Amphetamine
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Amphetamine — also known as speed — is a synthetic stimulant of the phenethylamine class. It is the structural parent of methamphetamine and MDMA. It works by reversing dopamine and norepinephrine transporters,[1] flooding the synapse with these neurotransmitters and driving its characteristic stimulation.[2]
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methamphetamine, cocaine, methylphenidate +1 moremethamphetamine, cocaine, methylphenidate, other dopaminergic stimulants show less
First synthesized in 1887, its stimulant properties went unrecognized until Gordon Alles self-administered it in 1927.[3] It spread widely in the twentieth century — issued to soldiers in World War II, then prescribed for depression, obesity, and narcolepsy. Today it remains a first-line ADHD medication,[4] available as mixed salts, extended-release preparations, and lisdexamfetamine.[5]
Subjective effects include euphoria, increased energy, heightened focus, appetite suppression, and talkativeness. The experience has a driven, physically activating clarity — a steady stimulation that channels into sustained productivity or social confidence depending on context. Insomnia, jaw tension, anxiety, and prolonged fatigue are characteristic unsought effects.
Psychological dependence liability is high, and cardiovascular toxicity — elevated heart rate, blood pressure, and heart damage with chronic heavy use[6] — is the primary organ risk. Tolerance to euphoria develops fast while the drive to use intensifies, creating escalating compulsion with diminishing reward.[7] Amphetamine is among the most extensively studied stimulants, though long-term neurotoxicity data specific to amphetamine remain limited.
History[edit]
Discovery
Amphetamine was first synthesized in 1887 but its stimulant properties went unrecognized for four decades.[3] In 1927, Gordon Alles independently resynthesized it, self-administered it, and documented its stimulant and sympathomimetic effects.[3] These observations launched its clinical trajectory.
Clinical and cultural significance
Commercial production began in 1933 as Benzedrine, marketed as a nasal decongestant but quickly used for obesity, narcolepsy, and depression.[3] Benzedrine tablets were distributed to Allied soldiers in World War II to sustain performance on extended missions.[8] This institutional use normalized stimulant consumption in ways that carried into peacetime civilian life.
Regulation and modern use
Escalating non-medical use led to Schedule II classification in the United States in 1970.[3] Amphetamine remains among the most effective ADHD medications across age groups, confirmed by large-scale network meta-analysis.[4] Modern formulations include mixed amphetamine salts (Adderall), extended-release versions, and lisdexamfetamine (Vyvanse) — a prodrug with lower abuse potential.[5]
The name "amphetamine" is a contraction of its chemical name: alpha-methyl-phenethylamine. Street names — speed, bennies, uppers — reflect decades of non-medical use. The substance holds a dual identity: a legitimate medication prescribed to millions for ADHD, and a drug associated with overwork, academic pressure, and all-night productivity culture.
Chemistry[edit]
Structural class
Amphetamine belongs to the phenethylamine class — the same chemical family as methamphetamine and MDMA. Its molecular formula is C₉H₁₃N (molecular weight 135.21 g/mol).[5]
An alpha-methyl group in its structure slows breakdown by monoamine oxidase and allows it to cross the blood-brain barrier readily,[9] enabling oral activity and its characteristic multi-hour duration.
Pharmacology[edit]
Mechanism of action
Amphetamine enters nerve terminals via the same transporters that normally clear dopamine and norepinephrine from the synapse.[10] Once inside, it disrupts neurotransmitter storage and reverses those transporters, flooding the synapse with both neurotransmitters.[10][2] Norepinephrine release drives physical activation, appetite suppression, and wakefulness; dopamine release drives euphoria and reinforcement.[1][11]
Behavioral sensitization
Repeated intermittent use progressively enhances the neurochemical response to subsequent doses.[12] This sensitization amplifies drug-seeking ("wanting") while hedonic response develops tolerance.[7]
Pharmacokinetics
Amphetamine is well absorbed orally, reaching peak levels in 2–3 hours for immediate-release forms, with a half-life of roughly 10–12 hours in adults.[5][9] Kidney elimination is strongly pH-dependent: acidic urine speeds excretion; alkaline urine prolongs effects significantly — a factor in both overdose management and drug combinations.[5]
Neuroscience[edit]
Reward pathways and prefrontal function
Amphetamine potentiates dopamine release along reward circuits — producing euphoria — and in the prefrontal cortex, shaping attention and executive function.[12] PET imaging confirms that striatal dopamine release correlates directly with subjective euphoria.[13] In ADHD, therapeutic doses correct deficient prefrontal signaling, improving attention; this benefit does not extend to healthy adults.[14][15]
Sensitization and the incentive-salience model
Repeated use progressively amplifies the dopamine response upon re-exposure.[12] Circuits governing drug-seeking ("wanting") become more reactive while circuits governing pleasure ("liking") develop tolerance[7] — escalating compulsion with diminishing reward. This sensitization can drive dopamine release toward profiles seen in first-episode psychosis;[13] amphetamine psychosis was the original model for the dopamine hypothesis of schizophrenia.[16]
The extent to which a brake mechanism (TAAR1) limits dopamine output at human-relevant doses remains uncertain — it is far weaker in humans than in rodent models.[17] The dose and duration at which amphetamine — as distinct from methamphetamine — damages dopamine terminals in humans has not been established.[18]
Subjective Effects[edit]
Amphetamine's character is physical as much as mental — a driven, activating clarity rather than a purely cerebral lift. The stimulation is steady and channels easily into sustained work or social engagement. Set and context shape it strongly; individual differences in catecholamine baseline produce wide variation in how the experience feels.
Compared to cocaine, the experience is longer and steadier, with a more gradual onset and a slower, more extended recovery period. Relative to methylphenidate, amphetamine's transporter-reversing mechanism produces a qualitatively fuller effect — more euphoric and more physically activating — with correspondingly greater reinforcement potential.
Effect Grid
At common doses (15–30 mg oral), the full stimulant profile is established: pronounced euphoria, significant motivation enhancement, confidence increase, and sustained focus. Thought acceleration is marked, with rapid ideation and increased talkativeness. Emotional enhancement produces feelings of well-being and sociability. Time distortion may occur, with hours passing unnoticed during engaged tasks.
Physical stimulation is substantial: elevated heart rate and blood pressure, appetite suppression (eating becomes difficult or unappealing), jaw tension, and increased body temperature. Sweating and peripheral vasoconstriction are common. Sexual arousal may be enhanced at the lower end of this range.
Sleep is impossible for 6–10 hours after dosing. Compulsive redosing urges may emerge as peak effects begin to wane.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Visual acuity enhancement · Visual processing acceleration · Tracers · Brightness alteration · Auditory misinterpretation · Peripheral misidentification · Tinnitus · Geometry · Auditory hallucinations · External hallucinations · Shadow people · Object transformations · Internal hallucinations · Persisting hallucinations
Auditory misinterpretation · Peripheral misidentification · Tinnitus · Geometry · Auditory hallucinations · External hallucinations · Shadow people · Object transformations · Internal hallucinations · Persisting hallucinations
Pupil dilation · Physical fatigue · Insomnia · Restlessness · Respiratory stimulation · Dehydration sensation · Dry mouth · Body high · Spontaneous body sensations · Excessive sweating · Bruxism · Heart rate perception changes · Muscle tension · Tactile euphoria · Temperature dysregulation · Sexual arousal enhancement · Tingling / electric sensations · Vibrations / buzzing · Nausea · Sexual arousal suppression · Constipation · Headache · Pain suppression · Increased urination · Dizziness · Trembling · Involuntary body movements · Vomiting · Seizure threshold reduction
Restlessness · Respiratory stimulation · Dehydration sensation · Dry mouth · Body high · Spontaneous body sensations · Excessive sweating · Bruxism · Heart rate perception changes · Muscle tension · Tactile euphoria · Sexual arousal enhancement · Tingling / electric sensations · Vibrations / buzzing · Nausea · Sexual arousal suppression · Constipation · Headache · Pain suppression · Increased urination · Dizziness · Trembling · Involuntary body movements · Vomiting · Seizure threshold reduction
Cognitive fatigue · Motivation enhancement · Cognitive flexibility · Motivation suppression · Immersion enhancement · Thought organization · Analysis enhancement · Information processing enhancement · Memory enhancement · Aesthetic enhancement · Language enhancement · Novelty enhancement · Pattern recognition enhancement · Thought connectivity · Suggestibility suppression · Cognitive dysphoria · Multiple thought streams · Creativity enhancement · Thought loops · Cognitive impairment · Confusion · Thought disorganization · Delusions · Delirium
Motivation suppression · Immersion enhancement · Thought organization · Analysis enhancement · Information processing enhancement · Memory enhancement · Aesthetic enhancement · Language enhancement · Novelty enhancement · Pattern recognition enhancement · Thought connectivity · Suggestibility suppression · Cognitive dysphoria · Multiple thought streams · Creativity enhancement · Thought loops · Cognitive impairment · Confusion · Thought disorganization · Delirium
Irritability · Anhedonia · Emotional enhancement · Emotional suppression · Emotional lability · Empathy enhancement · Mania · Suicidal ideation
Emotional suppression · Emotional lability · Empathy enhancement · Suicidal ideation
Disinhibition · Flow state · Social connection · Self-control enhancement · Depersonalization · Derealization
Depersonalization · Derealization
Timeline
First alerts emerge as subtle wakefulness and a faint brightening of mood. Physical awareness of increased heart rate may precede cognitive effects.
Stimulation builds steadily. Focus sharpens, motivation increases, and mood elevation becomes unmistakable. Appetite suppression begins.
Maximum euphoria, confidence, and cognitive drive. Thought acceleration, talkativeness, and task engagement are at their highest. Physical stimulation — tachycardia, vasoconstriction, jaw tension — is most pronounced.
Euphoria gradually fades while functional stimulation persists. Focus and wakefulness continue but with diminishing hedonic quality. Compulsive redosing urges often emerge during this phase.
Stimulation wanes. Fatigue, irritability, and mild dysphoria surface as catecholamine stores deplete. Appetite begins to return.
Residual effects include fatigue, low mood, difficulty concentrating, and disrupted sleep architecture. Some users experience rebound hypersomnia and increased appetite over 12–24 hours.
⚠ Do not drive or operate machinery during the comedown and crash period, as reaction time and judgment remain impaired despite subjective feelings of sobriety.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- Moderate
- Tolerance buildup
- rapid
- Tolerance reset
- 14 days
- Physical
- Low
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- Moderate
- Cross-tol.
- methamphetamine · cocaine · methylphenidate
Toxicity
Acute toxicity
Acute overdose produces rapid heart rate, high blood pressure, dangerously elevated body temperature, tremors, agitation, and rapid breathing.[20] Severe cases progress to seizures, irregular heart rhythms, bleeding in the brain, muscle breakdown, and death.
Benzodiazepines are the first-line treatment for agitation and seizures. Antipsychotics are controversial — a systematic review found limited supporting evidence and noted risks including lowered seizure threshold and impaired temperature regulation.[21]
For suspected amphetamine overdose: contact emergency services immediately. Manage seizures with benzodiazepines. Actively cool elevated body temperature. Monitor heart rhythm continuously. Do not delay seeking medical care.
Cardiovascular toxicity
Acute effects include rapid heart rate, high blood pressure, blood vessel spasm, and increased cardiac output.[20] Chronic high-dose use is associated with heart muscle damage, accelerated artery hardening, elevated lung blood pressure, and irregular heart rhythms.[6][22]
One documented case showed severely reduced heart pumping function (ejection fraction 10–15%), an enlarged heart, and severe coronary artery disease after five years of high-dose dextroamphetamine use.[23] Long-term therapeutic use produces modest but meaningful increases in heart rate and blood pressure.[24]
Cerebrovascular toxicity
Amphetamine abuse is associated with stroke and brain hemorrhage, driven primarily by acute blood pressure spikes, blood vessel spasm, and clot formation.[6]
Neurotoxicity
At high doses, amphetamine-type stimulants can damage dopamine-producing nerve terminals through oxidative stress.[18] Most published human data concerns methamphetamine users; amphetamine-specific chronic neurotoxicity evidence in humans is sparse.
Pregnancy
Amphetamine use during pregnancy is associated with birth defects and adverse outcomes.[25][26] Animal studies show lasting changes in dopamine system development following prenatal exposure.[19]
Psychological risks
High doses or chronic use can produce paranoia, hallucinations, and delusional thinking — a psychosis clinically indistinguishable from paranoid schizophrenia.[12][16] PET imaging confirms repeated exposure can sensitize dopamine release toward levels seen in psychotic disorders.[13]
Those with pre-existing psychotic spectrum disorders or bipolar disorder face elevated risk. Chronic use can produce a persistent paranoid cognitive style that may not fully resolve after stopping.
Tolerance & dependence
Tolerance to euphoria develops within days of repeated use as dopamine receptor sensitivity decreases. Functional effects — attention, appetite suppression, wakefulness — develop tolerance more slowly, which is why therapeutic efficacy persists with chronic ADHD dosing.[5] Cross-tolerance exists with Methamphetamine, cocaine, methylphenidate, and other dopaminergic stimulants.[5]
Psychological dependence is high: the incentive-sensitization mechanism progressively amplifies drug-seeking while the pleasure of use diminishes — compulsive use that persists long after meaningful reward is gone.[7] Withdrawal is primarily psychological: low mood, fatigue, excessive sleep, appetite enhancement, anhedonia, and craving. Physical withdrawal is mild compared to opioid or benzodiazepine withdrawal.
Drug interactions
The most dangerous combination is with monoamine oxidase inhibitors (MAOIs). Combining amphetamine with an MAOI can trigger a potentially fatal blood pressure spike and serotonin syndrome — dangerous overheating and seizures. This is an absolute contraindication; a minimum 14-day washout after stopping an MAOI is required.[27]
Combined use with MDMA dramatically amplifies release across dopamine, norepinephrine, and serotonin systems, elevating serotonin syndrome risk, dangerous body temperature rise, and cardiovascular toxicity. Tramadol carries meaningful serotonin syndrome risk as well.safety citation needed
Other stimulants (Cocaine, Methamphetamine, caffeine) add cardiovascular strain. Alcohol combined with amphetamine is concerning — the stimulant masks intoxication, leading to overconsumption and delayed recognition of impairment.
Urinary pH alters duration significantly: acidifying agents (ascorbic acid, ammonium chloride) speed excretion; alkalinizing agents (sodium bicarbonate, acetazolamide) prolong effects.[5]
Contraindications
Absolute contraindications:
- MAOI co-administration: Risk of hypertensive crisis and serotonin syndrome. Minimum 14-day washout required after MAOI discontinuation.[27]
- Structural heart disease or advanced cardiovascular disease: Amphetamine increases cardiovascular stress in the setting of existing heart damage.[6]
- Pregnancy: Associated with birth defects and adverse outcomes.[25]
Relative contraindications:
- High blood pressure: Amphetamine raises blood pressure in a dose-dependent way.
- Overactive thyroid: Excess thyroid hormone amplifies sensitivity to stimulant cardiovascular effects.
- Glaucoma: pupil dilation from sympathomimetic effects can trigger dangerously elevated eye pressure.
- History of psychosis or bipolar disorder: Dopamine stimulation can trigger psychotic episodes or mood destabilization.[12]
- Seizure disorders: Amphetamine may lower seizure threshold at high doses.
Harm Reduction[edit]
Forms & Identification
Pharmaceutical amphetamine comes in tablet and capsule forms with consistent dosing. Non-pharmaceutical supply — pressed pills or powder — may contain unknown quantities of amphetamine, methamphetamine, or other substitutes entirely.
Reagent testing distinguishes amphetamine from many common adulterants but cannot confirm purity or precise dose. Test any non-pharmaceutical stimulant powder with fentanyl test strips — fentanyl contamination of stimulant supply has been documented in multiple regions.
Guidelines
- Test non-pharmaceutical supply with reagent kits and fentanyl test strips before use
- Start with the lowest effective dose, especially with unfamiliar supply — redosing extends duration significantly and increases cardiovascular strain
- Eat a substantial meal before use — amphetamine suppresses appetite strongly, and failing to eat beforehand often means not eating for many hours
- Stay hydrated throughout with steady moderate fluid intake
- Set an alarm or checkpoint time to prevent dose stacking and enforce a stopping point
- Avoid use late in the day — the long half-life (10–12 hours) makes late dosing a reliable path to insomnia
Set & Setting
Amphetamine's long duration requires planning — residual stimulation and insomnia can extend well beyond the primary effects. Stimulant effects mask fatigue and dehydration, making physical overexertion a real risk in active or social settings.
Having a defined endpoint — a time to stop, leave, or begin winding down — counteracts the tendency to extend use or redose as effects wane.
Aftercare & integration. The post-amphetamine period typically involves fatigue, low mood, appetite enhancement, and difficulty concentrating — a comedown reflecting temporary depletion of dopamine and norepinephrine that typically resolves within 24–72 hours.
Prioritize sleep above all else. Eat nutritious meals even if appetite has not fully returned. Avoid caffeine or additional stimulants to compensate for fatigue, as this extends the recovery period. If low mood persists beyond several days or includes suicidal thoughts, seek professional support.
Recovery & Support
Amphetamine dependence is primarily psychological — the absence of severe physical withdrawal can create the illusion that stopping is simple, when in practice the pull of sensitized wanting makes relapse common. Professional support options include cognitive-behavioral therapy, contingency management, and peer support programs.
No pharmacotherapy is currently approved specifically for amphetamine use disorder, though research into substitution therapy and other approaches continues. SAMHSA's National Helpline (1-800-662-4357) provides free referrals. Sensitized craving pathways gradually normalize with sustained abstinence — recovery is a process with well-understood neuroscience behind it.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: chest pain, seizures, loss of consciousness, body temperature hot to the touch through clothing, severe confusion, or aggressive paranoia indicate a medical emergency — not just discomfort.
Immediate steps:
- 1. Call emergency services
- 2. Do not leave the person alone
- 3. If conscious, move to a cool, quiet environment and remove excess clothing
- 4. If unconscious but breathing, place in the recovery position
- 5. Do not attempt to restrain unless there is immediate danger of self-harm
- 6. Do not give food or water to an unconscious person
What to tell the dispatcher: State that a stimulant was taken, the approximate amount and time, and describe current symptoms (heart rate, temperature, consciousness level). Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Legal Status[edit]
Amphetamine is controlled in every major jurisdiction, with recognized medical applications for ADHD, narcolepsy, and binge eating disorder.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Schedule II (Controlled Substances Act, 1970) | High abuse potential with accepted medical use; prescription required; no refills; DEA-registered prescribers only[3] |
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Prescription-only for medical use; unauthorized supply is a criminal offense[3] |
| Canada | Schedule I (CDSA) | Severe restrictions; medical use permitted under strict oversight[3] |
| Australia | Schedule 8 (Controlled Drug) | Prescribing requires specialist authorization in most states[3] |
| European Union | Varies by member state | Prescription-only where available; dexamfetamine licensed in some countries for ADHD and narcolepsy; not marketed in others |
Analog and prodrug considerations
Lisdexamfetamine holds its own Schedule II classification in the United States and equivalent classifications elsewhere.[28] Its lower abuse potential compared to immediate-release forms reflects its rate-limited conversion to active d-amphetamine.
Legal status information derives from web-retrieved regulatory sources and should be verified against current national scheduling databases. Scheduling status is subject to change.
references
- [1] ^abRothman RB, Baumann MH, Dersch CM, Romero DV, Rice KC, Carroll FI, Partilla JS (2001) Amphetamine-type central nervous system stimulants release norepinephrine more potently than they release dopamine and serotonin — Synapse PMID:11071707
- [2] ^abJones SR, Gainetdinov RR, Wightman RM, Caron MG (1998) Mechanisms of Amphetamine Action Revealed in Mice Lacking the Dopamine Transporter — Journal of Neuroscience doi:10.1523/jneurosci.18-06-01979.1998
- [3]
- [4] ^abCortese S, Adamo N, Del Giovane C, et al. (2018) Comparative efficacy and tolerability of medications for ADHD in children, adolescents, and adults: a systematic review and network meta-analysis — The Lancet Psychiatry doi:10.1016/s2215-0366(18)30269-4
- [5]
- [6] ^abcdO'Connor AD, Rusyniak DE, Bruno A (2005) Cerebrovascular and cardiovascular complications of alcohol and sympathomimetic drug abuse — Medical Clinics of North America PMID:16105252