Scope & clinical relevance

Use of classic hallucinogens (LSD, psilocybin), dissociatives (ketamine, PCP), and novel psychoactive substances can result in adverse psychological effects. While most acute effects resolve, some patients develop persistent distressing symptoms or functional impairment requiring medical or psychiatric care.

Presentations

• Acute intoxication: perceptual distortions, visual hallucinations, depersonalisation, anxiety, paranoia, agitation.
• Substance‑induced psychotic disorder: persistent psychotic symptoms following use (delusions, hallucinations, disorganized thinking) lasting days to weeks.
• Hallucinogen Persisting Perception Disorder (HPPD): recurrent, distressing visual disturbances (e.g., trailing, halos, geometric patterns) persisting after substance use has ceased.
• Anxiety, panic or depressive episodes temporally linked to hallucinogen exposure.

Assessment — immediate priorities

1. Ensure safety: assess risk to self/others, intoxicant level and medical stability (airway, breathing, circulation).
2. Gather collateral: what was taken (drug, dose, route), time since use, co‑ingestants (alcohol, stimulants), and past psychiatric history.
3. Mental state exam: orientation, perception, thought content, insight and suicidality.
4. Basic investigations where indicated: glucose, electrolytes, ECG, tox screen, and consider imaging if focal neurological signs or head injury suspected.

Immediate management — acute intoxication

• Calm, low‑stimulus environment; reassure and provide verbal de‑escalation — often sufficient for anxiety/paranoid reactions.
• Benzodiazepines (e.g., lorazepam) are first‑line for severe agitation, anxiety or panic; titrate to effect and monitor for respiratory depression if combined with other sedatives.
• Avoid routine antipsychotics for classic hallucinogen intoxication unless psychosis is severe or prolonged; if needed, use low doses and monitor cardiac and extrapyramidal side effects.
• Consider hospital admission if persistent psychosis, severe agitation, intoxication with unknown substances, or co‑ingestant harm (e.g., stimulants causing hyperthermia).

Managing Hallucinogen Persisting Perception Disorder (HPPD)

• HPPD is a clinical diagnosis — visual disturbances after hallucinogen use that cause distress or impairment.
• Rule out other causes: migrainous phenomena, epilepsy, intoxication, or primary visual/neurological disorders.
• Treatment evidence is limited: first‑line management focuses on psychoeducation, reassurance, avoidance of re‑exposure, and CBT for distress related to perceptual symptoms.
• Pharmacological options with mixed evidence include clonazepam (some reports of benefit), selective use of antipsychotics (may worsen symptoms in some patients), and off‑label agents (e.g., lamotrigine) in specialist settings — consult psychiatry.

Treatment of persistent psychiatric presentations

• Substance‑induced psychosis: if symptoms persist beyond expected intoxication window, consider short‑term antipsychotic treatment and close follow‑up; re‑evaluate for primary psychotic disorder if symptoms continue after washout.
• Anxiety/depression linked to hallucinogen use: offer CBT, SSRIs if clinically indicated, and avoid restarting hallucinogens; involve addiction services where appropriate.
• Referral for specialist neuropsychiatric assessment for complex or refractory cases, especially when HPPD or cognitive deficits are prominent.

Harm reduction & patient advice

• Advise avoidance of further psychedelic use until symptoms fully resolve; counsel on risks of mixing with alcohol or other drugs.
• Encourage sleep hygiene, stress reduction techniques and avoiding bright/flashing lights which may worsen visual symptoms.
• Provide information on support groups, crisis contacts and when to seek urgent care (worsening psychosis, suicidal ideation, physical harm).

Key takeaways

• Most hallucinogen‑related reactions resolve with a calm environment and short‑term supportive care.
• Benzodiazepines are first‑line for severe agitation or panic; antipsychotics reserved for persistent or severe psychosis.
• HPPD requires careful assessment and reassurance — limited pharmacologic options exist and specialist input is often needed.
• Provide harm reduction advice and arrange timely follow‑up; escalate urgently for safety concerns or persistent psychosis.