By Marcello Cherchi, MD PhD
For patients
Phencyclidine (PCP) is an illegal drug that can make a person hallucinate and behave violently. The drug can change your heart rate, blood pressure, breathing and body temperature. It can also cause abnormal eye movements.
For clinicians
Overview
Phencyclidine (PCP) is an illegal drug that can be consumed by inhalation, ingestion, or intravenous injection. Acute intoxication can manifest with behavioral abnormalities (altered mental status, agitation, violent behavior, hallucinations, delusions), physical examination findings (ataxia, tachycardia, hypertension, fever), ocular findings (miosis) and ocular motor findings (various forms of nystagmus, dysconjugate gaze). The mechanism by which PCP exerts these effects is not understood.
Introduction
Phencyclidine, short for phenyl-cyclohexyl-piperidine hydrochloride (PCP), was originally synthesized in the 1950s (Mozayani 2003) by Park, Davis and Co. (Pradhan 1984) as an anesthetic for humans, but its medical application in humans was discontinued because of the post-exposure behavioral and psychological disturbances. However, reports of the illicit use of PCP began to appear in 1965 (Pradhan 1984).
PCP can be consumed by inhalation, ingestion, or intravenous injection (Pradhan 1984).
PCP can have a variety of effects, and these are not predictable; it “may act as a stimulant, depressant, or hallucinogen, or as a combination of these” (Schwartz and Einhorn 1986) and as an analgesic (Mozayani 2003) and dissociative anesthetic (Dominici et al. 2015; McCarron et al. 1981).
Clinical manifestations of acute PCP intoxication are often difficult to isolate since the drug is frequently consumed in conjunction with others (Dominici et al. 2015; McCarron et al. 1981).
Epidemiology
Dominici and colleagues (Dominici et al. 2015), citing the National Survey on Drug Use and Health, state that as of 2011, 6.1 million Americans age 12 years and older reported using PCP in their lifetime.
Pathophysiological mechanism of disease
Acute PCP intoxication has been associated with several eye movement abnormalities, particularly nystagmus, though the mechanism underlying this finding is unknown (Barton, Sterling, Vaziri 1981). PCP is thought to have sympathomimetic and anticholinergic activity, yet some of its autonomic manifestations (e.g., diaphoresis, hypersalivation, bronchospasm) instead suggest either pro-cholinergic or anti-adrenergic activity (McCarron et al. 1981).
Clinical presentation
Acute PCP intoxication typically presents with some combination of behavioral abnormalities (altered mental status, agitation, violent behavior, hallucinations, delusions) (Barton, Sterling, Vaziri 1981; McCarron et al. 1981).
Physical examination
Acute PCP intoxication can present with a variety of physical examination findings, including ataxia, tachycardia, hypertension and mild fever (Barton, Sterling, Vaziri 1981; McCarron et al. 1981).
Ocular motor examination
Ocular and ocular motor findings can include miosis (Liden, Lovejoy, Costello 1975), dysconjugate gaze (Schwartz and Einhorn 1986) and various forms of nystagmus (Barton, Sterling, Vaziri 1981; Dominici et al. 2015; Herskowitz and Oppenheimer 1977; Liden, Lovejoy, Costello 1975; McCarron et al. 1981; Mozayani 2003; Pradhan 1984; Schwartz and Einhorn 1986; Tennant 1988).
Barton and colleagues studied a series of 27 cases of acute PCP intoxication and reported nystagmus in 24 (89%) of them (Barton, Sterling, Vaziri 1981).
Dominici and colleagues studied a series of 184 cases of acute PCP intoxication and reported horizontal nystagmus in 118 (64.1%), vertical nystagmus in 90 (48.9%) and torsional nystagmus in 3 (2.6%) (Dominici et al. 2015).
McCarron and colleagues (McCarron et al. 1981) studied 1000 cases of acute PCP intoxication that presented to an emergency department. They reported that 574 cases (57.4%) exhibited “horizontal, vertical or rotary nystagmus… Some patients had two or three types of nystagmus simultaneously.”
Herskowitz and Oppenheimer (Herskowitz and Oppenheimer 1977) reported the cases of two males (age 14 and 17) with acute PCP intoxication whose examinations showed, “On vertical or horizontal gaze, striking bursts of irregular, shuddery, jerk nystagmus occurred in the direction of gaze. Nystagmus was greatest in amplitude on upward gaze.”
Pradhan studied experimental subjects in a controlled military laboratory setting and reported that, “The residual effects (e.g., numbness, light headedness, vertigo, ataxia and lateral nystagmus) persisted for at least 4 hours postinjection” (Pradhan 1984). In contrast, Herskowitz and Oppenheimer reported the persistence of nystagmus as long as 4 days after acute intoxication (Herskowitz and Oppenheimer 1977).
Schwartz and Einhorn (Schwartz and Einhorn 1986) studied a series of 7 children with acute PCP intoxication and reported that 57% exhibited some form of nystagmus, and 27% exhibited dysconjugate gaze.
Testing: vestibular
As of this writing there were no published studies of instrumented vestibular testing in patients with acute PCP intoxication.
Treatment
Management of acute PCP intoxication may include haloperidol and benzodiazepines, which usually happens in an emergency room setting. After a patient has been stabilized, they are generally admitted to the hospital for subacute monitoring and care.
References
Barton CH, Sterling ML, Vaziri ND (1981) Phencyclidine intoxication: clinical experience in 27 cases confirmed by urine assay. Ann Emerg Med 10: 243-6. doi: 10.1016/s0196-0644(81)80048-0
Dominici P, Kopec K, Manur R, Khalid A, Damiron K, Rowden A (2015) Phencyclidine Intoxication Case Series Study. J Med Toxicol 11: 321-5. doi: 10.1007/s13181-014-0453-9
Herskowitz J, Oppenheimer EY (1977) More about poisoning by phencyclidine (“PCP”, “angel dust”). N Engl J Med 297: 1405.
Liden CB, Lovejoy FH, Jr., Costello CE (1975) Phencyclidine. Nine cases of poisoning. Jama 234: 513-6. doi: 10.1001/jama.234.5.513
McCarron MM, Schulze BW, Thompson GA, Conder MC, Goetz WA (1981) Acute phencyclidine intoxication: incidence of clinical findings in 1,000 cases. Ann Emerg Med 10: 237-42. doi: 10.1016/s0196-0644(81)80047-9
Mozayani A (2003) Phencyclidine – Effects on Human Performance and Behavior. Forensic Sci Rev 15: 61-74.
Pradhan SN (1984) Phencyclidine (PCP): some human studies. Neurosci Biobehav Rev 8: 493-501. doi: 10.1016/0149-7634(84)90006-x
Schwartz RH, Einhorn A (1986) PCP intoxication in seven young children. Pediatr Emerg Care 2: 238-41. doi: 10.1097/00006565-198612000-00008
Tennant F (1988) The rapid eye test to detect drug abuse. Postgrad Med 84: 108-14. doi: 10.1080/00325481.1988.11700339
