Home > Encyclopedia of Drugs, Alcohol, and Addictive Behavior > Phencyclidine (Pcp): Adverse Effects

HISTORY

Phencyclidine was developed in the 1950s for use as an anesthetic, but its use was discontinued because patients developed delusions, severe anxiety, or frank psychosis after their operation. It was also used by veterinarians as an anesthetic for some years; at present, however, all PCP sold on the street is manufactured illegally. The initials "PCP" are derived from a nickname, "The Peace Pill." The history of PCP as a drug of abuse began in the United States in the mid-1960s, when it was primarily taken by ingestion; but the real epidemic of PCP abuse occurred in the 1970s, when smoking and insufflation ("snorting") became the more common forms of use (Burns & Lerner, 1976). Because it is not difficult for an experienced chemist to synthesize the drug, PCP and its abuse spread rapidly, peaking about 1978. After 1980, its prevalence declined—however, PCP abuse continues to occur precisely because the drug is relatively easy to make. National Institute on Drug Abuse surveys show that more Americans have experimented with PCP than with heroin, and the prevalence of recent use of PCP is about the same as with heroin, so it remains a significant public-health problem (National Institute on Drug Abuse, 1991). As of 1999, most PCP abusers either inject the drug or smoke it by sprinkling it on smoking material (mint leaves, parsley, marijuana, or tobacco).

PSYCHOLOGICAL EFFECTS OF PCP

The psychological effects of PCP abuse can be discussed under three headings: (1) the effects accompanying acute intoxication, (2) the personality disturbances that can sometimes develop in PCP abusers, especially when associated with chronic use, and (3) the possible neurobehavioral toxicity that might result from chronic use.

SIGNS AND SYMPTOMS OF PCP INTOXICATION

Low Dose.

Dreamy carefree state, mood elevation, heightened or altered perception, impaired judgment, partial amnesia.

Intermediate Dose.

Inebriation, motor incoordination, dissociation and depersonalization, confusion and disorientation, perceptual distortions and preoccupation with abnormal body sensations, diminished pain sensitivity, partial amnesia, and sometimes exaggerated mood swings and panic.

High Dose.

Catatonia, "blank stare," drooling, nystagmus (eye-rolling), delirium and hallucinations, psychotic behavior, severe motor incoordination, total amnesia.

ACUTE PCP INTOXICATION

As with all drugs, the effects of PCP depend on the dose that is taken. The section above lists the typical effects of PCP at various doses. PCP abusers usually adjust their dosage to experience only the low-dose effects. High-dose effects are similar to a mild type of dissociative anesthesia.

Experienced drug abusers can readily distinguish the experience of PCP intoxication from that produced by other drugs such as MARIJUANA, MESCALINE, and LYSERGIC ACID DIETHYLAMIDE (LSD). Users typically report a feeling of dissociation from the environment and abnormal body sensations and body image. The perceptual distortions often cause things to appear far away or abnormal in size. Compared to LSD, the effects of PCP are not very PSYCHEDELIC.

The most dangerous effects of PCP intoxication arise from the impaired judgment and altered perceptions that occur. People can engage in risk-taking behavior and harm themselves or others. DRIVING, swimming, or other activities requiring coordination and good judgment become extremely dangerous. Someone on PCP may also engage in casual but high-risk sexual behaviors. PCP users experience profound mood swings—where what begins as a pleasant experience can turn into panic and terror—and their behavior is unpredictable. Sometimes these "bad trips" can lead to violent and uncharacteristic behaviors with disastrous results. In cases of high-dose intoxication, users can experience a toxic psychotic episode with DELIRIUM, profound HALLUCINATIONS, and paranoia. In cases of severe overdose, seizures, stroke, or kidney failure may lead to death (Burns & Lerner, 1976).

MEDICAL TREATMENT

As of 2000, there is no medication that can serve as an antagonist to the effects of PCP or that can speed up its excretion. PCP is easily soluble in fats, thus can remain in the central nervous system for long periods. A patient who has overdosed on PCP must be placed on life support. Patients with anxiety or seizures can be given diazepam (Valium). Patients with psychotic episodes are usually treated with haloperidol (Haldol). Chlorpromazine (Thorazine) should not be given to patients who have taken PCP, as it may produce hypotension. Patients with severe hypertension due to PCP should be given diazoxide (Proglycem). Gastric lavage has been used successfully to treat patients who have ingested PCP directly.

PCP intoxication is considered a psychiatric emergency. It is recommended that these patients be placed in a secure room under observation. The health professional should not attempt to "talk the patient down." Physical restraints or a sedative such as lorazepam (Ativan) may be needed if the patient becomes violent.

LONG-TERM USE

In persons who abuse PCP in large amounts over a long period, or in those who have psychological problems that make them especially vulnerable, a chronic psychosis may develop. This PCP psychosis is evident even when abusers are not high on PCP, and it may be quite difficult to treat. The symptoms of PCP psychosis differ considerably from person to person, but patients may show many features of SCHIZOPHRENIA, including the appearance of a thought disorder, paranoid ideation, hallucinations, mood changes, and aberrant behavior. These patients often require psychiatric hospitalization and treatment with ANTIPSYCHOTIC medications.

In research studies where PCP has been given repeatedly to animals, it has been possible to show the development of PHYSICAL DEPENDENCE (e.g., Balster & Woolverton, 1980). The doses required for dependence are quite high, so it may be that dependence in human PCP abusers is difficult to develop. There have been some clinical reports of withdrawal effects in heavy PCP abusers, but these do not appear to be present in most individuals needing treatment for PCP abuse. There are no specialized treatment methods for PCP abusers, and since many PCP abusers also abuse other drugs and/or alcohol, they are usually helped by the same counseling and psychotherapy programs that are used for other forms of drug abuse.

NEUROPSYCHOLOGICAL AFTEREFFECTS OF PCP ABUSE

It is not known for certain whether or not PCP causes brain damage or long-term neurological or behavioral impairment in chronic abusers. Although some PCP abusers develop neurobehavioral impairment, controlled experiments of the type that would need to be carried out to show that PCP alone was the cause of the problems have not been done. PCP abusers typically abuse many other drugs in addition to PCP, which may contribute to their problems, and they may have lifestyles and health habits that lead to neuropsychological dys-function. For example, while under the influence of PCP, they may be involved in an accident resulting in brain injury, so the risk factors that accompany PCP abuse may be responsible for the clinical problems sometimes seen in abusers. It should be pointed out that PCP was used in humans for medical research for a number of years, and ketamine—a close analog of PCP—is, even in the early 1990s, given to thousands of patients. No legacy of neuropsychological impairment is seen in these individuals.

Does this mean that chronic PCP abuse does not cause neuropsychological impairment? Certainly, PCP—like all drugs—must be considered as a possible source of neural damage. In animal testing, it was found that even a single injection of a fairly high dose of PCP produced reversible pathomorphological changes in neurons of the cingulate and retrosplenial cortex in the brains of rats (Olney, Labruyere, & Price, 1989). Although it is not known if PCP produces these effects in humans, it is possible that it does and that this could lead to adverse health effects. Another possibly important basis for concern comes from studies which show that PCP, and related drugs, impair learning and memory in various animal models. PCP's ability to do this may be greater than for other classes of drugs of abuse, possibly due to PCP's ability to interfere with specific brain mechanisms for learning that involve N-methyl-D-aspartate (NMDA) RECEPTORS.

PCP AND VIOLENCE

Many people associate the abuse of PCP with violence and aggression, so this concern deserves special mention. Those under the influence of PCP often behave erratically and exercise poor judgment. These effects of PCP could certainly lead to violent behavior, and there are certainly numerous examples of extremely violent acts being performed by persons under the influence of PCP. This raises the question of whether PCP is uniquely associated with the production of violence and aggression: Is someone intoxicated with PCP more likely to be violent than someone who is intoxicated with COCAINE or alcohol?

Unfortunately, the answer to this question is not known. A great deal of criminal conduct in the United States is certainly carried out by people under the influence of alcohol or drugs. In addition, the public often associates drug use they do not understand with criminal and violent behavior. Every new drug epidemic is greeted with public concern that this drug causes violence. There is also the common practice of criminal attorneys using the defense of diminished capacity, because of drug use, to lessen the responsibility that their clients might bear for criminal conduct. All these factors undoubtedly contribute to the public attention focused on the relationship of PCP to violence.

Few good research studies have attempted to determine the specific role that PCP abuse may have in crime and violence. In one study (Wish, 1986) of nearly five thousand arrestees in New York City in 1984 who agreed to leave a urine specimen for drug analysis, it was found that 56 percent tested positive for at least one drug of abuse. For those who had used PCP recently, most had committed robbery, not bizarre violent offenses. In fact, assault was more common among arrestees who had not used PCP than among those who had. These results support the conclusion that PCP may be no more likely to cause violence than some other drugs of abuse—but, clearly, more research on this question is needed.

The NATIONAL INSTITUTE ON DRUG ABUSE estimates that as many as six million Americans have tried PCP at least once. The very large majority of these occasions of PCP use were not associated with violent acts; however, if some users prone to violence take PCP and are faced with a threatening situation, they may act unpredictably and violently. Although there is no scientific evidence that PCP actually increases muscular strength, PCP users unmindful of their own potential safety or injuries can be a formidable risk, so law enforcement personnel are on guard against these dangerous situations. Alternatively, it should not be assumed that most people who abuse PCP will become violent—nor should every inexplicable act of violence be casually or speculatively attributed to PCP abuse.

(SEE ALSO: Addiction: Concepts and Definitions; Amphetamine Epidemics; ; Crime and Drugs; Tolerance and Physical Dependence)

ROBERT L. BALSTER

REVISED BY REBECCA J. FREY AND

REBECCA MARLOW-FERGUSON