Phencyclidine, or 1-(1-phenylcyclohexyl) piperidine hydrochloride (PCP), is an illegal drug once used as a nonnarcotic anesthetic in the United States until legally banned in the late 1970s. It became a popular recreational drug, available in powder, liquid, tablet, and crystal forms and in various combinations with cigarettes and marijuana. PCP is a hallucinogenic known to produce visual and auditory distortions in users. Other effects of low doses are numbness, relaxation, a sense of well-being, trouble concentrating, slurred speech, loss of motor coordination, misperceptions of abilities, and erratic behavior. High doses may lead to hallucinations, delusions, high blood pressure, increased heart rate, breathing problems, raised body temperature, anxiety, and panic. Adverse effects of some home-synthesized PCP include diarrhea, abdominal cramps, and hematemesis.

Trauma rather than overdose has been more likely to cause accidental death in PCP users. Among young children, exposure to PCP is often related to accidental exposure to a caregiver's stash. PCP added to methamphetamine and LSD increase chances for inadvertent exposure and overdose.

Severe toxicity may be reached when combined with other drugs, and when PCP users pack their body cavities to avoid detection by law enforcement and toxic levels of the drug enter their bloodstream. Intoxication, overdose, or a tainted batch can lead to severe complications of seizures, violent outburst, muscle rigidity, hyperreflexia, catatonia, rhabdomyolysis, coma, and death.

PCP abusers continue to use the drug because it confers feelings of strength, power, and invulnerability. PCP is addictive and repeated use can lead to cravings and a compulsion to find and consume the drug regardless of negative consequences. Long-term abuse symptoms include memory loss, difficulties with speech and thinking, depression, and weight loss.