Legal, illicit, and prescription agents prone to abuse and intoxication — mechanism, dosing thresholds, and front-line through critical-care management, at the resuscitation continuum's every stage.
Benzoylmethylecgonine
Cocaine is a competitive inhibitor of the presynaptic monoamine transporters — dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT) — blocking reuptake and flooding the synaptic cleft with dopamine, norepinephrine, and serotonin. The dopaminergic surge in the mesolimbic reward pathway (nucleus accumbens) drives euphoria and reinforcement; the noradrenergic surge drives the peripheral sympathomimetic toxidrome.
Cocaine is also a class Ic-like sodium-channel blocker (local anesthetic property, the basis of its historical surgical use), which underlies its proarrhythmic and pro-convulsant potential — wide-complex dysrhythmias mimic tricyclic antidepressant overdose. Chronic use produces coronary vasospasm and accelerated atherosclerosis via endothelin-1 upregulation, platelet activation, and impaired nitric-oxide-mediated vasodilation, independent of any acute overdose event.[1,2]
| Route | Onset | Peak effect | Duration |
|---|---|---|---|
| Intranasal | 1–3 min | 15–20 min | 60–90 min |
| Smoked (crack/freebase) | <15 sec | 2–5 min | 5–15 min |
| IV | <30 sec | 3–5 min | 20–30 min |
| Oral / mucosal | 10–30 min | 60 min | 60–90 min |
Hepatic and plasma-esterase metabolism produces benzoylecgonine (the standard immunoassay target) and ecgonine methyl ester; elimination half-life of the parent compound is only ~1 hour, but benzoylecgonine remains detectable in urine 2–4 days after a binge, longer with heavy chronic use.[3]
| Route | Signature complications |
|---|---|
| Snorted | Nasal septal perforation, chronic rhinosinusitis, ischemic stroke |
| Smoked (crack) | "Crack lung" — diffuse alveolar hemorrhage, eosinophilic pneumonitis, barotrauma/pneumomediastinum from Valsalva-style inhalation |
| Injected | Infective endocarditis, bacteremia, skin/soft-tissue infection, bloodborne viral transmission (HIV/HCV) |
| Swallowed (body packing/stuffing) | Massive overdose if packet rupture; bowel obstruction/perforation |
Urine drug screen: cocaine immunoassays target benzoylecgonine specifically — there is essentially no cross-reactive substance in modern assays, so a positive result is almost never a true false positive. That reliability does not extend to attributing every symptom in front of you to the positive result.[4]
Classic sympathomimetic triad: tachycardia, hypertension, and mydriasis, layered with diaphoresis, agitation, and — in heavy or binge use — paranoia and formication-type tactile hallucinations. Chest pain and palpitations are common presenting complaints even without infarction.
Painful retiform purpura with a predilection for the ears, cheeks, and nose, occurring alongside agranulocytosis/neutropenia and high-titer dual p-ANCA/c-ANCA positivity, is essentially diagnostic of levamisole-adulterated cocaine toxicity — an adulterant present in up to 70–80% of the current US supply. Seeing bilateral ear necrosis in a young patient should trigger this diagnosis before an autoimmune vasculitis workup.[7]
Cocaine-induced midline destructive lesions (CIMDL) — septal perforation with palatal/nasal cartilage destruction from chronic insufflation — mimic granulomatosis with polyangiitis on exam and imaging, but lack the pulmonary-renal involvement of true GPA.
Believe the positive UDS, but don't anchor on it. The route of use predicts the complication — always ask how the patient uses. And once acute intoxication resolves, don't reflexively withhold guideline-indicated beta-blocker therapy (e.g., HFrEF, prior MI) on the basis of remote cocaine history alone.
Mixed amphetamine salts (Adderall), lisdexamfetamine (Vyvanse, a prodrug)
Amphetamine is primarily a transporter-mediated releaser, not just a reuptake blocker. It is taken up into the presynaptic terminal via DAT and NET, then reverses their normal direction of transport (via interaction with VMAT2 and phosphorylation of the transporters), causing dopamine and norepinephrine to be released into the synapse independent of neuronal firing. It also inhibits monoamine oxidase (MAO) at higher concentrations, further prolonging the extracellular monoamine surge.[1]
Lisdexamfetamine is inactive until cleaved by red-blood-cell peptidases to release dextroamphetamine, which blunts the abuse-deterrent kinetics somewhat (slower onset, harder to achieve an IV/insufflation rush) compared to immediate-release salts.
Oral bioavailability is high with peak plasma levels around 3 hours (immediate-release) to 7 hours (extended-release/lisdexamfetamine). Elimination half-life is 10–13 hours in adults and is pH-dependent — acidic urine accelerates renal elimination, alkaline urine prolongs it. Misuse routes include oral supratherapeutic dosing, insufflation of crushed IR/ER tablets, and rarely IV injection of dissolved tablets (which carries embolic risk from tablet fillers/binders).
| Level | Typical picture |
|---|---|
| Therapeutic (ADHD dosing) | 5–60 mg/day divided, titrated to effect |
| Misuse/diversion dose | Often 2–10× prescribed dose; insufflation for rapid onset |
| Toxic | Agitation, mydriasis, tremor, hyperreflexia, tachycardia, hypertension |
| Severe/life-threatening | Hyperthermia, seizures, wide-complex dysrhythmia, intracranial hemorrhage |
Mydriasis, tremor, agitation, hyperreflexia, combative or paranoid behavior, and — at high doses — hallucinations, delirium, and choreoathetoid movements. Insomnia and anorexia dominate at prescribed doses; the picture escalates toward the full sympathomimetic toxidrome only in supratherapeutic misuse.
Amphetamine intoxication has no exam finding that distinguishes it from methamphetamine or other stimulant toxicity — the toxidrome, dosing thresholds, and management are shared across the class. The clinical distinguishing feature is context: a prescribed ADHD medication history, a crushed/insufflated tablet, or an adolescent/young-adult diversion pattern.
Prescription stimulant misuse is a legal-substance problem with an illegal-substance toxidrome. Screen for diversion in any patient with a new sympathomimetic presentation and an ADHD diagnosis — theirs, a sibling's, or a classmate's.
N-methylamphetamine
Methamphetamine shares amphetamine's transporter-reversal mechanism (DAT/NET-mediated dopamine and norepinephrine release, with weaker serotonergic activity) but is more lipophilic, crosses the blood-brain barrier faster, and is a more potent CNS stimulant with greater neurotoxic potential. Chronic high-dose use depletes dopaminergic terminals and is associated with methamphetamine-induced psychosis and long-term neurocognitive deficits distinct from acute intoxication.[1,2]
Oral onset in 2–4 hours; smoking, snorting, and injection produce effects within minutes. Elimination half-life is markedly longer than cocaine's — 6–15 hours (commonly cited as 11–12 hours) versus cocaine's ~1 hour — which is why methamphetamine intoxication and its downstream complications (agitation, psychosis) tend to be more prolonged and resource-intensive in the ED. Metabolized via CYP2D6 to active amphetamine plus inactive p-OH-amphetamine and norephedrine; renal excretion is enhanced by urinary acidification.[1]
Sympathomimetic toxidrome across cardiovascular (tachycardia, hypertension, dysrhythmia), CNS (agitation, psychosis, seizures, intracranial hemorrhage), renal (rhabdomyolysis-driven AKI), and GI systems. >150,000 US ED visits annually are attributed to methamphetamine toxicity.[2]
Acute intoxication produces the standard sympathomimetic picture — tachycardia, hypertension, mydriasis, agitation, and psychosis — but methamphetamine's chronic-use stigmata are unusually distinctive and often visible before a history is even obtained.
"Meth mouth" — rampant interproximal and buccal caries at the cementoenamel junction with a blackened, crumbling appearance, combined with severe xerostomia and bruxism/trismus — is a chronic-use finding specific enough that dental literature uses it as a recognition tool independent of history.[4]
Formication ("crank bugs," "meth mites") — the tactile hallucination of insects crawling under the skin — drives compulsive skin-picking with characteristic linear excoriations concentrated on the face, forearms, and lower legs. The combination of meth mouth plus formication-pattern excoriations in the same patient is highly specific for chronic methamphetamine use.[5]
Methamphetamine's long half-life means the agitation and hemodynamic instability you're managing at hour 1 may still be there at hour 8 — plan disposition and staffing accordingly rather than expecting a cocaine-length course.
3,4-Methylenedioxymethamphetamine / 3,4-Methylenedioxyamphetamine
MDMA is a potent serotonin releaser (SERT-mediated, analogous to amphetamine's DAT/NET mechanism) with additional dopamine and norepinephrine release — roughly one-tenth the pure CNS stimulant potency of amphetamine but a much larger serotonergic signature. Direct 5-HT2A agonism contributes to the perceptual/empathogenic effects. MDMA also stimulates arginine vasopressin (ADH) release, promoting free-water retention — a mechanism with no real analog in cocaine or methamphetamine and the direct cause of MDMA's signature hyponatremia risk, especially compounded by compulsive water intake at events.[1,2]
A subset of users are CYP2D6 poor metabolizers (or co-ingest a CYP2D6 inhibitor, e.g., ritonavir), leading to markedly prolonged and intensified exposure and higher risk of severe toxicity.
Oral onset 20–60 min, peak ~2 hours, duration 4–6 hours; half-life ~8–9 hours for a single dose, but repeated dosing autoinhibits its own metabolism, prolonging and intensifying toxicity ("stacking"/"boofing" behavior at multi-day events).
Mixed adrenergic-serotonergic picture: hypertension, tachycardia, mydriasis, diaphoresis, bruxism/trismus, plus hyperthermia and, when severe, frank serotonin syndrome (hyperthermia, clonus, hyperreflexia, altered mental status). The two dominant causes of MDMA death are hyperthermia and hyponatremia — not cardiac events, which distinguishes it from cocaine/methamphetamine mortality patterns.[1]
Bruxism and trismus (jaw clenching) are so consistent that users at raves and festivals often carry pacifiers or chewing gum specifically to manage it — a near-universal exam finding rather than an incidental one.
The combination of hyperthermia and hyponatremia in the same patient — rather than either alone — is distinctive for MDMA/MDA among the stimulants: no other agent on this list produces both a heat-generating sympathomimetic state and an ADH-mediated free-water retention problem simultaneously. Spontaneous or inducible clonus in this setting confirms serotonin-toxicity physiology (Hunter Criteria) over simple sympathomimetic excess.[1,3]
Two failure modes kill MDMA patients and they pull in opposite directions: treating everyone as "just dehydrated" and under-hydrating a hyperthermic patient, or treating everyone as "at risk of hyponatremia" and over-hydrating a normonatremic one. Check the sodium before you decide which patient you have.
Mephedrone, MDPV, methylone, alpha-PVP ("flakka"), and related designer analogs
Synthetic cathinones are ring-substituted derivatives of cathinone, the natural psychoactive compound in khat (Catha edulis). Structurally they sit within the phenethylamine/amphetamine family and act on the same DAT/NET/SERT machinery, but individual compounds vary widely in selectivity: MDPV is a potent, highly selective DAT/NET reuptake inhibitor (cocaine-like, not a releaser) with essentially no direct serotonergic activity, while mephedrone behaves more like a non-selective releaser closer to MDMA. This heterogeneity — new analogs appear faster than they can be characterized or scheduled — is why there is no single "cathinone toxidrome," only a family of related sympathomimetic-plus-serotonergic pictures.[1,2]
Tachycardia, hypertension, hyperthermia, mydriasis, diaphoresis, agitation, and — disproportionately compared to cocaine/methamphetamine — severe agitated psychosis, which is frequently the presenting complaint and the main driver of ED resource use. Deaths have been reported, generally from hyperthermia, seizure, or cardiovascular collapse in the setting of prolonged agitation.[3]
Routine immunoassay urine drug screens frequently do not detect synthetic cathinones; confirmation requires send-out testing to a forensic/reference lab, which is too slow to inform acute management. Clinical suspicion (young patient, new-onset psychosis/agitated delirium, negative standard tox screen) should drive treatment, not a lab result.
The presenting picture is the standard sympathomimetic toxidrome, but skewed heavily toward the psychiatric end of the spectrum — agitation and psychosis are frequently the chief complaint, out of proportion to the cardiovascular findings, and tend to be more prolonged than a comparable cocaine presentation.
No individual exam finding is unique to synthetic cathinones — the class is defined by structural heterogeneity (MDPV behaves like cocaine, mephedrone behaves more like MDMA), so the toxidrome varies by which analog was actually consumed. The strongest clinical clue is a mismatch between severe, prolonged agitated psychosis and a negative standard urine immunoassay — the assay simply doesn't detect this class, so a "clean" screen in a floridly psychotic young patient should raise suspicion rather than lower it.[4]
"Not for human consumption" on the packaging is the tell, not a disclaimer. If a young patient presents with new agitated psychosis and a negative standard urine tox screen, synthetic cathinones belong high on your differential — treat the syndrome you see, not the lab you don't have yet.
Ritalin (IR), Concerta/Metadate/Quillivant (ER), dexmethylphenidate (Focalin)
Unlike amphetamine, methylphenidate is a pure reuptake inhibitor — it blocks DAT (and to a lesser extent NET) without reversing transporter direction, so it does not directly trigger vesicular dopamine release the way amphetamine does. Functionally, in overdose the net result is the same excessive-extracellular-dopamine/norepinephrine picture, just reached by a different transporter mechanism — which is why its overdose toxidrome is described as clinically indistinguishable from amphetamine intoxication.[1,2]
Crushed tablets used intranasally or intravenously introduce insoluble tablet fillers (talc, cellulose) that cause pulmonary/retinal microembolization and, with repeated IV misuse, has been reported to precipitate multi-organ failure.[3]
Immediate-release: onset ~20–30 min, duration 3–4 hours, dosed 2–3×/day. Extended-release (osmotic-pump Concerta, biphasic Metadate CD, liquid Quillivant XR, transdermal patch): duration 8–12 hours, once-daily dosing. Formulation matters clinically — a crushed ER tablet can dump a full day's dose at once, and osmotic-pump "ghost tablets" may appear intact in stool despite full drug release.
Agitation, hallucinations, psychosis (can mimic cocaine- or amphetamine-induced psychosis, particularly with chronic insufflation "runs"), lethargy paradoxically at very high doses, seizures, tachycardia, dysrhythmias, hypertension, and hyperthermia. Effects are dose-dependent; death has been reported but is rare.[2]
The overdose picture is indistinguishable on exam from amphetamine toxicity — the same sympathomimetic and neuropsychiatric findings apply, and there is no clinical sign specific to methylphenidate over other stimulants of this class.
One formulation-specific clue is worth knowing rather than a true toxicity sign: the osmotic-release (OROS) shell of Concerta-type extended-release tablets can pass intact in the stool after the drug has been fully released, alarming caregivers who find a "whole pill" — this reflects normal pharmacokinetics of that delivery system, not treatment failure or non-absorption, and should not be mistaken for an unabsorbed, retrievable overdose.
A "prescribed" stimulant is not a "safe" stimulant once it's crushed and insufflated. Ask about route, not just substance — the same pill bottle can represent a therapeutic dose or an IV drug of abuse depending on how it was taken.
1,3,7-Trimethylxanthine
Caffeine is a nonselective antagonist of adenosine A1 and A2A receptors, blocking adenosine's normal inhibitory/sedating tone on the CNS and cardiovascular system — the opposite mechanistic family from the monoamine-transporter stimulants above. At toxic doses it additionally inhibits phosphodiesterase (raising intracellular cAMP) and promotes catecholamine release from the adrenal medulla and sympathetic terminals, which is what produces a sympathomimetic-like toxidrome despite the fundamentally different primary target.[1]
| Exposure | Amount |
|---|---|
| Typical cup of coffee | 40–150 mg |
| Daily consumption, ~85% of US adults | Variable, generally <400 mg/day without toxicity |
| Pure caffeine powder, 1 teaspoon | ~2,700 mg (≈28 cups of coffee) |
| Reported lethal serum level | 80–100 μg/mL |
| Estimated LD50 | 150–200 mg/kg (≈10–14 g in a 70 kg adult) |
Caffeine clearance varies up to 40-fold between individuals based on CYP1A2 genotype; pregnancy (third trimester) triples the half-life, and oral contraceptives roughly double it — the same nominal dose is not equally risky across patients.[1,2]
Tachycardia, hypertension progressing to hypotension in severe cases, tremor, anxiety, GI upset, and — at toxic serum levels — seizures and cardiac dysrhythmias, which are the dominant causes of fatality. Rhabdomyolysis, significant electrolyte disturbance (notably hypokalemia from catecholamine-driven intracellular potassium shift), and aspiration from airway compromise contribute to morbidity in severe overdose.[1,3]
Tremor, anxiety, GI upset, and tachycardia dominate mild-moderate toxicity; there is no skin, mucosal, or dental finding characteristic of caffeine the way there is for cocaine or methamphetamine — caffeine toxicity is a biochemical diagnosis more than an exam diagnosis.
Marked hypokalemia out of proportion to any GI losses, in a patient with tremor and tachycardia and no history of another sympathomimetic, is the closest caffeine comes to a distinguishing lab pattern — it reflects catecholamine-driven intracellular potassium shift rather than true total-body depletion, and over-correction with IV potassium risks rebound hyperkalemia as catecholamine excess resolves.
Caffeine is the one stimulant on this list where beta-blockade isn't a trap — esmolol is the actual first-line agent for its tachydysrhythmias. Don't extrapolate the "avoid unopposed beta-blockade" rule from cocaine onto every stimulant reflexively.
Diacetylmorphine — prodrug rapidly deacetylated to 6-monoacetylmorphine then morphine
Diacetylmorphine itself is largely inactive; its high lipophilicity allows rapid blood-brain-barrier penetration, after which it is deacetylated to 6-monoacetylmorphine (6-MAM, a potent, itself lipophilic metabolite) and then morphine. Both act as full agonists at the mu-opioid receptor, a Gi-coupled GPCR that inhibits adenylate cyclase, opens potassium channels, and closes voltage-gated calcium channels — the net effect is neuronal hyperpolarization and reduced neurotransmitter release, producing analgesia in the periaqueductal gray/spinal cord and euphoria via disinhibition of ventral tegmental dopamine neurons. Respiratory depression follows from mu-receptor-mediated blunting of the brainstem's response to hypercapnia.[1]
IV/IM onset seconds-to-minutes; smoked/insufflated onset within minutes. 6-MAM is the only metabolite specific to heroin (vs. other morphine-derived opioids) and is the forensic/urine marker distinguishing heroin use from poppy-seed exposure or prescribed morphine, but it is detectable for only a few hours.
Classic opioid toxidrome: miosis, respiratory depression (rate and depth both reduced), CNS depression, and hyporeflexia.
The triad of pinpoint pupils, depressed respiration, and depressed consciousness reversing promptly with naloxone is as close to a bedside-diagnostic sign as toxicology offers — response to the antidote confirms the diagnosis in real time. Track marks, skin-popping scars, and necrotic ulcers at injection sites support a chronic-use history; noncardiogenic pulmonary edema (heroin lung) shortly after use is a recognized, distinctive complication.[2]
Titrate naloxone to respiration, not wakefulness — over-reversal in an opioid-dependent patient buys you vomiting, aspiration, and a combative patient, not a better outcome.
Fentanyl, carfentanil, nitazenes (structurally distinct but functionally grouped here)
Full mu-opioid agonist, 50–100× more potent than morphine by weight, with extreme lipophilicity giving near-instant CNS penetration. Fentanyl and its analogs (carfentanil ~10,000× morphine potency, nitazenes with variable but often very high potency) share the same mu-receptor mechanism as heroin/morphine but bind with slower dissociation kinetics at high concentrations, which is the pharmacologic basis for concern about naloxone-resistant toxicity in mass-overdose events.[1]
Onset is faster and duration often shorter than heroin per dose, but illicit fentanyl's extreme potency-per-milligram and inconsistent adulteration of the drug supply make dosing unpredictable; rapid-onset apnea without the gradual sedation seen with lower-potency opioids is characteristic. High-dose fentanyl (including rapid IV push in anesthesia) can cause fentanyl-induced chest wall rigidity ("wooden chest syndrome") severe enough to prevent bag-mask ventilation.
Sudden apnea/cyanosis without the typical progressive sedation curve, especially in a cluster of overdoses tied to one supply source, points to fentanyl or an analog rather than heroin alone. Chest wall rigidity refractory to bag-mask ventilation after rapid high-dose fentanyl exposure is distinctive enough that it changes the immediate resuscitation plan (see below).[2]
Don't over-anchor on "naloxone won't work on fentanyl" — it does, at standard doses, in the overwhelming majority of cases. The real practice shift is infrastructure: plan for repeat dosing and infusions, not higher single-bolus doses.
Methadone (full mu agonist); buprenorphine (partial mu agonist / kappa antagonist)
Methadone is a full mu-opioid agonist with an additional NMDA-antagonist property (useful for opioid-tolerant pain and reducing withdrawal-related hyperalgesia) but also blocks the cardiac hERG potassium channel, prolonging the QT interval independent of opioid effect. Buprenorphine is a high-affinity partial mu agonist with a ceiling effect on respiratory depression and analgesia at higher doses, plus kappa-receptor antagonism and slow receptor dissociation — properties that make it safer in overdose but capable of precipitating withdrawal by displacing full agonists (heroin, fentanyl, methadone) from the receptor without providing equivalent activation.[1,2]
Methadone half-life 8–59 hours (highly variable, accumulates with repeat dosing) — a major reason methadone overdose is more dangerous and prolonged than its single-dose potency suggests. Buprenorphine sublingual bioavailability is high; its ceiling effect and slow dissociation give it a long duration of action (24+ hours) with a wide safety margin as monotherapy, though combination with other CNS depressants removes much of that margin.
Both present with the standard opioid toxidrome. Methadone's distinguishing feature is QT prolongation and torsades risk disproportionate to its opioid effect — an ECG showing a long QT in an opioid-toxic patient should prompt methadone suspicion even without a confirmed history.
A patient in buprenorphine-precipitated withdrawal needs more buprenorphine, not less — the instinct to stop the "causative" drug is backwards here.
Tramadol (weak mu agonist + SNRI); loperamide (peripheral mu agonist, antidiarrheal)
Tramadol is a weak mu-opioid agonist whose analgesic effect depends heavily on its serotonin-norepinephrine reuptake inhibition — a mechanism shared with SNRI antidepressants rather than classic opioids, which is why it can cause both seizures and serotonin syndrome independent of any co-ingested serotonergic agent.[1] Loperamide is a peripherally restricted mu agonist at therapeutic dose (excluded from the CNS by P-glycoprotein efflux), but at grossly supratherapeutic doses (misused for opioid-like euphoria or self-treatment of withdrawal) it saturates P-glycoprotein, crosses into the CNS, and also blocks cardiac hERG potassium and sodium channels — a dual-channel cardiotoxicity distinct from any other opioid on this list.[2]
Seizures in a patient with an otherwise mild opioid toxidrome is characteristic of tramadol — an opioid causing convulsions at or near therapeutic doses is atypical enough to point directly at this agent. For loperamide, QRS widening and QT prolongation with torsades or ventricular tachycardia in a patient using antidiarrheal medication at absurd doses (case reports document >100 mg/day, sometimes hundreds of tablets) is the signature finding — a mechanism no other opioid on this list produces.[3,4]
"It's just an over-the-counter antidiarrheal" is exactly the assumption that delays recognizing loperamide cardiotoxicity — ask about dose, not just drug name.
Alprazolam, diazepam, lorazepam, clonazepam, and related agents
Positive allosteric modulators at the GABA-A receptor — they don't open the chloride channel directly but increase the frequency of channel opening in the presence of GABA, enhancing inhibitory neurotransmission throughout the CNS. This is mechanistically distinct from barbiturates (which increase channel duration and can activate the channel independent of GABA at high dose) — the reason benzodiazepines have a ceiling effect on respiratory depression as monotherapy while barbiturates do not.[1]
Sedation, ataxia, slurred speech, and — in isolated overdose — rarely progresses to significant respiratory depression or cardiovascular instability; the ceiling effect makes isolated benzodiazepine overdose one of the safer intentional overdoses in toxicology. Co-ingestion with alcohol, opioids, or other CNS depressants removes that safety margin and is the actual driver of most fatal benzodiazepine-involved overdoses.[2]
Deep coma, hyperreflexia/clonus, cardiovascular instability, or respiratory failure requiring ventilation in a suspected isolated benzodiazepine overdose should prompt a search for a co-ingestant (ethanol, opioids, TCAs) rather than confirming benzodiazepine severity — that clinical picture is not what benzodiazepines alone produce.[2]
Reach for flumazenil far less often than intuition suggests. In real-world mixed overdoses — which is most of them — the antidote causes more harm than the drug it's reversing.
Phenobarbital, secobarbital (barbiturates); zolpidem, zaleplon, eszopiclone (Z-drugs)
Barbiturates increase the duration of GABA-A chloride channel opening and, at high concentration, can activate the channel directly without GABA present — unlike benzodiazepines' GABA-dependent modulation, this gives barbiturates no ceiling effect and a narrow therapeutic index, making overdose far more dangerous. Z-drugs were designed to act more selectively at the alpha-1 GABA-A subunit (favoring sedation over the anxiolytic/muscle-relaxant effects of benzodiazepines) and behave clinically like low-toxicity benzodiazepines as monotherapy.[1]
Barbiturate overdose: dose-dependent progression from sedation to respiratory failure, hypotension, and cardiogenic shock — potentially fatal even in isolated ingestion, unlike benzodiazepines. Z-drug overdose: sedation is the dominant finding; coma, respiratory depression, and cardiovascular instability are rare as monotherapy, mirroring benzodiazepines' relative safety.[1]
Don't lump barbiturates in with the "benzos are basically safe" mental model — the no-ceiling-effect mechanism makes isolated barbiturate overdose genuinely lethal in a way isolated benzodiazepine overdose rarely is.
Gamma-hydroxybutyrate; gamma-butyrolactone and 1,4-butanediol are prodrugs converted to GHB in vivo
GHB is an endogenous CNS metabolite of GABA that acts at two distinct sites: a specific, excitatory GHB receptor, and — at the higher concentrations reached with exogenous use — as a weak GABA-B receptor agonist, which is the inhibitory action responsible for its sedative-hypnotic and euphoric-disinhibiting effects. GBL and 1,4-BD are not active themselves but are rapidly converted to GHB by lactonase and alcohol/aldehyde dehydrogenase respectively, functioning as prodrugs with the same downstream toxicity.[1,2]
Extremely short half-life (~27–30 minutes), which produces a narrow, unpredictable dose-response curve — the difference between an intoxicating dose and a coma-inducing dose is small, and effects can end almost as abruptly as they began.
Abrupt-onset coma with unpredictable, rapid spontaneous recovery within a few hours — a patient who is deeply unresponsive one hour and abruptly awake, agitated, and trying to self-extubate the next — is the classic GHB presentation and distinguishes it from virtually every other sedative-hypnotic on this list, which have more gradual onset/offset. This kinetic signature is often more diagnostic than any lab test, since GHB is not detected on routine screens.[3]
Don't mistake GHB withdrawal for a milder cousin of alcohol withdrawal — its onset is faster, it can be just as lethal, and standard benzodiazepine dosing often needs to go higher and faster than for alcohol withdrawal protocols.
Arylcyclohexylamines
Both are non-competitive antagonists at the NMDA glutamate receptor, blocking the channel pore in an open-channel, use-dependent manner. This produces functional disconnection between the cortex and limbic/thalamic structures — the "dissociative" state — along with analgesia (ketamine's clinical anesthetic use) and, at high concentration, catalepsy. PCP additionally has dopaminergic and sigma-receptor activity contributing to its more prominent and prolonged psychotomimetic effects compared to ketamine.[1]
Nystagmus (classically vertical or rotatory, a distinguishing feature from most other intoxications), dissociation, catatonia, hypertension, tachycardia, and — especially with PCP — violent, unpredictable agitation. Overdose can produce coma; death is rare from either agent alone but co-ingestion risk (CNS depressants) compounds respiratory risk.
Vertical or rotary nystagmus combined with a dissociative/catatonic state is distinctive for this class among recreational drugs — most other intoxications produce horizontal nystagmus if any. The emergence reaction — bizarre behavior, vivid dreams, derealization, or frank psychosis appearing specifically during the recovery phase rather than at peak intoxication — is a named, recognized phenomenon unique to ketamine/PCP recovery.[1] Chronic ketamine use also produces a distinctive ulcerative cystitis with dysuria, frequency, and hematuria not seen with other dissociatives or stimulants.
Vertical nystagmus in an agitated patient is your fastest bedside clue to this class — check for it before reaching for a broad differential.
DXM (OTC cough suppressant); N2O (medical/industrial gas)
DXM is an NMDA-receptor antagonist structurally related to opioids (a dextrorotatory morphinan) but with negligible mu-opioid activity at typical misuse doses — its dissociative effects come from the same NMDA-blockade mechanism as ketamine/PCP. It also inhibits serotonin reuptake, creating meaningful serotonin-syndrome risk, especially in combination with MAOIs or other serotonergic agents — a risk not shared by ketamine or PCP.[1] Nitrous oxide's mechanism is distinct entirely: it is a weak NMDA antagonist and GABA-A modulator producing rapid-onset, rapid-offset dissociation and euphoria, but its most clinically important effect is irreversible oxidation of the cobalt ion in vitamin B12, inactivating it as a coenzyme and producing a functional B12 deficiency with chronic use.[2,3]
For nitrous oxide: subacute combined degeneration of the spinal cord — ascending paresthesias, gait ataxia, and absent reflexes progressing over days-to-weeks in an otherwise healthy young person — in the setting of a normal-to-borderline serum B12 (because it's the functional cobalamin activity, not the serum level, that's impaired) should trigger suspicion for chronic nitrous use specifically; standard toxicology screens do not detect it.[3,4] DXM has no comparably distinctive sign — its dissociative "plateaus" are a dose-dependent continuum shared conceptually with ketamine.
A normal serum B12 does not rule out nitrous-induced cord disease — treat the clinical syndrome, and don't let a "normal" lab talk you out of starting B12 while you wait on further workup.
Lysergic acid diethylamide; psilocybin/psilocin; mescaline
All three act primarily as agonists at the serotonin 5-HT2A receptor, with LSD showing additional affinity at 5-HT1A/2C and dopamine receptors. 5-HT2A activation in cortical layer V pyramidal neurons is thought to underlie the characteristic perceptual and cognitive distortions, via altered thalamocortical gating and reduced precision-weighting of prior beliefs (the basis of current "REBUS" models of psychedelic action).[1,2]
The acute medical toxicity of classic psychedelics at typical recreational doses is low — no documented LSD fatalities from direct pharmacologic toxicity exist in the literature, and psilocybin's safety margin is similarly wide. The overwhelming majority of ED presentations relate to acute anxiety/panic ("bad trip"), trauma from impaired judgment, or (rarely) exacerbation of underlying psychiatric illness rather than organ toxicity. True serotonin toxicity is uncommon with these agents alone but has been reported, particularly with LSD combined with serotonergic antidepressants.[3]
Most of what brings these patients to the ED is the environment and the fear, not the pharmacology — a quiet room and reassurance outperforms a medication cabinet for the majority of presentations.
25I-NBOMe, 25C-NBOMe, and related N-benzyl phenethylamines
NBOMe compounds are full agonists at 5-HT2A with far greater receptor affinity than LSD, developed originally as research radioligands rather than intended recreational drugs. Critically, they are frequently sold on blotter paper marketed and mistaken as LSD — but their mechanism produces a substantially more dangerous, stimulant-heavy toxidrome layered on top of the hallucinogenic effect, unlike true LSD.[1]
Tachycardia (62%), hypertension (52%), hallucinations (81%), agitation, seizures, hyperthermia, rhabdomyolysis, and — in a meaningful minority — death. A literature review of 42 published cases found 9 fatalities, in sharp contrast to LSD's essentially zero-fatality record from direct toxicity.[2]
A patient who believes they took "acid" (LSD) but presents with seizures, hyperthermia, severe hypertension, and rhabdomyolysis almost certainly did not — this severity profile is essentially diagnostic of NBOMe misrepresented as LSD, since true LSD toxicity this severe is exceptionally rare. Fatal cases have also shown toxic leukoencephalopathy on imaging in survivors with severe or prolonged exposure.[3,4]
"Bad acid trip" with seizures and hyperthermia is a red flag, not a description — real LSD essentially never does this. Treat it as NBOMe until proven otherwise.
Delta-9-tetrahydrocannabinol
THC is a partial agonist at CB1 receptors (dense in the CNS, especially basal ganglia, cerebellum, and hippocampus) and CB2 receptors (predominantly peripheral/immune). CB1 activation inhibits presynaptic neurotransmitter release across multiple systems, producing the euphoric, anxiolytic-at-low-dose/anxiogenic-at-high-dose, and appetite-stimulating effects. Modern concentrate products (dabs, vape carts) can exceed 70-90% THC by weight, versus roughly 10-25% in traditional flower — a potency shift responsible for much of the rise in acute ED presentations.
Tachycardia, conjunctival injection, dry mouth, impaired coordination, anxiety/panic at high dose, and — with edibles specifically — delayed, unpredictable onset (30-90+ minutes) that drives accidental re-dosing and disproportionately severe presentations in naive users, especially children.
Cannabinoid hyperemesis syndrome — cyclical, severe nausea and vomiting in a chronic heavy user, classically relieved by compulsive hot showers or baths — is distinctive enough that the hot-water-seeking behavior itself is considered a diagnostic clue, despite marijuana's well-known antiemetic reputation making this paradoxical presentation easy to miss for years.[1,2]
Cyclical vomiting plus compulsive hot showers in a heavy cannabis user is CHS until proven otherwise — it can take years and an extensive, expensive workup to reach this diagnosis if nobody asks about cannabis use directly.
JWH-018, AB-CHMINACA, MDMB-CHMICA, and related designer compounds
Unlike THC's partial agonism, most synthetic cannabinoids are full agonists at CB1 with far higher receptor affinity — a mechanistic difference that translates directly into greater toxicity, longer duration, and a much higher seizure/psychosis rate than natural cannabis, independent of dose comparisons.[1]
Tachycardia and seizures are the most common findings across systematic review; third-generation compounds carry a higher rate of neuropsychiatric symptoms including psychosis. Standard cannabinoid immunoassays do not detect most synthetic cannabinoids, which is a major reason for delayed recognition.[1]
Unexplained coagulopathy with bleeding (hematuria, epistaxis, GI bleeding, bruising disproportionate to injury) in a synthetic cannabinoid user is diagnostic of brodifacoum (superwarfarin rodenticide) contamination — a 2018 multistate outbreak traced hundreds of cases to tainted product supply. This finding is unrelated to the drug's own pharmacology and is entirely an adulterant effect, but it is specific enough to this class that any unexplained vitamin-K-responsive coagulopathy in a young patient should prompt this history.[2,3]
"Fake weed" with unexplained bleeding is a public-health-outbreak pattern, not a coincidence — think brodifacoum, not just synthetic cannabinoid toxicity itself, and expect a long vitamin K taper, not a single dose.
Toluene, butane, propane (solvents/aerosols); isobutyl/amyl nitrite (poppers)
Volatile solvents (toluene and related hydrocarbons) are CNS depressants by a nonspecific mechanism resembling inhaled anesthetics — membrane fluidization and enhancement of GABA-A/glycine receptor function — but their most dangerous property is direct cardiac toxicity: sensitization of the myocardium to circulating catecholamines, producing a substrate for sudden fatal ventricular dysrhythmia. Alkyl nitrites work by an entirely different mechanism — they are potent oxidizing agents that convert hemoglobin's ferrous (Fe2+) iron to the ferric (Fe3+) state, producing methemoglobin, which cannot carry oxygen.[1,2]
Solvents: euphoria, hallucinations, headache, dizziness progressing to ataxia, seizures, and coma with heavy exposure; chronic use causes metabolic acidosis, renal tubular acidosis, and hepatic/renal impairment. Nitrites: headache, syncope, and — the hallmark — cyanosis and hypoxemia that does not correct with supplemental oxygen, reflecting methemoglobinemia rather than true hypoxia.[3]
"Sudden sniffing death" — cardiac arrest from ventricular fibrillation occurring during or shortly after a single inhalation session in an otherwise healthy young person, often precipitated by a sudden catecholamine surge (e.g., being startled and running) — is a recognized, distinctive fatal syndrome specific to volatile solvent abuse. For nitrites: cyanosis with a normal pulse oximetry reading that doesn't match the clinical picture, or a chocolate-brown arterial blood sample, is classic for methemoglobinemia — pulse oximeters cannot distinguish methemoglobin from normal hemoglobin and will overestimate true oxygen saturation.[4,5]
A normal-looking pulse oximeter reading does not clear methemoglobinemia — if the clinical cyanosis doesn't match the number on the monitor, trust the patient and send a co-oximetry gas.
Diphenhydramine (first-generation antihistamine); atropine/scopolamine (Datura stramonium alkaloids)
Competitive antagonism of acetylcholine at central and peripheral muscarinic receptors, blocking parasympathetic tone throughout the body. Diphenhydramine has the added complication of being a sodium-channel blocker at high dose — a mechanism entirely separate from its anticholinergic activity and the reason its overdose can produce QRS widening and TCA-like cardiotoxicity, unlike pure anticholinergics such as atropine or scopolamine.[1,2]
The classic anticholinergic (more precisely antimuscarinic) toxidrome is captured by the mnemonic: hot as a hare (hyperthermia), blind as a bat (mydriasis, blurred vision), mad as a hatter (delirium, often with mumbling speech and repetitive "picking" behaviors), red as a beet (flushed skin), dry as a bone (dry mucous membranes/axillae), and full as a flask (urinary retention) — plus tachycardia and decreased bowel sounds.[3,4]
The full six-feature mnemonic constellation together — dry, flushed, hot skin; mydriasis; urinary retention; absent bowel sounds; and a mumbling, "picking" delirium — is genuinely distinctive for this toxidrome as a whole, even though no single feature is unique in isolation. Hallucinations described as Lilliputian (seeing tiny people) or Alice-in-Wonderland-type distortions of size are classically associated with anticholinergic delirium specifically.[5]
Diphenhydramine is not a "pure" anticholinergic — its sodium-channel blockade means physostigmine, the classic antidote taught for this toxidrome, is often the wrong move for this specific, most common cause of it.
Ethyl alcohol
Ethanol potentiates GABA-A receptor function and inhibits NMDA glutamate receptors — a dual mechanism (enhancing inhibition, blocking excitation) that explains both its acute sedative/disinhibiting effects and the severity of withdrawal, which represents unmasked NMDA-receptor hyperexcitability and reduced GABA tone once the drug is removed after chronic adaptation.[1]
Dose-dependent CNS depression from disinhibition through ataxia, slurred speech, and — at high blood alcohol concentrations — respiratory depression, aspiration risk, and coma. Chronic use produces tolerance that shifts the dose-response curve, meaning a "normal" blood alcohol level in a naive user can be lethal while a dependent user may be conversant at levels that would incapacitate others.
Acute intoxication has no distinguishing exam finding beyond the odor and standard CNS-depressant picture. Withdrawal, however, has a distinctive, staged natural history worth knowing cold: tremulousness at 6-12 hours, withdrawal seizures at 12-48 hours, alcoholic hallucinosis (clear sensorium with isolated hallucinations) at 12-24 hours, and delirium tremens — autonomic storm plus true delirium — at 2-7 days after the last drink, occurring in only 3-5% of hospitalized withdrawal patients but carrying meaningful mortality if unrecognized.[2,3]
The emergency isn't usually the drunk patient in front of you — it's the withdrawal that hasn't started yet. Ask about last drink and typical daily intake on every alcohol-involved visit, not just the ones who look intoxicated.
Methanol (windshield washer fluid, bootleg liquor); ethylene glycol (antifreeze)
Both are relatively nontoxic in their parent form — the danger comes entirely from their metabolism by alcohol dehydrogenase (ADH), the same enzyme that metabolizes ethanol. Methanol is converted to formaldehyde and then formic acid, which is directly toxic to the optic nerve and retina. Ethylene glycol is converted through a cascade to glycolic acid (the main driver of the severe anion-gap metabolic acidosis) and then oxalic acid, which precipitates as calcium oxalate crystals in the renal tubules, causing acute kidney injury.[1,2]
Both present initially with an ethanol-like inebriation (sometimes minimal), followed after a latent period — as the parent compound is metabolized into its toxic acid — by severe high-anion-gap metabolic acidosis. Methanol's distinguishing late feature is visual disturbance progressing to blindness; ethylene glycol's is acute kidney injury.
For methanol: "snowstorm" or blurred vision progressing to complete blindness, with fundoscopic exam showing optic disc hyperemia/edema, is the hallmark finding pointing directly at formic-acid-mediated optic neurotoxicity. For ethylene glycol: calcium oxalate crystals in the urine (envelope-shaped or needle-shaped) combined with hypocalcemia and an elevated anion gap in a patient with a nontoxic or absent blood alcohol level is close to diagnostic — and a fluorescent antifreeze dye under a Wood's lamp on skin/clothing/vomitus is an old but real supporting clue.[3,4]
Don't wait for the send-out toxic alcohol level to start treatment — an elevated osmolar gap plus anion gap acidosis in the right clinical context is enough to start fomepizole today, not in two days when the confirmatory result arrives.
Nicotine; e-liquid also contains propylene glycol/vegetable glycerin as carrier
Nicotine is an agonist at nicotinic acetylcholine receptors throughout the peripheral and central nervous system — both at ganglionic synapses (sympathetic and parasympathetic) and at the neuromuscular junction. This dual autonomic activation is why nicotine toxicity produces a classically biphasic picture: an initial stimulatory phase (sympathetic ganglion activation) followed by a later depressor phase as ganglionic transmission is overwhelmed and blocked (depolarizing blockade), flipping the clinical picture from hyperactivity to depression within the same overdose.[1]
Liquid nicotine concentration varies enormously across products (often 20-60 mg/mL, with some "nic salt" formulations higher), and ingested dose correlates poorly with resulting symptom severity across case reports, making risk stratification by history alone unreliable — any pediatric e-liquid ingestion should be treated as potentially serious regardless of the stated concentration.[2]
The biphasic syndrome — early nausea, hypertension, tachycardia, tremor, and possibly seizures, followed hours later by hypotension, bradycardia, weakness, and CNS/respiratory depression in the same patient — is the signature, well-described pattern of significant nicotine toxicity and should prompt extended observation even after apparent early improvement, since the second (depressor) phase can be the more dangerous one.[3]
Don't discharge a significant e-liquid ingestion just because the early stimulatory phase has settled down — the depressor phase can arrive later and be the more dangerous half of the same overdose.
Mitragyna speciosa — active alkaloids mitragynine and 7-hydroxymitragynine
Mitragynine is a partial mu-opioid receptor agonist (with kappa/delta antagonism) using G-protein-biased signaling with limited beta-arrestin recruitment — theoretically less respiratory depression than classic full agonist opioids, though clinically significant respiratory depression is still reported, especially in combination with other CNS depressants. Its minor but far more potent metabolite/co-constituent, 7-hydroxymitragynine, has roughly 10-fold greater mu-receptor affinity than mitragynine itself and is disproportionately responsible for toxicity in concentrated extracts. Additional activity at alpha-2 adrenergic and serotonin receptors produces the mixed stimulant-at-low-dose/opioid-at-high-dose clinical picture users describe.[1,2]
Low doses: stimulant-like energy and alertness. Higher doses: opioid-like sedation, analgesia, and — in overdose or with concentrated/adulterated products — respiratory depression, seizures, and rarely cardiac arrest (primarily reported with polydrug use).[3]
Cholestatic hepatotoxicity — jaundice with markedly elevated bilirubin (case reports exceeding 20 mg/dL) developing over 1-8 weeks of regular use, generally reversible with cessation — is a distinctive pattern for kratom among the substances in this reference, most of which don't cause liver injury as a primary toxicity. Kratom does not appear on standard opioid immunoassays and can cause a false-negative standard opioid screen even in a patient with a genuinely opioid-like clinical picture.[3]
A negative opioid screen does not clear kratom off your differential for an opioid-like presentation — the standard immunoassay simply doesn't see it.
Testosterone esters, nandrolone, stanozolol, trenbolone, and related compounds
Full agonists at the androgen receptor, driving increased protein synthesis and muscle hypertrophy (the anabolic effect) alongside masculinizing effects (the androgenic effect) that cannot be pharmacologically separated. 17-alpha-alkylated oral formulations (methandrostenolone, stanozolol, oxandrolone) resist first-pass hepatic metabolism to achieve oral bioavailability, but this same structural modification is directly responsible for their disproportionate hepatotoxicity compared to injectable, non-alkylated esters.[1,2]
Cardiovascular: left ventricular hypertrophy, diastolic dysfunction, dyslipidemia (reduced HDL), hypertension, prothrombotic state, and sudden cardiac death in young, otherwise healthy athletes/bodybuilders — a pattern increasingly documented on forensic autopsy series. Hepatic: cholestatic jaundice with 17-alpha-alkylated agents, and rare but serious peliosis hepatis (blood-filled hepatic cysts) or hepatocellular adenoma/carcinoma with prolonged use. Renal: focal segmental glomerulosclerosis and chronic kidney disease from direct toxicity, hypertension, and rhabdomyolysis related to intense training.[3,4,5]
Peliosis hepatis — blood-filled cystic cavities within the liver, which can present with spontaneous hepatic rupture or subcapsular hematoma — is a distinctive, if rare, complication strongly associated with 17-alpha-alkylated AAS use and rarely seen from other causes in an otherwise healthy young adult. In a young bodybuilder-type patient, the combination of marked polycythemia (elevated hematocrit), significant left ventricular hypertrophy on echo without a hypertensive or valvular explanation, and gynecomastia together points strongly toward chronic AAS use even without a volunteered history.[4,6]
Unexplained LVH, polycythemia, or a liver lesion in a young, muscular patient deserves a direct, nonjudgmental question about AAS and supplement use — this population underreports use to physicians far more than the prevalence data would suggest.
Every entry follows the locked schema: identity/legal status → mechanism → pharmacokinetics → intoxication thresholds → toxidrome → symptomology with pathognomonic-or-honestly-flagged findings → front-line bedside management → critical-care escalation → practice-shift pearl → citations. Use the search bar above to jump straight to a substance by symptom, sign, street name, or treatment.
Not yet covered, for future lateral expansion: individual tricyclic/SSRI/SNRI antidepressants in overdose, lithium, digoxin, salicylates/NSAIDs, acetaminophen, antipsychotics, novel psychoactive "research chemical" fentanyl analogs beyond the class overview given, and khat in its unprocessed leaf form as distinct from synthetic cathinones.