Hallucinogens - The Mind Benders
- Classic Hallucinogens: Lysergic acid diethylamide (LSD), psilocybin, mescaline.
- Mechanism of Action: Primarily serotonin 5-HT2A receptor agonists, altering perception and mood.
- Intoxication Syndrome:
- Profound perceptual changes: visual illusions & hallucinations, synesthesia (e.g., "hearing colors").
- Psychic effects: depersonalization, derealization, anxiety, paranoia ("bad trip").
- Sympathomimetic signs: ↑ HR, ↑ BP, mydriasis.
- Hallucinogen Persisting Perception Disorder (HPPD):
- Spontaneous, transient recurrences of perceptual disturbances ("flashbacks") causing significant distress or impairment.
⭐ Unlike intoxication, HPPD flashbacks occur without recent drug use and are a key diagnostic feature.
Classic Hallucinogens - Serotonin's Wild Ride
- Mechanism: Primarily agonists at serotonin 5-HT2A receptors, altering perception and mood.
| Feature | Lysergic Acid Diethylamide (LSD) | Psilocybin (Magic Mushrooms) | Mescaline (Peyote Cactus) |
|---|---|---|---|
| Onset & Duration | Onset: 30-90 min; Duration: 6-12 hrs | Onset: 20-40 min; Duration: 4-6 hrs | Onset: 1-2 hrs; Duration: ~12 hrs |
| Intoxication | Visual hallucinations, synesthesia, delusions, pupillary dilation, tachycardia, tremors. | Similar to LSD but often more visual and less panic-inducing. | Vivid visual hallucinations, anxiety, tachycardia, diaphoresis, nausea/vomiting. |
| Unique Trait | 📌 "Flashbacks" or Hallucinogen Persisting Perception Disorder (HPPD) can occur long after use. | Often described as more "natural" or "spiritual" experiences. | Strong association with nausea and vomiting during onset. |
⭐ Exam Favorite: Hallucinogen Persisting Perception Disorder (HPPD) involves spontaneous, transient recurrences of visual disturbances reminiscent of acute intoxication. It's a diagnosis of exclusion and can be distressing, often triggered by stressors or other substance use.
PCP & Ketamine - Dissociative Disconnect
- Mechanism: Non-competitive NMDA receptor antagonists; inhibit excitatory glutamate neurotransmission.
- Clinical Presentation: Dissociative state with analgesia, amnesia, and a feeling of detachment. Key signs include aggression, impulsivity, ataxia, and nystagmus (horizontal, vertical, or rotary).
- 📌 Mnemonic (PCP): RED DANES - Rage, Erythema (red skin), Delusions, Amnesia, Nystagmus, Excitation, Skin dryness.
- Management: Focus on supportive care in a low-stimulus environment.
- Agitation/Seizures: Benzodiazepines (e.g., lorazepam) are first-line.
- Severe Psychosis: Antipsychotics like haloperidol may be used cautiously.
- Monitor for rhabdomyolysis (CK levels) and hyperthermia.
⭐ Vertical or rotary nystagmus is highly suggestive of PCP intoxication.
Management - Calm, Cool, Collected
- Initial approach focuses on supportive care and verbal de-escalation (“talking down”).
- Place patient in a low-stimulus environment (quiet, dimly lit room) to minimize perceptual distortions.
- Avoid physical restraints if possible, as they may increase agitation and risk of rhabdomyolysis.
- For severe agitation or psychosis unresponsive to environmental management, pharmacotherapy is indicated.
⭐ In PCP intoxication, avoid antipsychotics like haloperidol. They lower the seizure threshold and have anticholinergic effects that can worsen hyperthermia.
High‑Yield Points - ⚡ Biggest Takeaways
- LSD intoxication is marked by visual hallucinations and synesthesias; reality testing is typically intact.
- Hallucinogen Persisting Perception Disorder (HPPD), or "flashbacks," is a key long-term risk with LSD.
- PCP is notorious for causing nystagmus (rotary, vertical), aggression, and dissociation. Use benzodiazepines for management.
- MDMA (Ecstasy) toxicity can precipitate serotonin syndrome and life-threatening hyponatremia from SIADH and excess water intake.
- Unlike opioids or alcohol, classic hallucinogens have no significant withdrawal syndrome.
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