Hallucinogens

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• Serotonergic Agents (LSD, Psilocybin, Mescaline): These classic psychedelics share structural similarities with endogenous serotonin (5-hydroxytryptamine [5-HT]). They primarily exert their effects by agonizing the 5-HT2A receptor subtype, which directly alters thought, mood, perception, and consciousness. Psilocybin ("magic mushrooms") is rapidly dephosphorylated in the body by alkaline phosphatase into the active, highly psychoactive chemical psilocin, which acts on these central serotonergic neurons.
• Dissociative Agents (PCP, Ketamine, Dextromethorphan): The core mechanism of toxicity for dissociative hallucinogens is the potent blockade of the N-methyl-D-aspartate (NMDA) receptor. The NMDA receptor is a neuronal ion channel normally activated by glutamate or glycine; when blocked by agents like phencyclidine (PCP) or ketamine, it disrupts neuronal plasticity and memory, leading to profound environmental dissociation, analgesia, and amnesia. These agents also have complex secondary pharmacology affecting dopamine, norepinephrine, and serotonin reuptake pumps, which drives their sympathomimetic side effects.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• De-escalation & Environment: For mild anxiety or panic reactions from hallucinogens, place the patient in a calm, quiet, low-stimulus environment; many can be verbally de-escalated with minimal clinical intervention.
• Initial Resuscitation: Check Airway, Breathing, and Circulation, and immediately obtain a point-of-care capillary glucose to rapidly reverse hypoglycemia, which can mimic intoxication. Provide supplemental oxygen to correct any hypoxia.
• Chemical Sedation: For agitated patients, intravenous (IV) or oral benzodiazepines (e.g., diazepam or lorazepam) are the cornerstone of medical therapy. If the patient exhibits extreme, violent agitation (frequently seen with PCP), rapidly administer butyrophenone antipsychotic agents such as haloperidol or droperidol to decrease the danger to the patient and staff.
• Hyperthermia Management: If the patient presents with hyperthermia and severe neuromuscular hyperactivity, they are at high risk for rhabdomyolysis and multiorgan failure. Escalate sedation aggressively; if refractory, this mandates rapid sequence intubation, neuromuscular paralysis, and active external cooling.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• The "Can't-Miss" Mimics:
• Hypoglycemia & Hypoxia: Easily reversible metabolic mimics of altered mental status.
• CNS Catastrophes: Traumatic brain injury, intracranial hemorrhage, or meningitis/encephalitis (patients intoxicated with PCP frequently sustain occult trauma due to violent behavior and analgesia).
• Anticholinergic Toxicity: Can cause delirium and tachycardia but is distinguished by extremely dry, flushed skin, urinary retention, and absent bowel sounds.
• Acute Psychiatric Illness: Schizophrenia typically presents with auditory hallucinations and stable vital signs, whereas organic/toxic hallucinogen ingestions present with visual hallucinations and abnormal vital signs.
• Prioritized Diagnostic Workup:
• Venous Blood Gas (VBG), Serum Chemistries, & Creatine Kinase (CK): Essential to screen for rhabdomyolysis and severe metabolic derangements (especially in agitated/hyperthermic patients).
• Electrolyte Panel: Actively screen for hyponatremia, which is a known complication of certain hallucinogenic amphetamine derivatives (like MDMA) and mescaline.
• Urine Drug Screen (UDS): Do not use UDS to guide clinical management. Qualitative immunoassays are highly inaccurate, miss novel synthetic hallucinogens, and cannot differentiate between remote and recent drug use.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• The 12-Lead ECG: Mandatory for all severe intoxications to actively identify QRS widening or QTc interval prolongation. These findings suggest the presence of dangerous, hidden co-ingestants (such as tricyclic antidepressants).
• The Physical Exam Visuals (Nystagmus): Carefully examine the eyes. The presence of both horizontal and vertical nystagmus is the classic, hallmark physical exam finding of PCP intoxication. Pupils are typically midsized and reactive, though miosis or mydriasis can occur.
• Non-Contrast CT Brain: If the patient demonstrates rotary nystagmus, this is uncharacteristic for simple PCP toxicity and should immediately prompt advanced neuroimaging to rule out a severe head injury or an intracranial space-occupying lesion.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• The 8-to-12 Hour Rule: Patients who present with altered mental status or paranoia that does not normalize after 8 to 12 hours of observation in the ED require formal hospital admission to a monitored setting for serial reassessments.
• Discharge Criteria: Hallucinogens generally possess a large acute safety ratio. Patients whose acute toxicity resolves and who respond well to simple sedation can be medically cleared for discharge. It is strictly recommended that they are discharged into the care of a responsible, non-intoxicated family member or friend.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The Diagnostic Anchoring Trap: Pitfall: Ascribing all abnormal behavior strictly to the known hallucinogen ingestion without considering co-morbidities. Critical Action: Because PCP causes profound analgesia, patients frequently sustain severe, occult traumatic injuries. A thorough trauma survey and consideration of head CT is mandated if the clinical picture is atypical.
• The UDS Reliance Pitfall: Pitfall: Delaying treatment or psychiatric clearance while waiting for a urine drug screen. Critical Action: The use of urine immunoassays should not guide the clinical management of patients with suspected hallucinogen poisoning.
• The Rotary Nystagmus Trap: Pitfall: Assuming all bizarre eye movements in a PCP user are drug-induced. Critical Action: While horizontal and vertical nystagmus are hallmarks of PCP, rotary nystagmus is a critical red flag requiring an immediate search for an intracranial lesion or head trauma.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzwords: "Horizontal and vertical nystagmus," "bizarre/violent behavior," and "superhuman strength." Exam Answer: Phencyclidine (PCP) intoxication.
• Buzzwords: "Ingestion of morning glory seeds" or "Hawaiian baby wood rose." Exam Answer: These plants contain alkaloids structurally similar to LSD and will produce an identical serotonergic hallucinogenic toxidrome.
• Buzzwords: "Small brown mushrooms that turn greenish-blue when bruised/cut." Exam Answer: Psilocybe species ("magic mushrooms"), which contain psilocybin.
• Distractor: An exam question describes a patient with severe visual hallucinations, hypertension, and tachycardia, and offers "Acute Schizophrenia" as the diagnosis. Correction: Schizophrenia typically presents with auditory hallucinations and normal vital signs; visual hallucinations coupled with autonomic instability strongly suggest an organic or toxicological cause (hallucinogens).

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Initial Resuscitation: "The patient is exhibiting severe, violent agitation and visual hallucinations with stable hemodynamics. My immediate priority is to ensure staff and patient safety. I will place the patient in a quiet, low-stimulus room and order a STAT bedside capillary blood glucose to rule out hypoglycemia. Concurrently, I am ordering intravenous lorazepam, and if the violent behavior persists, I will escalate to intravenous haloperidol."
• The Diagnostic Workup: "I will not rely on a urine drug screen to guide my management, as it is notoriously inaccurate for synthetic hallucinogens. Because of the extreme neuromuscular agitation, I am ordering a serum creatine kinase (CK), a basic metabolic panel to screen for hyponatremia, and a venous blood gas to evaluate for rhabdomyolysis and metabolic derangements. I also want a 12-lead ECG to rule out cardiotoxic co-ingestants."
• Addressing Complications & Disposition: "The patient demonstrates horizontal and vertical nystagmus, consistent with PCP, but I am actively assessing for rotary nystagmus or focal deficits, which would mandate a STAT head CT. If the patient's mental status does not return to baseline after 8 to 12 hours of ED observation, I will admit them to a monitored setting."