Stimulant Use Disorder — Cocaine and Amphetamines

• Dopamine System Dysregulation — Primary Mechanism: Cocaine and amphetamines increase synaptic dopamine through distinct mechanisms. Cocaine acts as a reuptake inhibitor of dopamine transporters (DAT), blocking the removal of dopamine from the synaptic cleft and increasing its concentration 2-3 fold within minutes. Amphetamines work through multiple pathways: they inhibit DAT (less potently than cocaine) but also promote dopamine release from presynaptic vesicles via interactions with the vesicular monoamine transporter (VMAT2), and they inhibit monoamine oxidase (MAO), reducing dopamine catabolism. This results in supraphysiologic dopamine levels in the nucleus accumbens and ventral tegmental area, producing intense euphoria and reinforcement. Repeated stimulation causes downregulation of dopamine D2 receptors and reduced dopaminergic tone in reward circuits during abstinence, driving craving and relapse.

• Noradrenergic and Sympathomimetic Effects: Both cocaine and amphetamines inhibit norepinephrine reuptake, increasing synaptic NE and producing sympathomimetic effects including tachycardia, hypertension, hyperthermia, mydriasis, and vasoconstriction. This is mediated through alpha-1 and beta-adrenergic receptors. The vasoconstriction is particularly significant in coronary vessels, which combined with increased myocardial oxygen demand and potential prothrombotic effects (via platelet activation), explains the high incidence of myocardial infarction even in young patients without atherosclerotic disease. The peripheral vasoconstriction can be profound, leading to digital gangrene, limb ischemia, and tissue necrosis, especially with chronic use or intraarterial injection.

• Serotonergic System Involvement: Both drugs inhibit serotonin reuptake to varying degrees, with amphetamines having more pronounced effects. This contributes to mood elevation acutely but also to dysphoria, anhedonia, and depression during withdrawal as serotonergic tone decreases. In chronic users, serotonergic dysfunction may persist and contribute to psychiatric comorbidities.

• Neuroadaptation and Withdrawal Physiology: Chronic stimulant use produces profound neuroadaptation including receptor downregulation (particularly D2 receptors), altered gene expression, reduced dopamine synthesis, and impaired stress response systems. Upon cessation, these maladaptive changes create a hypodopaminergic state characterized by anhedonia, dysphoria, fatigue, and hypersomnia lasting days to weeks. Unlike opioid withdrawal, stimulant withdrawal is not medically dangerous but is extremely aversive psychologically, driving high relapse rates. The dopamine deficit hypothesis suggests that stimulant users may have underlying dopaminergic hypofunctioning (genetic or developmental) predisposing to use and self-medication.

• Neurotoxic Effects of Amphetamines: Chronic methamphetamine use causes selective neurotoxicity to dopaminergic and serotonergic neurons through multiple mechanisms including oxidative stress (via MAO inhibition producing hydrogen peroxide), mitochondrial dysfunction, excitotoxicity, hyperthermia, and neuroinflammation. Neuroimaging studies demonstrate reduced striatal dopamine transporter density correlating with duration of use. This neurotoxicity can produce persistent cognitive deficits (attention, memory, executive function), motor abnormalities resembling Parkinson's disease, and psychosis even after extended abstinence.

• Immunomodulation and Infection Risk: Stimulants impair immune function through direct effects on lymphocytes and macrophages, reducing antiviral responses. Combined with behavioral factors (injecting, poor hygiene, sexual risk-taking), this produces markedly elevated HIV, hepatitis C, and other bloodborne pathogen risks in injection drug users. Additionally, stimulants may promote HIV replication and accelerate disease progression.

• Genetic Predisposition: Family studies demonstrate 40-60% heritability for cocaine and amphetamine use disorders. Specific genetic variants affecting dopamine regulation (including in DAT, COMT encoding catechol-O-methyltransferase, and BDNF) increase vulnerability. Individuals with reduced dopaminergic tone (assessed by lower baseline dopamine release or reduced D2 receptor availability) show greater reward sensitivity to stimulants and higher addiction risk. The COMT val158met polymorphism influences dopamine catabolism and modulates stimulant reward sensitivity.

• Psychiatric Comorbidity and Self-Medication: Attention-deficit/hyperactivity disorder (ADHD), depression, bipolar disorder, and anxiety disorders strongly predict stimulant use disorder development. Users often report self-medication for ADHD symptoms (particularly with methamphetamine and prescription amphetamines) or mood dysregulation. The shared dopaminergic dysregulation in ADHD makes individuals with this condition approximately 5-10 fold more likely to develop stimulant use disorder. Conversely, stimulant-induced psychiatric symptoms (paranoia, mania, depression) can worsen underlying conditions.

• Environmental and Social Factors: Socioeconomic disadvantage, peer influences, early substance use initiation, childhood trauma, and availability of drugs substantially increase risk. Cocaine epidemics have historically followed patterns of availability and marketing, whereas methamphetamine has become increasingly prevalent in rural and suburban areas. Incarceration history, housing instability, and social marginalization are associated with both use initiation and treatment engagement barriers.

• Age of Onset: Earlier age of first use (before age 18) is strongly associated with subsequent stimulant use disorder development, consistent with neurobiological evidence of ongoing prefrontal cortex development through the early 20s. Early use produces more severe long-term consequences and poorer treatment outcomes.

• Route of Administration: Intravenous and smoked (crack cocaine, methamphetamine) routes produce more rapid dopamine elevation and greater addiction potential compared to intranasal use. The speed of onset and offset of reward directly predicts addiction severity—smoked crack cocaine reaches the brain in 6-8 seconds producing intense but brief euphoria followed by rapid decline, driving frequent re-dosing and binge patterns.

• Specific Drug Factors: Cocaine's shorter duration of action (15-30 minutes) produces greater crash-induced dysphoria and craving compared to methamphetamine (8-24 hour duration), paradoxically making cocaine users more likely to seek treatment. Methamphetamine's longer duration promotes sustained use patterns and greater neurotoxic exposure. Synthetic cathinones ("bath salts") carry extreme addiction potential and severe psychiatric complications.

Acute Intoxication Phase (Minutes to Hours)

• Euphoria and Reward: Intense pleasurable sensation beginning within seconds to minutes (smoked) or 5-30 minutes (intranasal) represents the primary reinforcing effect driving repeated use. This rush results from rapid dopamine elevation in reward circuits and is described as "orgasm-like" or "whole-body pleasure."

• Sympathomimetic Constellation: Tachycardia (often >120 bpm), hypertension (systolic >180 mmHg common), tachypnea, hyperthermia (sometimes >39°C), and diaphoresis reflect noradrenergic activation. Blood pressure elevation is dose-dependent and can precipitate stroke or myocardial infarction even in young patients.

• Pupillary Dilation (Mydriasis): The classic finding of widely dilated pupils (often >6mm, with poor response to light) reflects sympathomimetic and dopaminergic effects. This persists throughout intoxication and helps distinguish stimulant toxicity from opioid intoxication.

• Agitation and Hyperactivity: Psychomotor acceleration with restlessness, rapid speech (pressured), increased goal-directed activity, and decreased need for sleep characterize acute intoxication. Users may engage in repetitive behaviors or stereotypies.

• Cognitive and Perceptual Changes: Enhanced focus and concentration during intoxication (contributing to subjective pleasure and work productivity—dangerous myth that drives use), followed by difficulty concentrating during withdrawal. High doses produce paranoia, hypervigilance, and formication (tactile hallucinations of insects crawling on or under the skin), particularly with chronic use or during binges. Visual and auditory hallucinations can occur, though less common than with chronic amphetamine use.

Acute Toxicity and Medical Complications (Hours)

• Cardiovascular Events: Myocardial infarction occurs in 0.5-5% of cocaine users and can occur even in first-time users and those without coronary disease. Mechanisms include coronary vasospasm (directly cocaine-mediated), increased myocardial oxygen demand (from tachycardia and hypertension), and prothrombotic effects (platelet aggregation, enhanced coagulation). Patients present with chest pain, diaphoresis, dyspnea, and ECG changes (ST elevation, T wave inversion). Arrhythmias including ventricular fibrillation, atrial fibrillation, and sudden cardiac death also occur from direct myocardial irritability. Acute aortic dissection and sudden death can occur.

• Seizures: Dose-dependent seizure risk occurs in 0.3-0.9% of cocaine exposures, particularly with high doses or in predisposed individuals. Mechanisms include increased neuronal excitability from dopaminergic stimulation, local anesthetic effects (cocaine blocks sodium channels), and hyperthermia. Seizures may be single or status epilepticus, which carries mortality risk.

• Hyperthermia and Heat Stroke: Cocaine and methamphetamine both impair thermoregulation and increase heat production. Combined with increased physical activity during binges, body temperatures >40°C can develop, leading to rhabdomyolysis, disseminated intravascular coagulation, acute kidney injury, and death. Hyperthermia is particularly common with methamphetamine use and represents a medical emergency.

• Psychosis and Behavioral Emergencies: Acute stimulant psychosis develops in chronic users or after high doses, characterized by paranoid delusions (often of persecution or of people following/watching), command hallucinations (particularly auditory), and formication. This may drive violent behavior and suicide attempts. The psychosis typically resolves within hours to days after drug clearance but can occasionally persist longer. Users may present with excited delirium—extreme agitation, confusion, paranoia, superhuman strength, and resistance to restraint—which can provoke dangerous police encounters and carry risk of sudden death from cardiac arrhythmias or hyperthermia.

Crash Phase (4-96 Hours Post-Use)

• Dysphoria and Anhedonia: As dopamine returns to subnormal levels, users experience profound mood depression, hopelessness, and inability to experience pleasure from normally rewarding activities. This represents the psychological nadir and primary driver of relapse seeking.

• Fatigue and Hypersomnia: Extreme lethargy and sleeping 16-20 hours daily occurs as the brain attempts to restore dopaminergic homeostasis. Users may be difficult to arouse.

• Cocaine-Induced Anxiety: Prominent anxiety, nervousness, and panic attacks occur during cocaine crash and can persist for days.

• Suicidality: Crash dysphoria carries significant suicide risk, particularly when combined with access to lethal means or underlying mood disorders.

Chronic Use Manifestations (Weeks to Years)

• Nasal Pathology with Intranasal Use: Chronic cocaine snorting causes nasal septal perforation (from direct vasoconstriction causing tissue necrosis), chronic sinusitis, epistaxis, nasal obstruction, and osteonecrosis of nasal structures. Users present with persistent rhinorrhea, epistaxis, or nasal deformity.

• Pulmonary Complications with Smoked Routes: Crack cocaine smoking causes acute respiratory symptoms (cough, hemoptysis, dyspnea), chronic bronchitis, bronchial hyperresponsiveness, and pulmonary edema. Barotrauma from deep inhalation can produce pneumothorax or pneumomediastinum. Increased infection risk includes tuberculosis and fungal infections.

• Neuropsychiatric Sequelae: Persistent cognitive deficits (particularly with methamphetamine), depression, anxiety disorders, sleep disturbance, and psychosis can persist months after cessation. Methamphetamine-associated psychosis may recur for years even during abstinence.

• Dental Deterioration ("Meth Mouth"): Severe dental caries, tooth loss, and gum disease occur with methamphetamine use from multiple factors: direct caustic effects, xerostomia (from sympathomimetic effects and poor hygiene), poor nutritional intake, and bruxism (teeth grinding). This is a visible stigma of chronic methamphetamine use.

• Weight Loss and Malnutrition: Appetite suppression from chronic stimulant use produces severe weight loss, micronutrient deficiencies, and general physical deterioration. Users often present cachetic and malnourished.

• Skin and Soft Tissue Infections: Intravenous users develop abscess, cellulitis, thrombophlebitis at injection sites, osteomyelitis, and endocarditis. Track marks, scars, and abscesses are visible stigmata. Poor injection technique (using non-sterile equipment, injecting in non-traditional sites when arm veins are exhausted, sharing needles) increases infection risk dramatically.

• Infectious Disease Complications: IV methamphetamine and cocaine users have very high HIV seropositivity (20-40% in some urban cohorts), hepatitis C (70-90%), hepatitis B, and other bloodborne pathogens from needle sharing and sexual risk-taking.

Physical Examination Findings

• Acute intoxication: mydriasis, tachycardia, hypertension, hyperthermia, agitation, tremor, hyperreflexia
• Chronic use: poor dentition, nasal septal perforation (snorted cocaine), track marks/scars/abscesses (IV use), weight loss, poor hygiene, dermatitis from formication scratching
• Cardiovascular: new cardiac murmur (endocarditis), irregular pulse (arrhythmias), signs of heart failure

• DSM-5 Diagnostic Criteria: The disorder is diagnosed when a pattern of stimulant use within 12 months causes clinically significant impairment or distress, with at least 2 of the following 11 criteria present: (1) taking larger amounts or longer than intended, (2) persistent desire or unsuccessful efforts to cut down or control use, (3) substantial time spent obtaining, using, or recovering from effects, (4) intense craving, (5) recurrent use resulting in failure to meet major role obligations, (6) continued use despite persistent social or interpersonal problems, (7) important activities given up or reduced due to use, (8) recurrent use in physically hazardous situations, (9) continued use despite knowledge of physical or psychological problems likely caused by use, (10) tolerance (needing increased amounts for effect), (11) withdrawal symptoms. Severity is mild (2-3 criteria), moderate (4-5), or severe (6+). Importantly, stimulant withdrawal is DSM-5 coded but is not life-threatening (contrasting with alcohol or ben

Immediate stabilisation (acute intoxication/toxicity)

• Benzodiazepines (e.g., lorazepam or diazepam IV, titrated to sedation): first-line for agitation, tachycardia, hypertension, hyperthermia, and stimulant-induced seizures. They reduce central sympathetic outflow, so a single agent addresses several toxidrome features at once. The AHA scientific statement on cocaine-associated chest pain and myocardial infarction endorses benzodiazepines as initial therapy.
• Active external cooling: for core temperature elevation, use evaporative cooling or ice-water immersion plus deep sedation. Antipyretics are useless because the hypothalamic set point is normal — heat is generated by muscular hyperactivity.
• Isotonic crystalloid: for rhabdomyolysis and to protect against pigment-induced acute kidney injury.
• Sodium bicarbonate: for QRS widening, reflecting cocaine's local-anesthetic sodium-channel blockade.

Cocaine-associated chest pain

• Aspirin, nitroglycerin, and benzodiazepines form the core regimen (AHA scientific statement). Reserve phentolamine, a non-selective alpha blocker, or a non-dihydropyridine calcium channel blocker (verapamil) for refractory hypertension or coronary vasospasm.
• Primary PCI is definitive for true STEMI; interpret a new LBBB using Sgarbossa criteria rather than treating it as a stand-alone STEMI equivalent.
• Body packers/stuffers: whole-bowel irrigation with polyethylene glycol; emergency laparotomy if a packet ruptures or obstructs.

Contraindicated / avoid

• Beta blockers in acute cocaine toxicity — blocking beta-2 vasodilation leaves alpha-1 vasoconstriction unopposed, worsening hypertension and coronary spasm. This remains the expected board answer.
• Physical restraint without chemical sedation, which perpetuates isometric muscle activity, hyperthermia, and lactic acidosis.
• First-generation antipsychotics as first-line sedation — they lower the seizure threshold and impair heat dissipation; reserve antipsychotics for psychosis unresponsive to benzodiazepines.

Longitudinal management of the disorder

• Contingency management (escalating vouchers/incentives for stimulant-negative urines) has the strongest evidence and is prioritized by ASAM/SAMHSA; combine with CBT, community reinforcement, or the Matrix Model.
• No FDA-approved pharmacotherapy exists. Off-label options with modest support include bupropion–naltrexone (studied in the ADAPT-2 trial for methamphetamine), mirtazapine, and topiramate.
• Harm reduction: naloxone distribution (fentanyl adulteration), syringe services, and HIV/HCV testing with PrEP for those at risk (USPSTF-supported).

Cardiovascular (emergencies)

• Myocardial infarction: coronary vasospasm plus increased demand and platelet activation; signaled by chest pain with ischemic ECG changes in a young patient without atherosclerotic risk factors.
• Aortic dissection: abrupt hypertensive surge and shear stress; tearing chest pain radiating to the back, pulse or blood pressure differential between arms.
• Malignant arrhythmias: sodium-channel blockade widens QRS and potassium-channel effects prolong QT, predisposing to ventricular fibrillation/pulseless VT and torsades. Wide-complex tachycardia after cocaine is the cue for bicarbonate.
• Dilated cardiomyopathy: chronic catecholamine toxicity and myocarditis; reduced ejection fraction with heart failure symptoms.

Neurologic (emergencies)

• Intracerebral or subarachnoid hemorrhage: hypertensive surge, often unmasking an aneurysm or AVM; sudden thunderclap headache or focal deficit.
• Ischemic stroke: vasospasm and prothrombotic state.
• Seizures/status epilepticus: lowered seizure threshold plus local-anesthetic effect.

Hyperthermic–metabolic (emergency)

• Hyperthermia with rhabdomyolysis: muscular hyperactivity and impaired thermoregulation; markedly elevated CK, dark urine, hyperkalemia, and acute kidney injury. Severe cases progress to DIC and multiorgan failure.

Organ- and route-specific

• Mesenteric ischemia and bowel perforation: splanchnic vasoconstriction; disproportionate abdominal pain with lactic acidosis.
• Cocaine-induced midline destructive lesions: septal perforation and palatal destruction; often PR3-ANCA positive, mimicking granulomatosis with polyangiitis.
• Levamisole-adulterated cocaine: agranulocytosis and retiform purpura of the ears; check the differential count.
• Crack lung / barotrauma: diffuse alveolar hemorrhage, eosinophilic infiltrates, pneumomediastinum after deep inhalation.
• Obstetric: placental abruption, preterm birth, fetal growth restriction from uteroplacental vasoconstriction.
• Infectious: injection-related endocarditis (new murmur, septic emboli), HIV, HCV.

Treatment-related

• Benzodiazepine oversedation: respiratory depression — monitor capnography during aggressive titration.
• Antipsychotics: impaired heat dissipation, lowered seizure threshold, QT prolongation, and rarely neuroleptic malignant syndrome.
• Bupropion: dose-dependent seizure risk; avoid in patients with bulimia or prior withdrawal seizures.
• Naltrexone: precipitates withdrawal in patients using opioids concurrently — screen before initiation.

• The toxidrome: mydriasis, hypertension, tachycardia, hyperthermia, diaphoresis, and agitation. The distractor is opioid intoxication — miosis and respiratory depression. Anticholinergic toxicity also gives mydriasis and hyperthermia but with dry, flushed skin and absent bowel sounds; stimulant patients are diaphoretic with active bowel sounds.
• Single best next step in the agitated, hyperthermic stimulant patient: IV benzodiazepine plus active external cooling. Not haloperidol, not restraints alone, not antipyretics.
• The association examiners test most: beta blockers in acute cocaine toxicity cause unopposed alpha stimulation. Choose benzodiazepines, nitroglycerin, and phentolamine instead.
• Wide QRS after cocaine = sodium-channel blockade → sodium bicarbonate. Do not reflexively pick amiodarone or a class Ia/Ic agent.
• Levamisole-adulterated cocaine → agranulocytosis and retiform purpura of the ears; get a CBC with differential.
• Formication (cocaine bugs, or Magnan's sign) with excoriations, plus nasal septal perforation (intranasal) or meth mouth (methamphetamine), are the classic chronic-use giveaways.
• Withdrawal is dysphoric, not dangerous: crash with hypersomnia, hyperphagia, vivid dreams, and profound anhedonia — the opposite of the sympathetic storm of alcohol or benzodiazepine withdrawal, which can be lethal. Management is supportive with suicide risk assessment; no taper or substitution agent exists.
• Best evidence-based treatment for the disorder is behavioral, not pharmacologic: contingency management, endorsed by ASAM/SAMHSA, outperforms any medication. There is no FDA-approved pharmacotherapy for cocaine or methamphetamine use disorder — a favorite trap when opioid or alcohol agents (methadone, buprenorphine, acamprosate) appear as options.
• Urine testing: cocaine is detected as benzoylecgonine for a few days after use. Amphetamine immunoassays false-positive with bupropion, pseudoephedrine, and selegiline — confirm with GC-MS before acting on the result.