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Phencyclidine (PCP)-Related Psychiatric Disorders Workup

  • Author: Alan D Schmetzer, MD; Chief Editor: Iqbal Ahmed, MBBS, FRCPsych(UK)  more...
Updated: Dec 29, 2015

Laboratory Studies

Always obtain a urine drug screen for a person with agitation or psychosis, unless the patient is so well known to the treating physician and staff that there is no question at all regarding the cause of the abnormalities observed. Even then, if the clinical picture seems at all different from the usual presentation, a drug screen may be useful. Serum levels of specific drugs also may be available in some emergency departments. However, be aware that specific urine or serum levels may have little correlation with clinical manifestations, especially in the case of PCP intoxication.

Phencyclidine is excreted in the urine, both in unchanged form and as conjugated metabolites. The usual laboratory test for PCP is an enzyme immunoassay technique that detects both PCP and its metabolic analog, 1-[1-(2-thienyl)-cyclohexyl]-piperidine (TCP). This is a qualitative screening test; that is, it tells whether the drug is present or absent. Gas chromatography coupled with mass spectrometry (GC/MS), as with other drugs, is the confirmatory test providing the highest confidence level for PCP.

Because rhabdomyolysis is a potential complication of PCP intoxication, serum enzyme levels may be useful, particularly skeletal muscle creatine phosphokinase (CPK).


Imaging Studies

Imaging studies have not proved clinically useful as yet in delineating PCP-induced psychosis from other causes of such disorders. Brain imaging studies in small numbers of adult chronic PCP users suggest that they may have decreased right cerebral cortical blood flow and frontal glucose metabolism. Such abnormalities are similar to those found in patients diagnosed with schizophrenia. Eventually it is hoped that diagnostic clues to PCP psychosis may be found from more complex imaging techniques than those currently available.



PCP use may begin as recreational and intermittent, but some evidence suggests that people can progress to abuse and finally, possibly, to dependence.

In addition, assess for stage of change. This includes whether the patient is in the "precontemplation," "contemplation," "planning," "action," or "maintenance/relapse" phase of decision making (as described by Prochaska and DiClemente) regarding his or her use of PCP.

Contributor Information and Disclosures

Alan D Schmetzer, MD Professor Emeritus, Department of Psychiatry, Indiana University School of Medicine

Alan D Schmetzer, MD is a member of the following medical societies: American Academy of Addiction Psychiatry, American Academy of Clinical Psychiatrists, American Academy of Psychiatry and the Law, American Association for Physician Leadership, American Medical Association, American Psychiatric Association, International Society for ECT and Neurostimulation, American Neuropsychiatric Association

Disclosure: Nothing to disclose.


David R Diaz, MD, DFAPA Associate Professor of Clinical Psychiatry, Indiana University School of Medicine; Medical Director, Unit 3C, Larue D Carter Memorial Hospital

David R Diaz, MD, DFAPA is a member of the following medical societies: Academy of Psychosomatic Medicine, American Psychiatric Association, Indiana State Medical Association, National Hispanic Medical Association, Indiana Psychiatric Society, Indianapolis Medical Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Iqbal Ahmed, MBBS, FRCPsych(UK) Faculty, Department of Psychiatry, Tripler Army Medical Center; Clinical Professor of Psychiatry, Uniformed Services University of the Health Sciences; Clinical Professor of Psychiatry, Clinical Professor of Geriatric Medicine, University of Hawaii, John A Burns School of Medicine

Iqbal Ahmed, MBBS, FRCPsych(UK) is a member of the following medical societies: Academy of Psychosomatic Medicine, American Neuropsychiatric Association, American Society of Clinical Psychopharmacology, Royal College of Psychiatrists, American Association for Geriatric Psychiatry, American Psychiatric Association

Disclosure: Nothing to disclose.

Additional Contributors

Barry I Liskow, MD Professor of Psychiatry, Vice Chairman, Psychiatry Department, Director, Psychiatric Outpatient Clinic, The University of Kansas Medical Center

Disclosure: Nothing to disclose.

Roland McGrath, MD 

Roland McGrath, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.


The authors would like to acknowledge Indiana University School of Medicine, William Niles Wishard Memorial Hospital, and Larue D. Carter Memorial Hospital for their support of the faculty involved in the preparation of this Medscape Reference article.

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PCP molecule.
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