Common unspecified presentations

• Prolonged dissociative episodes not clearly fitting intoxication timelines.
• Mild‑to‑moderate persistent perceptual changes (visual or somatic) without clear HPPD criteria.
• Mixed presentations with overlapping stimulant/depressant features (e.g., PCP + methamphetamine) causing atypical signs.
• Functional impairment after a single high‑dose exposure without ongoing substance use.

Assessment priorities

1. Stabilise medically: ABCs, vitals, oxygen and cardiac monitoring if needed in acute cases.
2. Obtain focused history: substance(s), dose, route, timing, co‑ingestants, prior psychiatric history and any recent trauma or sleep deprivation.
3. Examine for red flags: focal neurology, fever, progressive cognitive decline, signs of rhabdomyolysis or renal impairment.
4. Use targeted investigations: ECG, electrolytes, CK, renal & liver function, urine tox screen and neuroimaging or EEG where indicated by examination.

Differential diagnosis

• Primary psychiatric disorders (brief psychotic disorder, schizophrenia) — consider family history and longitudinal course.
• Other substance effects or withdrawal states (benzodiazepine/alcohol withdrawal, stimulant intoxication).
• Neurological and medical causes: seizures, encephalitis, metabolic disturbances or head injury.

Immediate management

• For severe agitation or risk of harm: benzodiazepines (e.g., lorazepam) as first‑line; repeat to effect and monitor respiratory status.
• Consider antipsychotics for persistent psychosis after medical causes addressed; use cautiously and monitor for EPS and QTc prolongation.
• Treat medical complications (hyperthermia, rhabdomyolysis, aspiration) per standard protocols and involve ICU for instability.

Short‑term care and disposition

• Admit for observation if there is instability, altered consciousness, seizures, evidence of organ injury, or uncertain diagnosis.
• Outpatient follow‑up may be suitable for resolved, mild cases with good social supports — provide clear safety netting and rapid access to care if symptoms worsen.
• Offer brief motivational interviewing and referral to addiction services for ongoing or recurrent use.

Long‑term management

• Multidisciplinary approach: psychiatry, addiction services, neurology and rehabilitation as needed for persistent symptoms.
• Psychological treatments (CBT, trauma‑informed therapy) for persistent dissociation or distressing perceptual symptoms.
• Taper and avoid medications that may worsen dissociation or perception (e.g., stimulants) and counsel on abstinence from dissociatives.

Key takeaways

• Unspecified PCP‑related presentations are heterogeneous — prioritise safety, exclude medical causes and provide supportive care.
• Use benzodiazepines for acute agitation, involve specialists for persistent or complex symptoms, and offer addiction treatment where indicated.
• Provide clear discharge instructions, follow‑up and harm‑reduction advice to reduce recurrence and support recovery.