic stimulants, and methylphenidate — all confirmed by shared DAT-mediated mechanisms Markowitz & Patrick (2017 [Ref 1]).

### Dependence
**Psychological dependence:** High. **Physical dependence:** Low. Both consistent with brief seed data.

The dependence mechanism is best understood through the incentive-sensitization theory (Robinson & Berridge 1986/2016): repeated amphetamine exposure sensitizes mesolimbic DA circuits that attribute incentive salience ("wanting") to drug cues, while hedonic circuits (liking) simultaneously develop tolerance. The result is compulsive drug-seeking driven by cue-triggered craving, persisting long after cessation, even when consumption no longer produces significant pleasure Berridge & Robinson (2016 [Ref 17]).

TAAR1 agonism provides a partial but insufficient inhibitory constraint on dopaminergic output at recreational doses.

**Compulsive redosing:** High, consistent with brief (listed as a known effect in the taxonomy and dependence data).

### Withdrawal
Amphetamine withdrawal is characterized primarily by psychological symptoms: dysphoria, depression, fatigue, hypersomnia, increased appetite, anhedonia, and craving. Physical withdrawal is mild relative to opioids or benzodiazepines. A completed Phase 2 trial (NCT01215929) studied amphetamine withdrawal in humans with methamphetamine dependence.

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## Interactions

**MDMA — Dangerous** (consistent with brief):
Combined use produces additive monoaminergic release across DA, NE, and 5-HT systems. This combination dramatically elevates serotonin syndrome risk, hyperthermia, cardiovascular strain, and psychiatric toxicity. The amplified 5-HT release from MDMA, combined with amphetamine's catecholamine effects, represents a physiologically dangerous load. Evidence-level: mechanism-based + case series; no controlled human data exist (ethically prohibited).

**Tramadol — Lethal** (consistent with brief):
Tramadol is a weak serotonin reuptake inhibitor (and μ-opioid agonist). Combined with amphetamine's monoamine-releasing activity (including serotonin), this combination creates a meaningful risk of serotonin syndrome. The "lethal" designation in the brief is clinically plausible on mechanistic grounds. **Flag:** No published case reports of specific amphetamine+tramadol fatalities were found via PubMed search in this research run. The lethal severity rating requires editorial verification against primary toxicology literature or poison control databases. The mechanism (serotonin syndrome precipitated by combined serotonergic agents) is well-established for tramadol in combination with other serotonergic drugs.

**MAOIs — Contraindicated (lethal risk):**
MAO inhibitors (e.g., phenelzine, tranylcypromine, selegiline) combined with amphetamine produce severe, potentially fatal outcomes: hypertensive crisis (from potentiated NE/tyramine effects) and serotonin syndrome. This combination is an absolute contraindication in all clinical guidelines Ulrich et al. (2017 [Ref 19]).

**PCP — Dangerous** (consistent with brief):
Mechanism unclear; likely additive CNS toxicity from combined stimulant (catecholamine) and dissociative (NMDA antagonism) effects. No specific published interaction studies found.

**GHB/GBL — Unknown** (consistent with brief):
Stimulant-depressant combination. GHB is a GABA-B agonist and endogenous neuromodulator. The interaction is understudied; risk of GHB rebound and respiratory depression after the stimulant effect wanes is a theoretical concern. No published interaction studies found.

**Alcohol — Unknown** (consistent with brief):
Amphetamine may mask alcohol intoxication (stimulant counteracts CNS depression), leading to alcohol overconsumption and delayed recognition of impairment. Increased cardiovascular stress from combined adrenergic and alcohol-related vasodilation/arrhythmia mechanisms. No controlled interaction studies found.

**Cocaine — Unknown** (consistent with brief):
Additive dopaminergic and catecholamine effects; increased cardiovascular risk. Both increase extracellular DA, but via different mechanisms (release vs reuptake inhibition). Clinical interaction data absent.

**Caffeine — Unknown** (consistent with brief):
Additive stimulant effects via different mechanisms (adenosine antagonism vs monoamine release). Generally considered low-risk at typical caffeine doses but increases heart rate and blood pressure additively.

**Methamphetamine — Caution** (consistent with brief):
Additive dopaminergic stimulant effects with greater CNS and cardiovascular load. Cross-tolerance exists between the two.

**Urinary pH interactions:** Agents that acidify urine (e.g., ascorbic acid, ammonium chloride) significantly increase amphetamine renal clearance and reduce duration/intensity of effects. Alkalinizing agents (e.g., sodium bicarbonate, acetazolamide) markedly prolong amphetamine half-life and effects — clinically relevant interaction Markowitz & Patrick (2017 [Ref 1]).

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## Legal Status

**United States:** Schedule II controlled substance (Controlled Substances Act, 1970). High potential for abuse; currently accepted medical use with severe restrictions. Prescription required; no refills permitted. DEA-scheduled [Ref 26].

**United Kingdom:** Class B controlled drug (Misuse of Drugs Act 1971). Prescription-only for medical use; unauthorized supply is a criminal offense [Ref 26].

**Australia:** Schedule 8 (Controlled Drug) under the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP). Prescribing of amphetamine-type CNS stimulants (e.g., dexamfetamine) requires specialist authorization in most Australian states [Ref 26].

**Canada:** Schedule I controlled substance (Controlled Drugs and Substances Act, CDSA). Severe restrictions; medical use permitted under strict oversight [Ref 26].

**European Union:** Prescription-only in most EU member states; scheduling and availability vary by country. Dexamfetamine is licensed in some countries (e.g., UK) for ADHD and narcolepsy; not available in others.

**Note on sources:** Legal status information derives from web-retrieved sources (quality: web_retrieved) as regulatory databases are not indexed on PubMed/OpenAlex. Editorial should verify current scheduling status before publication, as it can change.

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## Clinical Trials

**ATLAS4Dependence (NCT not retrieved; PMID 41120148):**
- Phase: RCT (protocol published 2025)
- Status: Active — multi-centre, double-blind, placebo-controlled
- Intervention: Dextroamphetamine substitution treatment for amphetamine/methamphetamine dependence
- Conditions: Amphetamine dependence in marginalized populations
- Sponsor: Chalabianloo, Fadnes, et al. (Haukeland University Hospital / Norway)
- Relevance: Current evidence base for pharmacological treatment of amphetamine dependence

**NCT00248092 (completed):**
- Phase: Phase 1
- Status: Completed
- Title: Likeability, Safety, and Abuse Potential of NRP104 (lisdexamfetamine) vs d-amphetamine in adults with stimulant abuse histories
- Sponsor: New River Pharmaceuticals
- Relevance: Abuse potential comparison; lisdexamfetamine vs d-amphetamine pharmacology

**NCT01924429 (completed):**
- Phase: Phase 4
- Status: Completed
- Title: Neurobiological Basis of Response to Vyvanse (lisdexamfetamine) in Adults with ADHD: fMRI study
- Sponsor: Jeffrey Newcorn
- Relevance: Brain mechanisms of amphetamine-class drug action in ADHD

**NCT01215929 (completed):**
- Phase: Phase 2
- Status: Completed
- Title: Studying Amphetamine Withdrawal in Humans
- Conditions: Methamphetamine Dependence
- Sponsor: University of Arkansas
- Relevance: Characterization of amphetamine-type withdrawal in humans

**Network meta-analysis context:** Cortese et al. (2018 [Ref 18]) — Lancet Psychiatry NMA of ADHD medications — found amphetamines to be among the most efficacious treatments for ADHD across age groups, though the full results comparing amphetamine vs methylphenidate head-to-head were complex and age-dependent. This is the highest-quality systematic evidence for amphetamine's clinical efficacy.

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## Community Feedback Analysis

No community feedback was submitted in Part A2 of the brief. This section is therefore skipped per protocol.

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## Gaps & Flags

### Safety-Critical Values Requiring Editorial Review

1. **Tramadol interaction severity ("lethal"):** The lethal designation is mechanistically plausible (serotonin syndrome risk) but no published case reports of amphetamine+tramadol fatality were found via PubMed in this research run. This requires verification against primary toxicology literature, poison control databases, or case report series before retaining the "lethal" severity classification. FLAG FOR HUMAN REVIEW.

2. **Specific binding affinity values (Ki/EC50 in nM):** The API-retrieved abstract for Rothman et al. 2001 (PMID 11071707) was a cached summary without exact nM values. The EC50 estimates in the Pharmacology section (NE ~7 nM, DA ~25 nM, 5-HT ~1765 nM) are widely cited in the amphetamine literature as from this paper, but should be verified directly against the primary source before entering structured database fields. FLAG FOR HUMAN REVIEW.

3. **Human LD50:** Not established. No published value found. Consistent with brief. Do not populate.

4. **Chronic neurotoxicity — methamphetamine vs amphetamine:** Most published human neuroimaging and neurotoxicity data concern methamphetamine cohorts. Amphetamine-specific chronic neurotoxicity data in humans are sparse. Any claims about amphetamine neurotoxicity should be qualified as methamphetamine-cohort-derived or preclinical.

5. **Absolute oral bioavailability percentage:** High bioavailability is confirmed qualitatively but a precise percentage figure was not retrieved by API. de la Torre 2004 states "good oral bioavailability" without an exact percentage. Lisdexamfetamine studies show near-complete bioavailability for the prodrug, but for amphetamine itself the precise figure requires primary source verification.

6. **CYP enzymes specifically metabolizing amphetamine:** CYP2D6 is likely involved (consistent with general phenethylamine metabolism) but specific enzyme identities for amphetamine were not confirmed via API. Markowitz & Patrick 2017 note "multiple enzymes" with stereoselective biotransformations. This gap should be flagged.

7. **CAS number 300-62-9:** Well-established in chemical literature but not directly returned by the PubChem API in this run. Treat as web-retrieved rather than api_verified.

8. **SMILES string:** The canonical SMILES CC(N)Cc1ccccc1 is derived from the PubChem CID 3007 structure (consistent with IUPAC name and formula) but was not explicitly returned as a string by the API in this run. Should be confirmed directly from PubChem CID 3007.

9. **Melting point, solubility:** Not retrieved; not in brief. Data gap — not populated.

10. **PCP interaction mechanism:** Listed as "dangerous" in brief; no specific published interaction data found in this research run. Designation appears to be based on combined CNS toxicity inference rather than documented case reports or pharmacodynamic studies. Flag for editorial review.

11. **Legal status sources:** All legal scheduling information derives from web-retrieved sources, not primary regulatory databases or peer-reviewed publications. Current status should be verified directly with DEA, MHRA, TGA, and Health Canada databases before publication.

### No-Community-Feedback Note
Part A2 was empty. No community feedback items to investigate or flag.