Phencyclidine (PCP, Ketamine) Use Disorder

• The prevalence of PCP use disorder is unknown.
• Approximately 2.5% of the population in the United States reports having ever used PCP.^[1]
  • Use of ketamine (PCP-like substance) appears to be within the 1 to 2% range
• Males make up about 75% of PCP-related emergency room visits.^[2]

• 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.^[3]
• 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).^[4]
• Chronic PCP use can lead to cognitive deficits and speech difficulties that can last for several months.^[5]

• Little is known about risk factors for PCP use disorder.^[6]

A pattern of phencyclidine (or a pharmacologically similar substance like ketamine) use leading to clinically significant impairment or distress, as manifested by at least 2 of the following, occurring within a 12-month period:

1. Phencyclidine is often taken in larger amounts or over a longer period than was intended.
2. There is a persistent desire or unsuccessful efforts to cut down or control phencyclidine use.
3. A great deal of time is spent in activities necessary to obtain phencyclidine, use the phencyclidine, or recover from its effects.
4. Craving, or a strong desire or urge to use phencyclidine.
5. Recurrent phencyclidine use resulting in a failure to fulfill major role obligations at work, school, or home (e.g. - repeated absences from work or poor work performance related to phencyclidine use; phencyclidine-related absences, suspensions, or expulsions from school; neglect of children or household).
6. Continued phencyclidine use despite having persistent or recurrent social or inter personal problems caused or exacerbated by the effects of the phencyclidine (e.g. - arguments with a spouse about consequences of intoxication; physical fights).
7. Important social, occupational, or recreational activities are given up or reduced because of phencyclidine use.
8. Recurrent phencyclidine use in situations in which it is physically hazardous (e.g. - driving an automobile or operating a machine when impaired by a phencyclidine).
9. Phencyclidine use is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the phencyclidine.
10. Tolerance, as defined by either of the following:
    • A. A need for markedly increased amounts of the phencyclidine to achieve intoxication or desired effect.
    • B. A markedly diminished effect with continued use of the same amount of the phencyclidine.

• PCP and PCP-like substances produce feelings of separation from the mind and body (“dissociative”) in low doses.^[7]
  • PCP can also cause analgesia, nystagmus, and hypertension, with a risk for hypotension and shock.
  • At high doses, stupor and coma can result.
• There may be evidence of physical injuries from accidents, fights, and falls.

• PCP and PCP-like substances both fall under the diagnosis of PCP use disorder.^[8]
  • These substances are commonly smoked or used orally, but can also be snorted or injected.
• The mechanism of action of these substances is via non-competitive NMDA receptor antagonism and blockade.

• PCP is also known as “angel dust”, “embalming fluid”). It can be used orally in liquid form, or snorted as a powder.

• PCP-like substances that are less potent than PCP include ketamine, cyclohexamine, and dizocilpine. These substances were developed as dissociative anesthetics in the 1950s and later became street drugs in the 1960s.^[9]
• Ketamine is also known as “K,” “Special K,” “vitamin K,” “kitkat.”
• It can be used in oral form as a liquid or crystals, or intravenously

• Three three commonly used research questionnaires to assess the subjective effects of hallucinogens include:^[10]
  • Hallucinogen Rating Scale (HRS)
  • Mystical Experience Questionnaire (MEQ)
  • Addiction Research Center Inventory (ARCI)
• These are not used in routine clinical practice however.

• Like with all substance use disorders, there is a complex interplay between biological, social, psychological, and cultural factors.

• Other substance use disorders
  • Differentiating the effects of PCP from substances is important, sine PCP is a common adulterant/additive to other substances (e.g. - cannabis, cocaine).
• Schizophrenia and other mental disorders
  • The effects of PCP and PCP-like substances can resemble symptoms of other psychiatric disorders, in particular psychosis (schizophrenia), depression (major depressive disorder), aggressive behaviours (conduct disorder, antisocial personality disorder).
• PCP-induced psychotic disorder
  • A PCP-induced psychotic disorder should be considered when there are disturbances in perception and impaired reality testing after ingestion of PCP.

• PCP can be detected in the urine for up to 8 days or longer at high doses.

• The clinical history and physical exam (nystagmus, analgesia, and prominent hypertension) can differentiate PCP use from other hallucinogens.^[11]

• There are no approved treatments available for PCP use disorder outside of the acute intoxication period.
• Generally, routine clinical support and substance use disorder psychotherapies such as motivational interviewing are recommended.