An Evaluation of Phencyclidine (PCP) Psychosis:A Retrospective Analysis at a State Facility

Katie A. Carls, Pharm.D., B.C.P.P.,1 and

Valerie L. Ruehter, Pharm.D., B.C.P.P.2

1University of Minnesota Medical Center, Fairview Pharmaceutical Services,Minneapolis, Minnesota, USA

2University of Missouri-Kansas City School of Pharmacy,Kansas City, Missouri, USA

Abstract: It has been reported in the literature that phencyclidine (PCP)psychosis recovery may take up to 4–6 weeks. This retrospective review soughtto determine whether patients with a new onset of PCP psychosis have a longerhospitalization than those patients with new onset functional psychosis. ThePCP arm (N ¼ 20) was found to have a significantly shorter hospitalization thanthose with a new onset functional psychosis (N ¼ 20)—mean 4.8 days (range 1–9)versus 13.6 days (range 3–41), p < .05. In addition, patients with psychosis relatedto PCP use were treated more aggressively with conventional antipsychotics thanpatients with a new onset functional psychosis at this facility.

Keywords: Antipsychotic, PCP, phencyclidine, psychosis, treatment

BACKGROUND

In 1956 phencyclidine (PCP) was developed as an intravenous anesthetic(Sernyl, by Parke Davis), however it was removed from the market in1965 as many patients, post-operatively, suffered a drug-induced psychoticreaction consisting of excitation, paranoia, bizarre behaviors, concrete-ness of thought, and hallucinatory disturbances often lasting up to ten days(1–8). Soon after removal from the market it appeared on the illicit drugscene, as it was relatively inexpensive to manufacture, often misrepresentedfor THC, LSD, mescaline, psilocybin, and cocaine (7). Interestingly, while

Address correspondence to Katie A. Carls, Pharm.D., B.C.C.P., University ofMinnesota Medical Center, Fairview, Pharmaceutical Services, 2450 RiversideAve., Minneapolis, MN 55416, USA. E-mail: kcarls1@fairview.org

The American Journal of Drug and Alcohol Abuse, 32: 673–678, 2006

Copyright Q Informa Healthcare

ISSN: 0095-2990 print/1097-9891 online

DOI: 10.1080/00952990600920177

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symptoms of PCP intoxication closely resemble that of schizophrenia,making it difficult to distinguish between the two, literature has reportedcases of prolonged psychosis induced by PCP with complete recovery tak-ing up to 4–6 weeks regardless of treatments (8, 9). It is unknown whatcauses the persistence of psychotic symptoms, however several theorieshave been suggested—dose dependent, chronic use, or underlying psy-chotic disorder not yet established (9).

PCP has a receptor located within the N-methyl-D-aspartate(NMDA) receptor. This receptor inhibits NMDA function, which is nor-mally stimulated, at a separate site, by the excitatory amino acid L-gluta-mate (2, 5, 9). Inhibition of the NMDA receptor decreases GABA-ergicoutflow as similarly does dopamine acting at the D2 receptors (5). Anti-psychotics have not been found to significantly shorten the hospitalcourse in patients with PCP-induced psychosis, as they target the D2receptor, however they may be moderately effective in reducing the inten-sity of the symptoms (7, 9). Even so, studies regarding PCP-induced psy-chosis and its treatment are limited with most being published in the1970s and early 1980s, prior to the advent of atypical antipsychotics.In addition to psychotic behaviors, PCP-induced psychotic episodes areoften associated with violent and aggressive behaviors in which thepatients describe feelings of increased power and strength. With therecent resurgence of patients testing positive for PCP and observationof slow treatment responses, this study aims to determine if patients withpsychosis related to PCP use have longer hospitalizations than patientswith functional psychosis and to compare treatments between the groups.

METHODS

Two populations of patients hospitalized at Western Missouri MentalHealth Center were compared—patients with a new onset of psychosisthat are PCP positive and patients with a new onset of psychosis notrelated to drugs or organic causes. Inclusion critieria for the PCP armwere positive PCP urine drug screen (>25 ng=ml) and symptoms of psy-chosis. Exclusion criteria were a comorbid Axis I diagnosis: psychotic dis-order—schizophrenia-disorganized, catatonic, paranoid, or residual;schizophreniform; schizoaffective; delusional disorder; brief psychoticdisorder; psychotic disorder due to general medical condition—or pre-vious treatment of psychotic episode, depressive disorder, bipolar dis-order, and=or anxiety disorder. Inclusion criteria for the functionalpsychosis arm were new Axis I diagnosis for a psychotic disorder—schizophrenia-disorganized, catatonic, paranoid, residual; schizophren-iform; schizoaffective; delusional disorder; brief psychotic disorder; or

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psychosis NOS. Exclusion criteria were a positive urine drug screen forPCP, indication of psychosis related to PCP use without positive UDS,previous treatment of psychotic episode, and psychotic disorder due togeneral medical condition. The primary measure will compare length ofhospitalization between the two groups. Secondary measures includeantipsychotics prescribed, total time in seclusion=restraints, violent=aggressive=threatening presentation, discharged against medical advice,and future diagnosis of functional psychosis. PCP positive patients wereidentified from laboratory records with positive urine drug screens.Acutely psychotic patients were identified from a medical records searchby diagnostic code.

The power of the study was calculated using a standard deviationof 2.08 days, derived from the average acute adult hospitalization of 9.2days. In order to detect a difference of 3 days between study groups witha 90% power, 10 patients are needed for each group. However, to compen-sate for variability in the standard deviation, 20 patients for each groupwere to be included. The 20 most recently hospitalized patients, fitting studycriteria, from December 2002 back through January 2000 were included inorder to minimize any changes in the care and therapeutic managementover time. Length of hospital stay was analyzed by the Wilcoxon two-sample t-test. Secondary measures were analyzed by descriptive methods.

RESULTS

Twenty patients were identified for both study arms. Significant demo-graphic differences between the 2 groups were race, more African-Amer-ican patients in the PCP arm (19 versus 6; the remaining patients wereCaucasian), and positive marijuana drug screen, 14 patients in PCParm and 1 in the control arm. The mean age in the PCP arm was25.3 years versus 23.35 years in the control arm. There were thirteen malepatients in the PCP arm and 16 in the control arm. Four patients testedpositive for cocaine in the PCP arm and in the control arm. One patienttested positive for benzodiazepines in the PCP and in the control arm.One patient was positive for amphetamines in the control arm. Lengthof hospitalization was significantly shorter for patients in the PCP arm,mean 4.8 days (range 1–9 days) versus mean 13.6 days (range 3–41 days)in the control arm (p < .05). There were no trends identified with PCP ormarijuana urine drug screen concentrations and length of hospitalization;mean PCP concentration 374.5 ng=ml, range 46.22– >500 ng=ml, meanmarijuana concentration 100.34 ng=ml, range 26.17– >135 ng=ml (PCPpositive with concentrations >25 ng=ml; marijuana positive with con-centrations >20 ng=ml).

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Compared to patients with functional psychosis, patients with PCP-related psychosis appeared to receive lower doses of atypical antipsycho-tics and more scheduled conventional antipsychotics (see Table 1). It wasalso observed that the patients in the PCP arm received more prn antipsy-chotics and higher doses than the functional psychosis arm. In addition,6 of 20 patients in the phencyclidine arm were discharged on an antipsy-chotic; 17 of 20 patients in the control arm were discharged on anantipsychotic. Doses prescribed were on average lower in the PCP arm.There did not appear to be a relationship with antipsychotic prescribedand length of stay in the PCP study arm—olanzapine 4.7 days, risperi-done 4.3 days, haloperidol 5.7 days.

Five patients in the PCP arm versus 2 in the functional psychosis armpresented in a violent=aggressive=threatening manner. In addition,4 patients in the PCP arm spent time in restraints (mean time 137.5minutes, total time 550 minutes, range 45 minutes–3 hours 55 minutes),versus 1 in the functional psychosis arm (total time 240 minutes). Onepatient in the PCP arm was in seclusion, 2 hours 50 minutes; one patientin the functional psychosis arm was in seclusion, 3 hours 50 minutes. Ofthose patients with a violent=aggressive=threatening presentation in thePCP arm, one patient was positive for cocaine (>5000 ng=ml), 4 werepositive for marijuana (mean concentration 134.98 ng=ml, range of134.92– > 135 ng=ml). In the control arm, one patient was positive formarijuana (>135 ng=ml). There did not appear to be a concentration-relationship with PCP and a violent=aggressive=threatening presentation(range 46.22– > 500 ng=ml, mean concentration 262.2 ng=ml). Nopatients were discharged against medical advice and one patient in thePCP arm was readmitted with a diagnosis of schizoaffective disorder inthe study time period.

Table 1. Antipsychotics prescribed and mean daily dose

No. PCP Arm(n ¼ 20)

Mean doseper day�

No. controlarm (n ¼ 20)

Mean doseper day

ANTIPSYCHOTICOlanzapine 3 6.6 mg 6 9.0 mgQuetiapine 0 n=a 2 285.5 mgRisperidone 6 1.0 mg 10 1.8 mgHaloperidol 6�� 7.8 mg 0 n=aNone 4 n=a 2 n=a

�Mean dose of scheduled antipsychotics; calculated by the mean of eachpatient’s average daily dose.��One patient excluded—received only haloperidol prn.

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DISCUSSION

This retrospective review found that patients receiving first treatmentfor psychosis related to PCP use have a shorter hospitalization thanthose with new functional psychosis. This does not appear to be aPCP dose related phenomenon, however laboratory cut-off values area limitation for this observation. Other study limitations include poten-tially incomplete medical histories for previous treatments of psychosisas well as concurrent medications administered. While literature sug-gests that PCP may precipitate psychosis in patients who are predis-posed to develop a functional psychosis, this study’s limited timeframe also made it difficult to evaluate readmissions for a diagnosisof a psychotic disorder. It seems most likely that patients with a pro-longed psychotic episode is related to chronic PCP use leading to exten-sive neuronal damage and=or an early precipitation of psychosis inpatients predisposed.

Patients in the PCP study arm received slightly lower doses of atypi-cal antipsychotics and a significantly larger number were prescribedconventional antipsychotics. The higher use of prn antipsychotics inthe PCP arm may explain the lower doses of atypical antipsychotics,however there is limited evidence to support use of the conventionalagents over the atypical agents. Recent studies in rats suggest that atypi-cal antipsychotics function differently than conventional agents in PCPintoxication (10–12) and have more cognitive benefits (13). Regardless,with the recent discussions on ethnic influences on prescribing practices,it is worth noting the racial differences between the two groups—the PCParm having a larger number of African American patients—which isa possible explanation for the larger percentage of patients receivingconventional agents.

To address the reason why several patients in the functional psy-chosis arm received no antipsychotics during the hospitalizations and=ordischarge, two patients had refused treatment and the third patient notreceiving an antipsychotic on discharge was transferred to anotherhospital.

Finally, while the PCP intoxication is often stereotyped with overtlyaggressive, violent and threatening behaviors, only 25% (n ¼ 5=20) pre-sented in this manner, while 10% (n ¼ 2=20) with functional psychosisalso presented in this manner. It is also important to recognize that alarge number of PCP positive patients were excluded from the study ifno psychotic symptoms were present, further diminishing the ratio.One would concur, as suggested in literature, that this behavior is largelya function of environmental cues and the patient’s emotional state at thetime of ingestion and intoxication.

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ACKNOWLEDGMENT

Research approval was obtained from Western Missouri Mental HealthCenter Research Committee, the Missouri Department of Mental HealthInstitutional Review Board, and the University of Missouri Kansas CityInstitutional Review Board.

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