Characteristics of 68 chronic phencyclidine abusers who sought treatment

Phencyclidine Positivity on Urine Drug Screening in Patients Treated for Alcohol Withdrawal on a Dual-diagnosis Medically Assisted Withdrawal Unit

OBJECTIVES

Little contemporary research has explored phencyclidine (PCP) use in people with alcohol use disorder. Therefore, we sought to determine the prevalence of PCP positivity on urine toxicology screening among patients admitted for alcohol withdrawal, identify correlates of PCP positivity, and investigate PCP positivity's relationship to length of stay (LOS) and risk of facility readmission.

METHODS

This was a retrospective study of patients admitted to a dual-diagnosis medically assisted withdrawal unit for alcohol withdrawal from 2014 to 2019. Univariate tests and logistic regression were used to investigate potential correlates of PCP positivity on admission toxicology screening (primary outcome). Multivariable linear regression models and survival analyses analyzing LOS and risk of readmission (secondary outcomes) were also developed.

RESULTS

Ninety of 3731 patients (2.4%) screened positive for PCP. There were significant associations on univariate testing between PCP positivity and age, race, homeless status, and urine toxicology positivity for amphetamines, benzodiazepines, barbiturates, cocaine, tetrahydrocannabinol, and oxycodone. On multivariate logistic regression, only tetrahydrocannabinol, barbiturates, and cocaine positivity were associated with PCP positivity. Multivariate logistic regression and survival analysis found no statistically significant associations between PCP positivity and LOS or risk of readmission.

CONCLUSIONS

This study provides rare analysis of contemporary data on PCP use among patients undergoing medically assisted alcohol withdrawal. Phencyclidine positivity was uncommon, but use appears considerably higher among this patient population than the general population. There was no significant association between PCP positivity and LOS or readmission risk.

Involvement of serotonin in nicotine dependence: processes relevant to positive and negative regulation of drug intake

The neurobiological substrate of nicotine dependence has been the subject of extensive preclinical and clinical research. Many experimental reports have implicated the brain serotonin (5-HT) systems in processes relevant to nicotine dependence, but the specific role of this neurotransmitter system largely remains to be elucidated. This review will focus on the role of 5-HT in the acute and chronic effects of nicotine. In particular, the evidence for a role of 5-HT neurotransmission in brain processes thought to be involved in positive and negative control of nicotine use will be examined, and potential clinical implications discussed.

Withdrawal from chronic phencyclidine produces a pentylenetetrazol-like discriminative stimulus

Rats trained to discriminate the anxiogenic compound pentylenetetrazol (PTZ) from water were implanted with osmotic mini-pumps containing 7 mg/kg/day phencyclidine (PCP) or water. Rats were tested for generalization to PTZ 24 hours prior to pump removal, and 4 to 96 hours after pump removal. While the pumps were in place, rats did not generalize to PTZ. When the pumps were removed on day 10, rats in the water group did not generalize to PTZ, but 69% of the rats in the chronic PCP group responded on the PTZ lever at 4 and/or 24 hours after pump removal, suggesting that the PCP withdrawal state mimics the interoceptive cue produced by PTZ. This withdrawal phenomenon was repeatable, in that rats that generalized once to PTZ during PCP withdrawal, generalized a second time when the procedure was repeated. In addition, the phenomenon was dose-dependent, as rats that did not generalize to PTZ after 7 mg/kg/day PCP did generalize when the chronic dose of PCP was increased to 10 mg/kg/day. These findings suggest that there is an anxiogenic component of PCP withdrawal and that tolerance does not develop to this effect.

Does Phencyclidine (PCP) Use Increase Violent Crime?

Phencyclidine (PCP) has obtained a notorious reputation for provoking violent behavior. Because of this reputation and a number of methodological weaknesses in PCP-violence studies, the recent research literature on the relationship between PCP use and violent crime was reviewed. Studies were organized according to types of subjects studied (PCP users in treatment; PCP users in the criminal justice system; and PCP users at large in the community). Within each category, studies were evaluated in terms of the logical rigor of their research design and measurement. Of the three categories, investigations involving PCP users in the criminal justice system tended to have fewest problems. However, methodological weaknesses in some studies and contradictory findings in others did not allow one to adequately answer the question of whether PCP use increased violent crime. Unanswered questions and suggested directions for future research in the PCP-violence field are presented.

Alterations in rat brain [3H]-TCP binding following chronic phencyclidine administration

Rats were chronically infused with phencyclidine (PCP, 13.3 mg PCP.HCl/kg/day) or saline, s.c., for 10 days using osmotic minipumps (n = 5 for each group). Twenty-four hours after the cessation of dosing, the rats were sacrificed, and brains were removed for analysis of PCP receptor binding. Saturation studies of the binding of [3H]-TCP to brain homogenates revealed statistically significant increases in the maximum binding capacity (Bmax) and decreases in the affinity for [3H]-TCP in the PCP-treated group.

Perinatal outcome associated with PCP versus cocaine use

Phencyclidine (PCP) remains a widely used illicit drug, especially among adolescents and young adults. The pharmacologic effects of PCP are similar to those of cocaine; therefore, in this retrospective study 37 PCP-intoxicated parturients were matched for ethnicity, tobacco use, age, gravidity, and degree of prenatal care with 37 cocaine-intoxicated parturients. Infants exposed to PCP in utero, like those exposed to cocaine, had a high incidence of intrauterine growth retardation (32 vs 19%, N.S.), precipitate labor (43 vs 27%, N.S.), symptoms of neonatal drug withdrawal/intoxication, and prolonged neonatal hospitalizations. Moreover, they were more likely to have meconium-stained amniotic fluid (30 vs 19%, p = .05) and less likely to be born prematurely as cocaine-exposed infants. The comparison between the long-term developmental outcome of these groups awaits further study.

Inpatient treatment of PCP abusers and users

Screening of 155 consecutive admissions to a voluntary, 4-6 week substance abuse inpatient rehabilitation program revealed a 13% prevalence of PCP abuse (defined by DSM-III criteria) and a 23% prevalence of nonabusive PCP use. The 20 PCP abusers were significantly younger (31.6 vs 40.2 years) and had more prior arrests (2.0 vs 0.8) than the 36 nonabusive users, but did not differ in other sociodemographic characteristics. The age range of patients was older than previously reported in the literature, with three PCP abusers (15%) and 15 users (42%) 40 years of age or older. A majority of both abusers (80%) and users (97%) also abused other drugs, including alcohol (57%), opiates (29%), marijuana (29%), and stimulants (18%). The mean length of stay for PCP abusers was 27 days, with 11 completing inpatient treatment. Urine samples were collected upon admission from all patients and assayed for PCP by gas chromatography with N-P detection (sensitivity = 0.1 ng/mL). Patients with initial positive PCP results had follow-up urines collected at least weekly until the PCP assay was negative or they left the treatment program. Twenty-seven percent of patients had PCP detected in admission urine samples, one-third of whom initially denied PCP use. Six patients still had PCP detected after 4 weeks of hospitalization, without evidence of PCP reuse. These findings suggest that PCP abuse and use are common among unselected patients seeking substance abuse inpatient treatment and that they are not confined to the adolescent/young adult age group.

Behavioral dependence on phencyclidine in rats

The abuse of PCP continues to be an important medical problem in many urban areas. The probability that dependence on PCP may contribute to its compulsive use and relapse is supported by animal studies demonstrating its dependence liability. In the present study, five rats were housed in operant chambers and trained to respond on a lever under a fixed-ratio 30 schedule of food presentation. They obtained all their daily food during four 30-min response periods occurring every 6 hr. After stable baselines of behavior were established the rats were injected with PCP (3.0-7.5 mg/kg/injection), i.p., 1 hr before each response session for 7-10 days. Following chronic dosing, the drug injections were replaced with saline injections for 10 days. Disruptions in behavior were observed upon cessation of relatively brief chronic exposure to PCP (as little as 7 days) and at relatively low doses (5.6 mg/kg/6 hr = 22.4 mg/kg/day). The behavioral disruption was not accompanied by overt signs of abstinence and persisted for up to 48 hr.

Relationship between the development of behavioral tolerance and the biodisposition of phencyclidine in mice

Mice trained on a differential reinforcement of low rate 10-sec schedule (DRL 10) were treated daily with either IP saline or 10 mg/kg of phencyclidine hydrochloride (PCP). After 21 consecutive days of treatment, dose-effect determinations for PCP were obtained in both groups. Chronic treatment with PCP resulted in approximately 1.5-fold development of tolerance to the PCP-induced reduction of reinforcement rate. Following completion of the dose-effect determinations, the mice were treated for an additional 13 days with either saline or PCP (10 mg/kg, IP). On the fourteenth day, the biodisposition of 3H-PCP-HCl (10 mg/kg, IP) was studied in both groups. The ratio of the brain levels of PCP in the saline-trained animals to that in the PCP-trained animals was 1.3 to 1 which accounted in large part for the development of tolerance. It appears that dispositional factors are involved in the development of tolerance of mice to the disruptive effects of PCP on DRL performance.