Phencyclidine (PCP, Ketamine) Intoxication

Primer

Phencyclidine (PCP) Intoxication occurs when there is a clinically significant problematic physiological, behavioural or psychological change (e.g. - disorientation, confusion without hallucinations, hallucinations or delusions, a catatonic-like syndrome, and/or coma) that develops during, or shortly after ingestion.[1]

Epidemiology
  • Use of PCP or related substances can be extrapolate as a rough estimate of the prevalence of intoxication.
    • Approximately 2.5% of the population reports having ever used PCP.
Prognosis
  • The main psychoactive effects of PCP last for a few hours, but the total elimination time from the body typically takes 8 days or longer.
  • The hallucinogenic effects from PCP and PCP-like substances in certain individuals may last for weeks and can present like a persistent psychotic episode resembling schizophrenia.
  • Unlike most other substance use disorders, hallucinogens do not have a withdrawal syndrome.[2]
  • Violence and aggression can also occur with PCP use, as intoxicated individuals may believe that they are being attacked.
  • Acute PCP intoxication can lead to intracranial hemorrhage, rhabdomyolysis, respiratory problems, cardiovascular problems (including cardiac arrest), and neurological toxicity (e.g. - dystonia, dyskinesias, seizures, catalepsy, hypothermia or hyperthermia).[3]
  • Chronic PCP use can lead to cognitive deficits and speech difficulties that can last for several months.[4]
Risk Factors
  • Little is known about risk factors for PCP use disorder.[5]

DSM-5 Diagnostic Criteria

Criterion A

Recent use of phencyclidine (or a pharmacologically similar substance).

Criterion B

Clinically significant problematic behavioural changes (e.g. - belligerence, assaultiveness, impulsiveness, unpredictability, psychomotor agitation, impaired judgment) that developed during, or shortly after, phencyclidine use.

Criterion C

Within 1 hour, at least 2 of the following signs or symptoms:

  1. Vertical or horizontal nystagmus
  2. Hypertension or tachycardia
  3. Numbness or diminished responsiveness to pain (analgesia)
  4. Ataxia
  5. Dysarthria
  6. Muscle rigidity
  7. Seizures or coma
  8. Hyperacusis
Note: When the drug is smoked, “snorted,” or used intravenously, the onset may be particularly rapid.
Criterion D

The signs or symptoms are not attributable to another medical condition and are not better explained by another mental disorder, including intoxication with another substance.

Signs and Symptoms

  • Acute PCP intoxication can lead to intracranial hemorrhage, rhabdomyolysis, respiratory problems, cardiovascular problems (including cardiac arrest), and neurological toxicity (e.g. - dystonia, dyskinesias, seizures, catalepsy, hypothermia or hyperthermia).[6]

Differential Diagnosis

  • Other substance intoxication
    • PCP intoxication should be differentiated from intoxication due other hallucinogens, amphetamine, cocaine (or other stimulants), anticholinergics, and withdrawal from benzodiazepines. Nystagmus and bizarre and violent behavior can distinguish intoxication due to PCP from other substances.
  • Other mental disorders
    • Other conditions to consider include schizophrenia, depressive disorders, withdrawal from other drugs (e.g. - sedatives, alcohol).
  • Other medical conditions
    • Certain metabolic disorders including hypoglycemia, hyponatremia, central nervous system tumors, seizure disorders, sepsis, neuroleptic malignant syndrome, and vascular insults can have similar symptoms and presentation.[7]

Investigations

  • Although PCP is detectable in urine for up to 8 days following use, levels are only weakly associated with the individual's clinical presentation, and thus may not have an impact on clinical management.
  • Creatine phosphokinase (CK) and aspartate aminotransferase levels (AST) may be elevated.

Physical Exam

  • As directed by the clinical presentation.

Treatment

  • Individuals with acute PCP intoxication may have extensive cardiovascular and neurological issues, including seizures, dystonia, dyskinesias, catalepsy, hypothermia or hyperthermia.
  • Thus, treatment should be directed at the primary presenting problem or organ system issue.

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References

1) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
2) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
3) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
4) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
5) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
6) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
7) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.